Hi Neil,
I am attaching the patch file as I am seeing some issues with
copy-paste into the mail.
On Wed, Jun 17, 2009 at 3:45 PM, SandeepKsinha<sandeepksinha@xxxxxxxxx> wrote:
> Hi Neil,
> My Mistake. I missed "stg refresh". Here is the updated one.
> Sorry for the inconvinience.
>
> Signed-off-by: Sandeep K Sinha <sandeepksinha@xxxxxxxxx>
> Due to the lack of memory ordering guarantees, we may have races around
> mddev->conf. This patch addresses the same using rcu protection to avoid
> such race conditions.
> diff --git a/drivers/md/linear.c b/drivers/md/linear.c
> index 9ad6ec4..f254a8a 100644
> --- a/drivers/md/linear.c
> +++ b/drivers/md/linear.c
> @@ -28,10 +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;
> +
> lo = 0;
> hi = mddev->raid_disks - 1;
> + conf = rcu_dereference(mddev->private);
>
> /*
> * Binary Search
> @@ -45,7 +46,6 @@ static inline dev_info_t *which_dev(mddev_t *mddev,
> sector_t sector)
> else
> lo = mid + 1;
> }
> -
> return conf->disks + lo;
> }
>
> @@ -66,7 +66,9 @@ static int linear_mergeable_bvec(struct request_queue *q,
> unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
> sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
>
> + rcu_read_lock();
> dev0 = which_dev(mddev, sector);
> + rcu_read_unlock();
> maxsectors = dev0->end_sector - sector;
>
> if (maxsectors < bio_sectors)
> @@ -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;
> @@ -231,8 +245,15 @@ 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;
> +
> + /*
> + * We do not require rcu protection here since
> + * we hold reconfig_mutex for both linear_add and
> + * linear_stop, so they cannot race.
> + */
> +
> + conf = rcu_dereference(mddev->private);
> blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
> do {
> linear_conf_t *t = conf->prev;
> @@ -262,7 +283,9 @@ static int linear_make_request (struct request_queue *q,
> struct bio *bio)
> bio_sectors(bio));
> part_stat_unlock();
>
> + rcu_read_lock();
> tmp_dev = which_dev(mddev, bio->bi_sector);
> + rcu_read_unlock();
> start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
>
> if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
> --
> Regards,
> Sandeep.
>
>
>
>
>
>
> “To learn is to change. Education is a process that changes the learner.”
>
--
Regards,
Sandeep.
“To learn is to change. Education is a process that changes the learner.”
commit 848cea3974a6c63a8a810b8e74c87a42ea727399
Author: Sandeep K Sinha <sandeepksinha@xxxxxxxxx>
Date: Wed Jun 17 15:33:37 2009 +0530
Due to the lack of memory ordering guarantees, we may have races around
mddev->conf. This patch addresses the same using rcu protection to avoid
such race conditions.
diff --git a/drivers/md/linear.c b/drivers/md/linear.c
index 9ad6ec4..f254a8a 100644
--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -28,10 +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;
+
lo = 0;
hi = mddev->raid_disks - 1;
+ conf = rcu_dereference(mddev->private);
/*
* Binary Search
@@ -45,7 +46,6 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
else
lo = mid + 1;
}
-
return conf->disks + lo;
}
@@ -66,7 +66,9 @@ static int linear_mergeable_bvec(struct request_queue *q,
unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
+ rcu_read_lock();
dev0 = which_dev(mddev, sector);
+ rcu_read_unlock();
maxsectors = dev0->end_sector - sector;
if (maxsectors < bio_sectors)
@@ -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;
@@ -231,8 +245,15 @@ 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;
+
+ /*
+ * We do not require rcu protection here since
+ * we hold reconfig_mutex for both linear_add and
+ * linear_stop, so they cannot race.
+ */
+
+ conf = rcu_dereference(mddev->private);
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
do {
linear_conf_t *t = conf->prev;
@@ -262,7 +283,9 @@ static int linear_make_request (struct request_queue *q, struct bio *bio)
bio_sectors(bio));
part_stat_unlock();
+ rcu_read_lock();
tmp_dev = which_dev(mddev, bio->bi_sector);
+ rcu_read_unlock();
start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
