ext4_reserve_inode_write() in ext4_mark_inode_dirty() could fail on
error (e.g. EIO) and iloc.bh can be NULL in this case. But the error is
ignored in the following "if" condition and ext4_expand_extra_isize()
might be called with NULL iloc.bh set, which triggers NULL pointer
dereference.

This is uncovered by commit 8b4953e1 ("ext4: reserve code points for
the project quota feature"), which enlarges the ext4_inode size, and
run the following script on new kernel but with old mke2fs:

  #/bin/bash
  mnt=/mnt/ext4
  devname=ext4-error
  dev=/dev/mapper/$devname
  fsimg=/home/fs.img

  trap cleanup 0 1 2 3 9 15

  cleanup()
  {
          umount $mnt >/dev/null 2>&1
          dmsetup remove $devname
          losetup -d $backend_dev
          rm -f $fsimg
          exit 0
  }

  rm -f $fsimg
  fallocate -l 1g $fsimg
  backend_dev=`losetup -f --show $fsimg`
  devsize=`blockdev --getsz $backend_dev`

  good_tab="0 $devsize linear $backend_dev 0"
  error_tab="0 $devsize error $backend_dev 0"

  dmsetup create $devname --table "$good_tab"

  mkfs -t ext4 $dev
  mount -t ext4 -o errors=continue,strictatime $dev $mnt

  dmsetup load $devname --table "$error_tab" && dmsetup resume $devname
  echo 3 > /proc/sys/vm/drop_caches
  ls -l $mnt
  exit 0

[ Patch changed to simplify the function a tiny bit. -- Ted ]
Signed-off-by: NEryu Guan <guaneryu@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Using SEEK_DATA in a huge sparse file can easily lead to sotflockups as
ext4_seek_data() iterates hole block-by-block. Fix the problem by using
returned hole size from ext4_map_blocks() and thus skip the hole in one
go.

Update also SEEK_HOLE implementation to follow the same pattern as
SEEK_DATA to make future maintenance easier.

Furthermore we add cond_resched() to both ext4_seek_data() and
ext4_seek_hole() to avoid softlockups in case evil user creates huge
fragmented file and we have to go through lots of extents.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

ext4_dax_mmap_get_block() updates bh->b_state directly instead of using
ext4_update_bh_state(). This is mostly a cosmetic issue since DAX code
always passes on-stack buffer_head but clean this up to make code more
uniform.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently, ext4_map_blocks() just returns 0 when it finds a hole and
allocation is not requested. However we have all the information
available to tell how large the hole actually is and there are callers
of ext4_map_blocks() which would save some block-by-block hole iteration
if they knew this information. So fill in struct ext4_map_blocks even
for holes with the information we have. We keep returning 0 for holes to
maintain backward compatibility of the function.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Remove counter of pending io ends as it is unused.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

When mapping blocks for direct IO, we allocate io_end structure before
mapping blocks and store pointer to it in the inode. This creates a
requirement that any AIO DIO using io_end must be protected by i_mutex.
This created problems in the past with dioread_nolock mode which was
corrupting io_end pointers. Also io_end is allocated unnecessarily in
case where we don't need to convert any extents (which is a common case
for example when overwriting file).

We fix the problem by allocating io_end only once we return unwritten
extent from block mapping function for AIO DIO (so we can save some
pointless io_end allocations) and we pass pointer to it in bh->b_private
which generic DIO code later passes to our end IO callback. That way we
remove any need for global pointer to io_end structure and thus fix the
races.

The downside of this change is that the checking for unwritten IO in
flight in ext4_extents_can_be_merged() is more racy since we now
increment i_unwritten / set EXT4_STATE_DIO_UNWRITTEN only after dropping
i_data_sem. However the check has been racy already before because
ext4_writepages() already increment i_unwritten after dropping
i_data_sem and reserved blocks save us from hitting ENOSPC in the worst
case.
Signed-off-by: NJan Kara <jack@suse.cz>

There is no need to handle starting of a transaction and deferal of DIO
completion in _ext4_get_block() function. We can move this out to get
block functions for direct IO that need it. That way we can add stricter
checks verifying things work as we expect.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Rename ext4_get_blocks_write() to ext4_get_blocks_unwritten() to better
describe what it does. Also split out get blocks functions for direct
IO. Later we move functionality from _ext4_get_blocks() there. There's no
functional change in this patch.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Competing overwrite DIO in dioread_nolock mode will just overwrite
pointer to io_end in the inode. This may result in data corruption or
extent conversion happening from IO completion interrupt because we
don't properly set buffer_defer_completion() when unlocked DIO races
with locked DIO to unwritten extent.

