On Thu, 2013-02-21 at 13:57 +0800, Asias He wrote:
> This patch adds support for emulation of WRITE_SAME w/ UNMAP=1 within
> fd_execute_write_same_unmap() backend code.
>
> If the FILEIO backend is normal file, the emulation uses fallocate to
> punch hole to reclaim the free space used by the file. If the FILEIO
> backend is block device, the emulation uses blkdev_issue_discard().
>
> Tested with 512, 1k, 2k, and 4k block_sizes.
>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> Signed-off-by: Asias He <asias@xxxxxxxxxx>
> ---
> drivers/target/target_core_file.c | 48 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 48 insertions(+)
>
> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
> index 94383a5..2a9ce12 100644
> --- a/drivers/target/target_core_file.c
> +++ b/drivers/target/target_core_file.c
> @@ -30,6 +30,7 @@
> #include <linux/slab.h>
> #include <linux/spinlock.h>
> #include <linux/module.h>
> +#include <linux/falloc.h>
> #include <scsi/scsi.h>
> #include <scsi/scsi_host.h>
>
> @@ -442,6 +443,52 @@ fd_execute_write_same(struct se_cmd *cmd)
> }
>
> static sense_reason_t
> +fd_execute_write_same_unmap(struct se_cmd *cmd)
> +{
> + struct se_device *se_dev = cmd->se_dev;
> + struct fd_dev *fd_dev = FD_DEV(se_dev);
> + struct file *file = fd_dev->fd_file;
> + struct inode *inode = file->f_mapping->host;
> + sector_t nolb = spc_get_write_same_sectors(cmd);
> + int ret;
> +
> + if (!nolb) {
> + target_complete_cmd(cmd, SAM_STAT_GOOD);
> + return 0;
> + }
> +
> + if (S_ISBLK(inode->i_mode)) {
> + /* The backend is block device, use discard */
> + struct block_device *bdev = inode->i_bdev;
> +
> + ret = blkdev_issue_discard(bdev, cmd->t_task_lba,
> + nolb, GFP_KERNEL, 0);
> + if (ret < 0) {
> + pr_warn("FILEIO: blkdev_issue_discard() failed: %d\n",
> + ret);
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> + }
> + } else {
> + /* The backend is normal file, use fallocate */
> + loff_t pos = cmd->t_task_lba * se_dev->dev_attrib.block_size;
> + unsigned int len = nolb * se_dev->dev_attrib.block_size;
> + int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
> +
> + if (!file->f_op->fallocate)
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> +
> + ret = file->f_op->fallocate(file, mode, pos, len);
> + if (ret < 0) {
> + pr_warn("FILEIO: fallocate() failed: %d\n", ret);
> + return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
> + }
> + }
> +
> + target_complete_cmd(cmd, GOOD);
> + return 0;
> +}
> +
So you'll also need to set the various dev->dev_attrib.*unmap* values
for EVPD Block Limits at fd_configure_device() time.. Check out
iblock_configure_device() to see how this is currently done for the
underlying struct block_device case from request_queue->limits.
For the fallocate() case, you'll need to add some sane defaults here
too.
As for the direct blkdev_issue_discard usage() within FILEIO code, I
don't have a problem with it, but I'd really like to get hch's feedback
here..
--nab
> +static sense_reason_t
> fd_execute_rw(struct se_cmd *cmd)
> {
> struct scatterlist *sgl = cmd->t_data_sg;
> @@ -600,6 +647,7 @@ 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,
> + .execute_write_same_unmap = fd_execute_write_same_unmap,
> };
>
> static sense_reason_t
--
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