btrfs-progs: check: add option to skip qgroup accounting verification

Qgroup accounting verification can be expensive because it walks extents
and backrefs to recompute referenced/exclusive numbers.

Add --skip-qgroup-accounting so btrfs check can still load qgroup
status/info/relation items from the quota tree without verifying the
accounting numbers.

Reject the option with --repair and --qgroup-report, as both depend on
full accounting verification results.

Signed-off-by: Dongjiang Zhu <zhudongjiang@fnnas.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>

Author: pdzhu

Documentation/btrfs-check.rst

@@ -58,6 +58,16 @@ SAFE OR ADVISORY OPTIONS
         This expects that the filesystem is otherwise OK, and is basically an offline
         *scrub* that does not repair data from spare copies.
 
+--skip-qgroup-accounting
+        skip verification of qgroup referenced/exclusive accounting.
+
+        Qgroup status, info and relation items are still loaded from the quota
+        tree. This option cannot be used with *--repair* or *--qgroup-report*.
+
+        This can significantly reduce runtime on filesystems with many snapshots
+        or reflinked files, as full qgroup accounting verification can require
+        extensive backref walks.
+
 --chunk-root <bytenr>
         use the given offset *bytenr* for the chunk tree root
 

check/main.c

@@ -86,6 +86,7 @@ bool no_holes = false;
 bool is_free_space_tree = false;
 bool init_extent_tree = false;
 bool check_data_csum = false;
+static bool check_qgroup_accounting = true;
 static bool found_free_ino_cache = false;
 static bool found_unknown_key = false;
 struct cache_tree *roots_info_cache = NULL;
@@ -217,7 +218,9 @@ static void print_status_check_line(void *p)
 		"[5/7] checking csums against data             " :
 		"[5/7] checking csums (without verifying data) ",
 		"[6/7] checking root refs                      ",
-		"[7/7] checking quota groups                   ",
+		check_qgroup_accounting ?
+		"[7/7] checking quota groups                   " :
+		"[7/7] checking qgroups (no accounting verify) ",
 	};
 	time_t elapsed;
 	int hours;
@@ -10597,6 +10600,7 @@ static const char * const cmd_check_usage[] = {
 	"",
 	"Check and reporting options:",
 	OPTLINE("--check-data-csum", "verify checksums of data blocks"),
+	OPTLINE("--skip-qgroup-accounting", "skip quota group accounting verification"),
 	OPTLINE("-Q, --qgroup-report", "print a report on qgroup consistency"),
 	OPTLINE("-E, --subvol-extents SUBVOLID", "print subvolume extents and sharing state"),
 	OPTLINE("-p, --progress", "indicate progress"),
@@ -10636,7 +10640,7 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 			GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
 			GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
 			GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE,
-			GETOPT_VAL_FORCE };
+			GETOPT_VAL_FORCE, GETOPT_VAL_SKIP_QGROUP_ACCOUNTING };
 		static const struct option long_options[] = {
 			{ "super", required_argument, NULL, 's' },
 			{ "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -10647,6 +10651,8 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 				GETOPT_VAL_INIT_EXTENT },
 			{ "check-data-csum", no_argument, NULL,
 				GETOPT_VAL_CHECK_CSUM },
+			{ "skip-qgroup-accounting", no_argument, NULL,
+				GETOPT_VAL_SKIP_QGROUP_ACCOUNTING },
 			{ "backup", no_argument, NULL, 'b' },
 			{ "subvol-extents", required_argument, NULL, 'E' },
 			{ "qgroup-report", no_argument, NULL, 'Q' },
@@ -10719,6 +10725,9 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 			case GETOPT_VAL_CHECK_CSUM:
 				check_data_csum = true;
 				break;
+			case GETOPT_VAL_SKIP_QGROUP_ACCOUNTING:
+				check_qgroup_accounting = false;
+				break;
 			case GETOPT_VAL_MODE:
 				check_mode = parse_check_mode(optarg);
 				if (check_mode == CHECK_MODE_UNKNOWN) {
@@ -10762,6 +10771,15 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 		exit(1);
 	}
 
+	if (!check_qgroup_accounting && opt_check_repair) {
+		error("--skip-qgroup-accounting is not compatible with --repair");
+		exit(1);
+	}
+	if (!check_qgroup_accounting && qgroup_report) {
+		error("--skip-qgroup-accounting is not compatible with --qgroup-report");
+		exit(1);
+	}
+
 	if (opt_check_repair && !force) {
 		int delay = 10;
 
