diff options
| -rw-r--r-- | drivers/md/linear.c | 39 | ||||
| -rw-r--r-- | drivers/md/linear.h | 1 |
2 files changed, 35 insertions, 5 deletions
diff --git a/drivers/md/linear.c b/drivers/md/linear.c index 5975c9915684..26a73b2002cf 100644 --- a/drivers/md/linear.c +++ b/drivers/md/linear.c @@ -53,18 +53,26 @@ static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector) return conf->disks + lo; } +/* + * In linear_congested() conf->raid_disks is used as a copy of + * mddev->raid_disks to iterate conf->disks[], because conf->raid_disks + * and conf->disks[] are created in linear_conf(), they are always + * consitent with each other, but mddev->raid_disks does not. + */ static int linear_congested(struct mddev *mddev, int bits) { struct linear_conf *conf; int i, ret = 0; - conf = mddev->private; + rcu_read_lock(); + conf = rcu_dereference(mddev->private); - for (i = 0; i < mddev->raid_disks && !ret ; i++) { + for (i = 0; i < conf->raid_disks && !ret ; i++) { struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev); ret |= bdi_congested(&q->backing_dev_info, bits); } + rcu_read_unlock(); return ret; } @@ -144,6 +152,19 @@ static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks) conf->disks[i-1].end_sector + conf->disks[i].rdev->sectors; + /* + * conf->raid_disks is copy of mddev->raid_disks. The reason to + * keep a copy of mddev->raid_disks in struct linear_conf is, + * mddev->raid_disks may not be consistent with pointers number of + * conf->disks[] when it is updated in linear_add() and used to + * iterate old conf->disks[] earray in linear_congested(). + * Here conf->raid_disks is always consitent with number of + * pointers in conf->disks[] array, and mddev->private is updated + * with rcu_assign_pointer() in linear_addr(), such race can be + * avoided. + */ + conf->raid_disks = raid_disks; + return conf; out: @@ -196,15 +217,23 @@ static int linear_add(struct mddev *mddev, struct md_rdev *rdev) if (!newconf) return -ENOMEM; + /* newconf->raid_disks already keeps a copy of * the increased + * value of mddev->raid_disks, WARN_ONCE() is just used to make + * sure of this. It is possible that oldconf is still referenced + * in linear_congested(), therefore kfree_rcu() is used to free + * oldconf until no one uses it anymore. + */ mddev_suspend(mddev); - oldconf = mddev->private; + oldconf = rcu_dereference(mddev->private); mddev->raid_disks++; - mddev->private = newconf; + WARN_ONCE(mddev->raid_disks != newconf->raid_disks, + "copied raid_disks doesn't match mddev->raid_disks"); + rcu_assign_pointer(mddev->private, newconf); md_set_array_sectors(mddev, linear_size(mddev, 0, 0)); set_capacity(mddev->gendisk, mddev->array_sectors); mddev_resume(mddev); revalidate_disk(mddev->gendisk); - kfree(oldconf); + kfree_rcu(oldconf, rcu); return 0; } diff --git a/drivers/md/linear.h b/drivers/md/linear.h index b685ddd7d7f7..8d392e6098b3 100644 --- a/drivers/md/linear.h +++ b/drivers/md/linear.h @@ -10,6 +10,7 @@ struct linear_conf { struct rcu_head rcu; sector_t array_sectors; + int raid_disks; /* a copy of mddev->raid_disks */ struct dev_info disks[0]; }; #endif |