[PATCH v3 0/2] make logical_block_size configurable

[PATCH v3 0/2] make logical_block_size configurable

[linan666]

From: Li Nan <linan122@huawei.com>

v3:
 - logical_block_size must not exceed PAGE_SIZE for bio device.
 - Assign lim to mddev rather than to gendisk in mddev_stack_rdev_limits().
 - Remove the patch that modifies the return value.

v2: No new exported interfaces are introduced.

Li Nan (2):
  md: prevent adding disks with larger logical_block_size to active
    arrays
  md: allow configuring logical_block_size

 drivers/md/md.h                |  1 +
 include/uapi/linux/raid/md_p.h |  6 ++-
 drivers/md/md-linear.c         |  1 +
 drivers/md/md.c                | 82 ++++++++++++++++++++++++++++++++++
 drivers/md/raid0.c             |  1 +
 drivers/md/raid1.c             |  1 +
 drivers/md/raid10.c            |  1 +
 drivers/md/raid5.c             |  1 +
 8 files changed, 92 insertions(+), 2 deletions(-)

-- 
2.39.2

[PATCH v3 1/2] md: prevent adding disks with larger logical_block_size to active arrays

[linan666]

From: Li Nan <linan122@huawei.com>

When adding a disk to a md array, avoid updating the array's
logical_block_size to match the new disk. This prevents accidental
partition table loss that renders the array unusable.

The later patch will introduce a way to configure the array's
logical_block_size.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
---
 drivers/md/md.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index cea8fc96abd3..206434591b97 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6064,6 +6064,13 @@ int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
 	if (mddev_is_dm(mddev))
 		return 0;
 
+	if (queue_logical_block_size(rdev->bdev->bd_disk->queue) >
+	    queue_logical_block_size(mddev->gendisk->queue)) {
+		pr_err("%s: incompatible logical_block_size, can not add\n",
+		       mdname(mddev));
+		return -EINVAL;
+	}
+
 	lim = queue_limits_start_update(mddev->gendisk->queue);
 	queue_limits_stack_bdev(&lim, rdev->bdev, rdev->data_offset,
 				mddev->gendisk->disk_name);
-- 
2.39.2

[PATCH v3 2/2] md: allow configuring logical_block_size

[linan666]

From: Li Nan <linan122@huawei.com>

Previously, raid array used the maximum logical_block_size (LBS) of
all member disks. Adding a larger LBS during disk at runtime could
unexpectedly increase RAID's LBS, risking corruption of existing
partitions.
Simply restricting larger-LBS disks is inflexible. In some scenarios,
only disks with 512 LBS are available currently, but later, disks with
4k LBS may be added to the array.

Making LBS configurable is the best way to solve this scenario.
After this patch, the raid will:
  - stores LBS in disk metadata.
  - add a read-write sysfs 'mdX/logical_block_size'.

Future mdadm should support setting LBS via metadata field during RAID
creation and the new sysfs. Though the kernel allows runtime LBS changes,
users should avoid modifying it after creating partitions or filesystems
to prevent compatibility issues.

Note that many RAID paths rely on PAGE_SIZE alignment, including for
metadata I/O. A logical_block_size larger than PAGE_SIZE will result in
metadata reads/writes failures. So this config should be prevented.

