4.8-stable review patch. If anyone has any objections, please let me know.
------------------
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
commit 59c3b76cc61d1d676f965c192cc7969aa5cb2744 upstream.
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@xxxxxxxxxxxxxxxxxx>
Fixes: 6b12c1b37e55 ("fuse: Implement write_begin/write_end callbacks")
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/fuse/file.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1985,6 +1985,10 @@ static int fuse_write_end(struct file *f
{
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 *f
fuse_write_update_size(inode, pos + copied);
set_page_dirty(page);
+
+unlock:
unlock_page(page);
put_page(page);
--
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