[PATCH] dm: Maintain ordering when deferring bios

From: Joe Thornber <thornber@redhat.com>

Make sure that we maintain ordering when deferring bios.

diff --git a/drivers/md/dm-bio-list.h b/drivers/md/dm-bio-list.h
new file mode 100644 (file)
index 0000000..bc021e1
--- /dev/null
+++ b/drivers/md/dm-bio-list.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2004 Red Hat UK Ltd.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BIO_LIST_H
+#define DM_BIO_LIST_H
+
+#include <linux/bio.h>
+
+struct bio_list {
+       struct bio *head;
+       struct bio *tail;
+};
+
+static inline void bio_list_init(struct bio_list *bl)
+{
+       bl->head = bl->tail = NULL;
+}
+
+static inline void bio_list_add(struct bio_list *bl, struct bio *bio)
+{
+       bio->bi_next = NULL;
+
+       if (bl->tail)
+               bl->tail->bi_next = bio;
+       else
+               bl->head = bio;
+
+       bl->tail = bio;
+}
+
+static inline void bio_list_merge(struct bio_list *bl, struct bio_list *bl2)
+{
+       if (bl->tail)
+               bl->tail->bi_next = bl2->head;
+       else
+               bl->head = bl2->head;
+
+       bl->tail = bl2->tail;
+}
+
+static inline struct bio *bio_list_pop(struct bio_list *bl)
+{
+       struct bio *bio = bl->head;
+
+       if (bio) {
+               bl->head = bl->head->bi_next;
+               if (!bl->head)
+                       bl->tail = NULL;
+
+               bio->bi_next = NULL;
+       }
+
+       return bio;
+}
+
+static inline struct bio *bio_list_get(struct bio_list *bl)
+{
+       struct bio *bio = bl->head;
+
+       bl->head = bl->tail = NULL;
+
+       return bio;
+}
+
+#endif

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 938c2b6cff0377f45457dbb7efbc3a0442015c53..d5d13f965a16855c971ee4d2fed6ae63ed8ca3c3 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -5,6 +5,7 @@
  */
 
 #include "dm.h"
+#include "dm-bio-list.h"
 
 #include <linux/init.h>
 #include <linux/module.h>
@@ -47,7 +48,7 @@ struct mapped_device {
         */
        atomic_t pending;
        wait_queue_head_t wait;
-       struct bio *deferred;
+       struct bio_list deferred;
 
        /*
         * The current mapping.
@@ -195,8 +196,7 @@ static int queue_io(struct mapped_device *md, struct bio *bio)
                return 1;
        }
 
-       bio->bi_next = md->deferred;
-       md->deferred = bio;
+       bio_list_add(&md->deferred, bio);
 
        up_write(&md->lock);
        return 0;               /* deferred successfully */
@@ -822,8 +822,7 @@ int dm_resume(struct mapped_device *md)
        dm_table_resume_targets(md->map);
        clear_bit(DMF_SUSPENDED, &md->flags);
        clear_bit(DMF_BLOCK_IO, &md->flags);
-       def = md->deferred;
-       md->deferred = NULL;
+       def = bio_list_get(&md->deferred);
        up_write(&md->lock);
 
        flush_deferred_io(def);