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Commit f6970ad3 authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

target/iblock: Add WRITE_SAME w/ UNMAP=0 emulation support 



This patch adds support for emulation of WRITE_SAME w/ UNMAP=0 within
iblock_execute_write_same() backend code.

The emulation uses a bio_add_page() call for each sector, and by default
enforces a limit of max_write_same_len=0xFFFF (65536) sectors following
what scsi_debug reports per default for MAXIMUM WRITE SAME LENGTH.

It also sets max_write_same_len to the operational default at setup ->
iblock_configure_device() time.

(hch: Move unmap logic into iblock_execute_write_same_unmap + add
      check for single sector SGLs in iblock_execute_write_same)
(mkp: Update comment for 0xFFFF magic constant)
(nab: drop left-over max_write_same_len check in iblock_execute_write_same)

Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 773cbaf7

drivers/target/target_core_iblock.c

+79 −7
Original line number Diff line number Diff line
@@ -151,6 +151,11 @@ static int iblock_configure_device(struct se_device *dev) 
		pr_debug("IBLOCK: BLOCK Discard support available,"

				" disabled by default\n");

	}

	/*

	 * Enable write same emulation for IBLOCK and use 0xFFFF as

	 * the smaller WRITE_SAME(10) only has a two-byte block count.

	 */

	dev->dev_attrib.max_write_same_len = 0xFFFF;



	if (blk_queue_nonrot(q))

		dev->dev_attrib.is_nonrot = 1;
@@ -375,17 +380,20 @@ err: 
	return ret;

}



static struct bio *iblock_get_bio(struct se_cmd *, sector_t, u32);

static void iblock_submit_bios(struct bio_list *, int);

static void iblock_complete_cmd(struct se_cmd *);



static sense_reason_t

iblock_execute_write_same(struct se_cmd *cmd)

iblock_execute_write_same_unmap(struct se_cmd *cmd)

{

	struct iblock_dev *ib_dev = IBLOCK_DEV(cmd->se_dev);

	int ret;

	int rc;



	ret = blkdev_issue_discard(ib_dev->ibd_bd, cmd->t_task_lba,

				   spc_get_write_same_sectors(cmd), GFP_KERNEL,

				   0);

	if (ret < 0) {

		pr_debug("blkdev_issue_discard() failed for WRITE_SAME\n");

	rc = blkdev_issue_discard(ib_dev->ibd_bd, cmd->t_task_lba,

			spc_get_write_same_sectors(cmd), GFP_KERNEL, 0);

	if (rc < 0) {

		pr_warn("blkdev_issue_discard() failed: %d\n", rc);

		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	}
@@ -393,6 +401,69 @@ iblock_execute_write_same(struct se_cmd *cmd) 
	return 0;

}



static sense_reason_t

iblock_execute_write_same(struct se_cmd *cmd)

{

	struct iblock_req *ibr;

	struct scatterlist *sg;

	struct bio *bio;

	struct bio_list list;

	sector_t block_lba = cmd->t_task_lba;

	unsigned int sectors = spc_get_write_same_sectors(cmd);



	sg = &cmd->t_data_sg[0];



	if (cmd->t_data_nents > 1 ||

	    sg->length != cmd->se_dev->dev_attrib.block_size) {

		pr_err("WRITE_SAME: Illegal SGL t_data_nents: %u length: %u"

			" block_size: %u\n", cmd->t_data_nents, sg->length,

			cmd->se_dev->dev_attrib.block_size);

		return TCM_INVALID_CDB_FIELD;

	}



	ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);

	if (!ibr)

		goto fail;

	cmd->priv = ibr;



	bio = iblock_get_bio(cmd, block_lba, 1);

	if (!bio)

		goto fail_free_ibr;



	bio_list_init(&list);

	bio_list_add(&list, bio);



	atomic_set(&ibr->pending, 1);



	while (sectors) {

		while (bio_add_page(bio, sg_page(sg), sg->length, sg->offset)

				!= sg->length) {



			bio = iblock_get_bio(cmd, block_lba, 1);

			if (!bio)

				goto fail_put_bios;



			atomic_inc(&ibr->pending);

			bio_list_add(&list, bio);

		}



		/* Always in 512 byte units for Linux/Block */

		block_lba += sg->length >> IBLOCK_LBA_SHIFT;

		sectors -= 1;

	}



	iblock_submit_bios(&list, WRITE);

	return 0;



fail_put_bios:

	while ((bio = bio_list_pop(&list)))

		bio_put(bio);

fail_free_ibr:

	kfree(ibr);

fail:

	return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

}



enum {

	Opt_udev_path, Opt_readonly, Opt_force, Opt_err

};
@@ -701,6 +772,7 @@ static struct sbc_ops iblock_sbc_ops = { 
	.execute_rw		= iblock_execute_rw,

	.execute_sync_cache	= iblock_execute_sync_cache,

	.execute_write_same	= iblock_execute_write_same,

	.execute_write_same_unmap = iblock_execute_write_same_unmap,

	.execute_unmap		= iblock_execute_unmap,

};