On 09/28/2010 12:51 AM, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
>
> This patch adds UNMAP emulation support using Block layer DISCARD in fd_emulate_scsi_cdb()
> -> transport_generic_unmap(). This includes the use of blk_queue_discard() in
> fd_create_virtdevice() to determine when to set DEV_ATTRIB(dev)->emulate_tpe=1 to
> signal to TCM Core to perform the necessary control CDB emulation for TPE=1 / UNMAP.
>
> Note this patch igrab() + iput() when accessing struct block_device via
> I_BDEV(file->f_mapping->host) that is required for transport_generic_unmap()
> within fd_emulate_scsi_cdb().
>
> Also note that when (S_ISBLK(inode->i_mode) is NULL, the TPE=1 and UNMAP emulation
> are disabled for non BD struct file I/O.
>
> Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
> ---
> drivers/target/target_core_file.c | 53 ++++++++++++++++++++++++++++++++++++-
> 1 files changed, 52 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
> index 93d3f63..3b91556 100644
> --- a/drivers/target/target_core_file.c
> +++ b/drivers/target/target_core_file.c
> @@ -235,6 +235,17 @@ static struct se_device *fd_create_virtdevice(
>
> fd_dev->fd_dev_id = fd_host->fd_host_dev_id_count++;
> fd_dev->fd_queue_depth = dev->queue_depth;
> + /*
> + * Check for QUEUE_FLAG_DISCARD and enable TCM TPE emulation
> + * if present for struct block_device backend
> + */
> + if (S_ISBLK(inode->i_mode)) {
> + if (blk_queue_discard(bdev_get_queue(inode->i_bdev))) {
> + DEV_ATTRIB(dev)->emulate_tpe = 1;
> + printk(KERN_INFO "FILEIO: Enabling BLOCK Discard"
> + " and TPE=1 emulation\n");
> + }
> + }
>
> printk(KERN_INFO "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,
> @@ -388,9 +399,13 @@ static int fd_emulate_read_cap16(struct se_task *task)
> */
> static int fd_emulate_scsi_cdb(struct se_task *task)
> {
> - int ret;
> struct se_cmd *cmd = TASK_CMD(task);
> + struct fd_dev *fd_dev = (struct fd_dev *) task->se_dev->dev_ptr;
No need to typecast a void pointer
> struct fd_request *fd_req = (struct fd_request *) task->transport_req;
> + struct file *f = fd_dev->fd_file;
> + struct inode *i;
> + struct block_device *bd;
> + int ret;
>
> switch (fd_req->fd_scsi_cdb[0]) {
> case INQUIRY:
> @@ -433,6 +448,42 @@ static int fd_emulate_scsi_cdb(struct se_task *task)
> if (ret < 0)
> return ret;
> break;
> + case UNMAP:
> + i = igrab(f->f_mapping->host);
> + if (!(i)) {
You must have a reference on your fileio backend file, right?
This could be a BUG_ON()
> + printk(KERN_ERR "FILEIO: Unable to locate inode for"
> + " backend for UNMAP\n");
> + return PYX_TRANSPORT_LU_COMM_FAILURE;
> + }
> + /*
> + * Currently for struct file w/o a struct block_device
> + * backend we return a success..
> + */
> + if (!(S_ISBLK(i->i_mode))) {
I did not see in the first patch that you do this check when actually sending
the VPD page. I only saw that it is enabled if set from configfs. (Sorry for
the noise if I missed it). So you might want to call a target specific function
when sending the VPD page. This way this will never happen right?
> + printk(KERN_WARNING "Ignoring UNMAP for non BD"
> + " backend for struct file\n");
TODO: Lots of extent based filesystems could enjoy if you punch an hole
in the file. (Which will also send a proper discard).
So how to punch an hole in a file via vfs?
> + iput(i);
> + return PYX_TRANSPORT_LU_COMM_FAILURE;
> + }
> + bd = I_BDEV(f->f_mapping->host);
> + if (!(bd)) {
> + printk(KERN_ERR "FILEIO: Unable to locate struct"
> + " block_device for UNMAP\n");
> + iput(i);
> + return PYX_TRANSPORT_LU_COMM_FAILURE;
> + }
> + /*
> + * Now call the transport_generic_unmap() -> blkdev_issue_discard()
> + * wrapper to translate SCSI UNMAP into Linux/BLOCK discards on
> + * LBA+Range descriptors in the UNMAP write paylaod.
> + */
> + ret = transport_generic_unmap(cmd, bd);
> + if (ret < 0) {
> + iput(i);
> + return ret;
> + }
> + iput(i);
> + break;
> case ALLOW_MEDIUM_REMOVAL:
> case ERASE:
> case REZERO_UNIT:
Boaz
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