linux-kernel - Re: [PATCH -next] radi10: fix leak of 'r10bio->remaining' for recovery

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Message-ID: <7684548b-5e6b-975b-67c2-98c686a4925f@molgen.mpg.de>
Date:   Tue, 7 Mar 2023 10:53:27 +0100
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     song@...nel.org, neilb@...e.de, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next] radi10: fix leak of 'r10bio->remaining' for
 recovery

Dear Yu,


Thank you for your patch.

Am 07.03.23 um 03:27 schrieb Yu Kuai:
> From: Yu Kuai <yukuai3@...wei.com>

There is a small typo in the prefix of the commit message summary: raid10.

It also seems common to use md/raid10 as prefix.

> raid10_sync_request() will add 'r10bio->remaining' for both rdev and
> replacement rdev. However, if the read io failed,

fails (present tense for problem description/summary)

> recovery_request_write() will return without issuring the write io, in

1.  return*s*
2.  assuring?

> this case, end_sync_request() is only called once and 'remaining' is
> leaked, which will cause io hang.

leaked, causing an io hang.

> Fix the probleming by decreasing 'remaining' according to if 'bio' and

problem

> 'repl_bio' is valid.
> 
> Fixes: 24afd80d99f8 ("md/raid10: handle recovery of replacement devices.")
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   drivers/md/raid10.c | 23 +++++++++++++----------
>   1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index a8b5fecef136..f7002a1aa9cf 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -2611,11 +2611,22 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>   {
>   	struct r10conf *conf = mddev->private;
>   	int d;
> -	struct bio *wbio, *wbio2;
> +	struct bio *wbio = r10_bio->devs[1].bio;
> +	struct bio *wbio2 = r10_bio->devs[1].repl_bio;
> +
> +	/* Need to test wbio2->bi_end_io before we call
> +	 * submit_bio_noacct as if the former is NULL,
> +	 * the latter is free to free wbio2.
> +	 */
> +	if (wbio2 && !wbio2->bi_end_io)
> +		wbio2 = NULL;
>   
>   	if (!test_bit(R10BIO_Uptodate, &r10_bio->state)) {
>   		fix_recovery_read_error(r10_bio);
> -		end_sync_request(r10_bio);
> +		if (wbio->bi_end_io)
> +			end_sync_request(r10_bio);
> +		if (wbio2)
> +			end_sync_request(r10_bio);
>   		return;
>   	}
>   
> @@ -2624,14 +2635,6 @@ static void recovery_request_write(struct mddev *mddev, struct r10bio *r10_bio)
>   	 * and submit the write request
>   	 */
>   	d = r10_bio->devs[1].devnum;
> -	wbio = r10_bio->devs[1].bio;
> -	wbio2 = r10_bio->devs[1].repl_bio;
> -	/* Need to test wbio2->bi_end_io before we call
> -	 * submit_bio_noacct as if the former is NULL,
> -	 * the latter is free to free wbio2.
> -	 */
> -	if (wbio2 && !wbio2->bi_end_io)
> -		wbio2 = NULL;
>   	if (wbio->bi_end_io) {
>   		atomic_inc(&conf->mirrors[d].rdev->nr_pending);
>   		md_sync_acct(conf->mirrors[d].rdev->bdev, bio_sectors(wbio));


Kind regards,

Paul