From: Theodore Ts'o via B4 Relay <devnull+tytso.mit.edu@kernel.org>
To: tytso@mit.edu
Cc: linux-ext4@vger.kernel.org, linux-api@vger.kernel.org
Subject: [PATCH 3/3] ext4: implemet new ioctls to set and get superblock parameters
Date: Mon, 08 Sep 2025 23:15:50 -0400 [thread overview]
Message-ID: <20250908-tune2fs-v1-3-e3a6929f3355@mit.edu> (raw)
In-Reply-To: <20250908-tune2fs-v1-0-e3a6929f3355@mit.edu>
From: Theodore Ts'o <tytso@mit.edu>
Implement the EXT4_IOC_GET_TUNE_SB_PARAM and
EXT4_IOC_SET_TUNE_SB_PARAM ioctls, which allow certains superblock
parameters to be set while the file system is mounted, without needing
write access to the block device.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
fs/ext4/ioctl.c | 256 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
include/uapi/linux/ext4.h | 75 ++++++++++++++++++++++
2 files changed, 324 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 84e3c73952d72e436429489f5fc8b7ae1c01c7a1..569c98c962af63130c0119f60788a26a2807bd86 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -27,14 +27,16 @@
#include "fsmap.h"
#include <trace/events/ext4.h>
-typedef void ext4_update_sb_callback(struct ext4_super_block *es,
- const void *arg);
+typedef void ext4_update_sb_callback(struct ext4_sb_info *sbi,
+ struct ext4_super_block *es,
+ const void *arg);
/*
* Superblock modification callback function for changing file system
* label
*/
-static void ext4_sb_setlabel(struct ext4_super_block *es, const void *arg)
+static void ext4_sb_setlabel(struct ext4_sb_info *sbi,
+ struct ext4_super_block *es, const void *arg)
{
/* Sanity check, this should never happen */
BUILD_BUG_ON(sizeof(es->s_volume_name) < EXT4_LABEL_MAX);
@@ -46,7 +48,8 @@ static void ext4_sb_setlabel(struct ext4_super_block *es, const void *arg)
* Superblock modification callback function for changing file system
* UUID.
*/
-static void ext4_sb_setuuid(struct ext4_super_block *es, const void *arg)
+static void ext4_sb_setuuid(struct ext4_sb_info *sbi,
+ struct ext4_super_block *es, const void *arg)
{
memcpy(es->s_uuid, (__u8 *)arg, UUID_SIZE);
}
@@ -71,7 +74,7 @@ int ext4_update_primary_sb(struct super_block *sb, handle_t *handle,
goto out_err;
lock_buffer(bh);
- func(es, arg);
+ func(sbi, es, arg);
ext4_superblock_csum_set(sb);
unlock_buffer(bh);
@@ -149,7 +152,7 @@ static int ext4_update_backup_sb(struct super_block *sb,
unlock_buffer(bh);
goto out_bh;
}
- func(es, arg);
+ func(EXT4_SB(sb), es, arg);
if (ext4_has_feature_metadata_csum(sb))
es->s_checksum = ext4_superblock_csum(es);
set_buffer_uptodate(bh);
@@ -1230,6 +1233,239 @@ static int ext4_ioctl_setuuid(struct file *filp,
return ret;
}
+
+#define TUNE_OPS_SUPPORTED (EXT4_TUNE_FL_ERRORS_BEHAVIOR | \