Signed-off-by: Li Nan <linan122@huawei.com>
---
 drivers/md/md.h                |  1 +
 include/uapi/linux/raid/md_p.h |  6 ++-
 drivers/md/md-linear.c         |  1 +
 drivers/md/md.c                | 75 ++++++++++++++++++++++++++++++++++
 drivers/md/raid0.c             |  1 +
 drivers/md/raid1.c             |  1 +
 drivers/md/raid10.c            |  1 +
 drivers/md/raid5.c             |  1 +
 8 files changed, 85 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 1979c2d4fe89..0202f6feedea 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -432,6 +432,7 @@ struct mddev {
 	sector_t			array_sectors; /* exported array size */
 	int				external_size; /* size managed
 							* externally */
+	unsigned int			logical_block_size;
 	__u64				events;
 	/* If the last 'event' was simply a clean->dirty transition, and
 	 * we didn't write it to the spares, then it is safe and simple
diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
index ac74133a4768..190d493044a8 100644
--- a/include/uapi/linux/raid/md_p.h
+++ b/include/uapi/linux/raid/md_p.h
@@ -180,7 +180,8 @@ typedef struct mdp_superblock_s {
 	__u32 delta_disks;	/* 15 change in number of raid_disks	      */
 	__u32 new_layout;	/* 16 new layout			      */
 	__u32 new_chunk;	/* 17 new chunk size (bytes)		      */
-	__u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 18];
+	__u32 logical_block_size;	/* same as q->limits->logical_block_size */
+	__u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 19];
 
 	/*
 	 * Personality information
@@ -291,7 +292,8 @@ struct mdp_superblock_1 {
 	__le64	resync_offset;	/* data before this offset (from data_offset) known to be in sync */
 	__le32	sb_csum;	/* checksum up to devs[max_dev] */
 	__le32	max_dev;	/* size of devs[] array to consider */
-	__u8	pad3[64-32];	/* set to 0 when writing */
+	__le32  logical_block_size;	/* same as q->limits->logical_block_size */
+	__u8	pad3[64-36];	/* set to 0 when writing */
 
 	/* device state information. Indexed by dev_number.
 	 * 2 bytes per device
diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
index 5d9b08115375..da8babb8da59 100644
--- a/drivers/md/md-linear.c
+++ b/drivers/md/md-linear.c
@@ -72,6 +72,7 @@ static int linear_set_limits(struct mddev *mddev)
 
 	md_init_stacking_limits(&lim);
 	lim.max_hw_sectors = mddev->chunk_sectors;
+	lim.logical_block_size = mddev->logical_block_size;
 	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
 	lim.io_min = mddev->chunk_sectors << 9;
 	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 206434591b97..e78f80d39271 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1467,6 +1467,7 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *freshest, stru
 		mddev->bitmap_info.default_offset = MD_SB_BYTES >> 9;
 		mddev->bitmap_info.default_space = 64*2 - (MD_SB_BYTES >> 9);
 		mddev->reshape_backwards = 0;
+		mddev->logical_block_size = sb->logical_block_size;
 
 		if (mddev->minor_version >= 91) {
 			mddev->reshape_position = sb->reshape_position;
@@ -1629,6 +1630,7 @@ static void super_90_sync(struct mddev *mddev, struct md_rdev *rdev)
 
 	sb->layout = mddev->layout;
 	sb->chunk_size = mddev->chunk_sectors << 9;
+	sb->logical_block_size = mddev->logical_block_size;
 
 	if (mddev->bitmap && mddev->bitmap_info.file == NULL)
 		sb->state |= (1<<MD_SB_BITMAP_PRESENT);
@@ -1963,6 +1965,7 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 		mddev->layout = le32_to_cpu(sb->layout);
 		mddev->raid_disks = le32_to_cpu(sb->raid_disks);
 		mddev->dev_sectors = le64_to_cpu(sb->size);
+		mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
 		mddev->events = ev1;
 		mddev->bitmap_info.offset = 0;
 		mddev->bitmap_info.space = 0;
@@ -2172,6 +2175,7 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
 	sb->chunksize = cpu_to_le32(mddev->chunk_sectors);
 	sb->level = cpu_to_le32(mddev->level);
 	sb->layout = cpu_to_le32(mddev->layout);
+	sb->logical_block_size = cpu_to_le32(mddev->logical_block_size);
 	if (test_bit(FailFast, &rdev->flags))
 		sb->devflags |= FailFast1;
 	else
@@ -5900,6 +5904,64 @@ static struct md_sysfs_entry md_serialize_policy =
 __ATTR(serialize_policy, S_IRUGO | S_IWUSR, serialize_policy_show,
        serialize_policy_store);
 
