buffer.c 89.9 KB
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/*
 *  linux/fs/buffer.c
 *
 *  Copyright (C) 1991, 1992, 2002  Linus Torvalds
 */

/*
 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
 *
 * Removed a lot of unnecessary code and simplified things now that
 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
 *
 * Speed up hash, lru, and free list operations.  Use gfp() for allocating
 * hash table, use SLAB cache for buffer heads. SMP threading.  -DaveM
 *
 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
 *
 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
 */

#include <linux/kernel.h>
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#include <linux/sched/signal.h>
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#include <linux/syscalls.h>
#include <linux/fs.h>
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#include <linux/iomap.h>
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#include <linux/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
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#include <linux/capability.h>
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#include <linux/blkdev.h>
#include <linux/file.h>
#include <linux/quotaops.h>
#include <linux/highmem.h>
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#include <linux/export.h>
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#include <linux/backing-dev.h>
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#include <linux/writeback.h>
#include <linux/hash.h>
#include <linux/suspend.h>
#include <linux/buffer_head.h>
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#include <linux/task_io_accounting_ops.h>
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#include <linux/bio.h>
#include <linux/cpu.h>
#include <linux/bitops.h>
#include <linux/mpage.h>
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#include <linux/bit_spinlock.h>
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#include <linux/pagevec.h>
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#include <linux/sched/mm.h>
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#include <trace/events/block.h>
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static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
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static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
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			 enum rw_hint hint, struct writeback_control *wbc);
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#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)

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inline void touch_buffer(struct buffer_head *bh)
{
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	trace_block_touch_buffer(bh);
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	mark_page_accessed(bh->b_page);
}
EXPORT_SYMBOL(touch_buffer);

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void __lock_buffer(struct buffer_head *bh)
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{
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	wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
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}
EXPORT_SYMBOL(__lock_buffer);

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void unlock_buffer(struct buffer_head *bh)
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{
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	clear_bit_unlock(BH_Lock, &bh->b_state);
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	smp_mb__after_atomic();
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	wake_up_bit(&bh->b_state, BH_Lock);
}
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EXPORT_SYMBOL(unlock_buffer);
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/*
 * Returns if the page has dirty or writeback buffers. If all the buffers
 * are unlocked and clean then the PageDirty information is stale. If
 * any of the pages are locked, it is assumed they are locked for IO.
 */
void buffer_check_dirty_writeback(struct page *page,
				     bool *dirty, bool *writeback)
{
	struct buffer_head *head, *bh;
	*dirty = false;
	*writeback = false;

	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
		return;

	if (PageWriteback(page))
		*writeback = true;

	head = page_buffers(page);
	bh = head;
	do {
		if (buffer_locked(bh))
			*writeback = true;

		if (buffer_dirty(bh))
			*dirty = true;

		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(buffer_check_dirty_writeback);

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/*
 * Block until a buffer comes unlocked.  This doesn't stop it
 * from becoming locked again - you have to lock it yourself
 * if you want to preserve its state.
 */
void __wait_on_buffer(struct buffer_head * bh)
{
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	wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
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}
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EXPORT_SYMBOL(__wait_on_buffer);
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static void
__clear_page_buffers(struct page *page)
{
	ClearPagePrivate(page);
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	set_page_private(page, 0);
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	put_page(page);
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}

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static void buffer_io_error(struct buffer_head *bh, char *msg)
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{
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	if (!test_bit(BH_Quiet, &bh->b_state))
		printk_ratelimited(KERN_ERR
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			"Buffer I/O error on dev %pg, logical block %llu%s\n",
			bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
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}

/*
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 * End-of-IO handler helper function which does not touch the bh after
 * unlocking it.
 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
 * a race there is benign: unlock_buffer() only use the bh's address for
 * hashing after unlocking the buffer, so it doesn't actually touch the bh
 * itself.
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 */
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static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
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{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		/* This happens, due to failed read-ahead attempts. */
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		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
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}

/*
 * Default synchronous end-of-IO handler..  Just mark it up-to-date and
 * unlock the buffer. This is what ll_rw_block uses too.
 */
void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
{
	__end_buffer_read_notouch(bh, uptodate);
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	put_bh(bh);
}
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EXPORT_SYMBOL(end_buffer_read_sync);
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void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
{
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		buffer_io_error(bh, ", lost sync page write");
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		mark_buffer_write_io_error(bh);
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		clear_buffer_uptodate(bh);
	}
	unlock_buffer(bh);
	put_bh(bh);
}
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EXPORT_SYMBOL(end_buffer_write_sync);
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/*
 * Various filesystems appear to want __find_get_block to be non-blocking.
 * But it's the page lock which protects the buffers.  To get around this,
 * we get exclusion from try_to_free_buffers with the blockdev mapping's
 * private_lock.
 *
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 * Hack idea: for the blockdev mapping, private_lock contention
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 * may be quite high.  This code could TryLock the page, and if that
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 * succeeds, there is no need to take private_lock.
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 */
static struct buffer_head *
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__find_get_block_slow(struct block_device *bdev, sector_t block)
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{
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct buffer_head *ret = NULL;
	pgoff_t index;
	struct buffer_head *bh;
	struct buffer_head *head;
	struct page *page;
	int all_mapped = 1;

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	index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
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	page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
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	if (!page)
		goto out;

	spin_lock(&bd_mapping->private_lock);
	if (!page_has_buffers(page))
		goto out_unlock;
	head = page_buffers(page);
	bh = head;
	do {
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		if (!buffer_mapped(bh))
			all_mapped = 0;
		else if (bh->b_blocknr == block) {
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			ret = bh;
			get_bh(bh);
			goto out_unlock;
		}
		bh = bh->b_this_page;
	} while (bh != head);

	/* we might be here because some of the buffers on this page are
	 * not mapped.  This is due to various races between
	 * file io on the block device and getblk.  It gets dealt with
	 * elsewhere, don't buffer_error if we had some unmapped buffers
	 */
	if (all_mapped) {
		printk("__find_get_block_slow() failed. "
			"block=%llu, b_blocknr=%llu\n",
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			(unsigned long long)block,
			(unsigned long long)bh->b_blocknr);
		printk("b_state=0x%08lx, b_size=%zu\n",
			bh->b_state, bh->b_size);
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		printk("device %pg blocksize: %d\n", bdev,
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			1 << bd_inode->i_blkbits);
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	}
out_unlock:
	spin_unlock(&bd_mapping->private_lock);
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	put_page(page);
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out:
	return ret;
}

/*
 * I/O completion handler for block_read_full_page() - pages
 * which come unlocked at the end of I/O.
 */
static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
{
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;
	int page_uptodate = 1;

	BUG_ON(!buffer_async_read(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
		clear_buffer_uptodate(bh);
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		buffer_io_error(bh, ", async page read");
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		SetPageError(page);
	}

	/*
	 * Be _very_ careful from here on. Bad things can happen if
	 * two buffer heads end IO at almost the same time and both
	 * decide that the page is now completely done.
	 */
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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
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	clear_buffer_async_read(bh);
	unlock_buffer(bh);
	tmp = bh;
	do {
		if (!buffer_uptodate(tmp))
			page_uptodate = 0;
		if (buffer_async_read(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	} while (tmp != bh);
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	/*
	 * If none of the buffers had errors and they are all
	 * uptodate then we can set the page uptodate.
	 */
	if (page_uptodate && !PageError(page))
		SetPageUptodate(page);
	unlock_page(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}

/*
 * Completion handler for block_write_full_page() - pages which are unlocked
 * during I/O, and which have PageWriteback cleared upon I/O completion.
 */
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void end_buffer_async_write(struct buffer_head *bh, int uptodate)
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{
	unsigned long flags;
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	struct buffer_head *first;
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	struct buffer_head *tmp;
	struct page *page;

	BUG_ON(!buffer_async_write(bh));

	page = bh->b_page;
	if (uptodate) {
		set_buffer_uptodate(bh);
	} else {
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		buffer_io_error(bh, ", lost async page write");
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		mark_buffer_write_io_error(bh);
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		clear_buffer_uptodate(bh);
		SetPageError(page);
	}

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	first = page_buffers(page);
	local_irq_save(flags);
	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);

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	clear_buffer_async_write(bh);
	unlock_buffer(bh);
	tmp = bh->b_this_page;
	while (tmp != bh) {
		if (buffer_async_write(tmp)) {
			BUG_ON(!buffer_locked(tmp));
			goto still_busy;
		}
		tmp = tmp->b_this_page;
	}
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	end_page_writeback(page);
	return;

still_busy:
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	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
	local_irq_restore(flags);
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	return;
}
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EXPORT_SYMBOL(end_buffer_async_write);
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/*
 * If a page's buffers are under async readin (end_buffer_async_read
 * completion) then there is a possibility that another thread of
 * control could lock one of the buffers after it has completed
 * but while some of the other buffers have not completed.  This
 * locked buffer would confuse end_buffer_async_read() into not unlocking
 * the page.  So the absence of BH_Async_Read tells end_buffer_async_read()
 * that this buffer is not under async I/O.
 *
 * The page comes unlocked when it has no locked buffer_async buffers
 * left.
 *
 * PageLocked prevents anyone starting new async I/O reads any of
 * the buffers.
 *
 * PageWriteback is used to prevent simultaneous writeout of the same
 * page.
 *
 * PageLocked prevents anyone from starting writeback of a page which is
 * under read I/O (PageWriteback is only ever set against a locked page).
 */
static void mark_buffer_async_read(struct buffer_head *bh)
{
	bh->b_end_io = end_buffer_async_read;
	set_buffer_async_read(bh);
}

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static void mark_buffer_async_write_endio(struct buffer_head *bh,
					  bh_end_io_t *handler)
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{
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	bh->b_end_io = handler;
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	set_buffer_async_write(bh);
}
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void mark_buffer_async_write(struct buffer_head *bh)
{
	mark_buffer_async_write_endio(bh, end_buffer_async_write);
}
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EXPORT_SYMBOL(mark_buffer_async_write);


/*
 * fs/buffer.c contains helper functions for buffer-backed address space's
 * fsync functions.  A common requirement for buffer-based filesystems is
 * that certain data from the backing blockdev needs to be written out for
 * a successful fsync().  For example, ext2 indirect blocks need to be
 * written back and waited upon before fsync() returns.
 *
 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
 * management of a list of dependent buffers at ->i_mapping->private_list.
 *
 * Locking is a little subtle: try_to_free_buffers() will remove buffers
 * from their controlling inode's queue when they are being freed.  But
 * try_to_free_buffers() will be operating against the *blockdev* mapping
 * at the time, not against the S_ISREG file which depends on those buffers.
 * So the locking for private_list is via the private_lock in the address_space
 * which backs the buffers.  Which is different from the address_space 
 * against which the buffers are listed.  So for a particular address_space,
 * mapping->private_lock does *not* protect mapping->private_list!  In fact,
 * mapping->private_list will always be protected by the backing blockdev's
 * ->private_lock.
 *
 * Which introduces a requirement: all buffers on an address_space's
 * ->private_list must be from the same address_space: the blockdev's.
 *
 * address_spaces which do not place buffers at ->private_list via these
 * utility functions are free to use private_lock and private_list for
 * whatever they want.  The only requirement is that list_empty(private_list)
 * be true at clear_inode() time.
 *
 * FIXME: clear_inode should not call invalidate_inode_buffers().  The
 * filesystems should do that.  invalidate_inode_buffers() should just go
 * BUG_ON(!list_empty).
 *
 * FIXME: mark_buffer_dirty_inode() is a data-plane operation.  It should
 * take an address_space, not an inode.  And it should be called
 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
 * queued up.
 *
 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
 * list if it is already on a list.  Because if the buffer is on a list,
 * it *must* already be on the right one.  If not, the filesystem is being
 * silly.  This will save a ton of locking.  But first we have to ensure
 * that buffers are taken *off* the old inode's list when they are freed
 * (presumably in truncate).  That requires careful auditing of all
 * filesystems (do it inside bforget()).  It could also be done by bringing
 * b_inode back.
 */

/*
 * The buffer's backing address_space's private_lock must be held
 */
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static void __remove_assoc_queue(struct buffer_head *bh)
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{
	list_del_init(&bh->b_assoc_buffers);
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	WARN_ON(!bh->b_assoc_map);
	bh->b_assoc_map = NULL;
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}

int inode_has_buffers(struct inode *inode)
{
	return !list_empty(&inode->i_data.private_list);
}

/*
 * osync is designed to support O_SYNC io.  It waits synchronously for
 * all already-submitted IO to complete, but does not queue any new
 * writes to the disk.
 *
 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
 * you dirty the buffers, and then use osync_inode_buffers to wait for
 * completion.  Any other dirty buffers which are not yet queued for
 * write will not be flushed to disk by the osync.
 */
static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head *p;
	int err = 0;

	spin_lock(lock);
repeat:
	list_for_each_prev(p, list) {
		bh = BH_ENTRY(p);
		if (buffer_locked(bh)) {
			get_bh(bh);
			spin_unlock(lock);
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				err = -EIO;
			brelse(bh);
			spin_lock(lock);
			goto repeat;
		}
	}
	spin_unlock(lock);
	return err;
}

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void emergency_thaw_bdev(struct super_block *sb)
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{
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	while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
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		printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
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}
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/**
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 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
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 * @mapping: the mapping which wants those buffers written
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 *
 * Starts I/O against the buffers at mapping->private_list, and waits upon
 * that I/O.
 *
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 * Basically, this is a convenience function for fsync().
 * @mapping is a file or directory which needs those buffers to be written for
 * a successful fsync().
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 */
int sync_mapping_buffers(struct address_space *mapping)
{
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	struct address_space *buffer_mapping = mapping->private_data;
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	if (buffer_mapping == NULL || list_empty(&mapping->private_list))
		return 0;

	return fsync_buffers_list(&buffer_mapping->private_lock,
					&mapping->private_list);
}
EXPORT_SYMBOL(sync_mapping_buffers);

/*
 * Called when we've recently written block `bblock', and it is known that
 * `bblock' was for a buffer_boundary() buffer.  This means that the block at
 * `bblock + 1' is probably a dirty indirect block.  Hunt it down and, if it's
 * dirty, schedule it for IO.  So that indirects merge nicely with their data.
 */
void write_boundary_block(struct block_device *bdev,
			sector_t bblock, unsigned blocksize)
{
	struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
	if (bh) {
		if (buffer_dirty(bh))
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			ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
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		put_bh(bh);
	}
}

void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
{
	struct address_space *mapping = inode->i_mapping;
	struct address_space *buffer_mapping = bh->b_page->mapping;

	mark_buffer_dirty(bh);
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	if (!mapping->private_data) {
		mapping->private_data = buffer_mapping;
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	} else {
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		BUG_ON(mapping->private_data != buffer_mapping);
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	}
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	if (!bh->b_assoc_map) {
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		spin_lock(&buffer_mapping->private_lock);
		list_move_tail(&bh->b_assoc_buffers,
				&mapping->private_list);
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		bh->b_assoc_map = mapping;
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		spin_unlock(&buffer_mapping->private_lock);
	}
}
EXPORT_SYMBOL(mark_buffer_dirty_inode);

