The single-dev feature allows a device to be mounted regardless of
its fsid already being present in another device - in other words,
this feature disables RAID modes / metadata_uuid, allowing a single
device per filesystem. Its goal is mainly to allow mounting the
same fsid at the same time in the system.
Introduce hereby the feature to both mkfs (-O single-dev) and
btrfstune (--convert-to-single-device), syncing the kernel-shared
headers as well. The feature is a compat_ro, its kernel version was
set to v6.6.
Suggested-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
---
V3:
- Changed the small '-s' option on btrfstune to the
long version "--convert-to-single-device" (thanks Josef!).
- Moved the kernel version to v6.6.
common/fsfeatures.c | 7 ++++
kernel-shared/ctree.h | 3 +-
kernel-shared/uapi/btrfs.h | 7 ++++
mkfs/main.c | 4 +-
tune/main.c | 76 ++++++++++++++++++++++++--------------
5 files changed, 67 insertions(+), 30 deletions(-)
diff --git a/common/fsfeatures.c b/common/fsfeatures.c
index 00658fa5159f..8813de01d618 100644
--- a/common/fsfeatures.c
+++ b/common/fsfeatures.c
@@ -160,6 +160,13 @@ static const struct btrfs_feature mkfs_features[] = {
VERSION_NULL(default),
.desc = "RAID1 with 3 or 4 copies"
},
+ {
+ .name = "single-dev",
+ .compat_ro_flag = BTRFS_FEATURE_COMPAT_RO_SINGLE_DEV,
+ .sysfs_name = "single_dev",
+ VERSION_TO_STRING2(compat, 6,6),
+ .desc = "single device (allows same fsid mounting)"
+ },
#ifdef BTRFS_ZONED
{
.name = "zoned",
diff --git a/kernel-shared/ctree.h b/kernel-shared/ctree.h
index 59533879b939..e3fd834aa6dd 100644
--- a/kernel-shared/ctree.h
+++ b/kernel-shared/ctree.h
@@ -86,7 +86,8 @@ static inline u32 __BTRFS_LEAF_DATA_SIZE(u32 nodesize)
(BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE | \
BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID | \
BTRFS_FEATURE_COMPAT_RO_VERITY | \
- BTRFS_FEATURE_COMPAT_RO_BLOCK_GROUP_TREE)
+ BTRFS_FEATURE_COMPAT_RO_BLOCK_GROUP_TREE | \
+ BTRFS_FEATURE_COMPAT_RO_SINGLE_DEV)
#if EXPERIMENTAL
#define BTRFS_FEATURE_INCOMPAT_SUPP \
diff --git a/kernel-shared/uapi/btrfs.h b/kernel-shared/uapi/btrfs.h
index 85b04f89a2a9..2e0ee6ef6446 100644
--- a/kernel-shared/uapi/btrfs.h
+++ b/kernel-shared/uapi/btrfs.h
@@ -336,6 +336,13 @@ _static_assert(sizeof(struct btrfs_ioctl_fs_info_args) == 1024);
*/
#define BTRFS_FEATURE_COMPAT_RO_BLOCK_GROUP_TREE (1ULL << 3)
+/*
+ * Single devices (as flagged by the corresponding compat_ro flag) only
+ * gets scanned during mount time; also, a random fsid is generated for
+ * them, in order to cope with same-fsid filesystem mounts.
+ */
+#define BTRFS_FEATURE_COMPAT_RO_SINGLE_DEV (1ULL << 4)
+
#define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF (1ULL << 0)
#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL (1ULL << 1)
#define BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS (1ULL << 2)
diff --git a/mkfs/main.c b/mkfs/main.c
index 972ed1112ea6..429799932224 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -1025,6 +1025,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
char *label = NULL;
int nr_global_roots = sysconf(_SC_NPROCESSORS_ONLN);
char *source_dir = NULL;
+ bool single_dev;
cpu_detect_flags();
hash_init_accel();
@@ -1218,6 +1219,7 @@ int BOX_MAIN(mkfs)(int argc, char **argv)
usage(&mkfs_cmd, 1);
opt_zoned = !!(features.incompat_flags & BTRFS_FEATURE_INCOMPAT_ZONED);
+ single_dev = !!(features.compat_ro_flags & BTRFS_FEATURE_COMPAT_RO_SINGLE_DEV);
if (source_dir && device_count > 1) {
error("the option -r is limited to a single device");
@@ -1815,7 +1817,7 @@ out:
device_count = argc - optind;
while (device_count-- > 0) {
file = argv[optind++];
- if (path_is_block_device(file) == 1)
+ if (path_is_block_device(file) == 1 && !single_dev)
btrfs_register_one_device(file);
}
}
diff --git a/tune/main.c b/tune/main.c
index 0ca1e01282c9..7b8706274fcc 100644
--- a/tune/main.c
+++ b/tune/main.c
@@ -42,27 +42,31 @@
#include "tune/tune.h"
#include "check/clear-cache.h"
+#define SET_SUPER_FLAGS(type) \
+static int set_super_##type##_flags(struct btrfs_root *root, u64 flags) \
+{ \
+ struct btrfs_trans_handle *trans; \
+ struct btrfs_super_block *disk_super; \
+ u64 super_flags; \
+ int ret; \
+ \
+ disk_super = root->fs_info->super_copy; \
