xfs: refactor internal dfops initialization

The current transaction allocation code conditionally initializes
the ->t_dfops indirection pointer. Transaction commit/cancel check
the validity of the pointer to determine whether to finish/cancel
the internal dfops.

This disallows the ability to use the internal dfops list as a
temporary container (via xfs_trans_alloc_empty()). Refactor
transaction allocation to always initialize ->t_dfops and check
permanent reservation state on transaction commit/cancel.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 7bf5c12..12b6ad1 100644 (file)
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -281,13 +281,7 @@ xfs_trans_alloc(
        INIT_LIST_HEAD(&tp->t_items);
        INIT_LIST_HEAD(&tp->t_busy);
        tp->t_firstblock = NULLFSBLOCK;
-       /*
-        * We only roll transactions with permanent log reservation. Don't init
-        * ->t_dfops to skip attempts to finish or cancel an empty dfops with a
-        * non-permanent res.
-        */
-       if (resp->tr_logflags & XFS_TRANS_PERM_LOG_RES)
-               xfs_defer_init(tp, &tp->t_dfops_internal);
+       xfs_defer_init(tp, &tp->t_dfops_internal);
 
        error = xfs_trans_reserve(tp, resp, blocks, rtextents);
        if (error) {
@@ -931,8 +925,13 @@ __xfs_trans_commit(
 
        trace_xfs_trans_commit(tp, _RET_IP_);
 
-       /* finish deferred items on final commit */
-       if (!regrant && tp->t_dfops) {
+       /*
+        * Finish deferred items on final commit. Only permanent transactions
+        * should ever have deferred ops.
+        */
+       WARN_ON_ONCE(xfs_defer_has_unfinished_work(tp->t_dfops) &&
+                    !(tp->t_flags & XFS_TRANS_PERM_LOG_RES));
+       if (!regrant && (tp->t_flags & XFS_TRANS_PERM_LOG_RES)) {
                error = xfs_defer_finish_noroll(&tp);
                if (error) {
                        xfs_defer_cancel(tp);
@@ -1029,7 +1028,7 @@ xfs_trans_cancel(
 
        trace_xfs_trans_cancel(tp, _RET_IP_);
 
-       if (tp->t_dfops)
+       if (tp->t_flags & XFS_TRANS_PERM_LOG_RES)
                xfs_defer_cancel(tp);
 
        /*