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/*
 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
 * dirty.
 *
 * If warn is true, then emit a warning if the page is not uptodate and has
 * not been truncated.
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 *
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 * The caller must hold lock_page_memcg().
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 */
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void __set_page_dirty(struct page *page, struct address_space *mapping,
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			     int warn)
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{
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	unsigned long flags;

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	xa_lock_irqsave(&mapping->i_pages, flags);
579 580
	if (page->mapping) {	/* Race with truncate? */
		WARN_ON_ONCE(warn && !PageUptodate(page));
J
Johannes Weiner 已提交
581
		account_page_dirtied(page, mapping);
M
Matthew Wilcox 已提交
582
		radix_tree_tag_set(&mapping->i_pages,
583 584
				page_index(page), PAGECACHE_TAG_DIRTY);
	}
M
Matthew Wilcox 已提交
585
	xa_unlock_irqrestore(&mapping->i_pages, flags);
586
}
M
Matthew Wilcox 已提交
587
EXPORT_SYMBOL_GPL(__set_page_dirty);
588

L
Linus Torvalds 已提交
589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615
/*
 * Add a page to the dirty page list.
 *
 * It is a sad fact of life that this function is called from several places
 * deeply under spinlocking.  It may not sleep.
 *
 * If the page has buffers, the uptodate buffers are set dirty, to preserve
 * dirty-state coherency between the page and the buffers.  It the page does
 * not have buffers then when they are later attached they will all be set
 * dirty.
 *
 * The buffers are dirtied before the page is dirtied.  There's a small race
 * window in which a writepage caller may see the page cleanness but not the
 * buffer dirtiness.  That's fine.  If this code were to set the page dirty
 * before the buffers, a concurrent writepage caller could clear the page dirty
 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
 * page on the dirty page list.
 *
 * We use private_lock to lock against try_to_free_buffers while using the
 * page's buffer list.  Also use this to protect against clean buffers being
 * added to the page after it was set dirty.
 *
 * FIXME: may need to call ->reservepage here as well.  That's rather up to the
 * address_space though.
 */
int __set_page_dirty_buffers(struct page *page)
{
616
	int newly_dirty;
617
	struct address_space *mapping = page_mapping(page);
618 619 620

	if (unlikely(!mapping))
		return !TestSetPageDirty(page);
L
Linus Torvalds 已提交
621 622 623 624 625 626 627 628 629 630 631

	spin_lock(&mapping->private_lock);
	if (page_has_buffers(page)) {
		struct buffer_head *head = page_buffers(page);
		struct buffer_head *bh = head;

		do {
			set_buffer_dirty(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
632
	/*
633 634
	 * Lock out page->mem_cgroup migration to keep PageDirty
	 * synchronized with per-memcg dirty page counters.
635
	 */
J
Johannes Weiner 已提交
636
	lock_page_memcg(page);
637
	newly_dirty = !TestSetPageDirty(page);
L
Linus Torvalds 已提交
638 639
	spin_unlock(&mapping->private_lock);

640
	if (newly_dirty)
J
Johannes Weiner 已提交
641
		__set_page_dirty(page, mapping, 1);
642

J
Johannes Weiner 已提交
643
	unlock_page_memcg(page);
644 645 646 647

	if (newly_dirty)
		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);

648
	return newly_dirty;
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Linus Torvalds 已提交
649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674
}
EXPORT_SYMBOL(__set_page_dirty_buffers);

/*
 * Write out and wait upon a list of buffers.
 *
 * We have conflicting pressures: we want to make sure that all
 * initially dirty buffers get waited on, but that any subsequently
 * dirtied buffers don't.  After all, we don't want fsync to last
 * forever if somebody is actively writing to the file.
 *
 * Do this in two main stages: first we copy dirty buffers to a
 * temporary inode list, queueing the writes as we go.  Then we clean
 * up, waiting for those writes to complete.
 * 
 * During this second stage, any subsequent updates to the file may end
 * up refiling the buffer on the original inode's dirty list again, so
 * there is a chance we will end up with a buffer queued for write but
 * not yet completed on that list.  So, as a final cleanup we go through
 * the osync code to catch these locked, dirty buffers without requeuing
 * any newly dirty buffers for write.
 */
static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
{
	struct buffer_head *bh;
	struct list_head tmp;
J
Jens Axboe 已提交
675
	struct address_space *mapping;
L
Linus Torvalds 已提交
676
	int err = 0, err2;
J
Jens Axboe 已提交
677
	struct blk_plug plug;
L
Linus Torvalds 已提交
678 679

	INIT_LIST_HEAD(&tmp);
J
Jens Axboe 已提交
680
	blk_start_plug(&plug);
L
Linus Torvalds 已提交
681 682 683 684

	spin_lock(lock);
	while (!list_empty(list)) {
		bh = BH_ENTRY(list->next);
685
		mapping = bh->b_assoc_map;
686
		__remove_assoc_queue(bh);
687 688 689
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
L
Linus Torvalds 已提交
690 691
		if (buffer_dirty(bh) || buffer_locked(bh)) {
			list_add(&bh->b_assoc_buffers, &tmp);
692
			bh->b_assoc_map = mapping;
L
Linus Torvalds 已提交
693 694 695 696 697
			if (buffer_dirty(bh)) {
				get_bh(bh);
				spin_unlock(lock);
				/*
				 * Ensure any pending I/O completes so that
C
Christoph Hellwig 已提交
698 699 700 701
				 * write_dirty_buffer() actually writes the
				 * current contents - it is a noop if I/O is
				 * still in flight on potentially older
				 * contents.
L
Linus Torvalds 已提交
702
				 */
703
				write_dirty_buffer(bh, REQ_SYNC);
704 705 706 707 708 709 710

				/*
				 * Kick off IO for the previous mapping. Note
				 * that we will not run the very last mapping,
				 * wait_on_buffer() will do that for us
				 * through sync_buffer().
				 */
L
Linus Torvalds 已提交
711 712 713 714 715 716
				brelse(bh);
				spin_lock(lock);
			}
		}
	}

J
Jens Axboe 已提交
717 718 719 720
	spin_unlock(lock);
	blk_finish_plug(&plug);
	spin_lock(lock);

L
Linus Torvalds 已提交
721 722 723
	while (!list_empty(&tmp)) {
		bh = BH_ENTRY(tmp.prev);
		get_bh(bh);
724 725 726 727 728 729 730
		mapping = bh->b_assoc_map;
		__remove_assoc_queue(bh);
		/* Avoid race with mark_buffer_dirty_inode() which does
		 * a lockless check and we rely on seeing the dirty bit */
		smp_mb();
		if (buffer_dirty(bh)) {
			list_add(&bh->b_assoc_buffers,
731
				 &mapping->private_list);
732 733
			bh->b_assoc_map = mapping;
		}
L
Linus Torvalds 已提交
734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763
		spin_unlock(lock);
		wait_on_buffer(bh);
		if (!buffer_uptodate(bh))
			err = -EIO;
		brelse(bh);
		spin_lock(lock);
	}
	
	spin_unlock(lock);
	err2 = osync_buffers_list(lock, list);
	if (err)
		return err;
	else
		return err2;
}

/*
 * Invalidate any and all dirty buffers on a given inode.  We are
 * probably unmounting the fs, but that doesn't mean we have already
 * done a sync().  Just drop the buffers from the inode list.
 *
 * NOTE: we take the inode's blockdev's mapping's private_lock.  Which
 * assumes that all the buffers are against the blockdev.  Not true
 * for reiserfs.
 */
void invalidate_inode_buffers(struct inode *inode)
{
	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
764
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
765 766 767 768 769 770 771

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list))
			__remove_assoc_queue(BH_ENTRY(list->next));
		spin_unlock(&buffer_mapping->private_lock);
	}
}
J
Jan Kara 已提交
772
EXPORT_SYMBOL(invalidate_inode_buffers);
L
Linus Torvalds 已提交
773 774 775 776 777 778 779 780 781 782 783 784 785 786

/*
 * Remove any clean buffers from the inode's buffer list.  This is called
 * when we're trying to free the inode itself.  Those buffers can pin it.
 *
 * Returns true if all buffers were removed.
 */
int remove_inode_buffers(struct inode *inode)
{
	int ret = 1;

	if (inode_has_buffers(inode)) {
		struct address_space *mapping = &inode->i_data;
		struct list_head *list = &mapping->private_list;
787
		struct address_space *buffer_mapping = mapping->private_data;
L
Linus Torvalds 已提交
788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812

		spin_lock(&buffer_mapping->private_lock);
		while (!list_empty(list)) {
			struct buffer_head *bh = BH_ENTRY(list->next);
			if (buffer_dirty(bh)) {
				ret = 0;
				break;
			}
			__remove_assoc_queue(bh);
		}
		spin_unlock(&buffer_mapping->private_lock);
	}
	return ret;
}

/*
 * Create the appropriate buffers when given a page for data area and
 * the size of each buffer.. Use the bh->b_this_page linked list to
 * follow the buffers created.  Return NULL if unable to create more
 * buffers.
 *
 * The retry flag is used to differentiate async IO (paging, swapping)
 * which may not fail from ordinary buffer allocations.
 */
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
813
		bool retry)
L
Linus Torvalds 已提交
814 815
{
	struct buffer_head *bh, *head;
816
	gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
L
Linus Torvalds 已提交
817
	long offset;
818
	struct mem_cgroup *memcg;
L
Linus Torvalds 已提交
819

820 821 822
	if (retry)
		gfp |= __GFP_NOFAIL;

823 824 825
	memcg = get_mem_cgroup_from_page(page);
	memalloc_use_memcg(memcg);

L
Linus Torvalds 已提交
826 827 828
	head = NULL;
	offset = PAGE_SIZE;
	while ((offset -= size) >= 0) {
829
		bh = alloc_buffer_head(gfp);
L
Linus Torvalds 已提交
830 831 832 833 834 835 836 837 838 839 840 841
		if (!bh)
			goto no_grow;

		bh->b_this_page = head;
		bh->b_blocknr = -1;
		head = bh;

		bh->b_size = size;

		/* Link the buffer to its page */
		set_bh_page(bh, page, offset);
	}
842 843 844
out:
	memalloc_unuse_memcg();
	mem_cgroup_put(memcg);
L
Linus Torvalds 已提交
845 846 847 848 849 850 851 852 853 854 855 856 857
	return head;
/*
 * In case anything failed, we just free everything we got.
 */
no_grow:
	if (head) {
		do {
			bh = head;
			head = head->b_this_page;
			free_buffer_head(bh);
		} while (head);
	}

858
	goto out;
L
Linus Torvalds 已提交
859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875
}
EXPORT_SYMBOL_GPL(alloc_page_buffers);

static inline void
link_dev_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh, *tail;

	bh = head;
	do {
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;
	attach_page_buffers(page, head);
}

876 877 878 879 880 881 882 883 884 885 886 887
static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
{
	sector_t retval = ~((sector_t)0);
	loff_t sz = i_size_read(bdev->bd_inode);

	if (sz) {
		unsigned int sizebits = blksize_bits(size);
		retval = (sz >> sizebits);
	}
	return retval;
}

L
Linus Torvalds 已提交
888 889 890
/*
 * Initialise the state of a blockdev page's buffers.
 */ 
891
static sector_t
L
Linus Torvalds 已提交
892 893 894 895 896 897
init_page_buffers(struct page *page, struct block_device *bdev,
			sector_t block, int size)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh = head;
	int uptodate = PageUptodate(page);
898
	sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
L
Linus Torvalds 已提交
899 900 901

	do {
		if (!buffer_mapped(bh)) {
902 903
			bh->b_end_io = NULL;
			bh->b_private = NULL;
L
Linus Torvalds 已提交
904 905 906 907
			bh->b_bdev = bdev;
			bh->b_blocknr = block;
			if (uptodate)
				set_buffer_uptodate(bh);
908 909
			if (block < end_block)
				set_buffer_mapped(bh);
L
Linus Torvalds 已提交
910 911 912 913
		}
		block++;
		bh = bh->b_this_page;
	} while (bh != head);
914 915 916 917 918

	/*
	 * Caller needs to validate requested block against end of device.
	 */
	return end_block;
L
Linus Torvalds 已提交
919 920 921 922 923
}

/*
 * Create the page-cache page that contains the requested block.
 *
924
 * This is used purely for blockdev mappings.
L
Linus Torvalds 已提交
925
 */
926
static int
L
Linus Torvalds 已提交
927
grow_dev_page(struct block_device *bdev, sector_t block,
928
	      pgoff_t index, int size, int sizebits, gfp_t gfp)
L
Linus Torvalds 已提交
929 930 931 932
{
	struct inode *inode = bdev->bd_inode;
	struct page *page;
	struct buffer_head *bh;
933 934
	sector_t end_block;
	int ret = 0;		/* Will call free_more_memory() */
935
	gfp_t gfp_mask;
L
Linus Torvalds 已提交
936

937
	gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
938

939 940 941 942 943 944 945 946 947
	/*
	 * XXX: __getblk_slow() can not really deal with failure and
	 * will endlessly loop on improvised global reclaim.  Prefer
	 * looping in the allocator rather than here, at least that
	 * code knows what it's doing.
	 */
	gfp_mask |= __GFP_NOFAIL;

	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
L
Linus Torvalds 已提交
948

949
	BUG_ON(!PageLocked(page));
L
Linus Torvalds 已提交
950 951 952 953

	if (page_has_buffers(page)) {
		bh = page_buffers(page);
		if (bh->b_size == size) {
954
			end_block = init_page_buffers(page, bdev,
955 956
						(sector_t)index << sizebits,
						size);
957
			goto done;
L
Linus Torvalds 已提交
958 959 960 961 962 963 964 965
		}
		if (!try_to_free_buffers(page))
			goto failed;
	}

	/*
	 * Allocate some buffers for this page
	 */
966
	bh = alloc_page_buffers(page, size, true);
L
Linus Torvalds 已提交
967 968 969 970 971 972 973 974

	/*
	 * Link the page to the buffers and initialise them.  Take the
	 * lock to be atomic wrt __find_get_block(), which does not
	 * run under the page lock.
	 */
	spin_lock(&inode->i_mapping->private_lock);
	link_dev_buffers(page, bh);
975 976
	end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
			size);
L
Linus Torvalds 已提交
977
	spin_unlock(&inode->i_mapping->private_lock);
978 979
done:
	ret = (block < end_block) ? 1 : -ENXIO;
L
Linus Torvalds 已提交
980 981
failed:
	unlock_page(page);
982
	put_page(page);
983
	return ret;
L
Linus Torvalds 已提交
984 985 986 987 988 989
}

