[PATCH 4/7] sd: add support for WRITE SAME (16) with unmap bit

Christoph Hellwig
2009-08-29T23:11:21Z

[-- Attachment #1: discard-add-scsi-write-same-support --]
[-- Type: text/plain, Size: 3855 bytes --]

Add a prepare_discard function to sd that sends a WRITE SAME request with
the unmap bit set to the device if it advertises thin provisioning support.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/drivers/scsi/sd.c
===================================================================
--- linux-2.6.orig/drivers/scsi/sd.c 2009-08-29 19:19:36.067371669 -0300
+++ linux-2.6/drivers/scsi/sd.c 2009-08-29 19:26:20.723754241 -0300
@@ -911,6 +911,50 @@ static void sd_prepare_flush(struct requ
rq->cmd_len = 10;
}

+static int sd_prepare_discard(struct request_queue *q, struct request *rq,
+ struct bio *bio)
+{
+ struct scsi_device *sdp = q->queuedata;
+ struct page *page = alloc_page(GFP_KERNEL);
+
+ if (!page)
+ return -ENOMEM;
+
+ rq->cmd_type = REQ_TYPE_BLOCK_PC;
+ rq->timeout = SD_TIMEOUT;
+ rq->cmd[0] = WRITE_SAME_16;
+ rq->cmd[1] = 0x8; /* UNMAP bit */
+ rq->cmd[2] = sizeof(bio->bi_sector) > 4 ?
+ (unsigned char) (bio->bi_sector >> 56) & 0xff : 0;
+ rq->cmd[3] = sizeof(bio->bi_sector) > 4 ?
+ (unsigned char) (bio->bi_sector >> 48) & 0xff : 0;
+ rq->cmd[4] = sizeof(bio->bi_sector) > 4 ?
+ (unsigned char) (bio->bi_sector >> 40) & 0xff : 0;
+ rq->cmd[5] = sizeof(bio->bi_sector) > 4 ?
+ (unsigned char) (bio->bi_sector >> 32) & 0xff : 0;
+ rq->cmd[6] = (unsigned char) (bio->bi_sector >> 24) & 0xff;
+ rq->cmd[7] = (unsigned char) (bio->bi_sector >> 16) & 0xff;
+ rq->cmd[8] = (unsigned char) (bio->bi_sector >> 8) & 0xff;
+ rq->cmd[9] = (unsigned char) bio->bi_sector & 0xff;
+ rq->cmd[10] = (unsigned char) (bio_sectors(bio) >> 24) & 0xff;
+ rq->cmd[11] = (unsigned char) (bio_sectors(bio) >> 16) & 0xff;
+ rq->cmd[12] = (unsigned char) (bio_sectors(bio) >> 8) & 0xff;
+ rq->cmd[13] = (unsigned char) bio_sectors(bio) & 0xff;
+ rq->cmd[14] = 0;
+ rq->cmd[15] = 0;
+ rq->cmd_len = 16;
+
+ printk(KERN_INFO "umap, lba = 0x%lld, len = %d\n",
+ bio->bi_sector, bio_sectors(bio));
+
+ bio->bi_size = 0;
+ if (bio_add_pc_page(q, bio, page, sdp->sector_size, 0) <
+ sdp->sector_size)
+ return -EIO;
+
+ return 0;
+}
+
static void sd_rescan(struct device *dev)
{
struct scsi_disk *sdkp = scsi_disk_get_from_dev(dev);
@@ -1369,6 +1413,9 @@ static int read_capacity_16(struct scsi_
sd_printk(KERN_NOTICE, sdkp,
"physical block alignment offset: %u\n", alignment);

+ if (buffer[14] & 0x80)
+ sdkp->thin_provisioning = 1;
+
sdkp->capacity = lba + 1;
return sector_size;
}
@@ -1915,6 +1962,8 @@ static int sd_revalidate_disk(struct gen
ordered = QUEUE_ORDERED_DRAIN;

blk_queue_ordered(sdkp->disk->queue, ordered, sd_prepare_flush);
+ if (sdkp->thin_provisioning && !sdp->request_queue->prepare_discard_fn)
+ blk_queue_set_discard(sdkp->disk->queue, sd_prepare_discard);

set_capacity(disk, sdkp->capacity);
kfree(buffer);
Index: linux-2.6/include/scsi/scsi.h
===================================================================
--- linux-2.6.orig/include/scsi/scsi.h 2009-08-29 19:19:36.079340649 -0300
+++ linux-2.6/include/scsi/scsi.h 2009-08-29 19:20:01.995378150 -0300
@@ -122,6 +122,8 @@ struct scsi_cmnd;
#define READ_16 0x88
#define WRITE_16 0x8a
#define VERIFY_16 0x8f
+#define WRITE_SAME_16 0x93
+
#define SERVICE_ACTION_IN 0x9e
/* values for service action in */
#define SAI_READ_CAPACITY_16 0x10
Index: linux-2.6/drivers/scsi/sd.h
===================================================================
--- linux-2.6.orig/drivers/scsi/sd.h 2009-08-29 19:19:36.071341377 -0300
+++ linux-2.6/drivers/scsi/sd.h 2009-08-29 19:20:01.995378150 -0300
@@ -55,6 +55,7 @@ struct scsi_disk {
unsigned RCD : 1; /* state of disk RCD bit, unused */
unsigned DPOFUA : 1; /* state of disk DPOFUA bit */
unsigned first_scan : 1;
+ unsigned thin_provisioning : 1;
};
#define to_scsi_disk(obj) container_of(obj,struct scsi_disk,dev)