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

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Message-Id: <2d09972c-a864-45c3-b247-29e3d03ea2ff@fnnas.com>
Date: Sat, 27 Dec 2025 10:16:52 +0800
From: "Yu Kuai" <yukuai@...as.com>
To: <linan666@...weicloud.com>, <song@...nel.org>, <linan122@...wei.com>, 
	<xni@...hat.com>
Cc: <linux-raid@...r.kernel.org>, <linux-kernel@...r.kernel.org>, 
	<bugreports61@...il.com>, <yangerkun@...wei.com>, <yi.zhang@...wei.com>, 
	<yukuai@...as.com>
Subject: Re: [PATCH v3 2/2] md: Fix forward incompatibility from configurable logical block size

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

> From: Li Nan<linan122@...wei.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@...il.com>
> Closes:https://lore.kernel.org/linux-raid/825e532d-d1e1-44bb-5581-692b7c091796@huaweicloud.com/T/#t
> Signed-off-by: Li Nan<linan122@...wei.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