Commits
Nikolay Borisov committed dc59215d4f4
btrfs: remove unnecessary memory barrier in btrfs_direct_IO
Commit 38851cc19adb ("Btrfs: implement unlocked dio write") implemented
unlocked dio write, allowing multiple dio writers to write to
non-overlapping, and non-eof-extending regions. In doing so it also
introduced a broken memory barrier. It is broken due to 2 things:
1. Memory barriers _MUST_ always be paired, this is clearly not the case
here
2. Checkpatch actually produces a warning if a memory barrier is
introduced that doesn't have a comment explaining how it's being
paired.
Specifically for inode::i_dio_count that's wrapped inside
inode_dio_begin, there is no explicit barrier semantics attached, so
removing is fine as the atomic is used in common the waiter/wakeup
pattern.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ enhance changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>