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. Signed-off-by: Nikolay Borisov <nbori...@suse.com> --- fs/btrfs/inode.c | 1 - 1 file changed, 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 95c212037095..5e48d2c10152 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8731,7 +8731,6 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) return 0; inode_dio_begin(inode); - smp_mb__after_atomic(); /* * The generic stuff only does filemap_write_and_wait_range, which -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html