Since unlocked DIO doesn't need io_end for anything, just avoid
allocating it and corrupting pointer from inode for locked DIO.
A cleaner fix would be to avoid these games with io_end pointer from the
inode but that requires more intrusive changes so we leave that for
later.

Cc: stable@vger.kernel.org
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

ext4 can update bh->b_state non-atomically in _ext4_get_block() and
ext4_da_get_block_prep(). Usually this is fine since bh is just a
temporary storage for mapping information on stack but in some cases it
can be fully living bh attached to a page. In such case non-atomic
update of bh->b_state can race with an atomic update which then gets
lost. Usually when we are mapping bh and thus updating bh->b_state
non-atomically, nobody else touches the bh and so things work out fine
but there is one case to especially worry about: ext4_finish_bio() uses
BH_Uptodate_Lock on the first bh in the page to synchronize handling of
PageWriteback state. So when blocksize < pagesize, we can be atomically
modifying bh->b_state of a buffer that actually isn't under IO and thus
can race e.g. with delalloc trying to map that buffer. The result is
that we can mistakenly set / clear BH_Uptodate_Lock bit resulting in the
corruption of PageWriteback state or missed unlock of BH_Uptodate_Lock.

Fix the problem by always updating bh->b_state bits atomically.

CC: stable@vger.kernel.org
Reported-by: NNikolay Borisov <kernel@kyup.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NLi Xi <lixi@ddn.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NAndreas Dilger <adilger@dilger.ca>
Reviewed-by: NJan Kara <jack@suse.cz>

kmap() in page_follow_link_light() needed to go - allowing to hold
an arbitrary number of kmaps for long is a great way to deadlocking
the system.

new helper (inode_nohighmem(inode)) needs to be used for pagecache
symlinks inodes; done for all in-tree cases.  page_follow_link_light()
instrumented to yell about anything missed.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Make DAX fault path use pre-zeroed blocks to avoid races with extent
conversion and zeroing when two page faults to the same block happen.
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

DAX page fault path needs to get blocks that are pre-zeroed to avoid
races when two concurrent page faults happen in the same block of a
file. Implement support for this in ext4_map_blocks().
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Create new function ext4_issue_zeroout() to zeroout contiguous (both
logically and physically) part of inode data. We will need to issue
zeroout when extent structure is not readily available and this function
will allow us to do it without making up fake extent structures.
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

When dioread_nolock mode is enabled, we grab i_data_sem in
ext4_ext_direct_IO() and therefore we need to instruct _ext4_get_block()
not to grab i_data_sem again using EXT4_GET_BLOCKS_NO_LOCK. However
holding i_data_sem over overwrite direct IO isn't needed these days. We
have exclusion against truncate / hole punching because we increase
i_dio_count under i_mutex in ext4_ext_direct_IO() so once
ext4_file_write_iter() verifies blocks are allocated & written, they are
guaranteed to stay so during the whole direct IO even after we drop
i_mutex.

So we can just remove this locking abuse and the no longer necessary
EXT4_GET_BLOCKS_NO_LOCK flag.
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

When doing delayed allocation, update of on-disk inode size is postponed
until IO submission time. However hole punch or zero range fallocate
calls can end up discarding the tail page cache page and thus on-disk
inode size would never be properly updated.

Make sure the on-disk inode size is updated before truncating page
cache.
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

Currently, page faults and hole punching are completely unsynchronized.
This can result in page fault faulting in a page into a range that we
are punching after truncate_pagecache_range() has been called and thus
we can end up with a page mapped to disk blocks that will be shortly
freed. Filesystem corruption will shortly follow. Note that the same
race is avoided for truncate by checking page fault offset against
i_size but there isn't similar mechanism available for punching holes.