+static int mddev_set_logical_block_size(struct mddev *mddev,
+				unsigned int lbs)
+{
+	int err = 0;
+	struct queue_limits lim;
+
+	if (queue_logical_block_size(mddev->gendisk->queue) >= lbs) {
+		pr_err("%s: incompatible logical_block_size %u, can not set\n",
+		       mdname(mddev), lbs);
+		return -EINVAL;
+	}
+
+	lim = queue_limits_start_update(mddev->gendisk->queue);
+	lim.logical_block_size = lbs;
+	pr_info("%s: logical_block_size is changed, data may be lost\n",
+		mdname(mddev));
+	err = queue_limits_commit_update(mddev->gendisk->queue, &lim);
+	if (err)
+		return err;
+
+	mddev->logical_block_size = lbs;
+	md_update_sb(mddev, 1);
+
+	return 0;
+}
+
+static ssize_t
+lbs_show(struct mddev *mddev, char *page)
+{
+	return sprintf(page, "%u\n", mddev->logical_block_size);
+}
+
+static ssize_t
+lbs_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	unsigned int lbs;
+	int err = -EBUSY;
+
+	if (mddev->pers)
+		goto unlock;
+
+	err = kstrtouint(buf, 10, &lbs);
+	if (err < 0)
+		return err;
+
+	err = mddev_lock(mddev);
+	if (err)
+		return err;
+
+	err = mddev_set_logical_block_size(mddev, lbs);
+
+unlock:
+	mddev_unlock(mddev);
+	return err ?: len;
+}
+
+static struct md_sysfs_entry md_logical_block_size =
+__ATTR(logical_block_size, S_IRUGO|S_IWUSR, lbs_show, lbs_store);
 
 static struct attribute *md_default_attrs[] = {
 	&md_level.attr,
@@ -5933,6 +5995,7 @@ static struct attribute *md_redundancy_attrs[] = {
 	&md_scan_mode.attr,
 	&md_last_scan_mode.attr,
 	&md_mismatches.attr,
+	&md_logical_block_size.attr,
 	&md_sync_min.attr,
 	&md_sync_max.attr,
 	&md_sync_io_depth.attr,
@@ -6052,6 +6115,17 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
 			return -EINVAL;
 	}
 
+	/*
+	 * Before RAID adding folio support, the logical_block_size
+	 * should be smaller than the page size.
+	 */
+	if (lim->logical_block_size > PAGE_SIZE) {
+		pr_err("%s: logical_block_size must not larger than PAGE_SIZE\n",
+			mdname(mddev));
+		return -EINVAL;
+	}
+	mddev->logical_block_size = lim->logical_block_size;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(mddev_stack_rdev_limits);
@@ -6690,6 +6764,7 @@ static void md_clean(struct mddev *mddev)
 	mddev->chunk_sectors = 0;
 	mddev->ctime = mddev->utime = 0;
 	mddev->layout = 0;
+	mddev->logical_block_size = 0;
 	mddev->max_disks = 0;
 	mddev->events = 0;
 	mddev->can_decrease_events = 0;
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f1d8811a542a..705889a09fc1 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -382,6 +382,7 @@ static int raid0_set_limits(struct mddev *mddev)
 	md_init_stacking_limits(&lim);
 	lim.max_hw_sectors = mddev->chunk_sectors;
 	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
+	lim.logical_block_size = mddev->logical_block_size;
 	lim.io_min = mddev->chunk_sectors << 9;
 	lim.io_opt = lim.io_min * mddev->raid_disks;
 	lim.chunk_sectors = mddev->chunk_sectors;
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 0e792b9bfff8..3e422854cafb 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -3224,6 +3224,7 @@ static int raid1_set_limits(struct mddev *mddev)
 
