afs: Fix afs_write_end() when called with copied == 0 [ver #3]

3ad216ee · David Howells <[email protected]> · 2020-11-14 17:27:57 +00:00

When afs_write_end() is called with copied == 0, it tries to set the
dirty region, but there's no way to actually encode a 0-length region in
the encoding in page->private.

"0,0", for example, indicates a 1-byte region at offset 0.  The maths
miscalculates this and sets it incorrectly.

Fix it to just do nothing but unlock and put the page in this case.  We
don't actually need to mark the page dirty as nothing presumably
changed.

Fixes: 65dd2d6072d3 ("afs: Alter dirty range encoding in page->private")
Signed-off-by: David Howells <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 3ad216ee73abc554ed8f13f4f8b70845a7bef6da
Parents: f01c30de

Changes

1 files changed · +4 −1

File	Status	Add	Del	Content
fs/afs/write.c	modified	+4	−1	View file

fs/afs/write.c

View file

diff --git a/fs/afs/write.c b/fs/afs/write.c
index 5037120..c9195fc 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -169,11 +169,14 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 	unsigned int f, from = pos & (PAGE_SIZE - 1);
 	unsigned int t, to = from + copied;
 	loff_t i_size, maybe_i_size;
-	int ret;
+	int ret = 0;
 
 	_enter("{%llx:%llu},{%lx}",
 	       vnode->fid.vid, vnode->fid.vnode, page->index);
 
+	if (copied == 0)
+		goto out;
+
 	maybe_i_size = pos + copied;
 
 	i_size = i_size_read(&vnode->vfs_inode);