[PATCH RFC] btrfs: change commit txn to end txn in subvol_setflags ioctl

[Boris Burkov <boris@bur.io>]

Currently, btrfs_ioctl_subvol_setflags forces a btrfs_commit_transaction
while holding subvol_sem. As a result, we have seen workloads where
calling `btrfs property set -ts <subvol> ro false` hangs waiting for a
legitimately slow commit. This gets even worse if the workload tries to
set flags on multiple subvolumes and the ioctls pile up on subvol_sem.

Change the commit to a btrfs_end_transaction so that the ioctl can
return in a timely fashion and piggy back on a later commit.

Signed-off-by: Boris Burkov <boris@bur.io>
---
 fs/btrfs/ioctl.c       | 2 +-
 fs/btrfs/transaction.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index bd3511c5ca81..3ae484768ce7 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1985,7 +1985,7 @@ static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
 		goto out_reset;
 	}
 
-	ret = btrfs_commit_transaction(trans);
+	ret = btrfs_end_transaction(trans);
 
 out_reset:
 	if (ret)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 20c6ac1a5de7..1dc44209c2ae 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -47,7 +47,7 @@
  * | Will wait for previous running transaction to completely finish if there
  * | is one
  * |
- * | Then one of the following happes:
+ * | Then one of the following happens:
  * | - Wait for all other trans handle holders to release.
  * |   The btrfs_commit_transaction() caller will do the commit work.
  * | - Wait for current transaction to be committed by others.
@@ -60,7 +60,7 @@
  * |
  * | To next stage:
  * |  Caller is chosen to commit transaction N, and all other trans handle
- * |  haven been released.
+ * |  have been released.
  * V
  * Transaction N [[TRANS_STATE_COMMIT_DOING]]
  * |
-- 
2.24.1