linux-kernel - Re: [PATCH 09/12] badblocks: fix missing bad blocks on retry in _badblocks

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Message-ID: <e6iwuml7p5hql4zo4jzkxpr2wgcbqne75xpqva6onteqcxve43@kcr2qzes35ix>
Date: Fri, 21 Feb 2025 18:27:52 +0800
From: Coly Li <i@...y.li>
To: Zheng Qixing <zhengqixing@...weicloud.com>
Cc: axboe@...nel.dk, song@...nel.org, colyli@...nel.org, 
	yukuai3@...wei.com, dan.j.williams@...el.com, vishal.l.verma@...el.com, 
	dave.jiang@...el.com, ira.weiny@...el.com, dlemoal@...nel.org, yanjun.zhu@...ux.dev, 
	kch@...dia.com, hare@...e.de, zhengqixing@...wei.com, john.g.garry@...cle.com, 
	geliang@...nel.org, xni@...hat.com, colyli@...e.de, linux-block@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org, nvdimm@...ts.linux.dev, 
	yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH 09/12] badblocks: fix missing bad blocks on retry in
 _badblocks_check()

On Fri, Feb 21, 2025 at 04:11:06PM +0800, Zheng Qixing wrote:
> From: Zheng Qixing <zhengqixing@...wei.com>
> 
> The bad blocks check would miss bad blocks when retrying under contention,
> as checking parameters are not reset. These stale values from the previous
> attempt could lead to incorrect scanning in the subsequent retry.
> 
> Move seqlock to outer function and reinitialize checking state for each
> retry. This ensures a clean state for each check attempt, preventing any
> missed bad blocks.
> 
> Fixes: 3ea3354cb9f0 ("badblocks: improve badblocks_check() for multiple ranges handling")
> Signed-off-by: Zheng Qixing <zhengqixing@...wei.com>

Looks good to me.

Acked-by: Coly Li <colyli@...nel.org>

Thanks.

> ---
>  block/badblocks.c | 50 +++++++++++++++++++++++------------------------
>  1 file changed, 24 insertions(+), 26 deletions(-)
> 
> diff --git a/block/badblocks.c b/block/badblocks.c
> index 381f9db423d6..79d91be468c4 100644
> --- a/block/badblocks.c
> +++ b/block/badblocks.c
> @@ -1191,31 +1191,12 @@ static int _badblocks_clear(struct badblocks *bb, sector_t s, int sectors)
>  static int _badblocks_check(struct badblocks *bb, sector_t s, int sectors,
>  			    sector_t *first_bad, int *bad_sectors)
>  {
> -	int unacked_badblocks, acked_badblocks;
>  	int prev = -1, hint = -1, set = 0;
>  	struct badblocks_context bad;
> -	unsigned int seq;
> +	int unacked_badblocks = 0;
> +	int acked_badblocks = 0;
> +	u64 *p = bb->page;
>  	int len, rv;
> -	u64 *p;
> -
> -	WARN_ON(bb->shift < 0 || sectors == 0);
> -
> -	if (bb->shift > 0) {
> -		sector_t target;
> -
> -		/* round the start down, and the end up */
> -		target = s + sectors;
> -		rounddown(s, 1 << bb->shift);
> -		roundup(target, 1 << bb->shift);
> -		sectors = target - s;
> -	}
> -
> -retry:
> -	seq = read_seqbegin(&bb->lock);
> -
> -	p = bb->page;
> -	unacked_badblocks = 0;
> -	acked_badblocks = 0;
>  
>  re_check:
>  	bad.start = s;
> @@ -1281,9 +1262,6 @@ static int _badblocks_check(struct badblocks *bb, sector_t s, int sectors,
>  	else
>  		rv = 0;
>  
> -	if (read_seqretry(&bb->lock, seq))
> -		goto retry;
> -
>  	return rv;
>  }
>  
> @@ -1324,7 +1302,27 @@ static int _badblocks_check(struct badblocks *bb, sector_t s, int sectors,
>  int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
>  			sector_t *first_bad, int *bad_sectors)
>  {
> -	return _badblocks_check(bb, s, sectors, first_bad, bad_sectors);
> +	unsigned int seq;
> +	int rv;
> +
> +	WARN_ON(bb->shift < 0 || sectors == 0);
> +
> +	if (bb->shift > 0) {
> +		/* round the start down, and the end up */
> +		sector_t target = s + sectors;
> +
> +		rounddown(s, 1 << bb->shift);
> +		roundup(target, 1 << bb->shift);
> +		sectors = target - s;
> +	}
> +
> +retry:
> +	seq = read_seqbegin(&bb->lock);
> +	rv = _badblocks_check(bb, s, sectors, first_bad, bad_sectors);
> +	if (read_seqretry(&bb->lock, seq))
> +		goto retry;
> +
> +	return rv;
>  }
>  EXPORT_SYMBOL_GPL(badblocks_check);
>  
> -- 
> 2.39.2
> 

-- 
Coly Li