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Message-ID: <20060914214246.GQ3928@agk.surrey.redhat.com>
Date: Thu, 14 Sep 2006 22:42:46 +0100
From: Alasdair G Kergon <agk@...hat.com>
To: Andrew Morton <akpm@...l.org>
Cc: linux-kernel@...r.kernel.org, Mark McLoughlin <markmc@...hat.com>
Subject: [PATCH 09/25] dm snapshot: add workqueue
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@...hat.com>
Signed-off-by: Mark McLoughlin <markmc@...hat.com>
Index: linux-2.6.18-rc7/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.18-rc7.orig/drivers/md/dm-snap.c 2006-09-14 20:40:46.000000000 +0100
+++ linux-2.6.18-rc7/drivers/md/dm-snap.c 2006-09-14 20:44:39.000000000 +0100
@@ -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
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
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_targe
{
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);
Index: linux-2.6.18-rc7/drivers/md/dm-snap.h
===================================================================
--- linux-2.6.18-rc7.orig/drivers/md/dm-snap.h 2006-09-14 20:38:48.000000000 +0100
+++ linux-2.6.18-rc7/drivers/md/dm-snap.h 2006-09-14 20:44:39.000000000 +0100
@@ -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;
};
/*
-
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