+ EXT4_TUNE_FL_MNT_COUNT | EXT4_TUNE_FL_MAX_MNT_COUNT | \
+ EXT4_TUNE_FL_CHECKINTRVAL | EXT4_TUNE_FL_LAST_CHECK_TIME | \
+ EXT4_TUNE_FL_RESERVED_BLOCKS | EXT4_TUNE_FL_RESERVED_UID | \
+ EXT4_TUNE_FL_RESERVED_GID | EXT4_TUNE_FL_DEFAULT_MNT_OPTS | \
+ EXT4_TUNE_FL_DEF_HASH_ALG | EXT4_TUNE_FL_RAID_STRIDE | \
+ EXT4_TUNE_FL_RAID_STRIPE_WIDTH | EXT4_TUNE_FL_MOUNT_OPTS | \
+ EXT4_TUNE_FL_FEATURES | EXT4_TUNE_FL_EDIT_FEATURES | \
+ EXT4_TUNE_FL_FORCE_FSCK)
+
+static int ext4_ioctl_get_tune_sb(struct ext4_sb_info *sbi,
+ struct ext4_tune_sb_params __user *params)
+{
+ struct ext4_tune_sb_params ret;
+ struct ext4_super_block *es = sbi->s_es;
+
+ memset(&ret, 0, sizeof(ret));
+ ret.set_flags = TUNE_OPS_SUPPORTED;
+ ret.errors_behavior = es->s_errors;
+ ret.mnt_count = le16_to_cpu(es->s_mnt_count);
+ ret.max_mnt_count = le16_to_cpu(es->s_max_mnt_count);
+ ret.checkinterval = le32_to_cpu(es->s_checkinterval);
+ ret.last_check_time = le32_to_cpu(es->s_lastcheck);
+ ret.reserved_blocks = ext4_r_blocks_count(es);
+ ret.blocks_count = ext4_blocks_count(es);
+ ret.reserved_uid = ext4_get_resuid(es);
+ ret.reserved_gid = ext4_get_resgid(es);
+ ret.default_mnt_opts = le32_to_cpu(es->s_default_mount_opts);
+ ret.def_hash_alg = es->s_def_hash_version;
+ ret.raid_stride = le16_to_cpu(es->s_raid_stride);
+ ret.raid_stripe_width = le16_to_cpu(es->s_raid_stripe_width);
+ strscpy_pad(ret.mount_opts, es->s_mount_opts);
+ ret.feature_compat = le32_to_cpu(es->s_feature_compat);
+ ret.feature_incompat = le32_to_cpu(es->s_feature_incompat);
+ ret.feature_ro_compat = le32_to_cpu(es->s_feature_ro_compat);
+ ret.set_feature_compat_mask = EXT4_TUNE_SET_COMPAT_SUPP;
+ ret.set_feature_incompat_mask = EXT4_TUNE_SET_INCOMPAT_SUPP;
+ ret.set_feature_ro_compat_mask = EXT4_TUNE_SET_RO_COMPAT_SUPP;
+ ret.clear_feature_compat_mask = EXT4_TUNE_CLEAR_COMPAT_SUPP;
+ ret.clear_feature_incompat_mask = EXT4_TUNE_CLEAR_INCOMPAT_SUPP;
+ ret.clear_feature_ro_compat_mask = EXT4_TUNE_CLEAR_RO_COMPAT_SUPP;
+ if (copy_to_user(params, &ret, sizeof(ret)))
+ return -EFAULT;
+ return 0;
+}
+
+static void ext4_sb_setparams(struct ext4_sb_info *sbi,
+ struct ext4_super_block *es, const void *arg)
+{
+ const struct ext4_tune_sb_params *params = arg;
+
+ if (params->set_flags & EXT4_TUNE_FL_ERRORS_BEHAVIOR)
+ es->s_errors = cpu_to_le16(params->errors_behavior);
+ if (params->set_flags & EXT4_TUNE_FL_MNT_COUNT)
+ es->s_mnt_count = cpu_to_le16(params->mnt_count);
+ if (params->set_flags & EXT4_TUNE_FL_MAX_MNT_COUNT)
+ es->s_max_mnt_count = cpu_to_le16(params->max_mnt_count);
+ if (params->set_flags & EXT4_TUNE_FL_CHECKINTRVAL)
+ es->s_checkinterval = cpu_to_le32(params->checkinterval);
