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

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: 65dd2d6 ("afs: Alter dirty range encoding in page->private") Signed-off-by: David Howells <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
dabrace · Nov 14, 2020 · 3ad216e · 3ad216e
1 parent f01c30d
commit 3ad216e
Showing 1 changed file with 4 additions and 1 deletion.
diff --git 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);