Re: [PATCH 3/3] raid5: introduce MD_BROKEN

[Guoqing Jiang <guoqing.jiang@linux.dev>]

On 1/27/22 11:39 PM, Mariusz Tkaczyk wrote:
> Raid456 module had allowed to achieve failed state. It was fixed by
> fb73b357fb9 ("raid5: block failing device if raid will be failed").
> This fix introduces a bug, now if raid5 fails during IO, it may result
> with a hung task without completion. Faulty flag on the device is
> necessary to process all requests and is checked many times, mainly in
> analyze_stripe().
> Allow to set faulty on drive again and set MD_BROKEN if raid is failed.
>
> As a result, this level is allowed to achieve failed state again, but
> communication with userspace (via -EBUSY status) will be preserved.
>
> This restores possibility to fail array via #mdadm --set-faulty command
> and will be fixed by additional verification on mdadm side.

Again, you better to send mdadm change along with the series.

> Reproduction steps:
>   mdadm -CR imsm -e imsm -n 3 /dev/nvme[0-2]n1
>   mdadm -CR r5 -e imsm -l5 -n3 /dev/nvme[0-2]n1 --assume-clean
>   mkfs.xfs /dev/md126 -f
>   mount /dev/md126 /mnt/root/
>
>   fio --filename=/mnt/root/file --size=5GB --direct=1 --rw=randrw
> --bs=64k --ioengine=libaio --iodepth=64 --runtime=240 --numjobs=4
> --time_based --group_reporting --name=throughput-test-job
> --eta-newline=1 &
>
>   echo 1 > /sys/block/nvme2n1/device/device/remove
>   echo 1 > /sys/block/nvme1n1/device/device/remove
>
>   [ 1475.787779] Call Trace:
>   [ 1475.793111] __schedule+0x2a6/0x700
>   [ 1475.799460] schedule+0x38/0xa0
>   [ 1475.805454] raid5_get_active_stripe+0x469/0x5f0 [raid456]
>   [ 1475.813856] ? finish_wait+0x80/0x80
>   [ 1475.820332] raid5_make_request+0x180/0xb40 [raid456]
>   [ 1475.828281] ? finish_wait+0x80/0x80
>   [ 1475.834727] ? finish_wait+0x80/0x80
>   [ 1475.841127] ? finish_wait+0x80/0x80
>   [ 1475.847480] md_handle_request+0x119/0x190
>   [ 1475.854390] md_make_request+0x8a/0x190
>   [ 1475.861041] generic_make_request+0xcf/0x310
>   [ 1475.868145] submit_bio+0x3c/0x160
>   [ 1475.874355] iomap_dio_submit_bio.isra.20+0x51/0x60
>   [ 1475.882070] iomap_dio_bio_actor+0x175/0x390
>   [ 1475.889149] iomap_apply+0xff/0x310
>   [ 1475.895447] ? iomap_dio_bio_actor+0x390/0x390
>   [ 1475.902736] ? iomap_dio_bio_actor+0x390/0x390
>   [ 1475.909974] iomap_dio_rw+0x2f2/0x490
>   [ 1475.916415] ? iomap_dio_bio_actor+0x390/0x390
>   [ 1475.923680] ? atime_needs_update+0x77/0xe0
>   [ 1475.930674] ? xfs_file_dio_aio_read+0x6b/0xe0 [xfs]
>   [ 1475.938455] xfs_file_dio_aio_read+0x6b/0xe0 [xfs]
>   [ 1475.946084] xfs_file_read_iter+0xba/0xd0 [xfs]
>   [ 1475.953403] aio_read+0xd5/0x180
>   [ 1475.959395] ? _cond_resched+0x15/0x30
>   [ 1475.965907] io_submit_one+0x20b/0x3c0
>   [ 1475.972398] __x64_sys_io_submit+0xa2/0x180
>   [ 1475.979335] ? do_io_getevents+0x7c/0xc0
>   [ 1475.986009] do_syscall_64+0x5b/0x1a0
>   [ 1475.992419] entry_SYSCALL_64_after_hwframe+0x65/0xca
>   [ 1476.000255] RIP: 0033:0x7f11fc27978d
>   [ 1476.006631] Code: Bad RIP value.
>   [ 1476.073251] INFO: task fio:3877 blocked for more than 120 seconds.

