write zeroes is emulated by unmap if the target supports unmapping
an unmapped blocks read as zero. this emulation is only done if the
device was opened with BDRV_O_UNMAP and the request can be handled
within a single request. a failback to writev is performed otherwise.
Signed-off-by: Peter Lieven <p...@kamp.de>
---
block/iscsi.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/block/iscsi.c b/block/iscsi.c
index d31ee95..92e66a6 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -928,6 +928,49 @@ fail:
return 0;
}
+static int
+coroutine_fn iscsi_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
+ int nb_sectors)
+{
+ IscsiLun *iscsilun = bs->opaque;
+ struct IscsiTask iTask;
+ struct unmap_list list[1];
+
+ if (!iscsilun->lbprz || !iscsilun->lbpu || !(bs->open_flags &
BDRV_O_UNMAP) ||
+ nb_sectors * BDRV_SECTOR_SIZE / iscsilun->block_size >
iscsilun->max_unmap) {
+ /* fall back to writev */
+ return -ENOTSUP;
+ }
+
+ iscsi_co_init_iscsitask(iscsilun, &iTask);
+
+ list[0].lba = sector_qemu2lun(sector_num, iscsilun);
+ list[0].num = nb_sectors * BDRV_SECTOR_SIZE / iscsilun->block_size;
+
+retry:
+ if (iscsi_unmap_task(iscsilun->iscsi, iscsilun->lun, 0, 0, &list[0], 1,
+ iscsi_co_generic_cb, &iTask) == NULL) {
+ return -EIO;
+ }
+
+ while (!iTask.complete) {
+ iscsi_set_events(iscsilun);
+ qemu_coroutine_yield();
+ }
+
+ if (iTask.do_retry) {
+ goto retry;
+ }
+
+ if (iTask.status != SCSI_STATUS_GOOD) {
+ return -EIO;
+ }
+
+ scsi_free_scsi_task(iTask.task);
+
+ return 0;
+}
+
static int parse_chap(struct iscsi_context *iscsi, const char *target)
{
QemuOptsList *list;
@@ -1469,6 +1512,7 @@ static BlockDriver bdrv_iscsi = {
.bdrv_truncate = iscsi_truncate,
.bdrv_co_is_allocated = iscsi_co_is_allocated,
+ .bdrv_co_write_zeroes = iscsi_co_write_zeroes,
.bdrv_aio_readv = iscsi_aio_readv,
.bdrv_aio_writev = iscsi_aio_writev,
--
1.7.9.5