 	md_init_stacking_limits(&lim);
 	lim.max_write_zeroes_sectors = 0;
+	lim.logical_block_size = mddev->logical_block_size;
 	lim.features |= BLK_FEAT_ATOMIC_WRITES;
 	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
 	if (err)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 2411399a7352..2dfff3f9ec8e 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4005,6 +4005,7 @@ static int raid10_set_queue_limits(struct mddev *mddev)
 
 	md_init_stacking_limits(&lim);
 	lim.max_write_zeroes_sectors = 0;
+	lim.logical_block_size = mddev->logical_block_size;
 	lim.io_min = mddev->chunk_sectors << 9;
 	lim.chunk_sectors = mddev->chunk_sectors;
 	lim.io_opt = lim.io_min * raid10_nr_stripes(conf);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 2121f0ff5e30..c6bd6d2e4438 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7733,6 +7733,7 @@ static int raid5_set_limits(struct mddev *mddev)
 	stripe = roundup_pow_of_two(data_disks * (mddev->chunk_sectors << 9));
 
 	md_init_stacking_limits(&lim);
+	lim.logical_block_size = mddev->logical_block_size;
 	lim.io_min = mddev->chunk_sectors << 9;
 	lim.io_opt = lim.io_min * (conf->raid_disks - conf->max_degraded);
 	lim.features |= BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
-- 
2.39.2

Re: [PATCH v3 1/2] md: prevent adding disks with larger logical_block_size to active arrays

[Paul Menzel]

Dear Li,


Thank you for your patch.

Am 25.08.25 um 09:59 schrieb linan666@huaweicloud.com:
> From: Li Nan <linan122@huawei.com>
> 
> When adding a disk to a md array, avoid updating the array's
> logical_block_size to match the new disk. This prevents accidental
> partition table loss that renders the array unusable.

Do you have a reproducer to test this?

> The later patch will introduce a way to configure the array's
> logical_block_size.
> 
> Signed-off-by: Li Nan <linan122@huawei.com>
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>   drivers/md/md.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index cea8fc96abd3..206434591b97 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6064,6 +6064,13 @@ int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
>   	if (mddev_is_dm(mddev))
>   		return 0;
>   
> +	if (queue_logical_block_size(rdev->bdev->bd_disk->queue) >
> +	    queue_logical_block_size(mddev->gendisk->queue)) {
> +		pr_err("%s: incompatible logical_block_size, can not add\n",
> +		       mdname(mddev));
> +		return -EINVAL;
> +	}
> +
>   	lim = queue_limits_start_update(mddev->gendisk->queue);
>   	queue_limits_stack_bdev(&lim, rdev->bdev, rdev->data_offset,
>   				mddev->gendisk->disk_name);


Kind regards,

Paul

Re: [PATCH v3 1/2] md: prevent adding disks with larger logical_block_size to active arrays

[Li Nan]

在 2025/8/25 16:10, Paul Menzel 写道:
> Dear Li,
> 
> 
> Thank you for your patch.
> 
> Am 25.08.25 um 09:59 schrieb linan666@huaweicloud.com:
>> From: Li Nan <linan122@huawei.com>
>>
>> When adding a disk to a md array, avoid updating the array's
>> logical_block_size to match the new disk. This prevents accidental
>> partition table loss that renders the array unusable.
> 
> Do you have a reproducer to test this?