+ super_flags = btrfs_super_##type##_flags(disk_super); \
+ super_flags |= flags; \
+ trans = btrfs_start_transaction(root, 1); \
+ BUG_ON(IS_ERR(trans)); \
+ btrfs_set_super_##type##_flags(disk_super, super_flags); \
+ ret = btrfs_commit_transaction(trans, root); \
+ \
+ return ret; \
+}
+
+SET_SUPER_FLAGS(incompat)
+SET_SUPER_FLAGS(compat_ro)
+
static char *device;
static int force = 0;
-static int set_super_incompat_flags(struct btrfs_root *root, u64 flags)
-{
- struct btrfs_trans_handle *trans;
- struct btrfs_super_block *disk_super;
- u64 super_flags;
- int ret;
-
- disk_super = root->fs_info->super_copy;
- super_flags = btrfs_super_incompat_flags(disk_super);
- super_flags |= flags;
- trans = btrfs_start_transaction(root, 1);
- BUG_ON(IS_ERR(trans));
- btrfs_set_super_incompat_flags(disk_super, super_flags);
- ret = btrfs_commit_transaction(trans, root);
-
- return ret;
-}
-
static int convert_to_fst(struct btrfs_fs_info *fs_info)
{
int ret;
@@ -108,6 +112,8 @@ static const char * const tune_usage[] = {
OPTLINE("--convert-from-block-group-tree",
"convert the block group tree back to extent tree (remove the incompat bit)"),
OPTLINE("--convert-to-free-space-tree", "convert filesystem to use free space tree (v2 cache)"),
+ OPTLINE("--convert-to-single-device", "enable the single device feature "
+ "(mkfs: single-dev, allows same fsid mounting)"),
"",
"UUID changes:",
OPTLINE("-u", "rewrite fsid, use a random one"),
@@ -146,7 +152,8 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
int csum_type = -1;
char *new_fsid_str = NULL;
int ret;
- u64 super_flags = 0;
+ u64 compat_ro_flags = 0;
+ u64 incompat_flags = 0;
int fd = -1;
btrfs_config_init();
@@ -155,7 +162,8 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
enum { GETOPT_VAL_CSUM = GETOPT_VAL_FIRST,
GETOPT_VAL_ENABLE_BLOCK_GROUP_TREE,
GETOPT_VAL_DISABLE_BLOCK_GROUP_TREE,
- GETOPT_VAL_ENABLE_FREE_SPACE_TREE };
+ GETOPT_VAL_ENABLE_FREE_SPACE_TREE,
+ GETOPT_VAL_SINGLE_DEV };
static const struct option long_options[] = {
{ "help", no_argument, NULL, GETOPT_VAL_HELP},
{ "convert-to-block-group-tree", no_argument, NULL,
@@ -164,6 +172,8 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
GETOPT_VAL_DISABLE_BLOCK_GROUP_TREE},
{ "convert-to-free-space-tree", no_argument, NULL,
GETOPT_VAL_ENABLE_FREE_SPACE_TREE},
+ { "convert-to-single-device", no_argument, NULL,
+ GETOPT_VAL_SINGLE_DEV},
#if EXPERIMENTAL
{ "csum", required_argument, NULL, GETOPT_VAL_CSUM },
#endif
@@ -179,13 +189,13 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
seeding_value = arg_strtou64(optarg);
break;
case 'r':
- super_flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
+ incompat_flags |= BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF;
break;
case 'x':
- super_flags |= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA;
+ incompat_flags |= BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA;
break;
case 'n':
- super_flags |= BTRFS_FEATURE_INCOMPAT_NO_HOLES;
+ incompat_flags |= BTRFS_FEATURE_INCOMPAT_NO_HOLES;
break;
case 'f':
force = 1;
@@ -216,6 +226,9 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
case GETOPT_VAL_ENABLE_FREE_SPACE_TREE:
to_fst = true;
break;
+ case GETOPT_VAL_SINGLE_DEV:
+ compat_ro_flags |= BTRFS_FEATURE_COMPAT_RO_SINGLE_DEV;
+ break;
#if EXPERIMENTAL
case GETOPT_VAL_CSUM:
btrfs_warn_experimental(
@@ -239,9 +252,9 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
error("random fsid can't be used with specified fsid");
return 1;
}
- if (!super_flags && !seeding_flag && !(random_fsid || new_fsid_str) &&
- !change_metadata_uuid && csum_type == -1 && !to_bg_tree &&
- !to_extent_tree && !to_fst) {
+ if (!compat_ro_flags && !incompat_flags && !seeding_flag &&
+ !(random_fsid || new_fsid_str) && !change_metadata_uuid &&
+ csum_type == -1 && !to_bg_tree && !to_extent_tree && !to_fst) {
error("at least one option should be specified");
usage(&tune_cmd, 1);
return 1;
@@ -363,8 +376,15 @@ int BOX_MAIN(btrfstune)(int argc, char *argv[])
total++;
}
- if (super_flags) {
- ret = set_super_incompat_flags(root, super_flags);
+ if (incompat_flags) {
+ ret = set_super_incompat_flags(root, incompat_flags);
+ if (!ret)
+ success++;
+ total++;
+ }
+
+ if (compat_ro_flags) {
+ ret = set_super_compat_ro_flags(root, compat_ro_flags);
if (!ret)
success++;
total++;
