Re: [PATCH v2] md/raid1: Add check for missing source disk in process_checks()

[Yu Kuai <yukuai1@huaweicloud.com>]

Hi,

在 2025/04/08 22:38, Meir Elisha 写道:
> During recovery/check operations, the process_checks function loops
> through available disks to find a 'primary' source with successfully
> read data.
> 
> If no suitable source disk is found after checking all possibilities,
> the 'primary' index will reach conf->raid_disks * 2. Add an explicit
> check for this condition after the loop. If no source disk was found,
> print an error message and return early to prevent further processing
> without a valid primary source.
> 
> Signed-off-by: Meir Elisha <meir.elisha@volumez.com>
> ---

Just to be sure, do you tested this version?

Thanks,
Kuai

> Changes from v1:
> 	- Don't fix read errors on recovery/check
> 
> This was observed when forcefully disconnecting all iSCSI devices backing
> a RAID1 array(using --failfast flag) during a check operation, causing
> all reads within process_checks to fail. The resulting kernel oops shows:
> 
>    BUG: kernel NULL pointer dereference, address: 0000000000000040
>    RIP: 0010:process_checks+0x25e/0x5e0 [raid1]
>    Code: ... <4c> 8b 53 40 ... // mov r10,[rbx+0x40]
>    Call Trace:
>     process_checks
>     sync_request_write
>     raid1d
>     md_thread
>     kthread
>     ret_from_fork
> 
>   drivers/md/raid1.c | 26 ++++++++++++++++----------
>   1 file changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 0efc03cea24e..de9bccbe7337 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -2200,14 +2200,9 @@ static int fix_sync_read_error(struct r1bio *r1_bio)
>   				if (!rdev_set_badblocks(rdev, sect, s, 0))
>   					abort = 1;
>   			}
> -			if (abort) {
> -				conf->recovery_disabled =
> -					mddev->recovery_disabled;
> -				set_bit(MD_RECOVERY_INTR, &mddev->recovery);
> -				md_done_sync(mddev, r1_bio->sectors, 0);
> -				put_buf(r1_bio);
> +			if (abort)
>   				return 0;
> -			}
> +
>   			/* Try next page */
>   			sectors -= s;
>   			sect += s;
> @@ -2346,10 +2341,21 @@ static void sync_request_write(struct mddev *mddev, struct r1bio *r1_bio)
>   	int disks = conf->raid_disks * 2;
>   	struct bio *wbio;
>   
> -	if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
> -		/* ouch - failed to read all of that. */
> -		if (!fix_sync_read_error(r1_bio))
> +	if (!test_bit(R1BIO_Uptodate, &r1_bio->state)) {
> +		/*
> +		 * ouch - failed to read all of that.
> +		 * No need to fix read error for check/repair
> +		 * because all member disks are read.
> +		 */
> +		if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) ||
> +		    !fix_sync_read_error(r1_bio)) {
> +			conf->recovery_disabled = mddev->recovery_disabled;
> +			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
> +			md_done_sync(mddev, r1_bio->sectors, 0);
> +			put_buf(r1_bio);
>   			return;
> +		}
> +	}
>   
>   	if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
>   		process_checks(r1_bio);
>