From: Milan Broz <mbroz@redhat.com>
Introduce a bvec merge function for device mapper devices
for dynamic size restrictions.
This code ensures the requested biovec lies within a single
target and then calls a target-specific function to check
against any constraints imposed by underlying devices.
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
---
drivers/md/dm.c | 37 +++++++++++++++++++++++++++++++++++++
include/linux/device-mapper.h | 5 +++++
include/linux/dm-ioctl.h | 4 ++--
3 files changed, 44 insertions(+), 2 deletions(-)
Index: current-quilt/drivers/md/dm.c
===================================================================
--- current-quilt.orig/drivers/md/dm.c 2007-05-01 18:01:32.000000000 +0100
+++ current-quilt/drivers/md/dm.c 2007-05-01 18:28:30.000000000 +0100
@@ -792,6 +792,42 @@ static void __split_bio(struct mapped_de
* CRUD END
*---------------------------------------------------------------*/
+static int dm_merge_bvec(request_queue_t *q, struct bio *bio,
+ struct bio_vec *biovec)
+{
+ struct mapped_device *md = q->queuedata;
+ struct dm_table *map = dm_get_table(md);
+ struct dm_target *ti;
+ sector_t max_sectors;
+ int len;
+
+ if (unlikely(!map))
+ return 0;
+
+ ti = dm_table_find_target(map, bio->bi_sector);
+
+ /*
+ * Find maximum bytes of I/O that won't need splitting
+ */
+ max_sectors = min(max_io_len(md, bio->bi_sector, ti), (sector_t) BIO_MAX_SECTORS);
+ len = (max_sectors << SECTOR_SHIFT) - bio->bi_size;
+ if (len < 0)
+ len = 0;
+
+ if (len > 0 && ti->type->merge)
+ len = ti->type->merge(ti, bio, biovec, len);
+
+ /*
+ * Always allow an entire first page
+ */
+ if (len <= biovec->bv_len && bio_sectors(bio) == 0)
+ len = biovec->bv_len;
+
+ dm_table_put(map);
+
+ return len;
+}
+
/*
* The request function that just remaps the bio built up by
* dm_merge_bvec.
@@ -1003,6 +1039,7 @@ static struct mapped_device *alloc_dev(i
blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
md->queue->unplug_fn = dm_unplug_all;
md->queue->issue_flush_fn = dm_flush_all;
+ blk_queue_merge_bvec(md->queue, dm_merge_bvec);
md->io_pool = mempool_create_slab_pool(MIN_IOS, _io_cache);
if (!md->io_pool)
Index: current-quilt/include/linux/device-mapper.h
===================================================================
--- current-quilt.orig/include/linux/device-mapper.h 2007-05-01 18:01:31.000000000 +0100
+++ current-quilt/include/linux/device-mapper.h 2007-05-01 18:28:30.000000000 +0100
@@ -14,6 +14,7 @@ struct dm_target;
struct dm_table;
struct dm_dev;
struct mapped_device;
+struct bio_vec;
typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
@@ -72,6 +73,9 @@ typedef int (*dm_ioctl_fn) (struct dm_ta
struct file *filp, unsigned int cmd,
unsigned long arg);
+typedef int (*dm_merge_fn) (struct dm_target *ti, struct bio *bio,
+ struct bio_vec *biovec, int len);
+
void dm_error(const char *message);
/*
@@ -107,6 +111,7 @@ struct target_type {
dm_status_fn status;
dm_message_fn message;
dm_ioctl_fn ioctl;
+ dm_merge_fn merge;
};
struct io_restrictions {
Index: current-quilt/include/linux/dm-ioctl.h
===================================================================
--- current-quilt.orig/include/linux/dm-ioctl.h 2007-05-01 17:41:14.000000000 +0100
+++ current-quilt/include/linux/dm-ioctl.h 2007-05-01 18:28:30.000000000 +0100
@@ -285,9 +285,9 @@ typedef char ioctl_struct[308];
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
-#define DM_VERSION_MINOR 11
+#define DM_VERSION_MINOR 12
#define DM_VERSION_PATCHLEVEL 0
-#define DM_VERSION_EXTRA "-ioctl (2006-10-12)"
+#define DM_VERSION_EXTRA "-ioctl (2007-04-02)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */