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fuse: fix fuse_write_end() if zero bytes were copied 

If pos is at the beginning of a page and copied is zero then page is not
zeroed but is marked uptodate.

Fix by skipping everything except unlock/put of page if zero bytes were
copied.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 6b12c1b37e ("fuse: Implement write_begin/write_end callbacks")
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2016-08-18 09:10:44 +02:00
parent 0ce267ff95
commit 59c3b76cc6
1 changed files with 6 additions and 0 deletions
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6
fs/fuse/file.c
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@ -1985,6 +1985,10 @@ static int fuse_write_end(struct file *file, struct address_space *mapping,
{
struct inode *inode = page->mapping->host;
/* Haven't copied anything? Skip zeroing, size extending, dirtying. */
if (!copied)
goto unlock;
if (!PageUptodate(page)) {
/* Zero any unwritten bytes at the end of the page */
size_t endoff = (pos + copied) & ~PAGE_MASK;
@ -1995,6 +1999,8 @@ static int fuse_write_end(struct file *file, struct address_space *mapping,
fuse_write_update_size(inode, pos + copied);
set_page_dirty(page);
unlock:
unlock_page(page);
put_page(page);