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>

1 files changed, 0 insertions, 17 deletions

diff --git a/fs/sync.c b/fs/sync.c
index f15537452231..e8ba024a055b 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -222,23 +222,6 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
         return do_fsync(fd, 1);
 }
 
-/**
- * generic_write_sync - perform syncing after a write if file / inode is sync
- * @file:       file to which the write happened
- * @pos:        offset where the write started
- * @count:      length of the write
- *
- * This is just a simple wrapper about our general syncing function.
- */
-int generic_write_sync(struct file *file, loff_t pos, loff_t count)
-{
-        if (!(file->f_flags & O_DSYNC) && !IS_SYNC(file->f_mapping->host))
-                return 0;
-        return vfs_fsync_range(file, pos, pos + count - 1,
-                               (file->f_flags & __O_SYNC) ? 0 : 1);
-}
-EXPORT_SYMBOL(generic_write_sync);
-
 /*
  * sys_sync_file_range() permits finely controlled syncing over a segment of
  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is