/*
 * Create buffers for the specified block device block's page.  If
 * that page was dirty, the buffers are set dirty also.
 */
990
static int
991
grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
L
Linus Torvalds 已提交
992 993 994 995 996 997 998 999 1000 1001 1002
{
	pgoff_t index;
	int sizebits;

	sizebits = -1;
	do {
		sizebits++;
	} while ((size << sizebits) < PAGE_SIZE);

	index = block >> sizebits;

1003 1004 1005 1006 1007 1008
	/*
	 * Check for a block which wants to lie outside our maximum possible
	 * pagecache index.  (this comparison is done using sector_t types).
	 */
	if (unlikely(index != block >> sizebits)) {
		printk(KERN_ERR "%s: requested out-of-range block %llu for "
1009
			"device %pg\n",
1010
			__func__, (unsigned long long)block,
1011
			bdev);
1012 1013
		return -EIO;
	}
1014

L
Linus Torvalds 已提交
1015
	/* Create a page with the proper size buffers.. */
1016
	return grow_dev_page(bdev, block, index, size, sizebits, gfp);
L
Linus Torvalds 已提交
1017 1018
}

1019
static struct buffer_head *
1020 1021
__getblk_slow(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1022 1023
{
	/* Size must be multiple of hard sectorsize */
1024
	if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
L
Linus Torvalds 已提交
1025 1026 1027
			(size < 512 || size > PAGE_SIZE))) {
		printk(KERN_ERR "getblk(): invalid block size %d requested\n",
					size);
1028 1029
		printk(KERN_ERR "logical block size: %d\n",
					bdev_logical_block_size(bdev));
L
Linus Torvalds 已提交
1030 1031 1032 1033 1034

		dump_stack();
		return NULL;
	}

1035 1036 1037
	for (;;) {
		struct buffer_head *bh;
		int ret;
L
Linus Torvalds 已提交
1038 1039 1040 1041

		bh = __find_get_block(bdev, block, size);
		if (bh)
			return bh;
1042

1043
		ret = grow_buffers(bdev, block, size, gfp);
1044 1045
		if (ret < 0)
			return NULL;
L
Linus Torvalds 已提交
1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073
	}
}

/*
 * The relationship between dirty buffers and dirty pages:
 *
 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
 * the page is tagged dirty in its radix tree.
 *
 * At all times, the dirtiness of the buffers represents the dirtiness of
 * subsections of the page.  If the page has buffers, the page dirty bit is
 * merely a hint about the true dirty state.
 *
 * When a page is set dirty in its entirety, all its buffers are marked dirty
 * (if the page has buffers).
 *
 * When a buffer is marked dirty, its page is dirtied, but the page's other
 * buffers are not.
 *
 * Also.  When blockdev buffers are explicitly read with bread(), they
 * individually become uptodate.  But their backing page remains not
 * uptodate - even if all of its buffers are uptodate.  A subsequent
 * block_read_full_page() against that page will discover all the uptodate
 * buffers, will set the page uptodate and will perform no I/O.
 */

/**
 * mark_buffer_dirty - mark a buffer_head as needing writeout
1074
 * @bh: the buffer_head to mark dirty
L
Linus Torvalds 已提交
1075 1076 1077 1078 1079 1080 1081
 *
 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
 * backing page dirty, then tag the page as dirty in its address_space's radix
 * tree and then attach the address_space's inode to its superblock's dirty
 * inode list.
 *
 * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
M
Matthew Wilcox 已提交
1082
 * i_pages lock and mapping->host->i_lock.
L
Linus Torvalds 已提交
1083
 */
1084
void mark_buffer_dirty(struct buffer_head *bh)
L
Linus Torvalds 已提交
1085
{
1086
	WARN_ON_ONCE(!buffer_uptodate(bh));
1087

1088 1089
	trace_block_dirty_buffer(bh);

1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101
	/*
	 * Very *carefully* optimize the it-is-already-dirty case.
	 *
	 * Don't let the final "is it dirty" escape to before we
	 * perhaps modified the buffer.
	 */
	if (buffer_dirty(bh)) {
		smp_mb();
		if (buffer_dirty(bh))
			return;
	}

1102 1103
	if (!test_set_buffer_dirty(bh)) {
		struct page *page = bh->b_page;
1104 1105
		struct address_space *mapping = NULL;

J
Johannes Weiner 已提交
1106
		lock_page_memcg(page);
1107
		if (!TestSetPageDirty(page)) {
1108
			mapping = page_mapping(page);
1109
			if (mapping)
J
Johannes Weiner 已提交
1110
				__set_page_dirty(page, mapping, 0);
1111
		}
J
Johannes Weiner 已提交
1112
		unlock_page_memcg(page);
1113 1114
		if (mapping)
			__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1115
	}
L
Linus Torvalds 已提交
1116
}
1117
EXPORT_SYMBOL(mark_buffer_dirty);
L
Linus Torvalds 已提交
1118

1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
void mark_buffer_write_io_error(struct buffer_head *bh)
{
	set_buffer_write_io_error(bh);
	/* FIXME: do we need to set this in both places? */
	if (bh->b_page && bh->b_page->mapping)
		mapping_set_error(bh->b_page->mapping, -EIO);
	if (bh->b_assoc_map)
		mapping_set_error(bh->b_assoc_map, -EIO);
}
EXPORT_SYMBOL(mark_buffer_write_io_error);

L
Linus Torvalds 已提交
1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142
/*
 * Decrement a buffer_head's reference count.  If all buffers against a page
 * have zero reference count, are clean and unlocked, and if the page is clean
 * and unlocked then try_to_free_buffers() may strip the buffers from the page
 * in preparation for freeing it (sometimes, rarely, buffers are removed from
 * a page but it ends up not being freed, and buffers may later be reattached).
 */
void __brelse(struct buffer_head * buf)
{
	if (atomic_read(&buf->b_count)) {
		put_bh(buf);
		return;
	}
A
Arjan van de Ven 已提交
1143
	WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
L
Linus Torvalds 已提交
1144
}
1145
EXPORT_SYMBOL(__brelse);
L
Linus Torvalds 已提交
1146 1147 1148 1149 1150 1151 1152 1153

/*
 * bforget() is like brelse(), except it discards any
 * potentially dirty data.
 */
void __bforget(struct buffer_head *bh)
{
	clear_buffer_dirty(bh);
1154
	if (bh->b_assoc_map) {
L
Linus Torvalds 已提交
1155 1156 1157 1158
		struct address_space *buffer_mapping = bh->b_page->mapping;

		spin_lock(&buffer_mapping->private_lock);
		list_del_init(&bh->b_assoc_buffers);
1159
		bh->b_assoc_map = NULL;
L
Linus Torvalds 已提交
1160 1161 1162 1163
		spin_unlock(&buffer_mapping->private_lock);
	}
	__brelse(bh);
}
1164
EXPORT_SYMBOL(__bforget);
L
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1165 1166 1167 1168 1169 1170 1171 1172 1173 1174

static struct buffer_head *__bread_slow(struct buffer_head *bh)
{
	lock_buffer(bh);
	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return bh;
	} else {
		get_bh(bh);
		bh->b_end_io = end_buffer_read_sync;
1175
		submit_bh(REQ_OP_READ, 0, bh);
L
Linus Torvalds 已提交
1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197
		wait_on_buffer(bh);
		if (buffer_uptodate(bh))
			return bh;
	}
	brelse(bh);
	return NULL;
}

/*
 * Per-cpu buffer LRU implementation.  To reduce the cost of __find_get_block().
 * The bhs[] array is sorted - newest buffer is at bhs[0].  Buffers have their
 * refcount elevated by one when they're in an LRU.  A buffer can only appear
 * once in a particular CPU's LRU.  A single buffer can be present in multiple
 * CPU's LRUs at the same time.
 *
 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
 * sb_find_get_block().
 *
 * The LRUs themselves only need locking against invalidate_bh_lrus.  We use
 * a local interrupt disable for that.
 */

1198
#define BH_LRU_SIZE	16
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1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221

struct bh_lru {
	struct buffer_head *bhs[BH_LRU_SIZE];
};

static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};

#ifdef CONFIG_SMP
#define bh_lru_lock()	local_irq_disable()
#define bh_lru_unlock()	local_irq_enable()
#else
#define bh_lru_lock()	preempt_disable()
#define bh_lru_unlock()	preempt_enable()
#endif

static inline void check_irqs_on(void)
{
#ifdef irqs_disabled
	BUG_ON(irqs_disabled());
#endif
}

/*
1222 1223 1224
 * Install a buffer_head into this cpu's LRU.  If not already in the LRU, it is
 * inserted at the front, and the buffer_head at the back if any is evicted.
 * Or, if already in the LRU it is moved to the front.
L
Linus Torvalds 已提交
1225 1226 1227
 */
static void bh_lru_install(struct buffer_head *bh)
{
1228 1229 1230
	struct buffer_head *evictee = bh;
	struct bh_lru *b;
	int i;
L
Linus Torvalds 已提交
1231 1232 1233 1234

	check_irqs_on();
	bh_lru_lock();

1235 1236 1237 1238 1239 1240
	b = this_cpu_ptr(&bh_lrus);
	for (i = 0; i < BH_LRU_SIZE; i++) {
		swap(evictee, b->bhs[i]);
		if (evictee == bh) {
			bh_lru_unlock();
			return;
L
Linus Torvalds 已提交
1241 1242 1243
		}
	}

1244 1245 1246
	get_bh(bh);
	bh_lru_unlock();
	brelse(evictee);
L
Linus Torvalds 已提交
1247 1248 1249 1250 1251
}

/*
 * Look up the bh in this cpu's LRU.  If it's there, move it to the head.
 */
1252
static struct buffer_head *
1253
lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1254 1255
{
	struct buffer_head *ret = NULL;
1256
	unsigned int i;
L
Linus Torvalds 已提交
1257 1258 1259 1260

	check_irqs_on();
	bh_lru_lock();
	for (i = 0; i < BH_LRU_SIZE; i++) {
1261
		struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
L
Linus Torvalds 已提交
1262

1263 1264
		if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
		    bh->b_size == size) {
L
Linus Torvalds 已提交
1265 1266
			if (i) {
				while (i) {
1267 1268
					__this_cpu_write(bh_lrus.bhs[i],
						__this_cpu_read(bh_lrus.bhs[i - 1]));
L
Linus Torvalds 已提交
1269 1270
					i--;
				}
1271
				__this_cpu_write(bh_lrus.bhs[0], bh);
L
Linus Torvalds 已提交
1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287
			}
			get_bh(bh);
			ret = bh;
			break;
		}
	}
	bh_lru_unlock();
	return ret;
}

/*
 * Perform a pagecache lookup for the matching buffer.  If it's there, refresh
 * it in the LRU and mark it as accessed.  If it is not present then return
 * NULL
 */
struct buffer_head *
1288
__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1289 1290 1291 1292
{
	struct buffer_head *bh = lookup_bh_lru(bdev, block, size);

	if (bh == NULL) {
1293
		/* __find_get_block_slow will mark the page accessed */
1294
		bh = __find_get_block_slow(bdev, block);
L
Linus Torvalds 已提交
1295 1296
		if (bh)
			bh_lru_install(bh);
1297
	} else
L
Linus Torvalds 已提交
1298
		touch_buffer(bh);
1299

L
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1300 1301 1302 1303 1304
	return bh;
}
EXPORT_SYMBOL(__find_get_block);

/*
1305
 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
L
Linus Torvalds 已提交
1306 1307 1308
 * which corresponds to the passed block_device, block and size. The
 * returned buffer has its reference count incremented.
 *
1309 1310
 * __getblk_gfp() will lock up the machine if grow_dev_page's
 * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
L
Linus Torvalds 已提交
1311 1312
 */
struct buffer_head *
1313 1314
__getblk_gfp(struct block_device *bdev, sector_t block,
	     unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1315 1316 1317 1318 1319
{
	struct buffer_head *bh = __find_get_block(bdev, block, size);

	might_sleep();
	if (bh == NULL)
1320
		bh = __getblk_slow(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1321 1322
	return bh;
}
1323
EXPORT_SYMBOL(__getblk_gfp);
L
Linus Torvalds 已提交
1324 1325 1326 1327

/*
 * Do async read-ahead on a buffer..
 */
1328
void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
L
Linus Torvalds 已提交
1329 1330
{
	struct buffer_head *bh = __getblk(bdev, block, size);
A
Andrew Morton 已提交
1331
	if (likely(bh)) {
1332
		ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
A
Andrew Morton 已提交
1333 1334
		brelse(bh);
	}
L
Linus Torvalds 已提交
1335 1336 1337 1338
}
EXPORT_SYMBOL(__breadahead);

/**
1339
 *  __bread_gfp() - reads a specified block and returns the bh
1340
 *  @bdev: the block_device to read from
L
Linus Torvalds 已提交
1341 1342
 *  @block: number of block
 *  @size: size (in bytes) to read
1343 1344
 *  @gfp: page allocation flag
 *
L
Linus Torvalds 已提交
1345
 *  Reads a specified block, and returns buffer head that contains it.
1346 1347
 *  The page cache can be allocated from non-movable area
 *  not to prevent page migration if you set gfp to zero.
L
Linus Torvalds 已提交
1348 1349 1350
 *  It returns NULL if the block was unreadable.
 */
struct buffer_head *
1351 1352
__bread_gfp(struct block_device *bdev, sector_t block,
		   unsigned size, gfp_t gfp)
L
Linus Torvalds 已提交
1353
{
1354
	struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
L
Linus Torvalds 已提交
1355

A
Andrew Morton 已提交
1356
	if (likely(bh) && !buffer_uptodate(bh))
L
Linus Torvalds 已提交
1357 1358 1359
		bh = __bread_slow(bh);
	return bh;
}
1360
EXPORT_SYMBOL(__bread_gfp);
L
Linus Torvalds 已提交
1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377

/*
 * invalidate_bh_lrus() is called rarely - but not only at unmount.
 * This doesn't race because it runs in each cpu either in irq
 * or with preempt disabled.
 */
static void invalidate_bh_lru(void *arg)
{
	struct bh_lru *b = &get_cpu_var(bh_lrus);
	int i;

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
	put_cpu_var(bh_lrus);
}
1378 1379 1380 1381 1382

static bool has_bh_in_lru(int cpu, void *dummy)
{
	struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
	int i;
L
Linus Torvalds 已提交
1383
	
1384 1385 1386 1387 1388 1389 1390 1391
	for (i = 0; i < BH_LRU_SIZE; i++) {
		if (b->bhs[i])
			return 1;
	}

	return 0;
}

P
Peter Zijlstra 已提交
1392
void invalidate_bh_lrus(void)
L
Linus Torvalds 已提交
1393
{
1394
	on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
L
Linus Torvalds 已提交
1395
}
N
Nick Piggin 已提交
1396
EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
L
Linus Torvalds 已提交
1397 1398 1399 1400 1401

void set_bh_page(struct buffer_head *bh,
		struct page *page, unsigned long offset)
{
	bh->b_page = page;
1402
	BUG_ON(offset >= PAGE_SIZE);
L
Linus Torvalds 已提交
1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415
	if (PageHighMem(page))
		/*
		 * This catches illegal uses and preserves the offset:
		 */
		bh->b_data = (char *)(0 + offset);
	else
		bh->b_data = page_address(page) + offset;
}
EXPORT_SYMBOL(set_bh_page);

/*
 * Called when truncating a buffer on a page completely.
 */
1416 1417 1418 1419 1420 1421

/* Bits that are cleared during an invalidate */
#define BUFFER_FLAGS_DISCARD \
	(1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
	 1 << BH_Delay | 1 << BH_Unwritten)

1422
static void discard_buffer(struct buffer_head * bh)
L
Linus Torvalds 已提交
1423
{
1424 1425
	unsigned long b_state, b_state_old;

L
Linus Torvalds 已提交
1426 1427 1428
	lock_buffer(bh);
	clear_buffer_dirty(bh);
	bh->b_bdev = NULL;
1429 1430 1431 1432 1433 1434 1435 1436
	b_state = bh->b_state;
	for (;;) {
		b_state_old = cmpxchg(&bh->b_state, b_state,
				      (b_state & ~BUFFER_FLAGS_DISCARD));
		if (b_state_old == b_state)
			break;
		b_state = b_state_old;
	}
L
Linus Torvalds 已提交
1437 1438 1439 1440
	unlock_buffer(bh);
}

/**
1441
 * block_invalidatepage - invalidate part or all of a buffer-backed page
L
Linus Torvalds 已提交
1442 1443
 *
 * @page: the page which is affected
1444 1445
 * @offset: start of the range to invalidate
 * @length: length of the range to invalidate
L
Linus Torvalds 已提交
1446 1447
 *
 * block_invalidatepage() is called when all or part of the page has become
1448
 * invalidated by a truncate operation.
L
Linus Torvalds 已提交
1449 1450 1451 1452 1453 1454 1455
 *
 * block_invalidatepage() does not have to release all buffers, but it must
 * ensure that no dirty buffer is left outside @offset and that no I/O
 * is underway against any of the blocks which are outside the truncation
 * point.  Because the caller is about to free (and possibly reuse) those
 * blocks on-disk.
 */
1456 1457
void block_invalidatepage(struct page *page, unsigned int offset,
			  unsigned int length)
L
Linus Torvalds 已提交
1458 1459 1460
{
	struct buffer_head *head, *bh, *next;
	unsigned int curr_off = 0;
1461
	unsigned int stop = length + offset;
L
Linus Torvalds 已提交
1462 1463 1464 1465 1466

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		goto out;

1467 1468 1469
	/*
	 * Check for overflow
	 */
1470
	BUG_ON(stop > PAGE_SIZE || stop < length);
1471

L
Linus Torvalds 已提交
1472 1473 1474 1475 1476 1477
	head = page_buffers(page);
	bh = head;
	do {
		unsigned int next_off = curr_off + bh->b_size;
		next = bh->b_this_page;

1478 1479 1480 1481 1482 1483
		/*
		 * Are we still fully in range ?
		 */
		if (next_off > stop)
			goto out;

L
Linus Torvalds 已提交
1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497
		/*
		 * is this block fully invalidated?
		 */
		if (offset <= curr_off)
			discard_buffer(bh);
		curr_off = next_off;
		bh = next;
	} while (bh != head);

	/*
	 * We release buffers only if the entire page is being invalidated.
	 * The get_block cached value has been unconditionally invalidated,
	 * so real IO is not possible anymore.
	 */
1498
	if (length == PAGE_SIZE)
1499
		try_to_release_page(page, 0);
L
Linus Torvalds 已提交
1500
out:
1501
	return;
L
Linus Torvalds 已提交
1502 1503 1504
}
EXPORT_SYMBOL(block_invalidatepage);

1505

L
Linus Torvalds 已提交
1506 1507 1508 1509 1510 1511 1512 1513 1514 1515
/*
 * We attach and possibly dirty the buffers atomically wrt
 * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
 * is already excluded via the page lock.
 */
void create_empty_buffers(struct page *page,
			unsigned long blocksize, unsigned long b_state)
{
	struct buffer_head *bh, *head, *tail;

1516
	head = alloc_page_buffers(page, blocksize, true);
L
Linus Torvalds 已提交
1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540
	bh = head;
	do {
		bh->b_state |= b_state;
		tail = bh;
		bh = bh->b_this_page;
	} while (bh);
	tail->b_this_page = head;

	spin_lock(&page->mapping->private_lock);
	if (PageUptodate(page) || PageDirty(page)) {
		bh = head;
		do {
			if (PageDirty(page))
				set_buffer_dirty(bh);
			if (PageUptodate(page))
				set_buffer_uptodate(bh);
			bh = bh->b_this_page;
		} while (bh != head);
	}
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}
EXPORT_SYMBOL(create_empty_buffers);

1541 1542 1543 1544 1545
/**
 * clean_bdev_aliases: clean a range of buffers in block device
 * @bdev: Block device to clean buffers in
 * @block: Start of a range of blocks to clean
 * @len: Number of blocks to clean
L
Linus Torvalds 已提交
1546
 *
1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559
 * We are taking a range of blocks for data and we don't want writeback of any
 * buffer-cache aliases starting from return from this function and until the
 * moment when something will explicitly mark the buffer dirty (hopefully that
 * will not happen until we will free that block ;-) We don't even need to mark
 * it not-uptodate - nobody can expect anything from a newly allocated buffer
 * anyway. We used to use unmap_buffer() for such invalidation, but that was
 * wrong. We definitely don't want to mark the alias unmapped, for example - it
 * would confuse anyone who might pick it with bread() afterwards...
 *
 * Also..  Note that bforget() doesn't lock the buffer.  So there can be
 * writeout I/O going on against recently-freed buffers.  We don't wait on that
 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
 * need to.  That happens here.
L
Linus Torvalds 已提交
1560
 */
1561
void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
L
Linus Torvalds 已提交
1562
{
1563 1564 1565 1566 1567
	struct inode *bd_inode = bdev->bd_inode;
	struct address_space *bd_mapping = bd_inode->i_mapping;
	struct pagevec pvec;
	pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
	pgoff_t end;
1568
	int i, count;
1569 1570
	struct buffer_head *bh;
	struct buffer_head *head;
L
Linus Torvalds 已提交
1571

1572
	end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1573
	pagevec_init(&pvec);
1574
	while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1575 1576
		count = pagevec_count(&pvec);
		for (i = 0; i < count; i++) {
1577
			struct page *page = pvec.pages[i];
L
Linus Torvalds 已提交
1578

1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592
			if (!page_has_buffers(page))
				continue;
			/*
			 * We use page lock instead of bd_mapping->private_lock
			 * to pin buffers here since we can afford to sleep and
			 * it scales better than a global spinlock lock.
			 */
			lock_page(page);
			/* Recheck when the page is locked which pins bhs */
			if (!page_has_buffers(page))
				goto unlock_page;
			head = page_buffers(page);
			bh = head;
			do {
1593
				if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607
					goto next;
				if (bh->b_blocknr >= block + len)
					break;
				clear_buffer_dirty(bh);
				wait_on_buffer(bh);
				clear_buffer_req(bh);
next:
				bh = bh->b_this_page;
			} while (bh != head);
unlock_page:
			unlock_page(page);
		}
		pagevec_release(&pvec);
		cond_resched();
1608 1609 1610
		/* End of range already reached? */
		if (index > end || !index)
			break;
L
Linus Torvalds 已提交
1611 1612
	}
}
1613
EXPORT_SYMBOL(clean_bdev_aliases);
L
Linus Torvalds 已提交
1614

1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632
/*
 * Size is a power-of-two in the range 512..PAGE_SIZE,
 * and the case we care about most is PAGE_SIZE.
 *
 * So this *could* possibly be written with those
 * constraints in mind (relevant mostly if some
 * architecture has a slow bit-scan instruction)
 */
static inline int block_size_bits(unsigned int blocksize)
{
	return ilog2(blocksize);
}

static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
{
	BUG_ON(!PageLocked(page));

	if (!page_has_buffers(page))
1633 1634
		create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
				     b_state);
1635 1636 1637
	return page_buffers(page);
}

L
Linus Torvalds 已提交
1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661
/*
 * NOTE! All mapped/uptodate combinations are valid:
 *
 *	Mapped	Uptodate	Meaning
 *
 *	No	No		"unknown" - must do get_block()
 *	No	Yes		"hole" - zero-filled
 *	Yes	No		"allocated" - allocated on disk, not read in
 *	Yes	Yes		"valid" - allocated and up-to-date in memory.
 *
 * "Dirty" is valid only with the last case (mapped+uptodate).
 */

/*
 * While block_write_full_page is writing back the dirty buffers under
 * the page lock, whoever dirtied the buffers may decide to clean them
 * again at any time.  We handle that by only looking at the buffer
 * state inside lock_buffer().
 *
 * If block_write_full_page() is called for regular writeback
 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
 * locked buffer.   This only can happen if someone has written the buffer
 * directly, with submit_bh().  At the address_space level PageWriteback
 * prevents this contention from occurring.
1662 1663
 *
 * If block_write_full_page() is called with wbc->sync_mode ==
1664
 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
J
Jens Axboe 已提交
1665
 * causes the writes to be flagged as synchronous writes.
L
Linus Torvalds 已提交
1666
 */
1667
int __block_write_full_page(struct inode *inode, struct page *page,
1668 1669
			get_block_t *get_block, struct writeback_control *wbc,
			bh_end_io_t *handler)
L
Linus Torvalds 已提交
1670 1671 1672 1673
{
	int err;
	sector_t block;
	sector_t last_block;
1674
	struct buffer_head *bh, *head;
1675
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
1676
	int nr_underway = 0;
J
Jens Axboe 已提交
1677
	int write_flags = wbc_to_write_flags(wbc);
L
Linus Torvalds 已提交
1678

1679
	head = create_page_buffers(page, inode,
L
Linus Torvalds 已提交
1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692
					(1 << BH_Dirty)|(1 << BH_Uptodate));

	/*
	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
	 * here, and the (potentially unmapped) buffers may become dirty at
	 * any time.  If a buffer becomes dirty here after we've inspected it
	 * then we just miss that fact, and the page stays dirty.
	 *
	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
	 * handle that here by just cleaning them.
	 */

	bh = head;
1693 1694 1695
	blocksize = bh->b_size;
	bbits = block_size_bits(blocksize);

1696
	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1697
	last_block = (i_size_read(inode) - 1) >> bbits;
L
Linus Torvalds 已提交
1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714

	/*
	 * Get all the dirty buffers mapped to disk addresses and
	 * handle any aliases from the underlying blockdev's mapping.
	 */
	do {
		if (block > last_block) {
			/*
			 * mapped buffers outside i_size will occur, because
			 * this page can be outside i_size when there is a
			 * truncate in progress.
			 */
			/*
			 * The buffer was zeroed by block_write_full_page()
			 */
			clear_buffer_dirty(bh);
			set_buffer_uptodate(bh);
1715 1716
		} else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
			   buffer_dirty(bh)) {
1717
			WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
1718 1719 1720
			err = get_block(inode, block, bh, 1);
			if (err)
				goto recover;
1721
			clear_buffer_delay(bh);
L
Linus Torvalds 已提交
1722 1723 1724
			if (buffer_new(bh)) {
				/* blockdev mappings never come here */
				clear_buffer_new(bh);
1725
				clean_bdev_bh_alias(bh);
L
Linus Torvalds 已提交
1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737
			}
		}
		bh = bh->b_this_page;
		block++;
	} while (bh != head);

	do {
		if (!buffer_mapped(bh))
			continue;
		/*
		 * If it's a fully non-blocking write attempt and we cannot
		 * lock the buffer then redirty the page.  Note that this can
1738 1739 1740
		 * potentially cause a busy-wait loop from writeback threads
		 * and kswapd activity, but those code paths have their own
		 * higher-level throttling.
L
Linus Torvalds 已提交
1741
		 */
1742
		if (wbc->sync_mode != WB_SYNC_NONE) {
L
Linus Torvalds 已提交
1743
			lock_buffer(bh);
N
Nick Piggin 已提交
1744
		} else if (!trylock_buffer(bh)) {
L
Linus Torvalds 已提交
1745 1746 1747 1748
			redirty_page_for_writepage(wbc, page);
			continue;
		}
		if (test_clear_buffer_dirty(bh)) {
1749
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764
		} else {
			unlock_buffer(bh);
		}
	} while ((bh = bh->b_this_page) != head);

	/*
	 * The page and its buffers are protected by PageWriteback(), so we can
	 * drop the bh refcounts early.
	 */
	BUG_ON(PageWriteback(page));
	set_page_writeback(page);

	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
1765 1766
			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
					inode->i_write_hint, wbc);
L
Linus Torvalds 已提交
1767 1768 1769 1770
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1771
	unlock_page(page);
L
Linus Torvalds 已提交
1772 1773 1774 1775 1776 1777 1778 1779 1780 1781

	err = 0;
done:
	if (nr_underway == 0) {
		/*
		 * The page was marked dirty, but the buffers were
		 * clean.  Someone wrote them back by hand with
		 * ll_rw_block/submit_bh.  A rare case.
		 */
		end_page_writeback(page);
1782

L
Linus Torvalds 已提交
1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799
		/*
		 * The page and buffer_heads can be released at any time from
		 * here on.
		 */
	}
	return err;

recover:
	/*
	 * ENOSPC, or some other error.  We may already have added some
	 * blocks to the file, so we need to write these out to avoid
	 * exposing stale data.
	 * The page is currently locked and not marked for writeback
	 */
	bh = head;
	/* Recovery: lock and submit the mapped buffers */
	do {
1800 1801
		if (buffer_mapped(bh) && buffer_dirty(bh) &&
		    !buffer_delay(bh)) {
L
Linus Torvalds 已提交
1802
			lock_buffer(bh);
1803
			mark_buffer_async_write_endio(bh, handler);
L
Linus Torvalds 已提交
1804 1805 1806 1807 1808 1809 1810 1811 1812 1813
		} else {
			/*
			 * The buffer may have been set dirty during
			 * attachment to a dirty page.
			 */
			clear_buffer_dirty(bh);
		}
	} while ((bh = bh->b_this_page) != head);
	SetPageError(page);
	BUG_ON(PageWriteback(page));
1814
	mapping_set_error(page->mapping, err);
L
Linus Torvalds 已提交
1815 1816 1817 1818 1819
	set_page_writeback(page);
	do {
		struct buffer_head *next = bh->b_this_page;
		if (buffer_async_write(bh)) {
			clear_buffer_dirty(bh);
1820 1821
			submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
					inode->i_write_hint, wbc);
L
Linus Torvalds 已提交
1822 1823 1824 1825
			nr_underway++;
		}
		bh = next;
	} while (bh != head);
1826
	unlock_page(page);
L
Linus Torvalds 已提交
1827 1828
	goto done;
}
1829
EXPORT_SYMBOL(__block_write_full_page);
L
Linus Torvalds 已提交
1830

1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857
/*
 * If a page has any new buffers, zero them out here, and mark them uptodate
 * and dirty so they'll be written out (in order to prevent uninitialised
 * block data from leaking). And clear the new bit.
 */
void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
	unsigned int block_start, block_end;
	struct buffer_head *head, *bh;

	BUG_ON(!PageLocked(page));
	if (!page_has_buffers(page))
		return;

	bh = head = page_buffers(page);
	block_start = 0;
	do {
		block_end = block_start + bh->b_size;

		if (buffer_new(bh)) {
			if (block_end > from && block_start < to) {
				if (!PageUptodate(page)) {
					unsigned start, size;

					start = max(from, block_start);
					size = min(to, block_end) - start;

1858
					zero_user(page, start, size);
1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872
					set_buffer_uptodate(bh);
				}

				clear_buffer_new(bh);
				mark_buffer_dirty(bh);
			}
		}

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
}
EXPORT_SYMBOL(page_zero_new_buffers);

1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909
static void
iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
		struct iomap *iomap)
{
	loff_t offset = block << inode->i_blkbits;

	bh->b_bdev = iomap->bdev;

	/*
	 * Block points to offset in file we need to map, iomap contains
	 * the offset at which the map starts. If the map ends before the
	 * current block, then do not map the buffer and let the caller
	 * handle it.
	 */
	BUG_ON(offset >= iomap->offset + iomap->length);

	switch (iomap->type) {
	case IOMAP_HOLE:
		/*
		 * If the buffer is not up to date or beyond the current EOF,
		 * we need to mark it as new to ensure sub-block zeroing is
		 * executed if necessary.
		 */
		if (!buffer_uptodate(bh) ||
		    (offset >= i_size_read(inode)))
			set_buffer_new(bh);
		break;
	case IOMAP_DELALLOC:
		if (!buffer_uptodate(bh) ||
		    (offset >= i_size_read(inode)))
			set_buffer_new(bh);
		set_buffer_uptodate(bh);
		set_buffer_mapped(bh);
		set_buffer_delay(bh);
		break;
	case IOMAP_UNWRITTEN:
		/*
1910 1911 1912
		 * For unwritten regions, we always need to ensure that regions
		 * in the block we are not writing to are zeroed. Mark the
		 * buffer as new to ensure this.
1913 1914 1915 1916 1917
		 */
		set_buffer_new(bh);
		set_buffer_unwritten(bh);
		/* FALLTHRU */
	case IOMAP_MAPPED:
1918 1919
		if ((iomap->flags & IOMAP_F_NEW) ||
		    offset >= i_size_read(inode))
1920
			set_buffer_new(bh);
1921 1922
		bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
				inode->i_blkbits;
1923 1924 1925 1926 1927 1928 1929
		set_buffer_mapped(bh);
		break;
	}
}

int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
		get_block_t *get_block, struct iomap *iomap)
L
Linus Torvalds 已提交
1930
{
1931
	unsigned from = pos & (PAGE_SIZE - 1);
C
Christoph Hellwig 已提交
1932
	unsigned to = from + len;
1933
	struct inode *inode = page->mapping->host;
L
Linus Torvalds 已提交
1934 1935 1936 1937 1938 1939 1940
	unsigned block_start, block_end;
	sector_t block;
	int err = 0;
	unsigned blocksize, bbits;
	struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;

	BUG_ON(!PageLocked(page));
1941 1942
	BUG_ON(from > PAGE_SIZE);
	BUG_ON(to > PAGE_SIZE);
L
Linus Torvalds 已提交
1943 1944
	BUG_ON(from > to);

1945 1946 1947
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
1948

1949
	block = (sector_t)page->index << (PAGE_SHIFT - bbits);
L
Linus Torvalds 已提交
1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963

	for(bh = head, block_start = 0; bh != head || !block_start;
	    block++, block_start=block_end, bh = bh->b_this_page) {
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (PageUptodate(page)) {
				if (!buffer_uptodate(bh))
					set_buffer_uptodate(bh);
			}
			continue;
		}
		if (buffer_new(bh))
			clear_buffer_new(bh);
		if (!buffer_mapped(bh)) {
1964
			WARN_ON(bh->b_size != blocksize);
1965 1966 1967 1968 1969 1970 1971 1972
			if (get_block) {
				err = get_block(inode, block, bh, 1);
				if (err)
					break;
			} else {
				iomap_to_bh(inode, block, bh, iomap);
			}

L
Linus Torvalds 已提交
1973
			if (buffer_new(bh)) {
1974
				clean_bdev_bh_alias(bh);
L
Linus Torvalds 已提交
1975
				if (PageUptodate(page)) {
N
Nick Piggin 已提交
1976
					clear_buffer_new(bh);
L
Linus Torvalds 已提交
1977
					set_buffer_uptodate(bh);
N
Nick Piggin 已提交
1978
					mark_buffer_dirty(bh);
L
Linus Torvalds 已提交
1979 1980
					continue;
				}
1981 1982 1983 1984
				if (block_end > to || block_start < from)
					zero_user_segments(page,
						to, block_end,
						block_start, from);
L
Linus Torvalds 已提交
1985 1986 1987 1988 1989 1990 1991 1992 1993
				continue;
			}
		}
		if (PageUptodate(page)) {
			if (!buffer_uptodate(bh))
				set_buffer_uptodate(bh);
			continue; 
		}
		if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1994
		    !buffer_unwritten(bh) &&
L
Linus Torvalds 已提交
1995
		     (block_start < from || block_end > to)) {
1996
			ll_rw_block(REQ_OP_READ, 0, 1, &bh);
L
Linus Torvalds 已提交
1997 1998 1999 2000 2001 2002 2003 2004 2005
			*wait_bh++=bh;
		}
	}
	/*
	 * If we issued read requests - let them complete.
	 */
	while(wait_bh > wait) {
		wait_on_buffer(*--wait_bh);
		if (!buffer_uptodate(*wait_bh))
2006
			err = -EIO;
L
Linus Torvalds 已提交
2007
	}
2008
	if (unlikely(err))
2009
		page_zero_new_buffers(page, from, to);
L
Linus Torvalds 已提交
2010 2011
	return err;
}
2012 2013 2014 2015 2016 2017

int __block_write_begin(struct page *page, loff_t pos, unsigned len,
		get_block_t *get_block)
{
	return __block_write_begin_int(page, pos, len, get_block, NULL);
}
C
Christoph Hellwig 已提交
2018
EXPORT_SYMBOL(__block_write_begin);
L
Linus Torvalds 已提交
2019 2020 2021 2022 2023 2024 2025 2026 2027

static int __block_commit_write(struct inode *inode, struct page *page,
		unsigned from, unsigned to)
{
	unsigned block_start, block_end;
	int partial = 0;
	unsigned blocksize;
	struct buffer_head *bh, *head;

2028 2029
	bh = head = page_buffers(page);
	blocksize = bh->b_size;
L
Linus Torvalds 已提交
2030

2031 2032
	block_start = 0;
	do {
L
Linus Torvalds 已提交
2033 2034 2035 2036 2037 2038 2039 2040
		block_end = block_start + blocksize;
		if (block_end <= from || block_start >= to) {
			if (!buffer_uptodate(bh))
				partial = 1;
		} else {
			set_buffer_uptodate(bh);
			mark_buffer_dirty(bh);
		}
2041
		clear_buffer_new(bh);
2042 2043 2044 2045

		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);
L
Linus Torvalds 已提交
2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057

	/*
	 * If this is a partial write which happened to make all buffers
	 * uptodate then we can optimize away a bogus readpage() for
	 * the next read(). Here we 'discover' whether the page went
	 * uptodate as a result of this (potentially partial) write.
	 */
	if (!partial)
		SetPageUptodate(page);
	return 0;
}

2058
/*
2059 2060 2061
 * block_write_begin takes care of the basic task of block allocation and
 * bringing partial write blocks uptodate first.
 *
2062
 * The filesystem needs to handle block truncation upon failure.
2063
 */
2064 2065
int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
		unsigned flags, struct page **pagep, get_block_t *get_block)
2066
{
2067
	pgoff_t index = pos >> PAGE_SHIFT;
2068
	struct page *page;
2069
	int status;
2070

2071 2072 2073
	page = grab_cache_page_write_begin(mapping, index, flags);
	if (!page)
		return -ENOMEM;
2074

2075
	status = __block_write_begin(page, pos, len, get_block);
2076
	if (unlikely(status)) {
2077
		unlock_page(page);
2078
		put_page(page);
2079
		page = NULL;
2080 2081
	}

2082
	*pagep = page;
2083 2084 2085 2086
	return status;
}
EXPORT_SYMBOL(block_write_begin);

2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120
int __generic_write_end(struct inode *inode, loff_t pos, unsigned copied,
		struct page *page)
{
	loff_t old_size = inode->i_size;
	bool i_size_changed = false;

	/*
	 * No need to use i_size_read() here, the i_size cannot change under us
	 * because we hold i_rwsem.
	 *
	 * But it's important to update i_size while still holding page lock:
	 * page writeout could otherwise come in and zero beyond i_size.
	 */
	if (pos + copied > inode->i_size) {
		i_size_write(inode, pos + copied);
		i_size_changed = true;
	}

	unlock_page(page);
	put_page(page);

	if (old_size < pos)
		pagecache_isize_extended(inode, old_size, pos);
	/*
	 * Don't mark the inode dirty under page lock. First, it unnecessarily
	 * makes the holding time of page lock longer. Second, it forces lock
	 * ordering of page lock and transaction start for journaling
	 * filesystems.
	 */
	if (i_size_changed)
		mark_inode_dirty(inode);
	return copied;
}

2121 2122 2123 2124 2125 2126 2127
int block_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	struct inode *inode = mapping->host;
	unsigned start;

2128
	start = pos & (PAGE_SIZE - 1);
2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161

	if (unlikely(copied < len)) {
		/*
		 * The buffers that were written will now be uptodate, so we
		 * don't have to worry about a readpage reading them and
		 * overwriting a partial write. However if we have encountered
		 * a short write and only partially written into a buffer, it
		 * will not be marked uptodate, so a readpage might come in and
		 * destroy our partial write.
		 *
		 * Do the simplest thing, and just treat any short write to a
		 * non uptodate page as a zero-length write, and force the
		 * caller to redo the whole thing.
		 */
		if (!PageUptodate(page))
			copied = 0;

		page_zero_new_buffers(page, start+copied, start+len);
	}
	flush_dcache_page(page);

	/* This could be a short (even 0-length) commit */
	__block_commit_write(inode, page, start, start+copied);

	return copied;
}
EXPORT_SYMBOL(block_write_end);

int generic_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
{
	copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2162
	return __generic_write_end(mapping->host, pos, copied, page);
2163 2164 2165
}
EXPORT_SYMBOL(generic_write_end);

2166 2167 2168 2169 2170 2171 2172
/*
 * block_is_partially_uptodate checks whether buffers within a page are
 * uptodate or not.
 *
 * Returns true if all buffers which correspond to a file portion
 * we want to read are uptodate.
 */
2173 2174
int block_is_partially_uptodate(struct page *page, unsigned long from,
					unsigned long count)
2175 2176 2177 2178 2179 2180 2181 2182 2183
{
	unsigned block_start, block_end, blocksize;
	unsigned to;
	struct buffer_head *bh, *head;
	int ret = 1;

	if (!page_has_buffers(page))
		return 0;

2184 2185
	head = page_buffers(page);
	blocksize = head->b_size;
2186
	to = min_t(unsigned, PAGE_SIZE - from, count);
2187
	to = from + to;
2188
	if (from < blocksize && to > PAGE_SIZE - blocksize)
2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210
		return 0;

	bh = head;
	block_start = 0;
	do {
		block_end = block_start + blocksize;
		if (block_end > from && block_start < to) {
			if (!buffer_uptodate(bh)) {
				ret = 0;
				break;
			}
			if (block_end >= to)
				break;
		}
		block_start = block_end;
		bh = bh->b_this_page;
	} while (bh != head);

	return ret;
}
EXPORT_SYMBOL(block_is_partially_uptodate);

L
Linus Torvalds 已提交
2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222
/*
 * Generic "read page" function for block devices that have the normal
 * get_block functionality. This is most of the block device filesystems.
 * Reads the page asynchronously --- the unlock_buffer() and
 * set/clear_buffer_uptodate() functions propagate buffer state into the
 * page struct once IO has completed.
 */
int block_read_full_page(struct page *page, get_block_t *get_block)
{
	struct inode *inode = page->mapping->host;
	sector_t iblock, lblock;
	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2223
	unsigned int blocksize, bbits;
L
Linus Torvalds 已提交
2224 2225 2226
	int nr, i;
	int fully_mapped = 1;

2227 2228 2229
	head = create_page_buffers(page, inode, 0);
	blocksize = head->b_size;
	bbits = block_size_bits(blocksize);
L
Linus Torvalds 已提交
2230

2231
	iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2232
	lblock = (i_size_read(inode)+blocksize-1) >> bbits;
L
Linus Torvalds 已提交
2233 2234 2235 2236 2237 2238 2239 2240 2241
	bh = head;
	nr = 0;
	i = 0;

	do {
		if (buffer_uptodate(bh))
			continue;

		if (!buffer_mapped(bh)) {
2242 2243
			int err = 0;

L
Linus Torvalds 已提交
2244 2245
			fully_mapped = 0;
			if (iblock < lblock) {
2246
				WARN_ON(bh->b_size != blocksize);
2247 2248
				err = get_block(inode, iblock, bh, 0);
				if (err)
L
Linus Torvalds 已提交
2249 2250 2251
					SetPageError(page);
			}
			if (!buffer_mapped(bh)) {
2252
				zero_user(page, i * blocksize, blocksize);
2253 2254
				if (!err)
					set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297
				continue;
			}
			/*
			 * get_block() might have updated the buffer
			 * synchronously
			 */
			if (buffer_uptodate(bh))
				continue;
		}
		arr[nr++] = bh;
	} while (i++, iblock++, (bh = bh->b_this_page) != head);

	if (fully_mapped)
		SetPageMappedToDisk(page);

	if (!nr) {
		/*
		 * All buffers are uptodate - we can set the page uptodate
		 * as well. But not if get_block() returned an error.
		 */
		if (!PageError(page))
			SetPageUptodate(page);
		unlock_page(page);
		return 0;
	}

	/* Stage two: lock the buffers */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		lock_buffer(bh);
		mark_buffer_async_read(bh);
	}

	/*
	 * Stage 3: start the IO.  Check for uptodateness
	 * inside the buffer lock in case another process reading
	 * the underlying blockdev brought it uptodate (the sct fix).
	 */
	for (i = 0; i < nr; i++) {
		bh = arr[i];
		if (buffer_uptodate(bh))
			end_buffer_async_read(bh, 1);
		else
2298
			submit_bh(REQ_OP_READ, 0, bh);
L
Linus Torvalds 已提交
2299 2300 2301
	}
	return 0;
}
2302
EXPORT_SYMBOL(block_read_full_page);
L
Linus Torvalds 已提交
2303 2304

/* utility function for filesystems that need to do work on expanding
N
Nick Piggin 已提交
2305
 * truncates.  Uses filesystem pagecache writes to allow the filesystem to
L
Linus Torvalds 已提交
2306 2307
 * deal with the hole.  
 */
N
Nick Piggin 已提交
2308
int generic_cont_expand_simple(struct inode *inode, loff_t size)
L
Linus Torvalds 已提交
2309 2310 2311
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
N
Nick Piggin 已提交
2312
	void *fsdata;
L
Linus Torvalds 已提交
2313 2314
	int err;

N
npiggin@suse.de 已提交
2315 2316
	err = inode_newsize_ok(inode, size);
	if (err)
L
Linus Torvalds 已提交
2317 2318
		goto out;

N
Nick Piggin 已提交
2319
	err = pagecache_write_begin(NULL, mapping, size, 0,
2320
				    AOP_FLAG_CONT_EXPAND, &page, &fsdata);
N
Nick Piggin 已提交
2321
	if (err)
2322 2323
		goto out;

N
Nick Piggin 已提交
2324 2325
	err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
	BUG_ON(err > 0);
2326

L
Linus Torvalds 已提交
2327 2328 2329
out:
	return err;
}
2330
EXPORT_SYMBOL(generic_cont_expand_simple);
L
Linus Torvalds 已提交
2331

2332 2333
static int cont_expand_zero(struct file *file, struct address_space *mapping,
			    loff_t pos, loff_t *bytes)
L
Linus Torvalds 已提交
2334 2335
{
	struct inode *inode = mapping->host;
F
Fabian Frederick 已提交
2336
	unsigned int blocksize = i_blocksize(inode);
N
Nick Piggin 已提交
2337 2338 2339 2340 2341 2342
	struct page *page;
	void *fsdata;
	pgoff_t index, curidx;
	loff_t curpos;
	unsigned zerofrom, offset, len;
	int err = 0;
L
Linus Torvalds 已提交
2343

2344 2345
	index = pos >> PAGE_SHIFT;
	offset = pos & ~PAGE_MASK;
N
Nick Piggin 已提交
2346

2347 2348
	while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
		zerofrom = curpos & ~PAGE_MASK;
L
Linus Torvalds 已提交
2349 2350 2351 2352
		if (zerofrom & (blocksize-1)) {
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
2353
		len = PAGE_SIZE - zerofrom;
L
Linus Torvalds 已提交
2354

2355 2356
		err = pagecache_write_begin(file, mapping, curpos, len, 0,
					    &page, &fsdata);
N
Nick Piggin 已提交
2357 2358
		if (err)
			goto out;
2359
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2360 2361 2362 2363 2364 2365
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
2366 2367

		balance_dirty_pages_ratelimited(mapping);
2368 2369 2370 2371 2372

		if (unlikely(fatal_signal_pending(current))) {
			err = -EINTR;
			goto out;
		}
N
Nick Piggin 已提交
2373
	}
L
Linus Torvalds 已提交
2374

N
Nick Piggin 已提交
2375 2376
	/* page covers the boundary, find the boundary offset */
	if (index == curidx) {
2377
		zerofrom = curpos & ~PAGE_MASK;
L
Linus Torvalds 已提交
2378
		/* if we will expand the thing last block will be filled */
N
Nick Piggin 已提交
2379 2380 2381 2382
		if (offset <= zerofrom) {
			goto out;
		}
		if (zerofrom & (blocksize-1)) {
L
Linus Torvalds 已提交
2383 2384 2385
			*bytes |= (blocksize-1);
			(*bytes)++;
		}
N
Nick Piggin 已提交
2386
		len = offset - zerofrom;
L
Linus Torvalds 已提交
2387

2388 2389
		err = pagecache_write_begin(file, mapping, curpos, len, 0,
					    &page, &fsdata);
N
Nick Piggin 已提交
2390 2391
		if (err)
			goto out;
2392
		zero_user(page, zerofrom, len);
N
Nick Piggin 已提交
2393 2394 2395 2396 2397 2398
		err = pagecache_write_end(file, mapping, curpos, len, len,
						page, fsdata);
		if (err < 0)
			goto out;
		BUG_ON(err != len);
		err = 0;
L
Linus Torvalds 已提交
2399
	}
N
Nick Piggin 已提交
2400 2401 2402 2403 2404 2405 2406 2407
out:
	return err;
}

/*
 * For moronic filesystems that do not allow holes in file.
 * We may have to extend the file.
 */
2408
int cont_write_begin(struct file *file, struct address_space *mapping,
N
Nick Piggin 已提交
2409 2410 2411 2412 2413
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
			get_block_t *get_block, loff_t *bytes)
{
	struct inode *inode = mapping->host;
F
Fabian Frederick 已提交
2414 2415
	unsigned int blocksize = i_blocksize(inode);
	unsigned int zerofrom;
N
Nick Piggin 已提交
2416 2417 2418 2419
	int err;

	err = cont_expand_zero(file, mapping, pos, bytes);
	if (err)
2420
		return err;
N
Nick Piggin 已提交
2421

2422
	zerofrom = *bytes & ~PAGE_MASK;
N
Nick Piggin 已提交
2423 2424 2425
	if (pos+len > *bytes && zerofrom & (blocksize-1)) {
		*bytes |= (blocksize-1);
		(*bytes)++;
L
Linus Torvalds 已提交
2426 2427
	}

2428
	return block_write_begin(mapping, pos, len, flags, pagep, get_block);
L
Linus Torvalds 已提交
2429
}
2430
EXPORT_SYMBOL(cont_write_begin);
L
Linus Torvalds 已提交
2431 2432 2433 2434 2435 2436 2437

int block_commit_write(struct page *page, unsigned from, unsigned to)
{
	struct inode *inode = page->mapping->host;
	__block_commit_write(inode,page,from,to);
	return 0;
}
2438
EXPORT_SYMBOL(block_commit_write);
L
Linus Torvalds 已提交
2439

2440 2441 2442 2443 2444 2445 2446 2447 2448 2449
/*
 * block_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
2450
 * truncate writes the inode size before removing pages, once we have the
2451 2452 2453
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
2454
 *
2455
 * Direct callers of this function should protect against filesystem freezing
2456
 * using sb_start_pagefault() - sb_end_pagefault() functions.
2457
 */
2458
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2459
			 get_block_t get_block)
2460
{
2461
	struct page *page = vmf->page;
A
Al Viro 已提交
2462
	struct inode *inode = file_inode(vma->vm_file);
2463 2464
	unsigned long end;
	loff_t size;
2465
	int ret;
2466 2467 2468 2469

	lock_page(page);
	size = i_size_read(inode);
	if ((page->mapping != inode->i_mapping) ||
N
Nick Piggin 已提交
2470
	    (page_offset(page) > size)) {
2471 2472 2473
		/* We overload EFAULT to mean page got truncated */
		ret = -EFAULT;
		goto out_unlock;
2474 2475 2476
	}

	/* page is wholly or partially inside EOF */
2477 2478
	if (((page->index + 1) << PAGE_SHIFT) > size)
		end = size & ~PAGE_MASK;
2479
	else
2480
		end = PAGE_SIZE;
2481

C
Christoph Hellwig 已提交
2482
	ret = __block_write_begin(page, 0, end, get_block);
2483 2484 2485
	if (!ret)
		ret = block_commit_write(page, 0, end);

2486 2487
	if (unlikely(ret < 0))
		goto out_unlock;
2488
	set_page_dirty(page);
2489
	wait_for_stable_page(page);
2490 2491 2492
	return 0;
out_unlock:
	unlock_page(page);
2493
	return ret;
2494
}
2495
EXPORT_SYMBOL(block_page_mkwrite);
L
Linus Torvalds 已提交
2496 2497

/*
N
Nick Piggin 已提交
2498
 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
L
Linus Torvalds 已提交
2499 2500 2501 2502 2503
 * immediately, while under the page lock.  So it needs a special end_io
 * handler which does not touch the bh after unlocking it.
 */
static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
{
2504
	__end_buffer_read_notouch(bh, uptodate);
L
Linus Torvalds 已提交
2505 2506
}

N
Nick Piggin 已提交
2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530
/*
 * Attach the singly-linked list of buffers created by nobh_write_begin, to
 * the page (converting it to circular linked list and taking care of page
 * dirty races).
 */
static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
{
	struct buffer_head *bh;

	BUG_ON(!PageLocked(page));

	spin_lock(&page->mapping->private_lock);
	bh = head;
	do {
		if (PageDirty(page))
			set_buffer_dirty(bh);
		if (!bh->b_this_page)
			bh->b_this_page = head;
		bh = bh->b_this_page;
	} while (bh != head);
	attach_page_buffers(page, head);
	spin_unlock(&page->mapping->private_lock);
}

L
Linus Torvalds 已提交
2531
/*
2532 2533
 * On entry, the page is fully not uptodate.
 * On exit the page is fully uptodate in the areas outside (from,to)
2534
 * The filesystem needs to handle block truncation upon failure.
L
Linus Torvalds 已提交
2535
 */
2536
int nobh_write_begin(struct address_space *mapping,
N
Nick Piggin 已提交
2537 2538
			loff_t pos, unsigned len, unsigned flags,
			struct page **pagep, void **fsdata,
L
Linus Torvalds 已提交
2539 2540
			get_block_t *get_block)
{
N
Nick Piggin 已提交
2541
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2542 2543
	const unsigned blkbits = inode->i_blkbits;
	const unsigned blocksize = 1 << blkbits;
N
Nick Piggin 已提交
2544
	struct buffer_head *head, *bh;
N
Nick Piggin 已提交
2545 2546 2547
	struct page *page;
	pgoff_t index;
	unsigned from, to;
L
Linus Torvalds 已提交
2548
	unsigned block_in_page;
N
Nick Piggin 已提交
2549
	unsigned block_start, block_end;
L
Linus Torvalds 已提交
2550 2551 2552 2553 2554
	sector_t block_in_file;
	int nr_reads = 0;
	int ret = 0;
	int is_mapped_to_disk = 1;

2555 2556
	index = pos >> PAGE_SHIFT;
	from = pos & (PAGE_SIZE - 1);
N
Nick Piggin 已提交
2557 2558
	to = from + len;

2559
	page = grab_cache_page_write_begin(mapping, index, flags);
N
Nick Piggin 已提交
2560 2561 2562 2563 2564 2565
	if (!page)
		return -ENOMEM;
	*pagep = page;
	*fsdata = NULL;

	if (page_has_buffers(page)) {
2566 2567 2568 2569
		ret = __block_write_begin(page, pos, len, get_block);
		if (unlikely(ret))
			goto out_release;
		return ret;
N
Nick Piggin 已提交
2570
	}
N
Nick Piggin 已提交
2571

L
Linus Torvalds 已提交
2572 2573 2574
	if (PageMappedToDisk(page))
		return 0;

N
Nick Piggin 已提交
2575 2576 2577 2578 2579 2580 2581 2582 2583
	/*
	 * Allocate buffers so that we can keep track of state, and potentially
	 * attach them to the page if an error occurs. In the common case of
	 * no error, they will just be freed again without ever being attached
	 * to the page (which is all OK, because we're under the page lock).
	 *
	 * Be careful: the buffer linked list is a NULL terminated one, rather
	 * than the circular one we're used to.
	 */
2584
	head = alloc_page_buffers(page, blocksize, false);
N
Nick Piggin 已提交
2585 2586 2587 2588
	if (!head) {
		ret = -ENOMEM;
		goto out_release;
	}
N
Nick Piggin 已提交
2589

2590
	block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
L
Linus Torvalds 已提交
2591 2592 2593 2594 2595 2596

	/*
	 * We loop across all blocks in the page, whether or not they are
	 * part of the affected region.  This is so we can discover if the
	 * page is fully mapped-to-disk.
	 */
N
Nick Piggin 已提交
2597
	for (block_start = 0, block_in_page = 0, bh = head;
2598
		  block_start < PAGE_SIZE;
N
Nick Piggin 已提交
2599
		  block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2600 2601
		int create;

N
Nick Piggin 已提交
2602 2603
		block_end = block_start + blocksize;
		bh->b_state = 0;
L
Linus Torvalds 已提交
2604 2605 2606 2607
		create = 1;
		if (block_start >= to)
			create = 0;
		ret = get_block(inode, block_in_file + block_in_page,
N
Nick Piggin 已提交
2608
					bh, create);
L
Linus Torvalds 已提交
2609 2610
		if (ret)
			goto failed;
N
Nick Piggin 已提交
2611
		if (!buffer_mapped(bh))
L
Linus Torvalds 已提交
2612
			is_mapped_to_disk = 0;
N
Nick Piggin 已提交
2613
		if (buffer_new(bh))
2614
			clean_bdev_bh_alias(bh);
N
Nick Piggin 已提交
2615 2616
		if (PageUptodate(page)) {
			set_buffer_uptodate(bh);
L
Linus Torvalds 已提交
2617
			continue;
N
Nick Piggin 已提交
2618 2619
		}
		if (buffer_new(bh) || !buffer_mapped(bh)) {
2620 2621
			zero_user_segments(page, block_start, from,
							to, block_end);
L
Linus Torvalds 已提交
2622 2623
			continue;
		}
N
Nick Piggin 已提交
2624
		if (buffer_uptodate(bh))
L
Linus Torvalds 已提交
2625 2626
			continue;	/* reiserfs does this */
		if (block_start < from || block_end > to) {
N
Nick Piggin 已提交
2627 2628
			lock_buffer(bh);
			bh->b_end_io = end_buffer_read_nobh;
2629
			submit_bh(REQ_OP_READ, 0, bh);
N
Nick Piggin 已提交
2630
			nr_reads++;
L
Linus Torvalds 已提交
2631 2632 2633 2634 2635 2636 2637 2638 2639
		}
	}

	if (nr_reads) {
		/*
		 * The page is locked, so these buffers are protected from
		 * any VM or truncate activity.  Hence we don't need to care
		 * for the buffer_head refcounts.
		 */
N
Nick Piggin 已提交
2640
		for (bh = head; bh; bh = bh->b_this_page) {
L
Linus Torvalds 已提交
2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651
			wait_on_buffer(bh);
			if (!buffer_uptodate(bh))
				ret = -EIO;
		}
		if (ret)
			goto failed;
	}

	if (is_mapped_to_disk)
		SetPageMappedToDisk(page);

N
Nick Piggin 已提交
2652
	*fsdata = head; /* to be released by nobh_write_end */
N
Nick Piggin 已提交
2653

L
Linus Torvalds 已提交
2654 2655 2656
	return 0;

failed:
N
Nick Piggin 已提交
2657
	BUG_ON(!ret);
L
Linus Torvalds 已提交
2658
	/*
N
Nick Piggin 已提交
2659 2660 2661 2662 2663
	 * Error recovery is a bit difficult. We need to zero out blocks that
	 * were newly allocated, and dirty them to ensure they get written out.
	 * Buffers need to be attached to the page at this point, otherwise
	 * the handling of potential IO errors during writeout would be hard
	 * (could try doing synchronous writeout, but what if that fails too?)
L
Linus Torvalds 已提交
2664
	 */
N
Nick Piggin 已提交
2665 2666
	attach_nobh_buffers(page, head);
	page_zero_new_buffers(page, from, to);
N
Nick Piggin 已提交
2667

N
Nick Piggin 已提交
2668 2669
out_release:
	unlock_page(page);
2670
	put_page(page);
N
Nick Piggin 已提交
2671
	*pagep = NULL;
N
Nick Piggin 已提交
2672

2673 2674
	return ret;
}
N
Nick Piggin 已提交
2675
EXPORT_SYMBOL(nobh_write_begin);
L
Linus Torvalds 已提交
2676

N
Nick Piggin 已提交
2677 2678 2679
int nobh_write_end(struct file *file, struct address_space *mapping,
			loff_t pos, unsigned len, unsigned copied,
			struct page *page, void *fsdata)
L
Linus Torvalds 已提交
2680 2681
{
	struct inode *inode = page->mapping->host;
N
Nick Piggin 已提交
2682
	struct buffer_head *head = fsdata;
N
Nick Piggin 已提交
2683
	struct buffer_head *bh;
2684
	BUG_ON(fsdata != NULL && page_has_buffers(page));
L
Linus Torvalds 已提交
2685

2686
	if (unlikely(copied < len) && head)
2687 2688 2689 2690
		attach_nobh_buffers(page, head);
	if (page_has_buffers(page))
		return generic_write_end(file, mapping, pos, len,
					copied, page, fsdata);
N
Nick Piggin 已提交
2691

N
Nick Piggin 已提交
2692
	SetPageUptodate(page);
L
Linus Torvalds 已提交
2693
	set_page_dirty(page);
N
Nick Piggin 已提交
2694 2695
	if (pos+copied > inode->i_size) {
		i_size_write(inode, pos+copied);
L
Linus Torvalds 已提交
2696 2697
		mark_inode_dirty(inode);
	}
N
Nick Piggin 已提交
2698 2699

	unlock_page(page);
2700
	put_page(page);
N
Nick Piggin 已提交
2701 2702 2703 2704 2705 2706 2707 2708

	while (head) {
		bh = head;
		head = head->b_this_page;
		free_buffer_head(bh);
	}

	return copied;
L
Linus Torvalds 已提交
2709
}
N
Nick Piggin 已提交
2710
EXPORT_SYMBOL(nobh_write_end);
L
Linus Torvalds 已提交
2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721

/*
 * nobh_writepage() - based on block_full_write_page() except
 * that it tries to operate without attaching bufferheads to
 * the page.
 */
int nobh_writepage(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
2722
	const pgoff_t end_index = i_size >> PAGE_SHIFT;
L
Linus Torvalds 已提交
2723 2724 2725 2726 2727 2728 2729 2730
	unsigned offset;
	int ret;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
		goto out;

	/* Is the page fully outside i_size? (truncate in progress) */
2731
	offset = i_size & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
#if 0
		/* Not really sure about this  - do we need this ? */
		if (page->mapping->a_ops->invalidatepage)
			page->mapping->a_ops->invalidatepage(page, offset);
#endif
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
	 * writepage invocation because it may be mmapped.  "A file is mapped
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2754
	zero_user_segment(page, offset, PAGE_SIZE);
L
Linus Torvalds 已提交
2755 2756 2757
out:
	ret = mpage_writepage(page, get_block, wbc);
	if (ret == -EAGAIN)
2758 2759
		ret = __block_write_full_page(inode, page, get_block, wbc,
					      end_buffer_async_write);
L
Linus Torvalds 已提交
2760 2761 2762 2763
	return ret;
}
EXPORT_SYMBOL(nobh_writepage);

N
Nick Piggin 已提交
2764 2765
int nobh_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
L
Linus Torvalds 已提交
2766
{
2767 2768
	pgoff_t index = from >> PAGE_SHIFT;
	unsigned offset = from & (PAGE_SIZE-1);
N
Nick Piggin 已提交
2769 2770 2771 2772
	unsigned blocksize;
	sector_t iblock;
	unsigned length, pos;
	struct inode *inode = mapping->host;
L
Linus Torvalds 已提交
2773
	struct page *page;
N
Nick Piggin 已提交
2774 2775
	struct buffer_head map_bh;
	int err;
L
Linus Torvalds 已提交
2776

F
Fabian Frederick 已提交
2777
	blocksize = i_blocksize(inode);
N
Nick Piggin 已提交
2778 2779 2780 2781 2782 2783 2784
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
2785
	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2786 2787

	page = grab_cache_page(mapping, index);
N
Nick Piggin 已提交
2788
	err = -ENOMEM;
L
Linus Torvalds 已提交
2789 2790 2791
	if (!page)
		goto out;

N
Nick Piggin 已提交
2792 2793 2794
	if (page_has_buffers(page)) {
has_buffers:
		unlock_page(page);
2795
		put_page(page);
N
Nick Piggin 已提交
2796 2797 2798 2799 2800 2801 2802 2803 2804 2805
		return block_truncate_page(mapping, from, get_block);
	}

	/* Find the buffer that contains "offset" */
	pos = blocksize;
	while (offset >= pos) {
		iblock++;
		pos += blocksize;
	}

2806 2807
	map_bh.b_size = blocksize;
	map_bh.b_state = 0;
N
Nick Piggin 已提交
2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818
	err = get_block(inode, iblock, &map_bh, 0);
	if (err)
		goto unlock;
	/* unmapped? It's a hole - nothing to do */
	if (!buffer_mapped(&map_bh))
		goto unlock;

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (!PageUptodate(page)) {
		err = mapping->a_ops->readpage(NULL, page);
		if (err) {
2819
			put_page(page);
N
Nick Piggin 已提交
2820 2821 2822 2823 2824 2825 2826 2827 2828
			goto out;
		}
		lock_page(page);
		if (!PageUptodate(page)) {
			err = -EIO;
			goto unlock;
		}
		if (page_has_buffers(page))
			goto has_buffers;
L
Linus Torvalds 已提交
2829
	}
2830
	zero_user(page, offset, length);
N
Nick Piggin 已提交
2831 2832 2833 2834
	set_page_dirty(page);
	err = 0;

unlock:
L
Linus Torvalds 已提交
2835
	unlock_page(page);
2836
	put_page(page);
L
Linus Torvalds 已提交
2837
out:
N
Nick Piggin 已提交
2838
	return err;
L
Linus Torvalds 已提交
2839 2840 2841 2842 2843 2844
}
EXPORT_SYMBOL(nobh_truncate_page);

int block_truncate_page(struct address_space *mapping,
			loff_t from, get_block_t *get_block)
{
2845 2846
	pgoff_t index = from >> PAGE_SHIFT;
	unsigned offset = from & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2847
	unsigned blocksize;
2848
	sector_t iblock;
L
Linus Torvalds 已提交
2849 2850 2851 2852 2853 2854
	unsigned length, pos;
	struct inode *inode = mapping->host;
	struct page *page;
	struct buffer_head *bh;
	int err;

F
Fabian Frederick 已提交
2855
	blocksize = i_blocksize(inode);
L
Linus Torvalds 已提交
2856 2857 2858 2859 2860 2861 2862
	length = offset & (blocksize - 1);

	/* Block boundary? Nothing to do */
	if (!length)
		return 0;

	length = blocksize - length;
2863
	iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
L
Linus Torvalds 已提交
2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883
	
	page = grab_cache_page(mapping, index);
	err = -ENOMEM;
	if (!page)
		goto out;

	if (!page_has_buffers(page))
		create_empty_buffers(page, blocksize, 0);

	/* Find the buffer that contains "offset" */
	bh = page_buffers(page);
	pos = blocksize;
	while (offset >= pos) {
		bh = bh->b_this_page;
		iblock++;
		pos += blocksize;
	}

	err = 0;
	if (!buffer_mapped(bh)) {
2884
		WARN_ON(bh->b_size != blocksize);
L
Linus Torvalds 已提交
2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896
		err = get_block(inode, iblock, bh, 0);
		if (err)
			goto unlock;
		/* unmapped? It's a hole - nothing to do */
		if (!buffer_mapped(bh))
			goto unlock;
	}

	/* Ok, it's mapped. Make sure it's up-to-date */
	if (PageUptodate(page))
		set_buffer_uptodate(bh);

2897
	if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
L
Linus Torvalds 已提交
2898
		err = -EIO;
2899
		ll_rw_block(REQ_OP_READ, 0, 1, &bh);
L
Linus Torvalds 已提交
2900 2901 2902 2903 2904 2905
		wait_on_buffer(bh);
		/* Uhhuh. Read error. Complain and punt. */
		if (!buffer_uptodate(bh))
			goto unlock;
	}

2906
	zero_user(page, offset, length);
L
Linus Torvalds 已提交
2907 2908 2909 2910 2911
	mark_buffer_dirty(bh);
	err = 0;

unlock:
	unlock_page(page);
2912
	put_page(page);
L
Linus Torvalds 已提交
2913 2914 2915
out:
	return err;
}
2916
EXPORT_SYMBOL(block_truncate_page);
L
Linus Torvalds 已提交
2917 2918 2919 2920

/*
 * The generic ->writepage function for buffer-backed address_spaces
 */
2921 2922
int block_write_full_page(struct page *page, get_block_t *get_block,
			struct writeback_control *wbc)
L
Linus Torvalds 已提交
2923 2924 2925
{
	struct inode * const inode = page->mapping->host;
	loff_t i_size = i_size_read(inode);
2926
	const pgoff_t end_index = i_size >> PAGE_SHIFT;
L
Linus Torvalds 已提交
2927 2928 2929 2930
	unsigned offset;

	/* Is the page fully inside i_size? */
	if (page->index < end_index)
2931
		return __block_write_full_page(inode, page, get_block, wbc,
2932
					       end_buffer_async_write);
L
Linus Torvalds 已提交
2933 2934

	/* Is the page fully outside i_size? (truncate in progress) */
2935
	offset = i_size & (PAGE_SIZE-1);
L
Linus Torvalds 已提交
2936 2937 2938 2939 2940 2941
	if (page->index >= end_index+1 || !offset) {
		/*
		 * The page may have dirty, unmapped buffers.  For example,
		 * they may have been added in ext3_writepage().  Make them
		 * freeable here, so the page does not leak.
		 */
2942
		do_invalidatepage(page, 0, PAGE_SIZE);
L
Linus Torvalds 已提交
2943 2944 2945 2946 2947 2948
		unlock_page(page);
		return 0; /* don't care */
	}

	/*
	 * The page straddles i_size.  It must be zeroed out on each and every
2949
	 * writepage invocation because it may be mmapped.  "A file is mapped
L
Linus Torvalds 已提交
2950 2951 2952 2953
	 * in multiples of the page size.  For a file that is not a multiple of
	 * the  page size, the remaining memory is zeroed when mapped, and
	 * writes to that region are not written out to the file."
	 */
2954
	zero_user_segment(page, offset, PAGE_SIZE);
2955 2956
	return __block_write_full_page(inode, page, get_block, wbc,
							end_buffer_async_write);
2957
}
2958
EXPORT_SYMBOL(block_write_full_page);
2959

L
Linus Torvalds 已提交
2960 2961 2962 2963
sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
			    get_block_t *get_block)
{
	struct inode *inode = mapping->host;
2964 2965 2966 2967
	struct buffer_head tmp = {
		.b_size = i_blocksize(inode),
	};

L
Linus Torvalds 已提交
2968 2969 2970
	get_block(inode, block, &tmp, 0);
	return tmp.b_blocknr;
}
2971
EXPORT_SYMBOL(generic_block_bmap);
L
Linus Torvalds 已提交
2972

2973
static void end_bio_bh_io_sync(struct bio *bio)
L
Linus Torvalds 已提交
2974 2975 2976
{
	struct buffer_head *bh = bio->bi_private;

2977
	if (unlikely(bio_flagged(bio, BIO_QUIET)))
2978 2979
		set_bit(BH_Quiet, &bh->b_state);

2980
	bh->b_end_io(bh, !bio->bi_status);
L
Linus Torvalds 已提交
2981 2982 2983
	bio_put(bio);
}

2984 2985
/*
 * This allows us to do IO even on the odd last sectors
2986
 * of a device, even if the block size is some multiple
2987 2988 2989 2990 2991 2992 2993 2994 2995
 * of the physical sector size.
 *
 * We'll just truncate the bio to the size of the device,
 * and clear the end of the buffer head manually.
 *
 * Truly out-of-range accesses will turn into actual IO
 * errors, this only handles the "we need to be able to
 * do IO at the final sector" case.
 */
2996
void guard_bio_eod(int op, struct bio *bio)
2997 2998
{
	sector_t maxsector;
M
Ming Lei 已提交
2999
	struct bio_vec *bvec = bio_last_bvec_all(bio);
3000
	unsigned truncated_bytes;
3001 3002 3003 3004 3005 3006 3007 3008 3009
	struct hd_struct *part;

	rcu_read_lock();
	part = __disk_get_part(bio->bi_disk, bio->bi_partno);
	if (part)
		maxsector = part_nr_sects_read(part);
	else
		maxsector = get_capacity(bio->bi_disk);
	rcu_read_unlock();
3010 3011 3012 3013 3014 3015 3016 3017 3018

	if (!maxsector)
		return;

	/*
	 * If the *whole* IO is past the end of the device,
	 * let it through, and the IO layer will turn it into
	 * an EIO.
	 */
3019
	if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3020 3021
		return;

3022
	maxsector -= bio->bi_iter.bi_sector;
3023
	if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3024 3025
		return;

