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Commit 66ac0280 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: don't allocate a payload for discard request 



Allocating a fixed payload for discard requests always was a horrible hack,
and it's not coming to byte us when adding support for discard in DM/MD.

So change the code to leave the allocation of a payload to the lowlevel
driver.  Unfortunately that means we'll need another hack, which allows
us to update the various block layer length fields indicating that we
have a payload.  Instead of hiding this in sd.c, which we already partially
do for UNMAP support add a documented helper in the core block layer for it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Acked-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 08243900

block/blk-core.c

+32 −0
Original line number Diff line number Diff line
@@ -1135,6 +1135,38 @@ void blk_put_request(struct request *req) 
}

EXPORT_SYMBOL(blk_put_request);



/**

 * blk_add_request_payload - add a payload to a request

 * @rq: request to update

 * @page: page backing the payload

 * @len: length of the payload.

 *

 * This allows to later add a payload to an already submitted request by

 * a block driver.  The driver needs to take care of freeing the payload

 * itself.

 *

 * Note that this is a quite horrible hack and nothing but handling of

 * discard requests should ever use it.

 */

void blk_add_request_payload(struct request *rq, struct page *page,

		unsigned int len)

{

	struct bio *bio = rq->bio;



	bio->bi_io_vec->bv_page = page;

	bio->bi_io_vec->bv_offset = 0;

	bio->bi_io_vec->bv_len = len;



	bio->bi_size = len;

	bio->bi_vcnt = 1;

	bio->bi_phys_segments = 1;



	rq->__data_len = rq->resid_len = len;

	rq->nr_phys_segments = 1;

	rq->buffer = bio_data(bio);

}

EXPORT_SYMBOL_GPL(blk_add_request_payload);



void init_request_from_bio(struct request *req, struct bio *bio)

{

	req->cpu = bio->bi_comp_cpu;

block/blk-lib.c

+6 −27
Original line number Diff line number Diff line
@@ -19,7 +19,6 @@ static void blkdev_discard_end_io(struct bio *bio, int err) 


	if (bio->bi_private)

		complete(bio->bi_private);

	__free_page(bio_page(bio));



	bio_put(bio);

}
@@ -43,7 +42,6 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
	int type = flags & BLKDEV_IFL_BARRIER ?

		DISCARD_BARRIER : DISCARD_NOBARRIER;

	struct bio *bio;

	struct page *page;

	int ret = 0;



	if (!q)
@@ -53,35 +51,21 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
		return -EOPNOTSUPP;



	while (nr_sects && !ret) {

		unsigned int sector_size = q->limits.logical_block_size;

		unsigned int max_discard_sectors =

			min(q->limits.max_discard_sectors, UINT_MAX >> 9);



		bio = bio_alloc(gfp_mask, 1);

		if (!bio)

			goto out;

		if (!bio) {

			ret = -ENOMEM;

			break;

		}



		bio->bi_sector = sector;

		bio->bi_end_io = blkdev_discard_end_io;

		bio->bi_bdev = bdev;

		if (flags & BLKDEV_IFL_WAIT)

			bio->bi_private = &wait;



		/*

		 * Add a zeroed one-sector payload as that's what

		 * our current implementations need.  If we'll ever need

		 * more the interface will need revisiting.

		 */

		page = alloc_page(gfp_mask | __GFP_ZERO);

		if (!page)

			goto out_free_bio;

		if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)

			goto out_free_page;



		/*

		 * And override the bio size - the way discard works we

		 * touch many more blocks on disk than the actual payload

		 * length.

		 */

		if (nr_sects > max_discard_sectors) {

			bio->bi_size = max_discard_sectors << 9;

			nr_sects -= max_discard_sectors;
@@ -103,13 +87,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, 
			ret = -EIO;

		bio_put(bio);

	}



	return ret;

out_free_page:

	__free_page(page);

out_free_bio:

	bio_put(bio);

out:

	return -ENOMEM;

}

EXPORT_SYMBOL(blkdev_issue_discard);

drivers/scsi/sd.c

+34 −18
Original line number Diff line number Diff line
@@ -411,22 +411,25 @@ static void sd_prot_op(struct scsi_cmnd *scmd, unsigned int dif) 
}



/**

 * sd_prepare_discard - unmap blocks on thinly provisioned device

 * scsi_setup_discard_cmnd - unmap blocks on thinly provisioned device

 * @sdp: scsi device to operate one

 * @rq: Request to prepare

 *

 * Will issue either UNMAP or WRITE SAME(16) depending on preference

 * indicated by target device.

