[PATCH RFC 2/3] xfs: temporary transaction subsystem freeze hack

[Brian Foster <bfoster@redhat.com>]

Implement a quick hack to abuse the superblock freeze mechanism to
freeze the XFS transaction subsystem.

XXX: to be replaced

Not-Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/xfs_trans.c | 16 ++++++++++++++++
 fs/xfs/xfs_trans.h |  2 ++
 2 files changed, 18 insertions(+)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index ca18a040336a..5cb9cb44e963 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -1024,3 +1024,19 @@ xfs_trans_roll(
 	tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
 	return xfs_trans_reserve(*tpp, &tres, 0, 0);
 }
+
+void
+xfs_trans_freeze(
+	struct xfs_mount	*mp)
+{
+	struct super_block	*sb = mp->m_super;
+	percpu_down_write(sb->s_writers.rw_sem + SB_FREEZE_WRITE-1);
+}
+
+void
+xfs_trans_unfreeze(
+	struct xfs_mount	*mp)
+{
+	struct super_block	*sb = mp->m_super;
+	percpu_up_write(sb->s_writers.rw_sem + SB_FREEZE_WRITE-1);
+}
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index f46534b75236..ec1d5a5c2610 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -233,6 +233,8 @@ int		xfs_trans_commit(struct xfs_trans *);
 int		xfs_trans_roll(struct xfs_trans **);
 int		xfs_trans_roll_inode(struct xfs_trans **, struct xfs_inode *);
 void		xfs_trans_cancel(xfs_trans_t *);
+void		xfs_trans_freeze(struct xfs_mount *);
+void		xfs_trans_unfreeze(struct xfs_mount *);
 int		xfs_trans_ail_init(struct xfs_mount *);
 void		xfs_trans_ail_destroy(struct xfs_mount *);
 
-- 
2.25.4