[PATCH] md linear: Protecting mddev with rcu locks to avoid races in

SandeepKsinha
2009-06-06T15:24:09Z

Signed-off-by: Sandeep K Sinha <sandeepksinha@gmail.com>

Protecting mddev with barriers to avoid races.

diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index 9ad6ec4..a56095c 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -28,9 +28,11 @@
static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
{
int lo, mid, hi;
- linear_conf_t *conf = mddev_to_conf(mddev);
+ linear_conf_t *conf;

+ rcu_read_lock();
lo = 0;
+ conf = rcu_dereference(mddev->private);
hi = mddev->raid_disks - 1;

/*
@@ -45,7 +47,7 @@ static inline dev_info_t *which_dev(mddev_t *mddev,
sector_t sector)
else
lo = mid + 1;
}
-
+ rcu_read_unlock();
return conf->disks + lo;
}

@@ -86,36 +88,49 @@ static int linear_mergeable_bvec(struct request_queue *q,
static void linear_unplug(struct request_queue *q)
{
mddev_t *mddev = q->queuedata;
- linear_conf_t *conf = mddev_to_conf(mddev);
+ linear_conf_t *conf;
int i;

+ rcu_read_lock();
+ conf = rcu_dereference(mddev->private);
+
for (i=0; i < mddev->raid_disks; i++) {
struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
blk_unplug(r_queue);
}
+ rcu_read_unlock();
}

static int linear_congested(void *data, int bits)
{
mddev_t *mddev = data;
- linear_conf_t *conf = mddev_to_conf(mddev);
+ linear_conf_t *conf;
int i, ret = 0;

+ rcu_read_lock();
+ conf = rcu_dereference(mddev->private);
+
for (i = 0; i < mddev->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;
}

static sector_t linear_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
- linear_conf_t *conf = mddev_to_conf(mddev);
-
+ linear_conf_t *conf;
+ sector_t array_sectors;
+ rcu_read_lock();
+ conf = rcu_dereference(mddev->private);
WARN_ONCE(sectors || raid_disks,
"%s does not support generic reshape\n", __func__);
-
- return conf->array_sectors;
+ array_sectors = conf->array_sectors;
+ rcu_read_unlock();
+
+ return array_sectors;
}

static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
@@ -215,15 +230,14 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
return -EINVAL;

rdev->raid_disk = rdev->saved_raid_disk;
-
- newconf = linear_conf(mddev,mddev->raid_disks+1);
+ newconf = linear_conf(mddev,mddev->raid_disks + 1);

if (!newconf)
return -ENOMEM;

newconf->prev = mddev_to_conf(mddev);
- mddev->private = newconf;
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);
return 0;
@@ -231,14 +245,17 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)

static int linear_stop (mddev_t *mddev)
{
- linear_conf_t *conf = mddev_to_conf(mddev);
-
+ linear_conf_t *conf;
+
+ rcu_read_lock();
+ conf = rcu_dereference(mddev->private);
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
do {
linear_conf_t *t = conf->prev;
kfree(conf);
conf = t;
} while (conf);
+ rcu_read_unlock();

return 0;
}
--
Regards,
Sandeep.

“To learn is to change. Education is a process that changes the learner.”