3026 3027
	/* Uhhuh. We've got a bio that straddles the device size! */
	truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3028 3029

	/* Truncate the bio.. */
3030 3031
	bio->bi_iter.bi_size -= truncated_bytes;
	bvec->bv_len -= truncated_bytes;
3032 3033

	/* ..and clear the end of the buffer for reads */
3034
	if (op == REQ_OP_READ) {
3035 3036
		zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
				truncated_bytes);
3037 3038 3039
	}
}

3040
static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3041
			 enum rw_hint write_hint, struct writeback_control *wbc)
L
Linus Torvalds 已提交
3042 3043 3044 3045 3046 3047
{
	struct bio *bio;

	BUG_ON(!buffer_locked(bh));
	BUG_ON(!buffer_mapped(bh));
	BUG_ON(!bh->b_end_io);
3048 3049
	BUG_ON(buffer_delay(bh));
	BUG_ON(buffer_unwritten(bh));
L
Linus Torvalds 已提交
3050 3051

	/*
3052
	 * Only clear out a write error when rewriting
L
Linus Torvalds 已提交
3053
	 */
3054
	if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
L
Linus Torvalds 已提交
3055 3056 3057 3058 3059 3060 3061 3062
		clear_buffer_write_io_error(bh);

	/*
	 * from here on down, it's all bio -- do the initial mapping,
	 * submit_bio -> generic_make_request may further map this bio around
	 */
	bio = bio_alloc(GFP_NOIO, 1);

3063
	if (wbc) {
3064
		wbc_init_bio(wbc, bio);
3065 3066
		wbc_account_io(wbc, bh->b_page, bh->b_size);
	}
3067

3068
	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3069
	bio_set_dev(bio, bh->b_bdev);
3070
	bio->bi_write_hint = write_hint;
L
Linus Torvalds 已提交
3071

3072 3073
	bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
	BUG_ON(bio->bi_iter.bi_size != bh->b_size);
L
Linus Torvalds 已提交
3074 3075 3076 3077

	bio->bi_end_io = end_bio_bh_io_sync;
	bio->bi_private = bh;

3078
	/* Take care of bh's that straddle the end of the device */
3079
	guard_bio_eod(op, bio);
3080

3081
	if (buffer_meta(bh))
3082
		op_flags |= REQ_META;
3083
	if (buffer_prio(bh))
3084 3085
		op_flags |= REQ_PRIO;
	bio_set_op_attrs(bio, op, op_flags);
3086

3087
	submit_bio(bio);
3088
	return 0;
L
Linus Torvalds 已提交
3089
}
3090

E
Eric Biggers 已提交
3091
int submit_bh(int op, int op_flags, struct buffer_head *bh)
3092
{
3093
	return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3094
}
3095
EXPORT_SYMBOL(submit_bh);
L
Linus Torvalds 已提交
3096 3097 3098

/**
 * ll_rw_block: low-level access to block devices (DEPRECATED)
3099
 * @op: whether to %READ or %WRITE
3100
 * @op_flags: req_flag_bits
L
Linus Torvalds 已提交
3101 3102 3103
 * @nr: number of &struct buffer_heads in the array
 * @bhs: array of pointers to &struct buffer_head
 *
3104
 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3105 3106 3107
 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
 * @op_flags contains flags modifying the detailed I/O behavior, most notably
 * %REQ_RAHEAD.
L
Linus Torvalds 已提交
3108 3109
 *
 * This function drops any buffer that it cannot get a lock on (with the
C
Christoph Hellwig 已提交
3110 3111 3112 3113 3114
 * BH_Lock state bit), any buffer that appears to be clean when doing a write
 * request, and any buffer that appears to be up-to-date when doing read
 * request.  Further it marks as clean buffers that are processed for
 * writing (the buffer cache won't assume that they are actually clean
 * until the buffer gets unlocked).
L
Linus Torvalds 已提交
3115 3116
 *
 * ll_rw_block sets b_end_io to simple completion handler that marks
3117
 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
L
Linus Torvalds 已提交
3118 3119 3120 3121 3122
 * any waiters. 
 *
 * All of the buffers must be for the same device, and must also be a
 * multiple of the current approved size for the device.
 */
3123
void ll_rw_block(int op, int op_flags,  int nr, struct buffer_head *bhs[])
L
Linus Torvalds 已提交
3124 3125 3126 3127 3128 3129
{
	int i;

	for (i = 0; i < nr; i++) {
		struct buffer_head *bh = bhs[i];

C
Christoph Hellwig 已提交
3130
		if (!trylock_buffer(bh))
L
Linus Torvalds 已提交
3131
			continue;
3132
		if (op == WRITE) {
L
Linus Torvalds 已提交
3133
			if (test_clear_buffer_dirty(bh)) {
3134
				bh->b_end_io = end_buffer_write_sync;
3135
				get_bh(bh);
3136
				submit_bh(op, op_flags, bh);
L
Linus Torvalds 已提交
3137 3138 3139 3140
				continue;
			}
		} else {
			if (!buffer_uptodate(bh)) {
3141
				bh->b_end_io = end_buffer_read_sync;
3142
				get_bh(bh);
3143
				submit_bh(op, op_flags, bh);
L
Linus Torvalds 已提交
3144 3145 3146 3147 3148 3149
				continue;
			}
		}
		unlock_buffer(bh);
	}
}
3150
EXPORT_SYMBOL(ll_rw_block);
L
Linus Torvalds 已提交
3151

3152
void write_dirty_buffer(struct buffer_head *bh, int op_flags)
C
Christoph Hellwig 已提交
3153 3154 3155 3156 3157 3158 3159 3160
{
	lock_buffer(bh);
	if (!test_clear_buffer_dirty(bh)) {
		unlock_buffer(bh);
		return;
	}
	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
3161
	submit_bh(REQ_OP_WRITE, op_flags, bh);
C
Christoph Hellwig 已提交
3162 3163 3164
}
EXPORT_SYMBOL(write_dirty_buffer);

L
Linus Torvalds 已提交
3165 3166 3167 3168 3169
/*
 * For a data-integrity writeout, we need to wait upon any in-progress I/O
 * and then start new I/O and then wait upon it.  The caller must have a ref on
 * the buffer_head.
 */
3170
int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
L
Linus Torvalds 已提交
3171 3172 3173 3174 3175 3176 3177 3178
{
	int ret = 0;

	WARN_ON(atomic_read(&bh->b_count) < 1);
	lock_buffer(bh);
	if (test_clear_buffer_dirty(bh)) {
		get_bh(bh);
		bh->b_end_io = end_buffer_write_sync;
3179
		ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
L
Linus Torvalds 已提交
3180 3181 3182 3183 3184 3185 3186 3187
		wait_on_buffer(bh);
		if (!ret && !buffer_uptodate(bh))
			ret = -EIO;
	} else {
		unlock_buffer(bh);
	}
	return ret;
}
C
Christoph Hellwig 已提交
3188 3189 3190 3191
EXPORT_SYMBOL(__sync_dirty_buffer);

int sync_dirty_buffer(struct buffer_head *bh)
{
3192
	return __sync_dirty_buffer(bh, REQ_SYNC);
C
Christoph Hellwig 已提交
3193
}
3194
EXPORT_SYMBOL(sync_dirty_buffer);
L
Linus Torvalds 已提交
3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237

/*
 * try_to_free_buffers() checks if all the buffers on this particular page
 * are unused, and releases them if so.
 *
 * Exclusion against try_to_free_buffers may be obtained by either
 * locking the page or by holding its mapping's private_lock.
 *
 * If the page is dirty but all the buffers are clean then we need to
 * be sure to mark the page clean as well.  This is because the page
 * may be against a block device, and a later reattachment of buffers
 * to a dirty page will set *all* buffers dirty.  Which would corrupt
 * filesystem data on the same device.
 *
 * The same applies to regular filesystem pages: if all the buffers are
 * clean then we set the page clean and proceed.  To do that, we require
 * total exclusion from __set_page_dirty_buffers().  That is obtained with
 * private_lock.
 *
 * try_to_free_buffers() is non-blocking.
 */
static inline int buffer_busy(struct buffer_head *bh)
{
	return atomic_read(&bh->b_count) |
		(bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
}

static int
drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
{
	struct buffer_head *head = page_buffers(page);
	struct buffer_head *bh;

	bh = head;
	do {
		if (buffer_busy(bh))
			goto failed;
		bh = bh->b_this_page;
	} while (bh != head);

	do {
		struct buffer_head *next = bh->b_this_page;

3238
		if (bh->b_assoc_map)
L
Linus Torvalds 已提交
3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255
			__remove_assoc_queue(bh);
		bh = next;
	} while (bh != head);
	*buffers_to_free = head;
	__clear_page_buffers(page);
	return 1;
failed:
	return 0;
}

int try_to_free_buffers(struct page *page)
{
	struct address_space * const mapping = page->mapping;
	struct buffer_head *buffers_to_free = NULL;
	int ret = 0;

	BUG_ON(!PageLocked(page));
3256
	if (PageWriteback(page))
L
Linus Torvalds 已提交
3257 3258 3259 3260 3261 3262 3263 3264 3265
		return 0;

	if (mapping == NULL) {		/* can this still happen? */
		ret = drop_buffers(page, &buffers_to_free);
		goto out;
	}

	spin_lock(&mapping->private_lock);
	ret = drop_buffers(page, &buffers_to_free);
3266 3267 3268 3269 3270 3271 3272 3273 3274 3275

	/*
	 * If the filesystem writes its buffers by hand (eg ext3)
	 * then we can have clean buffers against a dirty page.  We
	 * clean the page here; otherwise the VM will never notice
	 * that the filesystem did any IO at all.
	 *
	 * Also, during truncate, discard_buffer will have marked all
	 * the page's buffers clean.  We discover that here and clean
	 * the page also.
3276 3277 3278 3279
	 *
	 * private_lock must be held over this entire operation in order
	 * to synchronise against __set_page_dirty_buffers and prevent the
	 * dirty bit from being lost.
3280
	 */
3281 3282
	if (ret)
		cancel_dirty_page(page);
3283
	spin_unlock(&mapping->private_lock);
L
Linus Torvalds 已提交
3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302
out:
	if (buffers_to_free) {
		struct buffer_head *bh = buffers_to_free;

		do {
			struct buffer_head *next = bh->b_this_page;
			free_buffer_head(bh);
			bh = next;
		} while (bh != buffers_to_free);
	}
	return ret;
}
EXPORT_SYMBOL(try_to_free_buffers);

/*
 * There are no bdflush tunables left.  But distributions are
 * still running obsolete flush daemons, so we terminate them here.
 *
 * Use of bdflush() is deprecated and will be removed in a future kernel.
3303
 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
L
Linus Torvalds 已提交
3304
 */
3305
SYSCALL_DEFINE2(bdflush, int, func, long, data)
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{
	static int msg_count;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (msg_count < 5) {
		msg_count++;
		printk(KERN_INFO
			"warning: process `%s' used the obsolete bdflush"
			" system call\n", current->comm);
		printk(KERN_INFO "Fix your initscripts?\n");
	}

	if (func == 1)
		do_exit(0);
	return 0;
}

/*
 * Buffer-head allocation
 */
3328
static struct kmem_cache *bh_cachep __read_mostly;
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/*
 * Once the number of bh's in the machine exceeds this level, we start
 * stripping them in writeback.
 */
3334
static unsigned long max_buffer_heads;
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int buffer_heads_over_limit;

struct bh_accounting {
	int nr;			/* Number of live bh's */
	int ratelimit;		/* Limit cacheline bouncing */
};

static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};

static void recalc_bh_state(void)
{
	int i;
	int tot = 0;

3350
	if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
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		return;
3352
	__this_cpu_write(bh_accounting.ratelimit, 0);
3353
	for_each_online_cpu(i)
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		tot += per_cpu(bh_accounting, i).nr;
	buffer_heads_over_limit = (tot > max_buffer_heads);
}
3357

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struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
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{
3360
	struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
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	if (ret) {
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		INIT_LIST_HEAD(&ret->b_assoc_buffers);
3363 3364
		preempt_disable();
		__this_cpu_inc(bh_accounting.nr);
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		recalc_bh_state();
3366
		preempt_enable();
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	}
	return ret;
}
EXPORT_SYMBOL(alloc_buffer_head);

void free_buffer_head(struct buffer_head *bh)
{
	BUG_ON(!list_empty(&bh->b_assoc_buffers));
	kmem_cache_free(bh_cachep, bh);
3376 3377
	preempt_disable();
	__this_cpu_dec(bh_accounting.nr);
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	recalc_bh_state();
3379
	preempt_enable();
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}
EXPORT_SYMBOL(free_buffer_head);

3383
static int buffer_exit_cpu_dead(unsigned int cpu)
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{
	int i;
	struct bh_lru *b = &per_cpu(bh_lrus, cpu);

	for (i = 0; i < BH_LRU_SIZE; i++) {
		brelse(b->bhs[i]);
		b->bhs[i] = NULL;
	}
3392
	this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3393
	per_cpu(bh_accounting, cpu).nr = 0;
3394
	return 0;
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}

3397
/**
3398
 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416
 * @bh: struct buffer_head
 *
 * Return true if the buffer is up-to-date and false,
 * with the buffer locked, if not.
 */
int bh_uptodate_or_lock(struct buffer_head *bh)
{
	if (!buffer_uptodate(bh)) {
		lock_buffer(bh);
		if (!buffer_uptodate(bh))
			return 0;
		unlock_buffer(bh);
	}
	return 1;
}
EXPORT_SYMBOL(bh_uptodate_or_lock);

/**
3417
 * bh_submit_read - Submit a locked buffer for reading
3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432
 * @bh: struct buffer_head
 *
 * Returns zero on success and -EIO on error.
 */
int bh_submit_read(struct buffer_head *bh)
{
	BUG_ON(!buffer_locked(bh));

	if (buffer_uptodate(bh)) {
		unlock_buffer(bh);
		return 0;
	}

	get_bh(bh);
	bh->b_end_io = end_buffer_read_sync;
3433
	submit_bh(REQ_OP_READ, 0, bh);
3434 3435 3436 3437 3438 3439 3440
	wait_on_buffer(bh);
	if (buffer_uptodate(bh))
		return 0;
	return -EIO;
}
EXPORT_SYMBOL(bh_submit_read);

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void __init buffer_init(void)
{
3443
	unsigned long nrpages;
3444
	int ret;
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3446 3447 3448 3449
	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
				(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
				SLAB_MEM_SPREAD),
3450
				NULL);
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	/*
	 * Limit the bh occupancy to 10% of ZONE_NORMAL
	 */
	nrpages = (nr_free_buffer_pages() * 10) / 100;
	max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3457 3458 3459
	ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
					NULL, buffer_exit_cpu_dead);
	WARN_ON(ret < 0);
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}