ISCSI: Add support for thin-provisioning via discard/UNMAP and bigger LUNs

Update the configure test for libiscsi support to detect version 1.3
or later.  Version 1.3 of libiscsi provides both READCAPACITY16 as well
as UNMAP commands.

Update the iscsi block layer to use READCAPACITY16 to detect the size of
the LUN instead of READCAPACITY10. This allows support for LUNs larger
than 2TB.

Update to implement bdrv_aio_discard() using the UNMAP command.
This allows us to use thin-provisioned LUNs from TGTD and other iSCSI
targets that support thin-provisioning.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
[squashed in subsequent patch from Ronnie to fix off-by-one in LBA count]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 73 insertions, 13 deletions

diff --git a/block/iscsi.c b/block/iscsi.c
index 5222726..d37c4ee 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -383,6 +383,65 @@ iscsi_aio_flush(BlockDriverState *bs,
     return &acb->common;
 }
 
+static void
+iscsi_unmap_cb(struct iscsi_context *iscsi, int status,
+                     void *command_data, void *opaque)
+{
+    IscsiAIOCB *acb = opaque;
+
+    if (acb->canceled != 0) {
+        qemu_aio_release(acb);
+        scsi_free_scsi_task(acb->task);
+        acb->task = NULL;
+        return;
+    }
+
+    acb->status = 0;
+    if (status < 0) {
+        error_report("Failed to unmap data on iSCSI lun. %s",
+                     iscsi_get_error(iscsi));
+        acb->status = -EIO;
+    }
+
+    iscsi_schedule_bh(iscsi_readv_writev_bh_cb, acb);
+    scsi_free_scsi_task(acb->task);
+    acb->task = NULL;
+}
+
+static BlockDriverAIOCB *
+iscsi_aio_discard(BlockDriverState *bs,
+                  int64_t sector_num, int nb_sectors,
+                  BlockDriverCompletionFunc *cb, void *opaque)
+{
+    IscsiLun *iscsilun = bs->opaque;
+    struct iscsi_context *iscsi = iscsilun->iscsi;
+    IscsiAIOCB *acb;
+    struct unmap_list list[1];
+
+    acb = qemu_aio_get(&iscsi_aio_pool, bs, cb, opaque);
+
+    acb->iscsilun = iscsilun;
+    acb->canceled   = 0;
+
+    list[0].lba = sector_qemu2lun(sector_num, iscsilun);
+    list[0].num = nb_sectors * BDRV_SECTOR_SIZE / iscsilun->block_size;
+
+    acb->task = iscsi_unmap_task(iscsi, iscsilun->lun,
+                                 0, 0, &list[0], 1,
+                                 iscsi_unmap_cb,
+                                 acb);
+    if (acb->task == NULL) {
+        error_report("iSCSI: Failed to send unmap command. %s",
+                     iscsi_get_error(iscsi));
+        qemu_aio_release(acb);
+        return NULL;
+    }
+
+    iscsi_set_events(iscsilun);
+
+    return &acb->common;
+}
+
 static int64_t
 iscsi_getlength(BlockDriverState *bs)
 {
@@ -396,11 +455,11 @@ iscsi_getlength(BlockDriverState *bs)
 }
 
 static void
-iscsi_readcapacity10_cb(struct iscsi_context *iscsi, int status,
+iscsi_readcapacity16_cb(struct iscsi_context *iscsi, int status,
                         void *command_data, void *opaque)
 {
     struct IscsiTask *itask = opaque;
-    struct scsi_readcapacity10 *rc10;
+    struct scsi_readcapacity16 *rc16;
     struct scsi_task *task = command_data;
 
     if (status != 0) {
@@ -412,26 +471,25 @@ iscsi_readcapacity10_cb(struct iscsi_context *iscsi, int status,
         return;
     }
 
-    rc10 = scsi_datain_unmarshall(task);
-    if (rc10 == NULL) {
-        error_report("iSCSI: Failed to unmarshall readcapacity10 data.");
+    rc16 = scsi_datain_unmarshall(task);
+    if (rc16 == NULL) {
+        error_report("iSCSI: Failed to unmarshall readcapacity16 data.");
         itask->status   = 1;
         itask->complete = 1;
         scsi_free_scsi_task(task);
         return;
     }
 
-    itask->iscsilun->block_size = rc10->block_size;
-    itask->iscsilun->num_blocks = rc10->lba;
-    itask->bs->total_sectors = (uint64_t)rc10->lba *
-                               rc10->block_size / BDRV_SECTOR_SIZE ;
+    itask->iscsilun->block_size = rc16->block_length;
+    itask->iscsilun->num_blocks = rc16->returned_lba + 1;
+    itask->bs->total_sectors    = itask->iscsilun->num_blocks *
+                               itask->iscsilun->block_size / BDRV_SECTOR_SIZE ;
 
     itask->status   = 0;
     itask->complete = 1;
     scsi_free_scsi_task(task);
 }
 
-
 static void
 iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data,
                  void *opaque)
@@ -445,10 +503,10 @@ iscsi_connect_cb(struct iscsi_context *iscsi, int status, void *command_data,
         return;
     }
 
-    task = iscsi_readcapacity10_task(iscsi, itask->iscsilun->lun, 0, 0,
-                                   iscsi_readcapacity10_cb, opaque);
+    task = iscsi_readcapacity16_task(iscsi, itask->iscsilun->lun,
+                                   iscsi_readcapacity16_cb, opaque);
     if (task == NULL) {
-        error_report("iSCSI: failed to send readcapacity command.");
+        error_report("iSCSI: failed to send readcapacity16 command.");
         itask->status   = 1;
         itask->complete = 1;
         return;
@@ -700,6 +758,8 @@ static BlockDriver bdrv_iscsi = {
     .bdrv_aio_readv  = iscsi_aio_readv,
     .bdrv_aio_writev = iscsi_aio_writev,
     .bdrv_aio_flush  = iscsi_aio_flush,
+
+    .bdrv_aio_discard = iscsi_aio_discard,
 };
 
 static void iscsi_block_init(void)