Fix the problem by creating new rw semaphore i_mmap_sem in inode and
grab it for writing over truncate, hole punching, and other functions
removing blocks from extent tree and for read over page faults. We
cannot easily use i_data_sem for this since that ranks below transaction
start and we need something ranking above it so that it can be held over
the whole truncate / hole punching operation. Also remove various
workarounds we had in the code to reduce race window when page fault
could have created pages with stale mapping information.
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

The function currently called "__block_page_mkwrite()" used to be called
"block_page_mkwrite()" until a wrapper for this function was added by:

commit 24da4fab ("vfs: Create __block_page_mkwrite() helper passing
	error values back")

This wrapper, the current "block_page_mkwrite()", is currently unused.
__block_page_mkwrite() is used directly by ext4, nilfs2 and xfs.

Remove the unused wrapper, rename __block_page_mkwrite() back to
block_page_mkwrite() and update the comment above block_page_mkwrite().
Signed-off-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: NJan Kara <jack@suse.com>
Cc: Jan Kara <jack@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.

Let's introduce a helper function which makes the restriction explicit and
easier to track.  This patch doesn't introduce any functional changes.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Create separate predicate functions to test/set/clear feature flags,
thereby replacing the wordy old macros.  Furthermore, clean out the
places where we open-coded feature tests.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

Instead of overloading EIO for CRC errors and corrupt structures,
return the same error codes that XFS returns for the same issues.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

If there is a error while copying data from userspace into the page
cache during a write(2) system call, in data=journal mode, in
ext4_journalled_write_end() were using page_zero_new_buffers() from
fs/buffer.c.  Unfortunately, this sets the buffer dirty flag, which is
no good if journalling is enabled.  This is a long-standing bug that
goes back for years and years in ext3, but a combination of (a)
data=journal not being very common, (b) in many case it only results
in a warning message. and (c) only very rarely causes the kernel hang,
means that we only really noticed this as a problem when commit
998ef75d caused this failure to happen frequently enough to cause
generic/208 to fail when run in data=journal mode.

The fix is to have our own version of this function that doesn't call
mark_dirty_buffer(), since we will end up calling
ext4_handle_dirty_metadata() on the buffer head(s) in questions very
shortly afterwards in ext4_journalled_write_end().

Thanks to Dave Hansen and Linus Torvalds for helping to identify the
root cause of the problem.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.com>

Since ext4_page_crypto() doesn't need an encryption context (at least
not any more), this allows us to simplify a number function signature
and also allows us to avoid needing to allocate a context in
ext4_block_write_begin().  It also means we no longer need a separate
ext4_decrypt_one() function.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

In cases where the file system block size is the same as the page
size, and ext4_writepage() is asked to write out a page which is
either has the unwritten bit set in the extent tree, or which does not
yet have a block assigned due to delayed allocation, we can bail out
early and, unlocking the page earlier and avoiding a round trip
through ext4_bio_write_page() with the attendant calls to
set_page_writeback() and redirty_page_for_writeback().
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

DAX wants different semantics from any currently-existing ext4 get_block
callback.  Unlike ext4_get_block_write(), it needs to honour the
'create' flag, and unlike ext4_get_block(), it needs to be able to
return unwritten extents.  So introduce a new ext4_get_block_dax() which
has those semantics.

We could also change ext4_get_block_write() to honour the 'create' flag,
but that might have consequences on other users that I do not currently
understand.
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In order to handle the !CONFIG_TRANSPARENT_HUGEPAGES case, we need to
return VM_FAULT_FALLBACK from the inlined dax_pmd_fault(), which is
defined in linux/mm.h.  Given that we don't want to include <linux/mm.h>
in <linux/fs.h>, the easiest solution is to move the DAX-related
functions to a new header, <linux/dax.h>.  We could also have moved
VM_FAULT_* definitions to a new header, or a different header that isn't
quite such a boil-the-ocean header as <linux/mm.h>, but this felt like
the best option.
Signed-off-by: NMatthew Wilcox <willy@linux.intel.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 3da40c7b ("ext4: only call ext4_truncate when size <= isize")
introduced a bug that c/mtime is not updated on truncate up.

Fix the issue by setting c/mtime explicitly in the truncate up case.

