Btrfs: avoid taking the trans_mutex in btrfs_end_transaction
I've been working on making our O_DIRECT latency not suck and I noticed we were
taking the trans_mutex in btrfs_end_transaction. So to do this we convert
num_writers and use_count to atomic_t's and just decrement them in
btrfs_end_transaction. Instead of deleting the transaction from the trans list
in put_transaction we do that in btrfs_commit_transaction() since that's the
only time it actually needs to be removed from the list. Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a272bfd..ef6865c 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3136,7 +3136,7 @@
btrfs_destroy_pinned_extent(root,
root->fs_info->pinned_extents);
- t->use_count = 0;
+ atomic_set(&t->use_count, 0);
list_del_init(&t->list);
memset(t, 0, sizeof(*t));
kmem_cache_free(btrfs_transaction_cachep, t);