+ if (params->set_flags & EXT4_TUNE_FL_LAST_CHECK_TIME)
+ es->s_lastcheck = cpu_to_le32(params->last_check_time);
+ if (params->set_flags & EXT4_TUNE_FL_RESERVED_BLOCKS) {
+ ext4_fsblk_t blk = params->reserved_blocks;
+
+ es->s_r_blocks_count_lo = cpu_to_le32((u32)blk);
+ es->s_r_blocks_count_hi = cpu_to_le32(blk >> 32);
+ }
+ if (params->set_flags & EXT4_TUNE_FL_RESERVED_UID) {
+ int uid = params->reserved_uid;
+
+ es->s_def_resuid = cpu_to_le16(uid & 0xFFFF);
+ es->s_def_resuid_hi = cpu_to_le16(uid >> 16);
+ }
+ if (params->set_flags & EXT4_TUNE_FL_RESERVED_GID) {
+ int gid = params->reserved_gid;
+
+ es->s_def_resgid = cpu_to_le16(gid & 0xFFFF);
+ es->s_def_resgid_hi = cpu_to_le16(gid >> 16);
+ }
+ if (params->set_flags & EXT4_TUNE_FL_DEFAULT_MNT_OPTS)
+ es->s_default_mount_opts = cpu_to_le32(params->default_mnt_opts);
+ if (params->set_flags & EXT4_TUNE_FL_DEF_HASH_ALG)
+ es->s_def_hash_version = params->def_hash_alg;
+ if (params->set_flags & EXT4_TUNE_FL_RAID_STRIDE)
+ es->s_raid_stride = cpu_to_le16(params->raid_stride);
+ if (params->set_flags & EXT4_TUNE_FL_RAID_STRIPE_WIDTH)
+ es->s_raid_stripe_width =
+ cpu_to_le16(params->raid_stripe_width);
+ strscpy_pad(es->s_mount_opts, params->mount_opts);
+ if (params->set_flags & EXT4_TUNE_FL_EDIT_FEATURES) {
+ es->s_feature_compat |=
+ cpu_to_le32(params->set_feature_compat_mask);
+ es->s_feature_incompat |=
+ cpu_to_le32(params->set_feature_incompat_mask);
+ es->s_feature_ro_compat |=
+ cpu_to_le32(params->set_feature_ro_compat_mask);
+ es->s_feature_compat &=
+ ~cpu_to_le32(params->clear_feature_compat_mask);
+ es->s_feature_incompat &=
+ ~cpu_to_le32(params->clear_feature_incompat_mask);
+ es->s_feature_ro_compat &=
+ ~cpu_to_le32(params->clear_feature_ro_compat_mask);
+ if (params->set_feature_compat_mask &
+ EXT4_FEATURE_COMPAT_DIR_INDEX)
+ es->s_def_hash_version = sbi->s_def_hash_version;
+ if (params->set_feature_incompat_mask &
+ EXT4_FEATURE_INCOMPAT_CSUM_SEED)
+ es->s_checksum_seed = cpu_to_le32(sbi->s_csum_seed);
+ }
+ if (params->set_flags & EXT4_TUNE_FL_FORCE_FSCK)
+ es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
+}
+
+static int ext4_ioctl_set_tune_sb(struct file *filp,
+ struct ext4_tune_sb_params __user *in)
+{
+ struct ext4_tune_sb_params params;
+ struct super_block *sb = file_inode(filp)->i_sb;
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ struct ext4_super_block *es = sbi->s_es;
+ int ret;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (copy_from_user(¶ms, in, sizeof(params)))
+ return -EFAULT;
+
+ if ((params.set_flags & ~TUNE_OPS_SUPPORTED) != 0)
+ return -EOPNOTSUPP;
+
+ if ((params.set_flags & EXT4_TUNE_FL_ERRORS_BEHAVIOR) &&
