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Subject[PATCH] btrfs: optimize barrier usage for Rmw atomics
Date
Use smp_mb__after_atomic() instead of smp_mb() and avoid the
unnecessary barrier for non LL/SC architectures, such as x86.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
fs/btrfs/btrfs_inode.h | 2 +-
fs/btrfs/file.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 4e12a477d32e..54e0d2ae22cc 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -325,7 +325,7 @@ struct btrfs_dio_private {
static inline void btrfs_inode_block_unlocked_dio(struct btrfs_inode *inode)
{
set_bit(BTRFS_INODE_READDIO_NEED_LOCK, &inode->runtime_flags);
- smp_mb();
+ smp_mb__after_atomic();
}

static inline void btrfs_inode_resume_unlocked_dio(struct btrfs_inode *inode)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index a16da274c9aa..ea79ab068079 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2143,7 +2143,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
}
atomic_inc(&root->log_batch);

- smp_mb();
+ smp_mb__after_atomic();
if (btrfs_inode_in_log(BTRFS_I(inode), fs_info->generation) ||
BTRFS_I(inode)->last_trans <= fs_info->last_trans_committed) {
/*
--
2.16.4
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