md: check level before create and exit io_acct_set

The bio_set (io_acct_set) is used by personalities to clone bio and
trace the timestamp of bio. Some personalities such as raid1/10 don't
need the bio_set, so add check to not create it unconditionally.

Also update the comment for md_account_bio to make it more clear.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Signed-off-by: Song Liu <song@kernel.org>

drivers/md/md.c

@@ -2341,7 +2341,8 @@ int md_integrity_register(struct mddev *mddev)
 
 	pr_debug("md: data integrity enabled on %s\n", mdname(mddev));
 	if (bioset_integrity_create(&mddev->bio_set, BIO_POOL_SIZE) ||
-	    bioset_integrity_create(&mddev->io_acct_set, BIO_POOL_SIZE)) {
+	    (mddev->level != 1 && mddev->level != 10 &&
+	     bioset_integrity_create(&mddev->io_acct_set, BIO_POOL_SIZE))) {
 		pr_err("md: failed to create integrity pool for %s\n",
 		       mdname(mddev));
 		return -EINVAL;
@@ -5570,7 +5571,8 @@ static void md_free(struct kobject *ko)
 
 	bioset_exit(&mddev->bio_set);
 	bioset_exit(&mddev->sync_set);
-	bioset_exit(&mddev->io_acct_set);
+	if (mddev->level != 1 && mddev->level != 10)
+		bioset_exit(&mddev->io_acct_set);
 	kfree(mddev);
 }
 
@@ -5866,7 +5868,8 @@ int md_run(struct mddev *mddev)
 		if (err)
 			goto exit_bio_set;
 	}
-	if (!bioset_initialized(&mddev->io_acct_set)) {
+	if (mddev->level != 1 && mddev->level != 10 &&
+	    !bioset_initialized(&mddev->io_acct_set)) {
 		err = bioset_init(&mddev->io_acct_set, BIO_POOL_SIZE,
 				  offsetof(struct md_io_acct, bio_clone), 0);
 		if (err)
@@ -6048,7 +6051,8 @@ int md_run(struct mddev *mddev)
 	module_put(pers->owner);
 	md_bitmap_destroy(mddev);
 abort:
-	bioset_exit(&mddev->io_acct_set);
+	if (mddev->level != 1 && mddev->level != 10)
+		bioset_exit(&mddev->io_acct_set);
 exit_sync_set:
 	bioset_exit(&mddev->sync_set);
 exit_bio_set:
@@ -6276,7 +6280,8 @@ void md_stop(struct mddev *mddev)
 	__md_stop(mddev);
 	bioset_exit(&mddev->bio_set);
 	bioset_exit(&mddev->sync_set);
-	bioset_exit(&mddev->io_acct_set);
+	if (mddev->level != 1 && mddev->level != 10)
+		bioset_exit(&mddev->io_acct_set);
 }
 
 EXPORT_SYMBOL_GPL(md_stop);
@@ -8593,7 +8598,10 @@ static void md_end_io_acct(struct bio *bio)
 	bio_endio(orig_bio);
 }
 
-/* used by personalities (raid0 and raid5) to account io stats */
+/*
+ * Used by personalities that don't already clone the bio and thus can't
+ * easily add the timestamp to their extended bio structure.
+ */
 void md_account_bio(struct mddev *mddev, struct bio **bio)
 {
 	struct md_io_acct *md_io_acct;