Please try the following script:

```
#sd[de] lbs is 512, sdf is 4096
mdadm -CR /dev/md0 -l1 -n2 /dev/sd[de] --assume-clean

#512
cat /sys/block/md0/queue/logical_block_size

#create md0p1
printf "g\nn\n\n\n\nw\n" | fdisk /dev/md0
lsblk | grep md0

mdadm --fail /dev/md0 /dev/sdd
mdadm --add /dev/md0 /dev/sdf

#4096
cat /sys/block/md0/queue/logical_block_size

#partition loss
partprobe /dev/md0
lsblk | grep md0
```

> 
>> The later patch will introduce a way to configure the array's
>> logical_block_size.
>>
>> Signed-off-by: Li Nan <linan122@huawei.com>
>> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
>> ---
>>   drivers/md/md.c | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index cea8fc96abd3..206434591b97 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -6064,6 +6064,13 @@ int mddev_stack_new_rdev(struct mddev *mddev, 
>> struct md_rdev *rdev)
>>       if (mddev_is_dm(mddev))
>>           return 0;
>> +    if (queue_logical_block_size(rdev->bdev->bd_disk->queue) >
>> +        queue_logical_block_size(mddev->gendisk->queue)) {
>> +        pr_err("%s: incompatible logical_block_size, can not add\n",
>> +               mdname(mddev));
>> +        return -EINVAL;
>> +    }
>> +
>>       lim = queue_limits_start_update(mddev->gendisk->queue);
>>       queue_limits_stack_bdev(&lim, rdev->bdev, rdev->data_offset,
>>                   mddev->gendisk->disk_name);
> 
> 
> Kind regards,
> 
> Paul
> 
> 
> .

-- 
Thanks,
Nan

Re: [PATCH v3 2/2] md: allow configuring logical_block_size

[Martin K. Petersen]

> Previously, raid array used the maximum logical_block_size (LBS) of
> all member disks. Adding a larger LBS during disk at runtime could
> unexpectedly increase RAID's LBS, risking corruption of existing
> partitions. Simply restricting larger-LBS disks is inflexible. In some
> scenarios, only disks with 512 LBS are available currently, but later,
> disks with 4k LBS may be added to the array.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen

Re: [PATCH v3 1/2] md: prevent adding disks with larger logical_block_size to active arrays

[Yu Kuai]

Hi,

在 2025/08/25 15:59, linan666@huaweicloud.com 写道:
> From: Li Nan <linan122@huawei.com>
> 
> When adding a disk to a md array, avoid updating the array's
> logical_block_size to match the new disk. This prevents accidental
> partition table loss that renders the array unusable.
> 
> The later patch will introduce a way to configure the array's
> logical_block_size.
> 
> Signed-off-by: Li Nan <linan122@huawei.com>
> Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
> ---
>   drivers/md/md.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 

Can you add a fix tag, as data loss is really serious.

Otherwise, feel free to add:

Reviewed-by: Yu Kuai <yukuai3@huawei.com>

> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index cea8fc96abd3..206434591b97 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6064,6 +6064,13 @@ int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
>   	if (mddev_is_dm(mddev))
>   		return 0;
>   
> +	if (queue_logical_block_size(rdev->bdev->bd_disk->queue) >
> +	    queue_logical_block_size(mddev->gendisk->queue)) {
> +		pr_err("%s: incompatible logical_block_size, can not add\n",
> +		       mdname(mddev));
> +		return -EINVAL;
> +	}
> +
>   	lim = queue_limits_start_update(mddev->gendisk->queue);
>   	queue_limits_stack_bdev(&lim, rdev->bdev, rdev->data_offset,
>   				mddev->gendisk->disk_name);
> 

Re: [PATCH v3 2/2] md: allow configuring logical_block_size

[Yu Kuai]

