Commit dc59215d authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba

btrfs: remove unnecessary memory barrier in btrfs_direct_IO

Commit 38851cc1 ("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: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
[ enhance changelog ]
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent b5d9071c
...@@ -8815,7 +8815,6 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) ...@@ -8815,7 +8815,6 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
return 0; return 0;
inode_dio_begin(inode); inode_dio_begin(inode);
smp_mb__after_atomic();
/* /*
* The generic stuff only does filemap_write_and_wait_range, which * The generic stuff only does filemap_write_and_wait_range, which
......
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