提交 6818173b 编写于 作者: M Miklos Szeredi 提交者: Jens Axboe

splice: implement default splice_read method

If f_op->splice_read() is not implemented, fall back to a plain read.
Use vfs_readv() to read into previously allocated pages.

This will allow splice and functions using splice, such as the loop
device, to work on all filesystems.  This includes "direct_io" files
in fuse which bypass the page cache.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>
上级 7c77f0b3
......@@ -709,10 +709,6 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
goto out_putf;
/* new backing store needs to support loop (eg splice_read) */
if (!inode->i_fop->splice_read)
goto out_putf;
/* size of the new backing store needs to be the same */
if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
goto out_putf;
......@@ -788,12 +784,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
error = -EINVAL;
if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
const struct address_space_operations *aops = mapping->a_ops;
/*
* If we can't read - sorry. If we only can't write - well,
* it's going to be read-only.
*/
if (!file->f_op->splice_read)
goto out_putf;
if (aops->write_begin)
lo_flags |= LO_FLAGS_USE_AOPS;
if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
......
......@@ -47,6 +47,8 @@ coda_file_splice_read(struct file *coda_file, loff_t *ppos,
struct pipe_inode_info *pipe, size_t count,
unsigned int flags)
{
ssize_t (*splice_read)(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
struct coda_file_info *cfi;
struct file *host_file;
......@@ -54,10 +56,11 @@ coda_file_splice_read(struct file *coda_file, loff_t *ppos,
BUG_ON(!cfi || cfi->cfi_magic != CODA_MAGIC);
host_file = cfi->cfi_container;
if (!host_file->f_op || !host_file->f_op->splice_read)
return -EINVAL;
splice_read = host_file->f_op->splice_read;
if (!splice_read)
splice_read = default_file_splice_read;
return host_file->f_op->splice_read(host_file, ppos, pipe, count,flags);
return splice_read(host_file, ppos, pipe, count, flags);
}
static ssize_t
......
......@@ -302,6 +302,20 @@ int generic_pipe_buf_confirm(struct pipe_inode_info *info,
return 0;
}
/**
* generic_pipe_buf_release - put a reference to a &struct pipe_buffer
* @pipe: the pipe that the buffer belongs to
* @buf: the buffer to put a reference to
*
* Description:
* This function releases a reference to @buf.
*/
void generic_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
page_cache_release(buf->page);
}
static const struct pipe_buf_operations anon_pipe_buf_ops = {
.can_merge = 1,
.map = generic_pipe_buf_map,
......
......@@ -805,12 +805,6 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
goto out;
if (!(in_file->f_mode & FMODE_READ))
goto fput_in;
retval = -EINVAL;
in_inode = in_file->f_path.dentry->d_inode;
if (!in_inode)
goto fput_in;
if (!in_file->f_op || !in_file->f_op->splice_read)
goto fput_in;
retval = -ESPIPE;
if (!ppos)
ppos = &in_file->f_pos;
......@@ -834,6 +828,7 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
retval = -EINVAL;
if (!out_file->f_op || !out_file->f_op->sendpage)
goto fput_out;
in_inode = in_file->f_path.dentry->d_inode;
out_inode = out_file->f_path.dentry->d_inode;
retval = rw_verify_area(WRITE, out_file, &out_file->f_pos, count);
if (retval < 0)
......
......@@ -507,9 +507,116 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
return ret;
}
EXPORT_SYMBOL(generic_file_splice_read);
static const struct pipe_buf_operations default_pipe_buf_ops = {
.can_merge = 0,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
unsigned long vlen, loff_t offset)
{
mm_segment_t old_fs;
loff_t pos = offset;
ssize_t res;
old_fs = get_fs();
set_fs(get_ds());
/* The cast to a user pointer is valid due to the set_fs() */
res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
set_fs(old_fs);
return res;
}
ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
unsigned int nr_pages;
unsigned int nr_freed;
size_t offset;
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct iovec vec[PIPE_BUFFERS];
pgoff_t index;
ssize_t res;
size_t this_len;
int error;
int i;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.flags = flags,
.ops = &default_pipe_buf_ops,
.spd_release = spd_release_page,
};
index = *ppos >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
for (i = 0; i < nr_pages && i < PIPE_BUFFERS && len; i++) {
struct page *page;
page = alloc_page(GFP_HIGHUSER);
error = -ENOMEM;
if (!page)
goto err;
this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
vec[i].iov_base = (void __user *) kmap(page);
vec[i].iov_len = this_len;
pages[i] = page;
spd.nr_pages++;
len -= this_len;
offset = 0;
}
res = kernel_readv(in, vec, spd.nr_pages, *ppos);
if (res < 0)
goto err;
error = 0;
if (!res)
goto err;
nr_freed = 0;
for (i = 0; i < spd.nr_pages; i++) {
kunmap(pages[i]);
this_len = min_t(size_t, vec[i].iov_len, res);
partial[i].offset = 0;
partial[i].len = this_len;
if (!this_len) {
__free_page(pages[i]);
pages[i] = NULL;
nr_freed++;
}
res -= this_len;
}
spd.nr_pages -= nr_freed;
res = splice_to_pipe(pipe, &spd);
if (res > 0)
*ppos += res;
return res;
err:
for (i = 0; i < spd.nr_pages; i++) {
kunmap(pages[i]);
__free_page(pages[i]);
}
return error;
}
EXPORT_SYMBOL(default_file_splice_read);
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
......@@ -933,11 +1040,10 @@ static long do_splice_to(struct file *in, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)
{
ssize_t (*splice_read)(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
int ret;
if (unlikely(!in->f_op || !in->f_op->splice_read))
return -EINVAL;
if (unlikely(!(in->f_mode & FMODE_READ)))
return -EBADF;
......@@ -945,7 +1051,11 @@ static long do_splice_to(struct file *in, loff_t *ppos,
if (unlikely(ret < 0))
return ret;
return in->f_op->splice_read(in, ppos, pipe, len, flags);
splice_read = in->f_op->splice_read;
if (!splice_read)
splice_read = default_file_splice_read;
return splice_read(in, ppos, pipe, len, flags);
}
/**
......
......@@ -2204,6 +2204,8 @@ extern int generic_segment_checks(const struct iovec *iov,
/* fs/splice.c */
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t default_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
struct file *, loff_t *, size_t, unsigned int);
extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
......
......@@ -152,5 +152,6 @@ void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void
void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
#endif
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