Re: [PATCH] target/file: Add WRITE_SAME w/ UNMAP=0 emulation support

[Asias He <asias@redhat.com>]

On 02/20/2013 09:43 AM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@linux-iscsi.org>
> 
> Hi mkp, hch, & Co,
> 
> Please review this patch to add support for WRITE_SAME w/ UNMAP=0
> emulation into FILEIO, as I'd really like to include this in the
> upcoming for-3.9 target merge.
> 
> Thank you,
> 
> --nab
> 
> ---------------------------------------------------------------------
> 
> 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.
> 
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Asias He <asias@redhat.com>
> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
> ---
>  drivers/target/target_core_file.c |  115 +++++++++++++++++++++++++++++++++++++
>  1 files changed, 115 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
> index b9c8849..0b71509 100644
> --- a/drivers/target/target_core_file.c
> +++ b/drivers/target/target_core_file.c
> @@ -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 +333,115 @@ 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 = vmalloc(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;
> +	}
> +	memset(iov, 0, sizeof(struct iovec) * iov_num);

Use vzalloc()?

> +	/*
> +	 * Map the single fabric received scatterlist block into each
> +	 * iovec for 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 +600,7 @@ 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
> 


-- 
Asias