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



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