Hi,

在 2025/08/25 15:59, linan666@huaweicloud.com 写道:
> From: Li Nan <linan122@huawei.com>
> 
> Previously, raid array used the maximum logical_block_size (LBS) of
> all member disks. Adding a larger LBS during disk at runtime could
> unexpectedly increase RAID's LBS, risking corruption of existing
> partitions.
> Simply restricting larger-LBS disks is inflexible. In some scenarios,
> only disks with 512 LBS are available currently, but later, disks with
> 4k LBS may be added to the array.
> 
> Making LBS configurable is the best way to solve this scenario.
> After this patch, the raid will:
>    - stores LBS in disk metadata.
>    - add a read-write sysfs 'mdX/logical_block_size'.
> 
> Future mdadm should support setting LBS via metadata field during RAID
> creation and the new sysfs. Though the kernel allows runtime LBS changes,
> users should avoid modifying it after creating partitions or filesystems
> to prevent compatibility issues.
> 
> Note that many RAID paths rely on PAGE_SIZE alignment, including for
> metadata I/O. A logical_block_size larger than PAGE_SIZE will result in
> metadata reads/writes failures. So this config should be prevented.
> 
> Signed-off-by: Li Nan <linan122@huawei.com>
> ---
>   drivers/md/md.h                |  1 +
>   include/uapi/linux/raid/md_p.h |  6 ++-
>   drivers/md/md-linear.c         |  1 +
>   drivers/md/md.c                | 75 ++++++++++++++++++++++++++++++++++
>   drivers/md/raid0.c             |  1 +
>   drivers/md/raid1.c             |  1 +
>   drivers/md/raid10.c            |  1 +
>   drivers/md/raid5.c             |  1 +
>   8 files changed, 85 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 1979c2d4fe89..0202f6feedea 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -432,6 +432,7 @@ struct mddev {
>   	sector_t			array_sectors; /* exported array size */
>   	int				external_size; /* size managed
>   							* externally */
> +	unsigned int			logical_block_size;
>   	__u64				events;
>   	/* If the last 'event' was simply a clean->dirty transition, and
>   	 * we didn't write it to the spares, then it is safe and simple
> diff --git a/include/uapi/linux/raid/md_p.h b/include/uapi/linux/raid/md_p.h
> index ac74133a4768..190d493044a8 100644
> --- a/include/uapi/linux/raid/md_p.h
> +++ b/include/uapi/linux/raid/md_p.h
> @@ -180,7 +180,8 @@ typedef struct mdp_superblock_s {
>   	__u32 delta_disks;	/* 15 change in number of raid_disks	      */
>   	__u32 new_layout;	/* 16 new layout			      */
>   	__u32 new_chunk;	/* 17 new chunk size (bytes)		      */
> -	__u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 18];
> +	__u32 logical_block_size;	/* same as q->limits->logical_block_size */
> +	__u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 19];
>   
>   	/*
>   	 * Personality information
