target/iblock: Convert WRITE_SAME to blkdev_issue_zeroout

The people who are actively using iblock_execute_write_same_direct() are
doing so in the context of ESX VAAI BlockZero, together with
EXTENDED_COPY and COMPARE_AND_WRITE primitives.

In practice though I've not seen any users of IBLOCK WRITE_SAME for
anything other than VAAI BlockZero, so just using blkdev_issue_zeroout()
when available, and falling back to iblock_execute_write_same() if the
WRITE_SAME buffer contains anything other than zeros should be OK.

(Hook up max_write_zeroes_sectors to signal LBPRZ feature bit in
 target_configure_unmap_from_queue - nab)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 8add07f387f9dbf38a1effc84a2a846b95fbd8f3..a5762e601fa19b50424f45374926132e8084c244 100644 (file)
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -851,7 +851,7 @@ bool target_configure_unmap_from_queue(struct se_dev_attrib *attrib,
        attrib->unmap_granularity = q->limits.discard_granularity / block_size;
        attrib->unmap_granularity_alignment = q->limits.discard_alignment /
                                                                block_size;
-       attrib->unmap_zeroes_data = 0;
+       attrib->unmap_zeroes_data = (q->limits.max_write_zeroes_sectors);
        return true;
 }
 EXPORT_SYMBOL(target_configure_unmap_from_queue);

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index bb069ebe4aa6c1abcce203c7133a446493abc7eb..b2044133d747c725a2ad653d347904592bdcec8c 100644 (file)
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -86,6 +86,7 @@ static int iblock_configure_device(struct se_device *dev)
        struct block_device *bd = NULL;
        struct blk_integrity *bi;
        fmode_t mode;
+       unsigned int max_write_zeroes_sectors;
        int ret = -ENOMEM;
 
        if (!(ib_dev->ibd_flags & IBDF_HAS_UDEV_PATH)) {
@@ -129,7 +130,11 @@ static int iblock_configure_device(struct se_device *dev)
         * Enable write same emulation for IBLOCK and use 0xFFFF as
         * the smaller WRITE_SAME(10) only has a two-byte block count.
         */
-       dev->dev_attrib.max_write_same_len = 0xFFFF;
+       max_write_zeroes_sectors = bdev_write_zeroes_sectors(bd);
+       if (max_write_zeroes_sectors)
+               dev->dev_attrib.max_write_same_len = max_write_zeroes_sectors;
+       else
+               dev->dev_attrib.max_write_same_len = 0xFFFF;
 
        if (blk_queue_nonrot(q))
                dev->dev_attrib.is_nonrot = 1;
@@ -415,28 +420,31 @@ iblock_execute_unmap(struct se_cmd *cmd, sector_t lba, sector_t nolb)
 }
 
 static sense_reason_t
-iblock_execute_write_same_direct(struct block_device *bdev, struct se_cmd *cmd)
+iblock_execute_zero_out(struct block_device *bdev, struct se_cmd *cmd)
 {
        struct se_device *dev = cmd->se_dev;
        struct scatterlist *sg = &cmd->t_data_sg[0];
-       struct page *page = NULL;
-       int ret;
+       unsigned char *buf, zero = 0x00, *p = &zero;
+       int rc, ret;
 
-       if (sg->offset) {
-               page = alloc_page(GFP_KERNEL);
-               if (!page)
-                       return TCM_OUT_OF_RESOURCES;
-               sg_copy_to_buffer(sg, cmd->t_data_nents, page_address(page),
-                                 dev->dev_attrib.block_size);
-       }
+       buf = kmap(sg_page(sg)) + sg->offset;
+       if (!buf)
+               return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
+       /*
+        * Fall back to block_execute_write_same() slow-path if
+        * incoming WRITE_SAME payload does not contain zeros.
+        */
+       rc = memcmp(buf, p, cmd->data_length);
+       kunmap(sg_page(sg));
+
+       if (rc)
+               return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
-       ret = blkdev_issue_write_same(bdev,
+       ret = blkdev_issue_zeroout(bdev,
                                target_to_linux_sector(dev, cmd->t_task_lba),
                                target_to_linux_sector(dev,
                                        sbc_get_write_same_sectors(cmd)),
-                               GFP_KERNEL, page ? page : sg_page(sg));
-       if (page)
-               __free_page(page);
+                               GFP_KERNEL, false);
        if (ret)
                return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 
@@ -472,8 +480,10 @@ iblock_execute_write_same(struct se_cmd *cmd)
                return TCM_INVALID_CDB_FIELD;
        }
 
-       if (bdev_write_same(bdev))
-               return iblock_execute_write_same_direct(bdev, cmd);
+       if (bdev_write_zeroes_sectors(bdev)) {
+               if (!iblock_execute_zero_out(bdev, cmd))
+                       return 0;
+       }
 
        ibr = kzalloc(sizeof(struct iblock_req), GFP_KERNEL);
        if (!ibr)