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Commit f6fccb12 authored by Milan Broz's avatar Milan Broz Committed by Alasdair G Kergon
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dm: introduce merge_bvec_fn 



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: default avatarMilan Broz <mbroz@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 92e86812

drivers/md/dm.c

+44 −0
Original line number Diff line number Diff line
@@ -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)

include/linux/device-mapper.h

+6 −0
Original line number Diff line number Diff line
@@ -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 {

include/linux/dm-ioctl.h

+2 −2
Original line number Diff line number Diff line
@@ -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 */