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[PATCH] dm snapshot: add workqueue

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Add a workqueue so that I/O can be queued up to be flushed from a separate
thread (e.g.  if local interrupts are disabled).

A new per-snapshot spinlock pe_lock is introduced to protect queued_bios.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Alasdair G Kergon 2006-10-03 01:15:30 -07:00 committed by Linus Torvalds
parent 9d493fa8c9
commit ca3a931fd3
2 changed files with 45 additions and 0 deletions
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33
drivers/md/dm-snap.c
View File

@ -39,6 +39,9 @@
*/
#define SNAPSHOT_PAGES 256
struct workqueue_struct *ksnapd;
static void flush_queued_bios(void *data);
struct pending_exception {
struct exception e;
@ -488,6 +491,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
s->active = 0;
s->last_percent = 0;
init_rwsem(&s->lock);
spin_lock_init(&s->pe_lock);
s->table = ti->table;
/* Allocate hash table for COW data */
@ -523,6 +527,9 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad6;
}
bio_list_init(&s->queued_bios);
INIT_WORK(&s->queued_bios_work, flush_queued_bios, s);
/* Add snapshot to the list of snapshots for this origin */
/* Exceptions aren't triggered till snapshot_resume() is called */
if (register_snapshot(s)) {
@ -561,6 +568,8 @@ static void snapshot_dtr(struct dm_target *ti)
{
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
flush_workqueue(ksnapd);
/* Prevent further origin writes from using this snapshot. */
/* After this returns there can be no new kcopyd jobs. */
unregister_snapshot(s);
@ -594,6 +603,19 @@ static void flush_bios(struct bio *bio)
}
}
static void flush_queued_bios(void *data)
{
struct dm_snapshot *s = (struct dm_snapshot *) data;
struct bio *queued_bios;
unsigned long flags;
spin_lock_irqsave(&s->pe_lock, flags);
queued_bios = bio_list_get(&s->queued_bios);
spin_unlock_irqrestore(&s->pe_lock, flags);
flush_bios(queued_bios);
}
/*
* Error a list of buffers.
*/
@ -1240,8 +1262,17 @@ static int __init dm_snapshot_init(void)
goto bad5;
}
ksnapd = create_singlethread_workqueue("ksnapd");
if (!ksnapd) {
DMERR("Failed to create ksnapd workqueue.");
r = -ENOMEM;
goto bad6;
}
return 0;
bad6:
mempool_destroy(pending_pool);
bad5:
kmem_cache_destroy(pending_cache);
bad4:
@ -1259,6 +1290,8 @@ static void __exit dm_snapshot_exit(void)
{
int r;
destroy_workqueue(ksnapd);
r = dm_unregister_target(&snapshot_target);
if (r)
DMERR("snapshot unregister failed %d", r);

12
drivers/md/dm-snap.h
View File

@ -10,7 +10,9 @@
#define DM_SNAPSHOT_H
#include "dm.h"
#include "dm-bio-list.h"
#include <linux/blkdev.h>
#include <linux/workqueue.h>
struct exception_table {
uint32_t hash_mask;
@ -112,10 +114,20 @@ struct dm_snapshot {
struct exception_table pending;
struct exception_table complete;
/*
* pe_lock protects all pending_exception operations and access
* as well as the snapshot_bios list.
*/
spinlock_t pe_lock;
/* The on disk metadata handler */
struct exception_store store;
struct kcopyd_client *kcopyd_client;
/* Queue of snapshot writes for ksnapd to flush */
struct bio_list queued_bios;
struct work_struct queued_bios_work;
};
/*