+ (params.errors_behavior > EXT4_ERRORS_PANIC))
+ return -EINVAL;
+
+ if ((params.set_flags & EXT4_TUNE_FL_RESERVED_BLOCKS) &&
+ (params.reserved_blocks > ext4_blocks_count(sbi->s_es) / 2))
+ return -EINVAL;
+ if ((params.set_flags & EXT4_TUNE_FL_DEF_HASH_ALG) &&
+ ((params.def_hash_alg > DX_HASH_LAST) ||
+ (params.def_hash_alg == DX_HASH_SIPHASH)))
+ return -EINVAL;
+ if ((params.set_flags & EXT4_TUNE_FL_FEATURES) &&
+ (params.set_flags & EXT4_TUNE_FL_EDIT_FEATURES))
+ return -EINVAL;
+
+ if (params.set_flags & EXT4_TUNE_FL_FEATURES) {
+ params.set_feature_compat_mask =
+ params.feature_compat &
+ ~le32_to_cpu(es->s_feature_compat);
+ params.set_feature_incompat_mask =
+ params.feature_incompat &
+ ~le32_to_cpu(es->s_feature_incompat);
+ params.set_feature_ro_compat_mask =
+ params.feature_ro_compat &
+ ~le32_to_cpu(es->s_feature_ro_compat);
+ params.clear_feature_compat_mask =
+ ~params.feature_compat &
+ le32_to_cpu(es->s_feature_compat);
+ params.clear_feature_incompat_mask =
+ ~params.feature_incompat &
+ le32_to_cpu(es->s_feature_incompat);
+ params.clear_feature_ro_compat_mask =
+ ~params.feature_ro_compat &
+ le32_to_cpu(es->s_feature_ro_compat);
+ params.set_flags |= EXT4_TUNE_FL_EDIT_FEATURES;
+ }
+ if (params.set_flags & EXT4_TUNE_FL_EDIT_FEATURES) {
+ if ((params.set_feature_compat_mask &
+ ~EXT4_TUNE_SET_COMPAT_SUPP) ||
+ (params.set_feature_incompat_mask &
+ ~EXT4_TUNE_SET_INCOMPAT_SUPP) ||
+ (params.set_feature_ro_compat_mask &
+ ~EXT4_TUNE_SET_RO_COMPAT_SUPP) ||
+ (params.clear_feature_compat_mask &
+ ~EXT4_TUNE_CLEAR_COMPAT_SUPP) ||
+ (params.clear_feature_incompat_mask &
+ ~EXT4_TUNE_CLEAR_INCOMPAT_SUPP) ||
+ (params.clear_feature_ro_compat_mask &
+ ~EXT4_TUNE_CLEAR_RO_COMPAT_SUPP))
+ return -EOPNOTSUPP;
+
+ /*
+ * Filter out the features that are already set from
+ * the set_mask.
+ */
+ params.set_feature_compat_mask &=
+ ~le32_to_cpu(es->s_feature_compat);
+ params.set_feature_incompat_mask &=
+ ~le32_to_cpu(es->s_feature_incompat);
+ params.set_feature_ro_compat_mask &=
+ ~le32_to_cpu(es->s_feature_ro_compat);
+ if ((params.set_feature_compat_mask &
+ EXT4_FEATURE_COMPAT_DIR_INDEX) &&
+ !ext4_has_feature_dir_index(sb)) {
+ uuid_t uu;
+
+ memcpy(&uu, sbi->s_hash_seed, UUID_SIZE);
+ if (uuid_is_null(&uu))
+ generate_random_uuid((char *)
+ &sbi->s_hash_seed);
+ if (params.set_flags & EXT4_TUNE_FL_DEF_HASH_ALG)
+ sbi->s_def_hash_version = params.def_hash_alg;
+ else if (sbi->s_def_hash_version == 0)
+ sbi->s_def_hash_version = DX_HASH_HALF_MD4;
+ if (!(es->s_flags &
+ cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH)) &&
+ !(es->s_flags &
+ cpu_to_le32(EXT2_FLAGS_SIGNED_HASH))) {
+#ifdef __CHAR_UNSIGNED__
