xfs: formalize the process of holding onto resources across a defer roll

Transaction users are allowed to flag up to two buffers and two inodes
for ownership preservation across a deferred transaction roll.  Hoist
the variables and code responsible for this out of xfs_defer_trans_roll
so that we can use it for the defer capture mechanism.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_defer.h b/fs/xfs/libxfs/xfs_defer.h
index 05472f71fffe..e095abb96f1a 100644
--- a/fs/xfs/libxfs/xfs_defer.h
+++ b/fs/xfs/libxfs/xfs_defer.h
@@ -65,6 +65,30 @@ extern const struct xfs_defer_op_type xfs_extent_free_defer_type;
 extern const struct xfs_defer_op_type xfs_agfl_free_defer_type;
 
 /*
+ * Deferred operation item relogging limits.
+ */
+#define XFS_DEFER_OPS_NR_INODES	2	/* join up to two inodes */
+#define XFS_DEFER_OPS_NR_BUFS	2	/* join up to two buffers */
+
+/* Resources that must be held across a transaction roll. */
+struct xfs_defer_resources {
+	/* held buffers */
+	struct xfs_buf		*dr_bp[XFS_DEFER_OPS_NR_BUFS];
+
+	/* inodes with no unlock flags */
+	struct xfs_inode	*dr_ip[XFS_DEFER_OPS_NR_INODES];
+
+	/* number of held buffers */
+	unsigned short		dr_bufs;
+
+	/* bitmap of ordered buffers */
+	unsigned short		dr_ordered;
+
+	/* number of held inodes */
+	unsigned short		dr_inos;
+};
+
+/*
  * This structure enables a dfops user to detach the chain of deferred
  * operations from a transaction so that they can be continued later.
  */