[PATCH v3 1/2] md: Fix logical_block_size configuration being overwritten

[PATCH v3 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>
Reviewed-by: Yu Kuai <yukuai@fnnas.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 v3 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 current LBS (queue/logical_block_size) 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>
---
v3:
  - fix comment: %s/writing 'enable'/writing current LBS/

v2:
  - move warn message to mddev_stack_rdev_limits
  - set current LBS to sysfs to enable feature instead of 'enable'

 drivers/md/md.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 44 insertions(+), 4 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 7c0dd94a4d25..d8e69d7f8ccb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5983,13 +5983,33 @@ lbs_store(struct mddev *mddev, const char *buf, size_t len)
 	if (mddev->major_version == 0)
 		return -EINVAL;
 
-	if (mddev->pers)
-		return -EBUSY;
-
 	err = kstrtouint(buf, 10, &lbs);
 	if (err < 0)
 		return -EINVAL;
 
+	if (mddev->pers) {
+		unsigned int curr_lbs;
+
+		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 current LBS — to prevent data
+		 * loss from LBS changes.
+		 */
+		curr_lbs = queue_logical_block_size(mddev->gendisk->queue);
+		if (lbs != curr_lbs)
+			return -EINVAL;
+
+		mddev->logical_block_size = curr_lbs;
+		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;
+	}
+
 	err = mddev_lock(mddev);
 	if (err)
 		goto unlock;
@@ -6165,7 +6185,27 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
 			mdname(mddev));
 		return -EINVAL;
 	}
-	mddev->logical_block_size = lim->logical_block_size;
+
+	/* Only 1.x meta needs to set logical block size */
+	if (mddev->major_version == 0)
+		return 0;
+
+	/*
+	 * 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) {
+		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;
+	}
+
+	if (!mddev->logical_block_size)
+		pr_warn("%s: echo current LBS to md/logical_block_size to prevent data loss issue from LBS changes.\n"
+			"\tNote: After setting, array will not be assembled in old kernels (<= 6.18)\n",
+			mdname(mddev));
 
 	return 0;
 }
-- 
2.39.2

Re: [PATCH v3 1/2] md: Fix logical_block_size configuration being overwritten

[Xiao Ni]

On Fri, Dec 26, 2025 at 10:54 AM <linan666@huaweicloud.com> wrote:
>
> 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>
> Reviewed-by: Yu Kuai <yukuai@fnnas.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
>

Reviewed-by: Xiao Ni <xni@redhat.com>

Re: [PATCH v3 1/2] md: Fix logical_block_size configuration being overwritten

[Yu Kuai]

在 2025/12/26 10:42, linan666@huaweicloud.com 写道:

> 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>
> Reviewed-by: Yu Kuai<yukuai@fnnas.com>
> ---
>   drivers/md/md.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)

Applied to md-6.19

-- 
Thansk,
Kuai

Re: [PATCH v3 2/2] md: Fix forward incompatibility from configurable logical block size

[Yu Kuai]

在 2025/12/26 10:42, 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 current LBS (queue/logical_block_size) 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>
> ---
> v3:
>    - fix comment: %s/writing 'enable'/writing current LBS/
>
> v2:
>    - move warn message to mddev_stack_rdev_limits
>    - set current LBS to sysfs to enable feature instead of 'enable'
>
>   drivers/md/md.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
>   1 file changed, 44 insertions(+), 4 deletions(-)

Applied to md-6.19 with a few wording changes:

   | Location            | Before                            | After                                      |
   |---------------------|-----------------------------------|--------------------------------------------|
   | Line 5994 (comment) | configured in old kernels array   | configured for arrays from old kernels     |
   | Line 6005 (pr_info) | config logical block size success | logical block size configured successfully |
   | Line 6192 (comment) | new array                         | new arrays                                 |
   | Line 6197 (pr_info) | configurable lbs support          | configurable LBS support                   |
   | Line 6203 (pr_warn) | data loss issue                   | data loss issues                           |

-- 
Thansk,
Kuai