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/transaction.h b/fs/btrfs/transaction.h
index 229a594..e441acc 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -27,11 +27,11 @@
* total writers in this transaction, it must be zero before the
* transaction can end
*/
- unsigned long num_writers;
+ atomic_t num_writers;
unsigned long num_joined;
int in_commit;
- int use_count;
+ atomic_t use_count;
int commit_done;
int blocked;
struct list_head list;