fix O_SYNC|O_APPEND syncing the wrong range on write()
It actually goes back to 2004 ([PATCH] Concurrent O_SYNC write support)
when sync_page_range() had been introduced; generic_file_write{,v}() correctly
synced
pos_after_write - written .. pos_after_write - 1
but generic_file_aio_write() synced
pos_before_write .. pos_before_write + written - 1
instead. Which is not the same thing with O_APPEND, obviously.
A couple of years later correct variant had been killed off when
everything switched to use of generic_file_aio_write().
All users of generic_file_aio_write() are affected, and the same bug
has been copied into other instances of ->aio_write().
The fix is trivial; the only subtle point is that generic_write_sync()
ought to be inlined to avoid calculations useless for the majority of
calls.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 853d6d1..a7eda8e 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2559,8 +2559,8 @@
if (rc > 0) {
ssize_t err;
- err = generic_write_sync(file, pos, rc);
- if (err < 0 && rc > 0)
+ err = generic_write_sync(file, iocb->ki_pos - rc, rc);
+ if (err < 0)
rc = err;
}