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dm: introduce merge_bvec_fn

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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>
This commit is contained in:
Milan Broz 2008-07-21 12:00:37 +01:00 committed by Alasdair G Kergon
parent 92e868122e
commit f6fccb1213
3 changed files with 52 additions and 2 deletions
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44
drivers/md/dm.c
View file

@ -829,6 +829,49 @@ static int __split_bio(struct mapped_device *md, struct bio *bio)
* CRUD END
*---------------------------------------------------------------*/
static int dm_merge_bvec(struct request_queue *q,
struct bvec_merge_data *bvm,
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 max_size;
if (unlikely(!map))
return 0;
ti = dm_table_find_target(map, bvm->bi_sector);
/*
* Find maximum amount of I/O that won't need splitting
*/
max_sectors = min(max_io_len(md, bvm->bi_sector, ti),
(sector_t) BIO_MAX_SECTORS);
max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
if (max_size < 0)
max_size = 0;
/*
* merge_bvec_fn() returns number of bytes
* it can accept at this offset
* max is precomputed maximal io size
*/
if (max_size && ti->type->merge)
max_size = ti->type->merge(ti, bvm, biovec, max_size);
/*
* Always allow an entire first page
*/
if (max_size <= biovec->bv_len && !(bvm->bi_size >> SECTOR_SHIFT))
max_size = biovec->bv_len;
dm_table_put(map);
return max_size;
}
/*
* The request function that just remaps the bio built up by
* dm_merge_bvec.
@ -1032,6 +1075,7 @@ static struct mapped_device *alloc_dev(int minor)
blk_queue_make_request(md->queue, dm_request);
blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
md->queue->unplug_fn = dm_unplug_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)

6
include/linux/device-mapper.h
View file

@ -9,11 +9,13 @@
#define _LINUX_DEVICE_MAPPER_H
#include <linux/bio.h>
#include <linux/blkdev.h>
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 +74,9 @@ typedef int (*dm_ioctl_fn) (struct dm_target *ti, struct inode *inode,
struct file *filp, unsigned int cmd,
unsigned long arg);
typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
struct bio_vec *biovec, int max_size);
void dm_error(const char *message);
/*
@ -107,6 +112,7 @@ struct target_type {
dm_status_fn status;
dm_message_fn message;
dm_ioctl_fn ioctl;
dm_merge_fn merge;
};
struct io_restrictions {

4
include/linux/dm-ioctl.h
View file

@ -256,9 +256,9 @@ enum {
#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 13
#define DM_VERSION_MINOR 14
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2007-10-18)"
#define DM_VERSION_EXTRA "-ioctl (2008-04-23)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */