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Subject[24/73] md: avoid spinlock problem in blk_throtl_exit
2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: NeilBrown <neilb@suse.de>

commit da9cf5050a2e3dbc3cf26a8d908482eb4485ed49 upstream.

blk_throtl_exit assumes that ->queue_lock still exists,
so make sure that it does.
To do this, we stop redirecting ->queue_lock to conf->device_lock
and leave it pointing where it is initialised - __queue_lock.

As the blk_plug functions check the ->queue_lock is held, we now
take that spin_lock explicitly around the plug functions. We don't
need the locking, just the warning removal.

This is needed for any kernel with the blk_throtl code, which is
which is 2.6.37 and later.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/md/linear.c | 1 -
drivers/md/multipath.c | 1 -
drivers/md/raid0.c | 1 -
drivers/md/raid1.c | 6 ++++--
drivers/md/raid10.c | 7 ++++---
drivers/md/raid5.c | 1 -
6 files changed, 8 insertions(+), 9 deletions(-)

--- a/drivers/md/linear.c
+++ b/drivers/md/linear.c
@@ -216,7 +216,6 @@ static int linear_run (mddev_t *mddev)

if (md_check_no_bitmap(mddev))
return -EINVAL;
- mddev->queue->queue_lock = &mddev->queue->__queue_lock;
conf = linear_conf(mddev, mddev->raid_disks);

if (!conf)
--- a/drivers/md/multipath.c
+++ b/drivers/md/multipath.c
@@ -435,7 +435,6 @@ static int multipath_run (mddev_t *mddev
* bookkeeping area. [whatever we allocate in multipath_run(),
* should be freed in multipath_stop()]
*/
- mddev->queue->queue_lock = &mddev->queue->__queue_lock;

conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
mddev->private = conf;
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -353,7 +353,6 @@ static int raid0_run(mddev_t *mddev)
if (md_check_no_bitmap(mddev))
return -EINVAL;
blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
- mddev->queue->queue_lock = &mddev->queue->__queue_lock;

/* if private is not null, we are here after takeover */
if (mddev->private == NULL) {
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -593,7 +593,10 @@ static int flush_pending_writes(conf_t *
if (conf->pending_bio_list.head) {
struct bio *bio;
bio = bio_list_get(&conf->pending_bio_list);
+ /* Only take the spinlock to quiet a warning */
+ spin_lock(conf->mddev->queue->queue_lock);
blk_remove_plug(conf->mddev->queue);
+ spin_unlock(conf->mddev->queue->queue_lock);
spin_unlock_irq(&conf->device_lock);
/* flush any pending bitmap writes to
* disk before proceeding w/ I/O */
@@ -959,7 +962,7 @@ static int make_request(mddev_t *mddev,
atomic_inc(&r1_bio->remaining);
spin_lock_irqsave(&conf->device_lock, flags);
bio_list_add(&conf->pending_bio_list, mbio);
- blk_plug_device(mddev->queue);
+ blk_plug_device_unlocked(mddev->queue);
spin_unlock_irqrestore(&conf->device_lock, flags);
}
r1_bio_write_done(r1_bio, bio->bi_vcnt, behind_pages, behind_pages != NULL);
@@ -2024,7 +2027,6 @@ static int run(mddev_t *mddev)
if (IS_ERR(conf))
return PTR_ERR(conf);

- mddev->queue->queue_lock = &conf->device_lock;
list_for_each_entry(rdev, &mddev->disks, same_set) {
disk_stack_limits(mddev->gendisk, rdev->bdev,
rdev->data_offset << 9);
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -662,7 +662,10 @@ static int flush_pending_writes(conf_t *
if (conf->pending_bio_list.head) {
struct bio *bio;
bio = bio_list_get(&conf->pending_bio_list);
+ /* Spinlock only taken to quiet a warning */
+ spin_lock(conf->mddev->queue->queue_lock);
blk_remove_plug(conf->mddev->queue);
+ spin_unlock(conf->mddev->queue->queue_lock);
spin_unlock_irq(&conf->device_lock);
/* flush any pending bitmap writes to disk
* before proceeding w/ I/O */
@@ -971,7 +974,7 @@ static int make_request(mddev_t *mddev,
atomic_inc(&r10_bio->remaining);
spin_lock_irqsave(&conf->device_lock, flags);
bio_list_add(&conf->pending_bio_list, mbio);
- blk_plug_device(mddev->queue);
+ blk_plug_device_unlocked(mddev->queue);
spin_unlock_irqrestore(&conf->device_lock, flags);
}

@@ -2303,8 +2306,6 @@ static int run(mddev_t *mddev)
if (!conf)
goto out;

- mddev->queue->queue_lock = &conf->device_lock;
-
mddev->thread = conf->thread;
conf->thread = NULL;

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5205,7 +5205,6 @@ static int run(mddev_t *mddev)

mddev->queue->backing_dev_info.congested_data = mddev;
mddev->queue->backing_dev_info.congested_fn = raid5_congested;
- mddev->queue->queue_lock = &conf->device_lock;
mddev->queue->unplug_fn = raid5_unplug_queue;

chunk_size = mddev->chunk_sectors << 9;



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