> @@ -291,7 +292,8 @@ struct mdp_superblock_1 {
>   	__le64	resync_offset;	/* data before this offset (from data_offset) known to be in sync */
>   	__le32	sb_csum;	/* checksum up to devs[max_dev] */
>   	__le32	max_dev;	/* size of devs[] array to consider */
> -	__u8	pad3[64-32];	/* set to 0 when writing */
> +	__le32  logical_block_size;	/* same as q->limits->logical_block_size */
> +	__u8	pad3[64-36];	/* set to 0 when writing */
>   
>   	/* device state information. Indexed by dev_number.
>   	 * 2 bytes per device
> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
> index 5d9b08115375..da8babb8da59 100644
> --- a/drivers/md/md-linear.c
> +++ b/drivers/md/md-linear.c
> @@ -72,6 +72,7 @@ static int linear_set_limits(struct mddev *mddev)
>   
>   	md_init_stacking_limits(&lim);
>   	lim.max_hw_sectors = mddev->chunk_sectors;
> +	lim.logical_block_size = mddev->logical_block_size;
>   	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
>   	lim.io_min = mddev->chunk_sectors << 9;
>   	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 206434591b97..e78f80d39271 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1467,6 +1467,7 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *freshest, stru
>   		mddev->bitmap_info.default_offset = MD_SB_BYTES >> 9;
>   		mddev->bitmap_info.default_space = 64*2 - (MD_SB_BYTES >> 9);
>   		mddev->reshape_backwards = 0;
> +		mddev->logical_block_size = sb->logical_block_size;
>   
>   		if (mddev->minor_version >= 91) {
>   			mddev->reshape_position = sb->reshape_position;
> @@ -1629,6 +1630,7 @@ static void super_90_sync(struct mddev *mddev, struct md_rdev *rdev)
>   
>   	sb->layout = mddev->layout;
>   	sb->chunk_size = mddev->chunk_sectors << 9;
> +	sb->logical_block_size = mddev->logical_block_size;
>   
>   	if (mddev->bitmap && mddev->bitmap_info.file == NULL)
>   		sb->state |= (1<<MD_SB_BITMAP_PRESENT);
> @@ -1963,6 +1965,7 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
>   		mddev->layout = le32_to_cpu(sb->layout);
>   		mddev->raid_disks = le32_to_cpu(sb->raid_disks);
>   		mddev->dev_sectors = le64_to_cpu(sb->size);
> +		mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
>   		mddev->events = ev1;
>   		mddev->bitmap_info.offset = 0;
>   		mddev->bitmap_info.space = 0;
> @@ -2172,6 +2175,7 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
>   	sb->chunksize = cpu_to_le32(mddev->chunk_sectors);
>   	sb->level = cpu_to_le32(mddev->level);
>   	sb->layout = cpu_to_le32(mddev->layout);
> +	sb->logical_block_size = cpu_to_le32(mddev->logical_block_size);
>   	if (test_bit(FailFast, &rdev->flags))
>   		sb->devflags |= FailFast1;
>   	else
> @@ -5900,6 +5904,64 @@ static struct md_sysfs_entry md_serialize_policy =
>   __ATTR(serialize_policy, S_IRUGO | S_IWUSR, serialize_policy_show,
>          serialize_policy_store);
>   

