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Commit 7b745c84 authored by Nicholas Bellinger's avatar Nicholas Bellinger
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target/file: Add WRITE_SAME w/ UNMAP=0 emulation support 



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

The emulation uses vfs_writev() to submit a locally populated buffer
from the received WRITE_SAME scatterlist block for duplication, and by
default enforces a limit of max_write_same_len=0x1000 (8192) sectors up
to the limit of 1024 iovec entries for the single call to vfs_writev().

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

Tested with 512, 1k, 2k, and 4k block_sizes.

(asias: convert to vzalloc)

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Asias He <asias@redhat.com>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent 6e545935

drivers/target/target_core_file.c

+114 −0
Original line number Diff line number Diff line
@@ -190,6 +190,11 @@ static int fd_configure_device(struct se_device *dev) 


	fd_dev->fd_dev_id = fd_host->fd_host_dev_id_count++;

	fd_dev->fd_queue_depth = dev->queue_depth;

	/*

	 * Limit WRITE_SAME w/ UNMAP=0 emulation to 8k Number of LBAs (NoLB)

	 * based upon struct iovec limit for vfs_writev()

	 */

	dev->dev_attrib.max_write_same_len = 0x1000;



	pr_debug("CORE_FILE[%u] - Added TCM FILEIO Device ID: %u at %s,"

		" %llu total bytes\n", fd_host->fd_host_id, fd_dev->fd_dev_id,
@@ -328,6 +333,114 @@ fd_execute_sync_cache(struct se_cmd *cmd) 
	return 0;

}



static unsigned char *

fd_setup_write_same_buf(struct se_cmd *cmd, struct scatterlist *sg,

		    unsigned int len)

{

	struct se_device *se_dev = cmd->se_dev;

	unsigned int block_size = se_dev->dev_attrib.block_size;

	unsigned int i = 0, end;

	unsigned char *buf, *p, *kmap_buf;



	buf = kzalloc(min_t(unsigned int, len, PAGE_SIZE), GFP_KERNEL);

	if (!buf) {

		pr_err("Unable to allocate fd_execute_write_same buf\n");

		return NULL;

	}



	kmap_buf = kmap(sg_page(sg)) + sg->offset;

	if (!kmap_buf) {

		pr_err("kmap() failed in fd_setup_write_same\n");

		kfree(buf);

		return NULL;

	}

	/*

	 * Fill local *buf to contain multiple WRITE_SAME blocks up to

	 * min(len, PAGE_SIZE)

	 */

	p = buf;

	end = min_t(unsigned int, len, PAGE_SIZE);



	while (i < end) {

		memcpy(p, kmap_buf, block_size);



		i += block_size;

		p += block_size;

	}

	kunmap(sg_page(sg));



	return buf;

}



static sense_reason_t

fd_execute_write_same(struct se_cmd *cmd)

{

	struct se_device *se_dev = cmd->se_dev;

	struct fd_dev *fd_dev = FD_DEV(se_dev);

	struct file *f = fd_dev->fd_file;

	struct scatterlist *sg;

	struct iovec *iov;

	mm_segment_t old_fs;

	sector_t nolb = spc_get_write_same_sectors(cmd);

	loff_t pos = cmd->t_task_lba * se_dev->dev_attrib.block_size;

	unsigned int len, len_tmp, iov_num;

	int i, rc;

	unsigned char *buf;



	if (!nolb) {

		target_complete_cmd(cmd, SAM_STAT_GOOD);

		return 0;

	}

	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;

	}



	len = len_tmp = nolb * se_dev->dev_attrib.block_size;

	iov_num = DIV_ROUND_UP(len, PAGE_SIZE);



	buf = fd_setup_write_same_buf(cmd, sg, len);

	if (!buf)

		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;



	iov = vzalloc(sizeof(struct iovec) * iov_num);

	if (!iov) {

		pr_err("Unable to allocate fd_execute_write_same iovecs\n");

		kfree(buf);

		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	}

	/*

	 * Map the single fabric received scatterlist block now populated

	 * in *buf into each iovec for I/O submission.

	 */

	for (i = 0; i < iov_num; i++) {

		iov[i].iov_base = buf;

		iov[i].iov_len = min_t(unsigned int, len_tmp, PAGE_SIZE);

		len_tmp -= iov[i].iov_len;

	}



	old_fs = get_fs();

	set_fs(get_ds());

	rc = vfs_writev(f, &iov[0], iov_num, &pos);

	set_fs(old_fs);



	vfree(iov);

	kfree(buf);



	if (rc < 0 || rc != len) {

		pr_err("vfs_writev() returned %d for write same\n", rc);

		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	}



	target_complete_cmd(cmd, SAM_STAT_GOOD);

	return 0;

}



static sense_reason_t

fd_execute_rw(struct se_cmd *cmd)

{
@@ -486,6 +599,7 @@ static sector_t fd_get_blocks(struct se_device *dev) 
static struct sbc_ops fd_sbc_ops = {

	.execute_rw		= fd_execute_rw,

	.execute_sync_cache	= fd_execute_sync_cache,

	.execute_write_same	= fd_execute_write_same,

};



static sense_reason_t