Does it also happen to non imsm array? And did you try to reproduce it with
revert fb73b357fb? I suppose fb73b357fb9 introduced the regression given
it is fixed by this one.

> Fixes: fb73b357fb9 ("raid5: block failing device if raid will be failed")
> Signed-off-by: Mariusz Tkaczyk<mariusz.tkaczyk@linux.intel.com>
> ---
>   drivers/md/raid1.c |  1 +
>   drivers/md/raid5.c | 49 +++++++++++++++++++++++-----------------------
>   2 files changed, 25 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index b222bafa1196..58c8eddb0f55 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1627,6 +1627,7 @@ static void raid1_status(struct seq_file *seq, struct mddev *mddev)
>    * - if is on @rdev is removed.
>    * - if is off, @rdev is not removed, but recovery from it is disabled (@rdev is
>    *   very likely to fail).
> + *

You probably don't want to touch raid1 file in this patch.

>    * In both cases, &MD_BROKEN will be set in &mddev->flags.
>    */
>   static void raid1_error(struct mddev *mddev, struct md_rdev *rdev)
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 1240a5c16af8..bee953c8007f 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -686,17 +686,21 @@ int raid5_calc_degraded(struct r5conf *conf)
>   	return degraded;
>   }
>   
> -static int has_failed(struct r5conf *conf)
> +static bool has_failed(struct r5conf *conf)
>   {
> -	int degraded;
> +	int degraded = conf->mddev->degraded;
>   
> -	if (conf->mddev->reshape_position == MaxSector)
> -		return conf->mddev->degraded > conf->max_degraded;
> +	if (test_bit(MD_BROKEN, &conf->mddev->flags))
> +		return true;

If one member disk was set Faulty which caused BROKEN was set, is it
possible to re-add the same member disk again?

[root@vm ~]# echo faulty > /sys/block/md0/md/dev-loop1/state
[root@vm ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 loop2[2] loop1[0](F)
       1046528 blocks super 1.2 level 5, 512k chunk, algorithm 2 [2/1] [_U]
       bitmap: 0/1 pages [0KB], 65536KB chunk

unused devices: <none>
[root@vm ~]# echo re-add > /sys/block/md0/md/dev-loop1/state
[root@vm ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 loop2[2] loop1[0]
       1046528 blocks super 1.2 level 5, 512k chunk, algorithm 2 [2/2] [UU]
       bitmap: 0/1 pages [0KB], 65536KB chunk

unused devices: <none>

And have you run mdadm test against the series?

> -	degraded = raid5_calc_degraded(conf);
> -	if (degraded > conf->max_degraded)
> -		return 1;
> -	return 0;
> +	if (conf->mddev->reshape_position != MaxSector)
> +		degraded = raid5_calc_degraded(conf);
> +
> +	if (degraded > conf->max_degraded) {
> +		set_bit(MD_BROKEN, &conf->mddev->flags);

Why not set BROKEN flags in err handler to align with other levels? Or
do it in md_error only.

> +		return true;
> +	}
> +	return false;
>   }
>   
>   struct stripe_head *
> @@ -2877,34 +2881,29 @@ static void raid5_error(struct mddev *mddev, struct md_rdev *rdev)
>   	unsigned long flags;
>   	pr_debug("raid456: error called\n");
>   
> +	pr_crit("md/raid:%s: Disk failure on %s, disabling device.\n",
> +		mdname(mddev), bdevname(rdev->bdev, b));
> +
>   	spin_lock_irqsave(&conf->device_lock, flags);
> +	set_bit(Faulty, &rdev->flags);
> +	clear_bit(In_sync, &rdev->flags);
> +	mddev->degraded = raid5_calc_degraded(conf);
>   
> -	if (test_bit(In_sync, &rdev->flags) &&
> -	    mddev->degraded == conf->max_degraded) {
> -		/*
> -		 * Don't allow to achieve failed state
> -		 * Don't try to recover this device
> -		 */
> +	if (has_failed(conf)) {
>   		conf->recovery_disabled = mddev->recovery_disabled;
> -		spin_unlock_irqrestore(&conf->device_lock, flags);
> -		return;

Ok, I think commit fb73b357fb985cc652a72a41541d25915c7f9635 is
effectively reverted by this hunk. So I would prefer to separate the
revert part from this patch, just my 0.02$.

Thanks,
Guoqing