Merge tag 'defer-elide-create-done-6.8_2023-12-06' of...

Merge tag 'defer-elide-create-done-6.8_2023-12-06' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.8-mergeA

xfs: elide defer work ->create_done if no intent

Christoph pointed out that the defer ops machinery doesn't need to call
->create_done if the deferred work item didn't generate a log intent
item in the first place.  Let's clean that up and save an indirect call
in the non-logged xattr update call path.

This has been lightly tested with fstests.  Enjoy!
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

* tag 'defer-elide-create-done-6.8_2023-12-06' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: elide ->create_done calls for unlogged deferred work
  xfs: document what LARP means

fs/xfs/libxfs/xfs_defer.c

@@ -201,6 +201,10 @@ xfs_defer_create_done(
 	const struct xfs_defer_op_type	*ops = defer_op_types[dfp->dfp_type];
 	struct xfs_log_item		*lip;
 
+	/* If there is no log intent item, there can be no log done item. */
+	if (!dfp->dfp_intent)
+		return;
+
 	/*
 	 * Mark the transaction dirty, even on error. This ensures the
 	 * transaction is aborted, which:

fs/xfs/xfs_attr_item.c

@@ -740,9 +740,6 @@ xfs_attr_create_done(
 	struct xfs_attri_log_item	*attrip;
 	struct xfs_attrd_log_item	*attrdp;
 
-	if (!intent)
-		return NULL;
-
 	attrip = ATTRI_ITEM(intent);
 
 	attrdp = kmem_cache_zalloc(xfs_attrd_cache, GFP_NOFS | __GFP_NOFAIL);

fs/xfs/xfs_sysfs.c

@@ -229,6 +229,15 @@ pwork_threads_show(
 }
 XFS_SYSFS_ATTR_RW(pwork_threads);
 
+/*
+ * The "LARP" (Logged extended Attribute Recovery Persistence) debugging knob
+ * sets the XFS_DA_OP_LOGGED flag on all xfs_attr_set operations performed on
+ * V5 filesystems.  As a result, the intermediate progress of all setxattr and
+ * removexattr operations are tracked via the log and can be restarted during
+ * recovery.  This is useful for testing xattr recovery prior to merging of the
+ * parent pointer feature which requires it to maintain consistency, and may be
+ * enabled for userspace xattrs in the future.
+ */
 static ssize_t
 larp_store(
 	struct kobject	*kobject,