btrfs: introduce new "rescue=ignoresuperflags" mount option

This new mount option allows the kernel to skip the super flags check,
it's mostly to allow the kernel to do a rescue mount of an interrupted
checksum conversion.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -2345,15 +2345,23 @@ int btrfs_validate_super(const struct btrfs_fs_info *fs_info,
 	u64 nodesize = btrfs_super_nodesize(sb);
 	u64 sectorsize = btrfs_super_sectorsize(sb);
 	int ret = 0;
+	const bool ignore_flags = btrfs_test_opt(fs_info, IGNORESUPERFLAGS);
 
 	if (btrfs_super_magic(sb) != BTRFS_MAGIC) {
 		btrfs_err(fs_info, "no valid FS found");
 		ret = -EINVAL;
 	}
-	if (btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP) {
+	if ((btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP)) {
-		btrfs_err(fs_info, "unrecognized or unsupported super flag: 0x%llx",
+		if (!ignore_flags) {
-				btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
+			btrfs_err(fs_info,
-		ret = -EINVAL;
+			"unrecognized or unsupported super flag 0x%llx",
+				  btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
+			ret = -EINVAL;
+		} else {
+			btrfs_info(fs_info,
+			"unrecognized or unsupported super flags: 0x%llx, ignored",
+				   btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
+		}
 	}
 	if (btrfs_super_root_level(sb) >= BTRFS_MAX_LEVEL) {
 		btrfs_err(fs_info, "tree_root level too big: %d >= %d",

fs/btrfs/fs.h

@@ -227,6 +227,7 @@ enum {
 	BTRFS_MOUNT_NODISCARD			= (1UL << 29),
 	BTRFS_MOUNT_NOSPACECACHE		= (1UL << 30),
 	BTRFS_MOUNT_IGNOREMETACSUMS		= (1UL << 31),
+	BTRFS_MOUNT_IGNORESUPERFLAGS		= (1ULL << 32),
 };
 
 /*

fs/btrfs/super.c

@@ -177,6 +177,7 @@ enum {
 	Opt_rescue_ignorebadroots,
 	Opt_rescue_ignoredatacsums,
 	Opt_rescue_ignoremetacsums,
+	Opt_rescue_ignoresuperflags,
 	Opt_rescue_parameter_all,
 };
 
@@ -187,8 +188,10 @@ static const struct constant_table btrfs_parameter_rescue[] = {
 	{ "ibadroots", Opt_rescue_ignorebadroots },
 	{ "ignoredatacsums", Opt_rescue_ignoredatacsums },
 	{ "ignoremetacsums", Opt_rescue_ignoremetacsums},
+	{ "ignoresuperflags", Opt_rescue_ignoresuperflags},
 	{ "idatacsums", Opt_rescue_ignoredatacsums },
 	{ "imetacsums", Opt_rescue_ignoremetacsums},
+	{ "isuperflags", Opt_rescue_ignoresuperflags},
 	{ "all", Opt_rescue_parameter_all },
 	{}
 };
@@ -577,9 +580,13 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		case Opt_rescue_ignoremetacsums:
 			btrfs_set_opt(ctx->mount_opt, IGNOREMETACSUMS);
 			break;
+		case Opt_rescue_ignoresuperflags:
+			btrfs_set_opt(ctx->mount_opt, IGNORESUPERFLAGS);
+			break;
 		case Opt_rescue_parameter_all:
 			btrfs_set_opt(ctx->mount_opt, IGNOREDATACSUMS);
 			btrfs_set_opt(ctx->mount_opt, IGNOREMETACSUMS);
+			btrfs_set_opt(ctx->mount_opt, IGNORESUPERFLAGS);
 			btrfs_set_opt(ctx->mount_opt, IGNOREBADROOTS);
 			btrfs_set_opt(ctx->mount_opt, NOLOGREPLAY);
 			break;
@@ -655,7 +662,8 @@ bool btrfs_check_options(const struct btrfs_fs_info *info, unsigned long *mount_
 	    (check_ro_option(info, *mount_opt, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay") ||
 	     check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREBADROOTS, "ignorebadroots") ||
 	     check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREDATACSUMS, "ignoredatacsums") ||
-	     check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREMETACSUMS, "ignoremetacsums")))
+	     check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNOREMETACSUMS, "ignoremetacsums") ||
+	     check_ro_option(info, *mount_opt, BTRFS_MOUNT_IGNORESUPERFLAGS, "ignoresuperflags")))
 		ret = false;
 
 	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
@@ -1073,6 +1081,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		print_rescue_option(seq, "ignoredatacsums", &printed);
 	if (btrfs_test_opt(info, IGNOREMETACSUMS))
 		print_rescue_option(seq, "ignoremetacsums", &printed);
+	if (btrfs_test_opt(info, IGNORESUPERFLAGS))
+		print_rescue_option(seq, "ignoresuperflags", &printed);
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
@@ -1431,6 +1441,7 @@ static void btrfs_emit_options(struct btrfs_fs_info *info,
 	btrfs_info_if_set(info, old, IGNOREBADROOTS, "ignoring bad roots");
 	btrfs_info_if_set(info, old, IGNOREDATACSUMS, "ignoring data csums");
 	btrfs_info_if_set(info, old, IGNOREMETACSUMS, "ignoring meta csums");
+	btrfs_info_if_set(info, old, IGNORESUPERFLAGS, "ignoring unknown super block flags");
 
 	btrfs_info_if_unset(info, old, NODATACOW, "setting datacow");
 	btrfs_info_if_unset(info, old, SSD, "not using ssd optimizations");

fs/btrfs/sysfs.c

@@ -386,6 +386,7 @@ static const char *rescue_opts[] = {
 	"ignorebadroots",
 	"ignoredatacsums",
 	"ignoremetacsums",
+	"ignoresuperflags",
 	"all",
 };