I'll prefer we only support to configre it in super 1, because super 90
support autodetect where all fields looks like have to be the default
value.

> +static int mddev_set_logical_block_size(struct mddev *mddev,
> +				unsigned int lbs)
> +{
> +	int err = 0;
> +	struct queue_limits lim;
> +
> +	if (queue_logical_block_size(mddev->gendisk->queue) >= lbs) {

I think this sysfs entry to configure lbs is useful only if user want to
build new array manually without user tools like mdadm, hence the
condition should be array is not running. And I feel it doesn't make
sense to change lbs with running array.

BTW, please add documentations about this new attribute.

Thanks,
Kuai

> +		pr_err("%s: incompatible logical_block_size %u, can not set\n",
> +		       mdname(mddev), lbs);
> +		return -EINVAL;
> +	}
> +
> +	lim = queue_limits_start_update(mddev->gendisk->queue);
> +	lim.logical_block_size = lbs;
> +	pr_info("%s: logical_block_size is changed, data may be lost\n",
> +		mdname(mddev));
> +	err = queue_limits_commit_update(mddev->gendisk->queue, &lim);
> +	if (err)
> +		return err;
> +
> +	mddev->logical_block_size = lbs;
> +	md_update_sb(mddev, 1);
> +
> +	return 0;
> +}
> +
> +static ssize_t
> +lbs_show(struct mddev *mddev, char *page)
> +{
> +	return sprintf(page, "%u\n", mddev->logical_block_size);
> +}
> +
> +static ssize_t
> +lbs_store(struct mddev *mddev, const char *buf, size_t len)
> +{
> +	unsigned int lbs;
> +	int err = -EBUSY;
> +
> +	if (mddev->pers)
> +		goto unlock;
> +
> +	err = kstrtouint(buf, 10, &lbs);
> +	if (err < 0)
> +		return err;
> +
> +	err = mddev_lock(mddev);
> +	if (err)
> +		return err;
> +
> +	err = mddev_set_logical_block_size(mddev, lbs);
> +
> +unlock:
> +	mddev_unlock(mddev);
> +	return err ?: len;
> +}
> +
> +static struct md_sysfs_entry md_logical_block_size =
> +__ATTR(logical_block_size, S_IRUGO|S_IWUSR, lbs_show, lbs_store);
>   
>   static struct attribute *md_default_attrs[] = {
>   	&md_level.attr,
> @@ -5933,6 +5995,7 @@ static struct attribute *md_redundancy_attrs[] = {
>   	&md_scan_mode.attr,
>   	&md_last_scan_mode.attr,
>   	&md_mismatches.attr,
> +	&md_logical_block_size.attr,
>   	&md_sync_min.attr,
>   	&md_sync_max.attr,
>   	&md_sync_io_depth.attr,
> @@ -6052,6 +6115,17 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
>   			return -EINVAL;
>   	}
>   
> +	/*
> +	 * Before RAID adding folio support, the logical_block_size
> +	 * should be smaller than the page size.
> +	 */
> +	if (lim->logical_block_size > PAGE_SIZE) {
> +		pr_err("%s: logical_block_size must not larger than PAGE_SIZE\n",
> +			mdname(mddev));
> +		return -EINVAL;
> +	}
> +	mddev->logical_block_size = lim->logical_block_size;
> +
>   	return 0;
>   }
>   EXPORT_SYMBOL_GPL(mddev_stack_rdev_limits);
> @@ -6690,6 +6764,7 @@ static void md_clean(struct mddev *mddev)
>   	mddev->chunk_sectors = 0;
>   	mddev->ctime = mddev->utime = 0;
>   	mddev->layout = 0;
> +	mddev->logical_block_size = 0;
>   	mddev->max_disks = 0;
>   	mddev->events = 0;
>   	mddev->can_decrease_events = 0;
> diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
> index f1d8811a542a..705889a09fc1 100644
> --- a/drivers/md/raid0.c
> +++ b/drivers/md/raid0.c
> @@ -382,6 +382,7 @@ static int raid0_set_limits(struct mddev *mddev)
>   	md_init_stacking_limits(&lim);
>   	lim.max_hw_sectors = mddev->chunk_sectors;
>   	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
> +	lim.logical_block_size = mddev->logical_block_size;
>   	lim.io_min = mddev->chunk_sectors << 9;
>   	lim.io_opt = lim.io_min * mddev->raid_disks;
>   	lim.chunk_sectors = mddev->chunk_sectors;
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 0e792b9bfff8..3e422854cafb 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -3224,6 +3224,7 @@ static int raid1_set_limits(struct mddev *mddev)
>   
>   	md_init_stacking_limits(&lim);
>   	lim.max_write_zeroes_sectors = 0;
> +	lim.logical_block_size = mddev->logical_block_size;
>   	lim.features |= BLK_FEAT_ATOMIC_WRITES;
>   	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>   	if (err)
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 2411399a7352..2dfff3f9ec8e 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -4005,6 +4005,7 @@ static int raid10_set_queue_limits(struct mddev *mddev)
>   
>   	md_init_stacking_limits(&lim);
>   	lim.max_write_zeroes_sectors = 0;
> +	lim.logical_block_size = mddev->logical_block_size;
>   	lim.io_min = mddev->chunk_sectors << 9;
>   	lim.chunk_sectors = mddev->chunk_sectors;
>   	lim.io_opt = lim.io_min * raid10_nr_stripes(conf);
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 2121f0ff5e30..c6bd6d2e4438 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -7733,6 +7733,7 @@ static int raid5_set_limits(struct mddev *mddev)
>   	stripe = roundup_pow_of_two(data_disks * (mddev->chunk_sectors << 9));
>   
>   	md_init_stacking_limits(&lim);
> +	lim.logical_block_size = mddev->logical_block_size;
>   	lim.io_min = mddev->chunk_sectors << 9;
>   	lim.io_opt = lim.io_min * (conf->raid_disks - conf->max_degraded);
>   	lim.features |= BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
>