 **/

static int sd_prepare_discard(struct request *rq)

static int scsi_setup_discard_cmnd(struct scsi_device *sdp, struct request *rq)

{

	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);

	struct bio *bio = rq->bio;

	sector_t sector = bio->bi_sector;

	unsigned int num = bio_sectors(bio);

	unsigned int nr_sectors = bio_sectors(bio);

	unsigned int len;

	struct page *page;



	if (sdkp->device->sector_size == 4096) {

		sector >>= 3;

		num >>= 3;

		nr_sectors >>= 3;

	}



	rq->cmd_type = REQ_TYPE_BLOCK_PC;
@@ -434,31 +437,35 @@ static int sd_prepare_discard(struct request *rq) 


	memset(rq->cmd, 0, rq->cmd_len);



	page = alloc_page(GFP_ATOMIC | __GFP_ZERO);

	if (!page)

		return BLKPREP_DEFER;



	if (sdkp->unmap) {

		char *buf = kmap_atomic(bio_page(bio), KM_USER0);

		char *buf = page_address(page);



		rq->cmd_len = 10;

		rq->cmd[0] = UNMAP;

		rq->cmd[8] = 24;

		rq->cmd_len = 10;



		/* Ensure that data length matches payload */

		rq->__data_len = bio->bi_size = bio->bi_io_vec->bv_len = 24;



		put_unaligned_be16(6 + 16, &buf[0]);

		put_unaligned_be16(16, &buf[2]);

		put_unaligned_be64(sector, &buf[8]);

		put_unaligned_be32(num, &buf[16]);

		put_unaligned_be32(nr_sectors, &buf[16]);



		kunmap_atomic(buf, KM_USER0);

		len = 24;

	} else {

		rq->cmd_len = 16;

		rq->cmd[0] = WRITE_SAME_16;

		rq->cmd[1] = 0x8; /* UNMAP */

		put_unaligned_be64(sector, &rq->cmd[2]);

		put_unaligned_be32(num, &rq->cmd[10]);

		rq->cmd_len = 16;

		put_unaligned_be32(nr_sectors, &rq->cmd[10]);



		len = sdkp->device->sector_size;

	}



	return BLKPREP_OK;

	blk_add_request_payload(rq, page, len);

	return scsi_setup_blk_pc_cmnd(sdp, rq);

}



/**
@@ -485,10 +492,10 @@ static int sd_prep_fn(struct request_queue *q, struct request *rq) 
	 * Discard request come in as REQ_TYPE_FS but we turn them into

	 * block PC requests to make life easier.

	 */

	if (rq->cmd_flags & REQ_DISCARD)

		ret = sd_prepare_discard(rq);



	if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {

	if (rq->cmd_flags & REQ_DISCARD) {

		ret = scsi_setup_discard_cmnd(sdp, rq);

		goto out;

	} else if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {

		ret = scsi_setup_blk_pc_cmnd(sdp, rq);

		goto out;

	} else if (rq->cmd_type != REQ_TYPE_FS) {
@@ -1163,6 +1170,15 @@ static int sd_done(struct scsi_cmnd *SCpnt) 
	int sense_valid = 0;

	int sense_deferred = 0;



	/*

	 * If this is a discard request that originated from the kernel

	 * we need to free our payload here.  Note that we need to check

	 * the request flag as the normal payload rules apply for

	 * pass-through UNMAP / WRITE SAME requests.

	 */

	if (SCpnt->request->cmd_flags & REQ_DISCARD)

		__free_page(bio_page(SCpnt->request->bio));



	if (result) {

		sense_valid = scsi_command_normalize_sense(SCpnt, &sshdr);

		if (sense_valid)

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -705,6 +705,8 @@ extern struct request *blk_make_request(struct request_queue *, struct bio *, 
					gfp_t);

extern void blk_insert_request(struct request_queue *, struct request *, int, void *);

extern void blk_requeue_request(struct request_queue *, struct request *);

extern void blk_add_request_payload(struct request *rq, struct page *page,

		unsigned int len);

extern int blk_rq_check_limits(struct request_queue *q, struct request *rq);

extern int blk_lld_busy(struct request_queue *q);

extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,