Note that ftruncate(2) is not affected, so you won't see this bug using
truncate(1) and xfs_io(1).
Signed-off-by: NZirong Lang <zorro.lang@gmail.com>
Signed-off-by: NEryu Guan <guaneryu@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

dquot_initialize() can now return error. Handle it where possible.
Acked-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NJan Kara <jack@suse.com>

On delalloc enabled file system on invalidatepage operation
in ext4_da_page_release_reservation() we want to clear the delayed
buffer and remove the extent covering the delayed buffer from the extent
status tree.

However currently there is a bug where on the systems with page size >
block size we will always remove extents from the start of the page
regardless where the actual delayed buffers are positioned in the page.
This leads to the errors like this:

EXT4-fs warning (device loop0): ext4_da_release_space:1225:
ext4_da_release_space: ino 13, to_free 1 with only 0 reserved data
blocks

This however can cause data loss on writeback time if the file system is
in ENOSPC condition because we're releasing reservation for someones
else delayed buffer.

Fix this by only removing extents that corresponds to the part of the
page we want to invalidate.

This problem is reproducible by the following fio receipt (however I was
only able to reproduce it with fio-2.1 or older.

[global]
bs=8k
iodepth=1024
iodepth_batch=60
randrepeat=1
size=1m
directory=/mnt/test
numjobs=20
[job1]
ioengine=sync
bs=1k
direct=1
rw=randread
filename=file1:file2
[job2]
ioengine=libaio
rw=randwrite
direct=1
filename=file1:file2
[job3]
bs=1k
ioengine=posixaio
rw=randwrite
direct=1
filename=file1:file2
[job5]
bs=1k
ioengine=sync
rw=randread
filename=file1:file2
[job7]
ioengine=libaio
rw=randwrite
filename=file1:file2
[job8]
ioengine=posixaio
rw=randwrite
filename=file1:file2
[job10]
ioengine=mmap
rw=randwrite
bs=1k
filename=file1:file2
[job11]
ioengine=mmap
rw=randwrite
direct=1
filename=file1:file2
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org

Commit 8f4d8558: "ext4: fix lazytime optimization" was not a
complete fix.  In the case where the inode number is a multiple of 16,
and we could still end up updating an inode with dirty timestamps
written to the wrong inode on disk.  Oops.

This can be easily reproduced by using generic/005 with a file system
with metadata_csum and lazytime enabled.
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

At LSF we decided that if we truncate up from isize we shouldn't trim
fallocated blocks that were fallocated with KEEP_SIZE and are past the
new i_size.  This patch fixes ext4 to do this.

[ Completely reworked patch so that i_disksize would actually get set
  when truncating up.  Also reworked the code for handling truncate so
  that it's easier to handle. -- tytso ]
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NLukas Czerner <lczerner@redhat.com>

Remove outdated comments and dead code from ext4_da_reserve_space.
Clean up its trace point, and relocate it to make it more useful.

While we're at it, fix a nearby conditional used to determine if
we have a non-bigalloc file system.  It doesn't match usage elsewhere
in the code, and misleadingly suggests that an s_cluster_ratio value
of 0 would be legal.
Signed-off-by: NEric Whitney <enwlinux@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

In order to prevent quota block tracking to be inaccurate when
ext4_quota_write() fails with ENOSPC, we make two changes.  The quota
file can now use the reserved block (since the quota file is arguably
file system metadata), and ext4_quota_write() now uses
ext4_should_retry_alloc() to retry the block allocation after a commit
has completed and released some blocks for allocation.

This fixes failures of xfstests generic/270:

Quota error (device vdc): write_blk: dquota write failed
Quota error (device vdc): qtree_write_dquot: Error -28 occurred while creating quota
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

The commit cf108bca: "ext4: Invert the locking order of page_lock
and transaction start" caused __ext4_journalled_writepage() to drop
the page lock before the page was written back, as part of changing
the locking order to jbd2_journal_start -> page_lock.  However, this
introduced a potential race if there was a truncate racing with the
data=journalled writeback mode.

Fix this by grabbing the page lock after starting the journal handle,
and then checking to see if page had gotten truncated out from under
us.

