linux-kernel - Re: [PATCH -next] md/raid1: fix data corruption for degraded array with slow disk

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Message-ID: <CAPhsuW5Q9_RymaSKHtfn1XUqmCG1Se-e9oT+iCh2Rb62-b4Svg@mail.gmail.com>
Date: Thu, 15 Aug 2024 13:41:41 -0700
From: Song Liu <song@...nel.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: mat.jonczyk@...pl, yukuai3@...wei.com, xni@...hat.com, 
	paul.e.luse@...ux.intel.com, linux-raid@...r.kernel.org, 
	linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next] md/raid1: fix data corruption for degraded array
 with slow disk

On Sat, Aug 3, 2024 at 2:15 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> read_balance() will avoid reading from slow disks as much as possible,
> however, if valid data only lands in slow disks, and a new normal disk
> is still in recovery, unrecovered data can be read:
>
> raid1_read_request
>  read_balance
>   raid1_should_read_first
>   -> return false
>   choose_best_rdev
>   -> normal disk is not recovered, return -1
>   choose_bb_rdev
>   -> missing the checking of recovery, return the normal disk
>  -> read unrecovered data
>
> Root cause is that the checking of recovery is missing in
> choose_bb_rdev(). Hence add such checking to fix the problem.
>
> Also fix similar problem in choose_slow_rdev().
>
> Fixes: 9f3ced792203 ("md/raid1: factor out choose_bb_rdev() from read_balance()")
> Fixes: dfa8ecd167c1 ("md/raid1: factor out choose_slow_rdev() from read_balance()")
> Reported-and-tested-by: Mateusz Jończyk <mat.jonczyk@...pl>
> Closes: https://lore.kernel.org/all/9952f532-2554-44bf-b906-4880b2e88e3a@o2.pl/
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>

Applied to md-6.11. Thanks for the fix!

Song