[PATCH 1/2] md: Fix logical_block_size configuration being overwritten

[PATCH 1/2] md: Fix logical_block_size configuration being overwritten

[linan666]

From: Li Nan <linan122@huawei.com>

In super_1_validate(), mddev->logical_block_size is directly overwritten
with the value from metadata. This causes the previously configured lbs
to be lost, making the configuration ineffective. Fix it.

Fixes: 62ed1b582246 ("md: allow configuring logical block size")
Signed-off-by: Li Nan <linan122@huawei.com>
---
 drivers/md/md.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index e5922a682953..7c0dd94a4d25 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1999,7 +1999,6 @@ 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;
@@ -2015,6 +2014,9 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 
 		mddev->max_disks =  (4096-256)/2;
 
+		if (!mddev->logical_block_size)
+			mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
+
 		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
 		    mddev->bitmap_info.file == NULL) {
 			mddev->bitmap_info.offset =
-- 
2.39.2

[PATCH 2/2] md: Fix forward incompatibility from configurable logical block size

[linan666]

From: Li Nan <linan122@huawei.com>

Commit 62ed1b582246 ("md: allow configuring logical block size") used
reserved pad to add 'logical_block_size' to metadata. RAID rejects
non-zero reserved pad, so arrays fail when rolling back to old kernels
after booting new ones.

Set 'logical_block_size' only for newly created arrays to support rollback
to old kernels. Importantly new arrays still won't work on old kernels to
prevent data loss issue from LBS changes.

For arrays created on old kernels which confirmed not to rollback,
configure LBS by echo 'enable' to md/logical_block_size.

Fixes: 62ed1b582246 ("md: allow configuring logical block size")
Reported-by: BugReports <bugreports61@gmail.com>
Closes: https://lore.kernel.org/linux-raid/825e532d-d1e1-44bb-5581-692b7c091796@huaweicloud.com/T/#t
Signed-off-by: Li Nan <linan122@huawei.com>
---
 drivers/md/md.c | 44 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7c0dd94a4d25..28c9435016fe 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2014,8 +2014,14 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 
 		mddev->max_disks =  (4096-256)/2;
 
-		if (!mddev->logical_block_size)
+		if (!mddev->logical_block_size) {
 			mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
+			if (!mddev->logical_block_size)
+				pr_warn("%s: echo 'enable' to md/logical_block_size to prevent data loss issue from LBS changes.\n"
+					"    Note: After enable, array will not be assembled in old kernels (<= 6.18)\n",
+					mdname(mddev));
+		}
+
 
 		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
 		    mddev->bitmap_info.file == NULL) {
@@ -5983,8 +5989,27 @@ lbs_store(struct mddev *mddev, const char *buf, size_t len)
 	if (mddev->major_version == 0)
 		return -EINVAL;
 
-	if (mddev->pers)
-		return -EBUSY;
+	if (mddev->pers) {
+		if (mddev->logical_block_size)
+			return -EBUSY;
+		/*
+		 * To fix forward compatibility issues, LBS is not
+		 * configured in old kernels array (<=6.18) by default.
+		 * If the user confirms no rollback to old kernels,
+		 * enable LBS by writing "enable" — to prevent data
+		 * loss from LBS changes.
+		 */
+		if (cmd_match(buf, "enable")) {
+			mddev->logical_block_size =
+				queue_logical_block_size(mddev->gendisk->queue);
+			set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+			pr_info("%s: config logical block size success, array will not be assembled in old kernels (<= 6.18)\n",
+				mdname(mddev));
+			return len;
+		} else {
+			return -EBUSY;
+		}
+	}
 
 	err = kstrtouint(buf, 10, &lbs);
 	if (err < 0)
@@ -6165,7 +6190,18 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
 			mdname(mddev));
 		return -EINVAL;
 	}
-	mddev->logical_block_size = lim->logical_block_size;
+
+	/*
+	 * Fix forward compatibility issue. Only set LBS by default for
+	 * new array, mddev->events == 0 indicates the array was just
+	 * created. When assembling an array, read LBS from the superblock
+	 * instead — LBS is 0 in superblocks created by old kernels.
+	 */
+	if (!mddev->events && mddev->major_version == 1) {
+		pr_info("%s: array will not be assembled in old kernels that lack configurable lbs support (<= 6.18)\n",
+			mdname(mddev));
+		mddev->logical_block_size = lim->logical_block_size;
+	}
 
 	return 0;
 }
-- 
2.39.2

Re: [PATCH 2/2] md: Fix forward incompatibility from configurable logical block size

[Yu Kuai]