+ sbi->s_hash_unsigned = 3;
+#else
+ sbi->s_hash_unsigned = 0;
+#endif
+ }
+ }
+ }
+
+
+ ret = mnt_want_write_file(filp);
+ if (ret)
+ return ret;
+
+ ret = ext4_update_superblocks_fn(sb, ext4_sb_setparams, ¶ms);
+ mnt_drop_write_file(filp);
+
+ if (params.set_flags & EXT4_TUNE_FL_DEF_HASH_ALG)
+ sbi->s_def_hash_version = params.def_hash_alg;
+
+ return ret;
+}
+
static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@@ -1616,6 +1852,11 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return ext4_ioctl_getuuid(EXT4_SB(sb), (void __user *)arg);
case EXT4_IOC_SETFSUUID:
return ext4_ioctl_setuuid(filp, (const void __user *)arg);
+ case EXT4_IOC_GET_TUNE_SB_PARAM:
+ return ext4_ioctl_get_tune_sb(EXT4_SB(sb),
+ (void __user *)arg);
+ case EXT4_IOC_SET_TUNE_SB_PARAM:
+ return ext4_ioctl_set_tune_sb(filp, (void __user *)arg);
default:
return -ENOTTY;
}
@@ -1703,7 +1944,8 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
}
#endif
-static void set_overhead(struct ext4_super_block *es, const void *arg)
+static void set_overhead(struct ext4_sb_info *sbi,
+ struct ext4_super_block *es, const void *arg)
{
es->s_overhead_clusters = cpu_to_le32(*((unsigned long *) arg));
}
diff --git a/include/uapi/linux/ext4.h b/include/uapi/linux/ext4.h
index 1c4c2dd29112cda9f7dc91d917492cffc33ee524..145875fd633772e76ce7fd8bc0fef136ff620d2d 100644
--- a/include/uapi/linux/ext4.h
+++ b/include/uapi/linux/ext4.h
@@ -33,6 +33,8 @@
#define EXT4_IOC_CHECKPOINT _IOW('f', 43, __u32)
#define EXT4_IOC_GETFSUUID _IOR('f', 44, struct fsuuid)
#define EXT4_IOC_SETFSUUID _IOW('f', 44, struct fsuuid)
+#define EXT4_IOC_GET_TUNE_SB_PARAM _IOR('f', 45, struct ext4_tune_sb_params)
+#define EXT4_IOC_SET_TUNE_SB_PARAM _IOW('f', 46, struct ext4_tune_sb_params)
#define EXT4_IOC_SHUTDOWN _IOR('X', 125, __u32)
@@ -108,6 +110,79 @@ struct ext4_new_group_input {
__u16 unused;
};
+struct ext4_tune_sb_params {
+ __u32 set_flags;
+ __u32 checkinterval;
+ __u16 errors_behavior;
+ __u16 mnt_count;
+ __u16 max_mnt_count;
+ __u16 raid_stride;
+ __u64 last_check_time;
+ __u64 reserved_blocks;
+ __u64 blocks_count;
+ __u32 default_mnt_opts;
+ __u32 reserved_uid;
+ __u32 reserved_gid;
+ __u32 raid_stripe_width;
+ __u8 def_hash_alg;
+ __u8 pad_1;
+ __u16 pad_2;
+ __u32 feature_compat;
+ __u32 feature_incompat;
+ __u32 feature_ro_compat;
+ __u32 set_feature_compat_mask;
+ __u32 set_feature_incompat_mask;
+ __u32 set_feature_ro_compat_mask;
+ __u32 clear_feature_compat_mask;
+ __u32 clear_feature_incompat_mask;
+ __u32 clear_feature_ro_compat_mask;
+ __u8 mount_opts[64];
+ __u8 pad[64];
+};
+
+#define EXT4_TUNE_FL_ERRORS_BEHAVIOR 0x00000001
+#define EXT4_TUNE_FL_MNT_COUNT 0x00000002
