[Qemu-devel] [PATCHv2 07/11] iscsi: let bdrv_create conditionally zero out the device

[Peter Lieven <pl@kamp.de>]

if the device supports unmapping and unmapped blocks read as
zero ensure that the whole device is unmapped and report
.has_zero_init = 1 in this case to speed up qemu-img convert.

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 block/iscsi.c |   72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/block/iscsi.c b/block/iscsi.c
index 92e66a6..621ca40 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1436,7 +1436,8 @@ static int iscsi_truncate(BlockDriverState *bs, int64_t offset)
 
 static int iscsi_has_zero_init(BlockDriverState *bs)
 {
-    return 0;
+    IscsiLun *iscsilun = bs->opaque;
+    return (iscsilun->lbpu && iscsilun->lbprz) ? 1 : 0;
 }
 
 static int iscsi_create(const char *filename, QEMUOptionParameter *options)
@@ -1446,6 +1447,7 @@ static int iscsi_create(const char *filename, QEMUOptionParameter *options)
     BlockDriverState bs;
     IscsiLun *iscsilun = NULL;
     QDict *bs_options;
+    struct scsi_task *task = NULL;
 
     memset(&bs, 0, sizeof(BlockDriverState));
 
@@ -1481,7 +1483,75 @@ static int iscsi_create(const char *filename, QEMUOptionParameter *options)
     }
 
     ret = 0;
+
+    if (iscsilun->lbpu && iscsilun->lbprz) {
+        uint64_t lba = 0;
+        while (lba < iscsilun->num_blocks) {
+            struct scsi_get_lba_status *lbas = NULL;
+            struct scsi_lba_status_descriptor *lbasd = NULL;
+            enum scsi_provisioning_type provisioning;
+            uint32_t nb_sectors;
+
+            task = iscsi_get_lba_status_sync(iscsilun->iscsi, iscsilun->lun,
+                                             lba, 8 + 16);
+            if (task == NULL || task->status != SCSI_STATUS_GOOD) {
+                error_report("iSCSI: Failed to get_lba_status on iSCSI lun. %s",
+                             iscsi_get_error(iscsilun->iscsi));
+                ret = -EINVAL;
+                goto out;
+            }
+
+            lbas = scsi_datain_unmarshall(task);
+            if (lbas == NULL) {
+                error_report("iSCSI: failed to unmarshall inquiry datain blob");
+                ret = -EINVAL;
+                goto out;
+            }
+            lbasd = &lbas->descriptors[0];
+            if (lbasd->lba != lba) {
+                ret = -EINVAL;
+                goto out;
+            }
+            nb_sectors = lbasd->num_blocks;
+            provisioning = lbasd->provisioning;
+            scsi_free_scsi_task(task);
+            task = NULL;
+
+            /* blocks from lba to lba + nb_sectors - 1 are not mapped
+             * and read as zero (lbprz==1) so we can skip them */
+            if (provisioning != SCSI_PROVISIONING_TYPE_MAPPED) {
+                lba += nb_sectors;
+                continue;
+            }
+
+            uint64_t lba2 = lba + nb_sectors;
+            while (lba < lba2) {
+                struct unmap_list list[1];
+                list[0].lba = lba;
+                list[0].num = iscsilun->max_unmap;
+                if (lba + list[0].num > iscsilun->num_blocks) {
+                    list[0].num = iscsilun->num_blocks - lba;
+                }
+                task = iscsi_unmap_sync(iscsilun->iscsi,
+                                        iscsilun->lun,
+                                        0, 0, &list[0], 1);
+                if (task == NULL || task->status != SCSI_STATUS_GOOD) {
+                    error_report("iSCSI: Failed to unmap data on iSCSI lun. %s",
+                                 iscsi_get_error(iscsilun->iscsi));
+                    ret = -EINVAL;
+                    goto out;
+                }
+                scsi_free_scsi_task(task);
+                task = NULL;
+                lba += list[0].num;
+            }
+        }
+    }
+
 out:
+    if (task) {
+        scsi_free_scsi_task(task);
+    }
     if (iscsilun->iscsi != NULL) {
         iscsi_destroy_context(iscsilun->iscsi);
     }
-- 
1.7.9.5