On 06/29/2014 03:34 PM, Christoph Hellwig wrote:
Simplify handling of write same requests by setting up the command directly
instead of initializing request fields and then calling
scsi_setup_blk_pc_cmnd to propagate the information into the command.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
drivers/scsi/sd.c | 44 ++++++++++++++++++++++++++++----------------
1 file changed, 28 insertions(+), 16 deletions(-)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 620d32f..25f25dd 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -799,14 +799,15 @@ out:
/**
* sd_setup_write_same_cmnd - write the same data to multiple blocks
- * @sdp: scsi device to operate one
- * @rq: Request to prepare
+ * @cmd: command to prepare
*
* Will issue either WRITE SAME(10) or WRITE SAME(16) depending on
* preference indicated by target device.
**/
-static int sd_setup_write_same_cmnd(struct scsi_device *sdp, struct request *rq)
+static int sd_setup_write_same_cmnd(struct scsi_cmnd *cmd)
{
+ struct request *rq = cmd->request;
+ struct scsi_device *sdp = cmd->device;
struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
struct bio *bio = rq->bio;
sector_t sector = blk_rq_pos(rq);
@@ -822,25 +823,36 @@ static int sd_setup_write_same_cmnd(struct scsi_device *sdp, struct request *rq)
sector >>= ilog2(sdp->sector_size) - 9;
nr_sectors >>= ilog2(sdp->sector_size) - 9;
- rq->__data_len = sdp->sector_size;
rq->timeout = SD_WRITE_SAME_TIMEOUT;
- memset(rq->cmd, 0, rq->cmd_len);
if (sdkp->ws16 || sector > 0xffffffff || nr_sectors > 0xffff) {
- rq->cmd_len = 16;
- rq->cmd[0] = WRITE_SAME_16;
- put_unaligned_be64(sector, &rq->cmd[2]);
- put_unaligned_be32(nr_sectors, &rq->cmd[10]);
+ cmd->cmd_len = 16;
+ cmd->cmnd[0] = WRITE_SAME_16;
+ put_unaligned_be64(sector, &cmd->cmnd[2]);
+ put_unaligned_be32(nr_sectors, &cmd->cmnd[10]);
} else {
- rq->cmd_len = 10;
- rq->cmd[0] = WRITE_SAME;
- put_unaligned_be32(sector, &rq->cmd[2]);
- put_unaligned_be16(nr_sectors, &rq->cmd[7]);
+ cmd->cmd_len = 10;
+ cmd->cmnd[0] = WRITE_SAME;
+ put_unaligned_be32(sector, &cmd->cmnd[2]);
+ put_unaligned_be16(nr_sectors, &cmd->cmnd[7]);
}
- ret = scsi_setup_blk_pc_cmnd(sdp, rq);
- rq->__data_len = nr_bytes;
+ cmd->transfersize = sdp->sector_size;
+ cmd->allowed = rq->retries;
+ /*
+ * For WRITE_SAME the data transferred in the DATA IN buffer is
+ * different from the amount of data actually written to the target.
+ *
+ * We set up __data_len to the amount of data transferred from the
+ * DATA IN buffer so that blk_rq_map_sg set up the proper S/G list
+ * to transfer a single sector of data first, but then reset it to
+ * the amount of data to be written right after so that the I/O path
+ * knows how much to actually write.
+ */
+ rq->__data_len = sdp->sector_size;
+ ret = scsi_init_io(cmd, GFP_ATOMIC);
+ rq->__data_len = nr_bytes;
return ret;
}
Hmm? __data_len is the amount of data written _on the target_.
Do we actually care about it?
And if so, why didn't it break with the original version?
In either case a short description in the patch would be nice.
@@ -894,7 +906,7 @@ static int sd_init_command(struct scsi_cmnd *SCpnt)
ret = sd_setup_discard_cmnd(sdp, rq);
goto out;
} else if (rq->cmd_flags & REQ_WRITE_SAME) {
- ret = sd_setup_write_same_cmnd(sdp, rq);
+ ret = sd_setup_write_same_cmnd(SCpnt);
goto out;
} else if (rq->cmd_flags & REQ_FLUSH) {
ret = sd_setup_flush_cmnd(SCpnt);
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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