+#define EXT4_TUNE_FL_MAX_MNT_COUNT 0x00000004
+#define EXT4_TUNE_FL_CHECKINTRVAL 0x00000008
+#define EXT4_TUNE_FL_LAST_CHECK_TIME 0x00000010
+#define EXT4_TUNE_FL_RESERVED_BLOCKS 0x00000020
+#define EXT4_TUNE_FL_RESERVED_UID 0x00000040
+#define EXT4_TUNE_FL_RESERVED_GID 0x00000080
+#define EXT4_TUNE_FL_DEFAULT_MNT_OPTS 0x00000100
+#define EXT4_TUNE_FL_DEF_HASH_ALG 0x00000200
+#define EXT4_TUNE_FL_RAID_STRIDE 0x00000400
+#define EXT4_TUNE_FL_RAID_STRIPE_WIDTH 0x00000800
+#define EXT4_TUNE_FL_MOUNT_OPTS 0x00001000
+#define EXT4_TUNE_FL_FEATURES 0x00002000
+#define EXT4_TUNE_FL_EDIT_FEATURES 0x00004000
+#define EXT4_TUNE_FL_FORCE_FSCK 0x00008000
+
+#define EXT4_TUNE_SET_COMPAT_SUPP \
+ (EXT4_FEATURE_COMPAT_DIR_INDEX | \
+ EXT4_FEATURE_COMPAT_STABLE_INODES)
+#define EXT4_TUNE_SET_INCOMPAT_SUPP \
+ (EXT4_FEATURE_INCOMPAT_EXTENTS | \
+ EXT4_FEATURE_INCOMPAT_EA_INODE | \
+ EXT4_FEATURE_INCOMPAT_ENCRYPT | \
+ EXT4_FEATURE_INCOMPAT_CSUM_SEED | \
+ EXT4_FEATURE_INCOMPAT_LARGEDIR | \
+ EXT4_FEATURE_INCOMPAT_CASEFOLD)
+#define EXT4_TUNE_SET_RO_COMPAT_SUPP \
+ (EXT4_FEATURE_RO_COMPAT_LARGE_FILE | \
+ EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \
+ EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE | \
+ EXT4_FEATURE_RO_COMPAT_READONLY | \
+ EXT4_FEATURE_RO_COMPAT_PROJECT | \
+ EXT4_FEATURE_RO_COMPAT_VERITY)
+
+#define EXT4_TUNE_CLEAR_COMPAT_SUPP (0)
+#define EXT4_TUNE_CLEAR_INCOMPAT_SUPP (0)
+#define EXT4_TUNE_CLEAR_RO_COMPAT_SUPP \
+ (EXT4_FEATURE_RO_COMPAT_LARGE_FILE | \
+ EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \
+ EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE | \
+ EXT4_FEATURE_RO_COMPAT_PROJECT)
+
/*
* Returned by EXT4_IOC_GET_ES_CACHE as an additional possible flag.
* It indicates that the entry in extent status cache is for a hole.
--
2.51.0
next prev parent reply other threads:[~2025-09-09 3:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 3:15 [PATCH 0/3] ext4: Add support for mounted updates to the superblock via an ioctl Theodore Ts'o via B4 Relay
2025-09-09 3:15 ` [PATCH 1/3] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options() Theodore Ts'o via B4 Relay
2025-09-11 22:27 ` Darrick J. Wong
2025-09-12 2:12 ` Theodore Ts'o
2025-09-09 3:15 ` [PATCH 2/3] ext4: add support for 32-bit default reserved uid and gid values Theodore Ts'o via B4 Relay
2025-09-11 22:31 ` Darrick J. Wong
2025-09-12 2:57 ` Theodore Ts'o
2025-09-09 3:15 ` Theodore Ts'o via B4 Relay [this message]
2025-09-09 21:33 ` [PATCH 3/3] ext4: implemet new ioctls to set and get superblock parameters kernel test robot
2025-09-11 22:40 ` Darrick J. Wong
2025-09-12 3:14 ` Theodore Ts'o
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