@@ -10882,7 +10900,7 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 
 	if (qgroup_report) {
 		printf("Print quota groups report for %s\nUUID: %s\n", argv[optind], uuidbuf);
-		ret = qgroup_verify_all(gfs_info);
+		ret = qgroup_verify(gfs_info, true);
 		err |= !!ret;
 		if (ret >= 0)
 			report_qgroups(1);
@@ -11143,26 +11161,32 @@ static int cmd_check(const struct cmd_struct *cmd, int argc, char **argv)
 
 	if (gfs_info->quota_enabled) {
 		if (!g_task_ctx.progress_enabled) {
-			fprintf(stderr, "[8/8] checking quota groups\n");
+			if (check_qgroup_accounting)
+				fprintf(stderr, "[8/8] checking quota groups\n");
+			else
+				fprintf(stderr,
+			"[8/8] checking quota groups (without verifying accounting)\n");
 		} else {
 			g_task_ctx.tp = TASK_QGROUPS;
 			task_start(g_task_ctx.info, &g_task_ctx.start_time, &g_task_ctx.item_count);
 		}
-		qgroup_verify_ret = qgroup_verify_all(gfs_info);
+		qgroup_verify_ret = qgroup_verify(gfs_info, check_qgroup_accounting);
 		task_stop(g_task_ctx.info);
 		if (qgroup_verify_ret < 0) {
 			error("failed to check quota groups");
 			err |= !!qgroup_verify_ret;
 			goto out;
 		}
-		report_qgroups(0);
-		ret = repair_qgroups(gfs_info, &qgroups_repaired, false);
-		if (ret) {
-			error("failed to repair quota groups");
-			goto out;
+		if (check_qgroup_accounting) {
+			report_qgroups(0);
+			ret = repair_qgroups(gfs_info, &qgroups_repaired, false);
+			if (ret) {
+				error("failed to repair quota groups");
+				goto out;
+			}
+			if (qgroup_verify_ret && (!qgroups_repaired || ret))
+				err |= !!qgroup_verify_ret;
 		}
-		if (qgroup_verify_ret && (!qgroups_repaired || ret))
-			err |= !!qgroup_verify_ret;
 		ret = 0;
 	} else {
 		fprintf(stderr,

check/qgroup-verify.c

@@ -1451,13 +1451,16 @@ static bool is_bad_qgroup(struct qgroup_count *count)
 }
 
 /*
- * Verify all qgroup numbers.
+ * Load qgroup items and optionally verify qgroup numbers.
+ *
+ * @check_accounting true: verify referenced/exclusive accounting.
+ * @check_accounting false: only load qgroup status/info/relation items.
  *
  * Return <0 for fatal errors (e.g. ENOMEM or failed to read quota tree)
- * Return 0 if all qgroup numbers are correct or no need to check (under rescan)
- * Return >0 if qgroup numbers are inconsistent.
+ * Return 0 if requested checks pass or accounting mismatches are ignored.
+ * Return >0 if qgroup numbers are inconsistent and not ignored.
  */
-int qgroup_verify_all(struct btrfs_fs_info *info)
+int qgroup_verify(struct btrfs_fs_info *info, bool check_accounting)
 {
 	struct rb_node *n;
 	int ret;
@@ -1486,6 +1489,9 @@ int qgroup_verify_all(struct btrfs_fs_info *info)
 	    counts.rescan_running == 0)
 		skip_err = true;
 
+	if (!check_accounting)
+		goto out;
+
 	/*
 	 * Put all extent refs into our rbtree
 	 */

check/qgroup-verify.h

@@ -24,7 +24,7 @@
 
 struct btrfs_fs_info;
 
-int qgroup_verify_all(struct btrfs_fs_info *info);
+int qgroup_verify(struct btrfs_fs_info *info, bool check_accounting);
 void report_qgroups(int all);
 int repair_qgroups(struct btrfs_fs_info *info, int *repaired, bool silent);
 

mkfs/main.c

@@ -1046,7 +1046,7 @@ static int setup_quota_root(struct btrfs_fs_info *fs_info)
 	 * Qgroup is setup but with wrong info, use qgroup-verify
 	 * infrastructure to repair them.  (Just acts as offline rescan)
 	 */
-	ret = qgroup_verify_all(fs_info);
+	ret = qgroup_verify(fs_info, true);
 	if (ret < 0) {
 		errno = -ret;
 		error("qgroup rescan failed: %m");