raid5: guarantee enough stripes to avoid reshape hang

If there aren't enough stripes, reshape will hang. We have a check for
this in new reshape, but miss it for reshape resume, hence we could see
hang in reshape resume. This patch forces enough stripes existed if
reshape resumes.

Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index da583bb43c84e5faaa0de0adfb2853b173221847..b95c54c0e596ab1a5ccd3d868361c1ff948237b4 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -6639,6 +6639,16 @@ static struct r5conf *setup_conf(struct mddev *mddev)
        }
 
        conf->min_nr_stripes = NR_STRIPES;
+       if (mddev->reshape_position != MaxSector) {
+               int stripes = max_t(int,
+                       ((mddev->chunk_sectors << 9) / STRIPE_SIZE) * 4,
+                       ((mddev->new_chunk_sectors << 9) / STRIPE_SIZE) * 4);
+               conf->min_nr_stripes = max(NR_STRIPES, stripes);
+               if (conf->min_nr_stripes != NR_STRIPES)
+                       printk(KERN_INFO
+                               "md/raid:%s: force stripe size %d for reshape\n",
+                               mdname(mddev), conf->min_nr_stripes);
+       }
        memory = conf->min_nr_stripes * (sizeof(struct stripe_head) +
                 max_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
        atomic_set(&conf->empty_inactive_list_nr, NR_STRIPE_HASH_LOCKS);