[PATCH] md: support reshaping raid1 arrays - adding or removing drives.

This allows the number of "raid_disks" in a raid1 to be changed.

This requires allocating a new pool of "r1bio" structures which a different
number of bios, suspending IO, and swapping the new pool in place of the old. 
(and a few other related changes).

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/raid/md_k.h b/include/linux/raid/md_k.h
index 1af736b37d0b..faa400cf25e4 100644
--- a/include/linux/raid/md_k.h
+++ b/include/linux/raid/md_k.h
@@ -280,6 +280,7 @@ struct mdk_personality_s
 	int (*spare_active) (mddev_t *mddev);
 	int (*sync_request)(mddev_t *mddev, sector_t sector_nr, int go_faster);
 	int (*resize) (mddev_t *mddev, sector_t sectors);
+	int (*reshape) (mddev_t *mddev, int raid_disks);
 };
 
 
diff --git a/include/linux/raid/raid1.h b/include/linux/raid/raid1.h
index 96abcad3a307..50965d9680b6 100644
--- a/include/linux/raid/raid1.h
+++ b/include/linux/raid/raid1.h
@@ -10,6 +10,20 @@ struct mirror_info {
 	sector_t	head_position;
 };
 
+/*
+ * memory pools need a pointer to the mddev, so they can force an unplug
+ * when memory is tight, and a count of the number of drives that the
+ * pool was allocated for, so they know how much to allocate and free.
+ * mddev->raid_disks cannot be used, as it can change while a pool is active
+ * These two datums are stored in a kmalloced struct.
+ */
+
+struct pool_info {
+	mddev_t *mddev;
+	int	raid_disks;
+};
+
+
 typedef struct r1bio_s r1bio_t;
 
 struct r1_private_data_s {
@@ -31,6 +45,8 @@ struct r1_private_data_s {
 	wait_queue_head_t	wait_idle;
 	wait_queue_head_t	wait_resume;
 
+	struct pool_info	*poolinfo;
+
 	mempool_t *r1bio_pool;
 	mempool_t *r1buf_pool;
 };