From 59c3b76cc61d1d676f965c192cc7969aa5cb2744 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 18 Aug 2016 09:10:44 +0200
Subject: [PATCH] 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: 6b12c1b37e55 ("fuse: Implement write_begin/write_end callbacks")
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/fuse/file.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index abc66a6237fd..2401c5dabb2a 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -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);