Btrfs: hash_lock is no longer needed

Before metadata is written to disk, it is updated to reflect that writeout
has begun.  Once this update is done, the block must be cow'd before it
can be modified again.

This update was originally synchronized by using a per-fs spinlock.  Today
the buffers for the metadata blocks are locked before writeout begins,
and everyone that tests the flag has the buffer locked as well.

So, the per-fs spinlock (called hash_lock for no good reason) is no
longer required.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index de103a8a815e..f2b8d26b0472 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -703,7 +703,6 @@ struct btrfs_fs_info {
         struct super_block *sb;
         struct inode *btree_inode;
         struct backing_dev_info bdi;
-        spinlock_t hash_lock;
         struct mutex trans_mutex;
         struct mutex tree_log_mutex;
         struct mutex transaction_kthread_mutex;