This fixes a number of different warnings or BUG_ON's when running
xfstests generic/086 in data=journalled mode, including:

jbd2_journal_dirty_metadata: vdc-8: bad jh for block 115643: transaction (ee3fe7
c0, 164), jh->b_transaction (  (null), 0), jh->b_next_transaction (  (null), 0), jlist 0

	      	      	  - and -

kernel BUG at /usr/projects/linux/ext4/fs/jbd2/transaction.c:2200!
    ...
Call Trace:
 [<c02b2ded>] ? __ext4_journalled_invalidatepage+0x117/0x117
 [<c02b2de5>] __ext4_journalled_invalidatepage+0x10f/0x117
 [<c02b2ded>] ? __ext4_journalled_invalidatepage+0x117/0x117
 [<c027d883>] ? lock_buffer+0x36/0x36
 [<c02b2dfa>] ext4_journalled_invalidatepage+0xd/0x22
 [<c0229139>] do_invalidatepage+0x22/0x26
 [<c0229198>] truncate_inode_page+0x5b/0x85
 [<c022934b>] truncate_inode_pages_range+0x156/0x38c
 [<c0229592>] truncate_inode_pages+0x11/0x15
 [<c022962d>] truncate_pagecache+0x55/0x71
 [<c02b913b>] ext4_setattr+0x4a9/0x560
 [<c01ca542>] ? current_kernel_time+0x10/0x44
 [<c026c4d8>] notify_change+0x1c7/0x2be
 [<c0256a00>] do_truncate+0x65/0x85
 [<c0226f31>] ? file_ra_state_init+0x12/0x29

	      	      	  - and -

WARNING: CPU: 1 PID: 1331 at /usr/projects/linux/ext4/fs/jbd2/transaction.c:1396
irty_metadata+0x14a/0x1ae()
    ...
Call Trace:
 [<c01b879f>] ? console_unlock+0x3a1/0x3ce
 [<c082cbb4>] dump_stack+0x48/0x60
 [<c0178b65>] warn_slowpath_common+0x89/0xa0
 [<c02ef2cf>] ? jbd2_journal_dirty_metadata+0x14a/0x1ae
 [<c0178bef>] warn_slowpath_null+0x14/0x18
 [<c02ef2cf>] jbd2_journal_dirty_metadata+0x14a/0x1ae
 [<c02d8615>] __ext4_handle_dirty_metadata+0xd4/0x19d
 [<c02b2f44>] write_end_fn+0x40/0x53
 [<c02b4a16>] ext4_walk_page_buffers+0x4e/0x6a
 [<c02b59e7>] ext4_writepage+0x354/0x3b8
 [<c02b2f04>] ? mpage_release_unused_pages+0xd4/0xd4
 [<c02b1b21>] ? wait_on_buffer+0x2c/0x2c
 [<c02b5a4b>] ? ext4_writepage+0x3b8/0x3b8
 [<c02b5a5b>] __writepage+0x10/0x2e
 [<c0225956>] write_cache_pages+0x22d/0x32c
 [<c02b5a4b>] ? ext4_writepage+0x3b8/0x3b8
 [<c02b6ee8>] ext4_writepages+0x102/0x607
 [<c019adfe>] ? sched_clock_local+0x10/0x10e
 [<c01a8a7c>] ? __lock_is_held+0x2e/0x44
 [<c01a8ad5>] ? lock_is_held+0x43/0x51
 [<c0226dff>] do_writepages+0x1c/0x29
 [<c0276bed>] __writeback_single_inode+0xc3/0x545
 [<c0277c07>] writeback_sb_inodes+0x21f/0x36d
    ...
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org

dax_fault() currently relies on the get_block callback to attach an
io completion callback to the mapping buffer head so that it can
run unwritten extent conversion after zeroing allocated blocks.

Instead of this hack, pass the conversion callback directly into
dax_fault() similar to the get_block callback. When the filesystem
allocates unwritten extents, it will set the buffer_unwritten()
flag, and hence the dax_fault code can call the completion function
in the contexts where it is necessary without overloading the
mapping buffer head.

Note: The changes to ext4 to use this interface are suspect at best.
In fact, the way ext4 did this end_io assignment in the first place
looks suspect because it only set a completion callback when there
wasn't already some other write() call taking place on the same
inode. The ext4 end_io code looks rather intricate and fragile with
all it's reference counting and passing to different contexts for
modification via inode private pointers that aren't protected by
locks...
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Acked-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDave Chinner <david@fromorbit.com>

We had a fencepost error in the lazytime optimization which means that
timestamp would get written to the wrong inode.

Cc: stable@vger.kernel.org
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

for fast symlinks only, of course...
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>