Hi,

在 2025/12/19 17:21, linan666@huaweicloud.com 写道:
> From: Li Nan <linan122@huawei.com>
>
> Commit 62ed1b582246 ("md: allow configuring logical block size") used
> reserved pad to add 'logical_block_size' to metadata. RAID rejects
> non-zero reserved pad, so arrays fail when rolling back to old kernels
> after booting new ones.
>
> Set 'logical_block_size' only for newly created arrays to support rollback
> to old kernels. Importantly new arrays still won't work on old kernels to
> prevent data loss issue from LBS changes.
>
> For arrays created on old kernels which confirmed not to rollback,
> configure LBS by echo 'enable' to md/logical_block_size.
>
> Fixes: 62ed1b582246 ("md: allow configuring logical block size")
> Reported-by: BugReports <bugreports61@gmail.com>
> Closes: https://lore.kernel.org/linux-raid/825e532d-d1e1-44bb-5581-692b7c091796@huaweicloud.com/T/#t
> Signed-off-by: Li Nan <linan122@huawei.com>
> ---
>   drivers/md/md.c | 44 ++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 40 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 7c0dd94a4d25..28c9435016fe 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2014,8 +2014,14 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
>   
>   		mddev->max_disks =  (4096-256)/2;
>   
> -		if (!mddev->logical_block_size)
> +		if (!mddev->logical_block_size) {
>   			mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
> +			if (!mddev->logical_block_size)
> +				pr_warn("%s: echo 'enable' to md/logical_block_size to prevent data loss issue from LBS changes.\n"
> +					"    Note: After enable, array will not be assembled in old kernels (<= 6.18)\n",
> +					mdname(mddev));

Looks like this will print the same message for every rdev added to this array, please move the warning to
mddev_stack_rdev_limits() as well.

> +		}
> +
>   
>   		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
>   		    mddev->bitmap_info.file == NULL) {
> @@ -5983,8 +5989,27 @@ lbs_store(struct mddev *mddev, const char *buf, size_t len)
>   	if (mddev->major_version == 0)
>   		return -EINVAL;
>   
> -	if (mddev->pers)
> -		return -EBUSY;
> +	if (mddev->pers) {
> +		if (mddev->logical_block_size)
> +			return -EBUSY;
> +		/*
> +		 * To fix forward compatibility issues, LBS is not
> +		 * configured in old kernels array (<=6.18) by default.
> +		 * If the user confirms no rollback to old kernels,
> +		 * enable LBS by writing "enable" — to prevent data
> +		 * loss from LBS changes.
> +		 */
> +		if (cmd_match(buf, "enable")) {
> +			mddev->logical_block_size =
> +				queue_logical_block_size(mddev->gendisk->queue);
> +			set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
> +			pr_info("%s: config logical block size success, array will not be assembled in old kernels (<= 6.18)\n",
> +				mdname(mddev));

Instead of a new string "enabled", I'll prefer to echo the exact lbs.

> +			return len;
> +		} else {
> +			return -EBUSY;
> +		}
> +	}
>   
>   	err = kstrtouint(buf, 10, &lbs);
>   	if (err < 0)
> @@ -6165,7 +6190,18 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
>   			mdname(mddev));
>   		return -EINVAL;
>   	}
> -	mddev->logical_block_size = lim->logical_block_size;
> +
> +	/*
> +	 * Fix forward compatibility issue. Only set LBS by default for
> +	 * new array, mddev->events == 0 indicates the array was just
> +	 * created. When assembling an array, read LBS from the superblock
> +	 * instead — LBS is 0 in superblocks created by old kernels.
> +	 */
> +	if (!mddev->events && mddev->major_version == 1) {
> +		pr_info("%s: array will not be assembled in old kernels that lack configurable lbs support (<= 6.18)\n",
> +			mdname(mddev));
> +		mddev->logical_block_size = lim->logical_block_size;
> +	}
>   
>   	return 0;
>   }

-- 
Thansk,
Kuai

Re: [PATCH 1/2] md: Fix logical_block_size configuration being overwritten

[Yu Kuai]

在 2025/12/19 17:21, linan666@huaweicloud.com 写道:

> From: Li Nan<linan122@huawei.com>
>
> In super_1_validate(), mddev->logical_block_size is directly overwritten
> with the value from metadata. This causes the previously configured lbs
> to be lost, making the configuration ineffective. Fix it.
>
> Fixes: 62ed1b582246 ("md: allow configuring logical block size")
> Signed-off-by: Li Nan<linan122@huawei.com>
> ---
>   drivers/md/md.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)\

LGTM
Reviewed-by: Yu Kuai <yukuai@fnnas.com>

-- 
Thansk,
Kuai