A bio-based DM device no longer defaults to having a fully initialized
request_queue (request_fn, elevator, etc). This means bio-based DM
devices no longer register elevator sysfs attributes ('iosched/' tree
or 'scheduler' other than "none").
In contrast, a request-based DM device will always have a full
request_queue and will register elevator sysfs attributes. Therefore
a user can determine a DM device's type by checking if elevator sysfs
attributes exist.
First allocate a minimalist request_queue structure for a DM device
(needed for both bio and request-based DM).
Initialization of a full request_queue is deferred until it is known
that the DM device is request-based -- at the end of the table load
sequence.
Factor DM device's request_queue initialization:
- common to both request-based and bio-based into dm_init_md_queue().
- specific to request-based into dm_init_request_based_queue().
The md->type_lock mutex is used to protect md->queue, in addition to
md->type, during table_load().
A DM device's first table_load will establish the immutable md->type.
But md->queue initialization, based on md->type, may fail at that time
(because blk_init_allocated_queue cannot allocate memory). Therefore
any subsequent table_load must (re)try dm_setup_md_queue independent of
establishing md->type.
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Acked-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
---
v5: revised patch header, no code changes
drivers/md/dm-ioctl.c | 11 +++++
drivers/md/dm.c | 94 ++++++++++++++++++++++++++++++++++++--------------
drivers/md/dm.h | 2 +
3 files changed, 80 insertions(+), 27 deletions(-)
Index: linux-2.6/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-ioctl.c
+++ linux-2.6/drivers/md/dm-ioctl.c
@@ -1176,7 +1176,7 @@ static int table_load(struct dm_ioctl *p
goto out;
}
- /* Protect md->type against concurrent table loads. */
+ /* Protect md->type and md->queue against concurrent table loads. */
dm_lock_md_type(md);
if (dm_get_md_type(md) == DM_TYPE_NONE) {
/* initial table load, set md's type based on table's type */
@@ -1188,6 +1188,15 @@ static int table_load(struct dm_ioctl *p
r = -EINVAL;
goto out;
}
+
+ /* setup md->queue to reflect md's type (may block) */
+ r = dm_setup_md_queue(md);
+ if (r) {
+ DMWARN("unable to setup device queue for this table.");
+ dm_table_destroy(t);
+ dm_unlock_md_type(md);
+ goto out;
+ }
dm_unlock_md_type(md);
/* stage inactive table */
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c
+++ linux-2.6/drivers/md/dm.c
@@ -124,7 +124,7 @@ struct mapped_device {
struct request_queue *queue;
unsigned type;
- /* Protect type against concurrent access. */
+ /* Protect queue and type against concurrent access. */
struct mutex type_lock;
struct gendisk *disk;
@@ -1853,6 +1853,28 @@ static const struct block_device_operati
static void dm_wq_work(struct work_struct *work);
static void dm_rq_barrier_work(struct work_struct *work);
+static void dm_init_md_queue(struct mapped_device *md)
+{
+ /*
+ * Request-based dm devices cannot be stacked on top of bio-based dm
+ * devices. The type of this dm device has not been decided yet.
+ * The type is decided at the first table loading time.
+ * To prevent problematic device stacking, clear the queue flag
+ * for request stacking support until then.
+ *
+ * This queue is new, so no concurrency on the queue_flags.
+ */
+ queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
+
+ md->queue->queuedata = md;
+ md->queue->backing_dev_info.congested_fn = dm_any_congested;
+ md->queue->backing_dev_info.congested_data = md;
+ blk_queue_make_request(md->queue, dm_request);
+ blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
+ md->queue->unplug_fn = dm_unplug_all;
+ blk_queue_merge_bvec(md->queue, dm_merge_bvec);
+}
+
/*
* Allocate and initialise a blank device with a given minor.
*/
@@ -1892,34 +1914,11 @@ static struct mapped_device *alloc_dev(i
INIT_LIST_HEAD(&md->uevent_list);
spin_lock_init(&md->uevent_lock);
- md->queue = blk_init_queue(dm_request_fn, NULL);
+ md->queue = blk_alloc_queue(GFP_KERNEL);
if (!md->queue)
goto bad_queue;
- /*
- * Request-based dm devices cannot be stacked on top of bio-based dm
- * devices. The type of this dm device has not been decided yet,
- * although we initialized the queue using blk_init_queue().
- * The type is decided at the first table loading time.
- * To prevent problematic device stacking, clear the queue flag
- * for request stacking support until then.
- *
- * This queue is new, so no concurrency on the queue_flags.
- */
- queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
- md->saved_make_request_fn = md->queue->make_request_fn;
- md->queue->queuedata = md;
- md->queue->backing_dev_info.congested_fn = dm_any_congested;
- md->queue->backing_dev_info.congested_data = md;
- blk_queue_make_request(md->queue, dm_request);
- blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
- md->queue->unplug_fn = dm_unplug_all;
- blk_queue_merge_bvec(md->queue, dm_merge_bvec);
- blk_queue_softirq_done(md->queue, dm_softirq_done);
- blk_queue_prep_rq(md->queue, dm_prep_fn);
- blk_queue_lld_busy(md->queue, dm_lld_busy);
- blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH,
- dm_rq_prepare_flush);
+ dm_init_md_queue(md);
md->disk = alloc_disk(1);
if (!md->disk)
@@ -2158,6 +2157,49 @@ unsigned dm_get_md_type(struct mapped_de
return md->type;
}
+/*
+ * Fully initialize a request-based queue (->elevator, ->request_fn, etc).
+ */
+static int dm_init_request_based_queue(struct mapped_device *md)
+{
+ struct request_queue *q = NULL;
+
+ if (md->queue->elevator)
+ return 1;
+
+ /* Fully initialize the queue */
+ q = blk_init_allocated_queue(md->queue, dm_request_fn, NULL);
+ if (!q)
+ return 0;
+
+ md->queue = q;
+ md->saved_make_request_fn = md->queue->make_request_fn;
+ dm_init_md_queue(md);
+ blk_queue_softirq_done(md->queue, dm_softirq_done);
+ blk_queue_prep_rq(md->queue, dm_prep_fn);
+ blk_queue_lld_busy(md->queue, dm_lld_busy);
+ blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN_FLUSH,
+ dm_rq_prepare_flush);
+
+ elv_register_queue(md->queue);
+
+ return 1;
+}
+
+/*
+ * Setup the DM device's queue based on md's type
+ */
+int dm_setup_md_queue(struct mapped_device *md)
+{
+ if ((dm_get_md_type(md) == DM_TYPE_REQUEST_BASED) &&
+ !dm_init_request_based_queue(md)) {
+ DMWARN("Cannot initialize queue for Request-based dm");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static struct mapped_device *dm_find_md(dev_t dev)
{
struct mapped_device *md;
Index: linux-2.6/drivers/md/dm.h
===================================================================
--- linux-2.6.orig/drivers/md/dm.h
+++ linux-2.6/drivers/md/dm.h
@@ -71,6 +71,8 @@ void dm_unlock_md_type(struct mapped_dev
void dm_set_md_type(struct mapped_device *md, unsigned type);
unsigned dm_get_md_type(struct mapped_device *md);
+int dm_setup_md_queue(struct mapped_device *md);
+
/*
* To check the return value from dm_table_find_target().
*/
--
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