Re: [PATCH 2/2] md/raid5: preserve active PPL log when removing a replacement

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] md/raid5: raid5_remove_disk() fails to clear slot beyond
  raid_disks with PPL
--

commit ade16f0f32de5eb72fa3bf67b1040d7514f41d37
Author: Yingjie Wang <x-professor@outlook.com>

md/raid5: preserve active PPL log when removing a replacement

This commit restricts the log_modify(conf, rdev, false) call in
raid5_remove_disk() to cases where the removed device is the slot's active
rdev rather than a replacement device, and moves clearing *rdevp after
log_modify().

> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 455e36ddceeed..2f4fe416113c0 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -8474,12 +8474,12 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
>  		err = -EBUSY;
>  		goto abort;
>  	}
> -	WRITE_ONCE(*rdevp, NULL);
> -	if (!err) {
> +	if (rdev == p->rdev) {
>  		err = log_modify(conf, rdev, false);
>  		if (err)
>  			goto abort;
>  	}
> +	WRITE_ONCE(*rdevp, NULL);

[Severity: Medium]
Does moving WRITE_ONCE(*rdevp, NULL) after log_modify() prevent removing a
disk in a slot where number >= conf->raid_disks when PPL is enabled?

After shrinking an array, conf->raid_disks is smaller than conf->pool_size
while extra disks remain in conf->disks[number].rdev.  If PPL is enabled
before those disks are detached, ppl_conf->count is initialized to
conf->raid_disks, and ppl_modify_log() rejects any slot at or beyond
conf->raid_disks:

drivers/md/raid5-ppl.c:ppl_modify_log() {
	...
	if (rdev->raid_disk >= ppl_conf->count)
		return -ENODEV;
	...
}

Jumping to abort on that error before clearing *rdevp leaves rdev stuck in
p->rdev, and every subsequent removal attempt fails with -ENODEV.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1794215128.git.x-professor@outlook.com?part=2