Implement discard support for xen_disk. It makes use of the existing
discard code in qemu.
The discard support is enabled unconditionally. The tool stack may
provide a property "discard-enable" in the backend node to optionally
disable discard support. This is helpful in case the backing file was
intentionally created non-sparse to avoid fragmentation.
Signed-off-by: Olaf Hering <o...@aepfle.de>
---
v2:
depends on "xen_disk: fix io accounting"
remove call to bdrv_acct_start
hw/block/xen_blkif.h | 12 ++++++++++++
hw/block/xen_disk.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/hw/block/xen_blkif.h b/hw/block/xen_blkif.h
index c0f4136..711b692 100644
--- a/hw/block/xen_blkif.h
+++ b/hw/block/xen_blkif.h
@@ -79,6 +79,12 @@ static inline void blkif_get_x86_32_req(blkif_request_t
*dst, blkif_x86_32_reque
dst->handle = src->handle;
dst->id = src->id;
dst->sector_number = src->sector_number;
+ if (src->operation == BLKIF_OP_DISCARD) {
+ struct blkif_request_discard *s = (void *)src;
+ struct blkif_request_discard *d = (void *)dst;
+ d->nr_sectors = s->nr_sectors;
+ return;
+ }
if (n > src->nr_segments)
n = src->nr_segments;
for (i = 0; i < n; i++)
@@ -94,6 +100,12 @@ static inline void blkif_get_x86_64_req(blkif_request_t
*dst, blkif_x86_64_reque
dst->handle = src->handle;
dst->id = src->id;
dst->sector_number = src->sector_number;
+ if (src->operation == BLKIF_OP_DISCARD) {
+ struct blkif_request_discard *s = (void *)src;
+ struct blkif_request_discard *d = (void *)dst;
+ d->nr_sectors = s->nr_sectors;
+ return;
+ }
if (n > src->nr_segments)
n = src->nr_segments;
for (i = 0; i < n; i++)
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 7f0f14a..841b016 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -114,6 +114,7 @@ struct XenBlkDev {
int requests_finished;
/* Persistent grants extension */
+ gboolean feature_discard;
gboolean feature_persistent;
GTree *persistent_gnts;
unsigned int persistent_gnt_count;
@@ -253,6 +254,8 @@ static int ioreq_parse(struct ioreq *ioreq)
case BLKIF_OP_WRITE:
ioreq->prot = PROT_READ; /* from memory */
break;
+ case BLKIF_OP_DISCARD:
+ return 0;
default:
xen_be_printf(&blkdev->xendev, 0, "error: unknown operation (%d)\n",
ioreq->req.operation);
@@ -492,6 +495,7 @@ static void qemu_aio_complete(void *opaque, int ret)
case BLKIF_OP_READ:
bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);
break;
+ case BLKIF_OP_DISCARD:
default:
break;
}
@@ -532,6 +536,15 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq)
&ioreq->v, ioreq->v.size / BLOCK_SIZE,
qemu_aio_complete, ioreq);
break;
+ case BLKIF_OP_DISCARD:
+ {
+ struct blkif_request_discard *discard_req = (void *)&ioreq->req;
+ ioreq->aio_inflight++;
+ bdrv_aio_discard(blkdev->bs,
+ discard_req->sector_number, discard_req->nr_sectors,
+ qemu_aio_complete, ioreq);
+ break;
+ }
default:
/* unknown operation (shouldn't happen -- parse catches this) */
goto err;
@@ -710,6 +723,21 @@ static void blk_alloc(struct XenDevice *xendev)
}
}
+static void blk_parse_discard(struct XenBlkDev *blkdev)
+{
+ int enable;
+
+ blkdev->feature_discard = true;
+
+ if (xenstore_read_be_int(&blkdev->xendev, "discard-enable", &enable) == 0)
{
+ blkdev->feature_discard = !!enable;
+ }
+
+ if (blkdev->feature_discard) {
+ xenstore_write_be_int(&blkdev->xendev, "feature-discard", 1);
+ }
+}
+
static int blk_init(struct XenDevice *xendev)
{
struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
@@ -777,6 +805,8 @@ static int blk_init(struct XenDevice *xendev)
xenstore_write_be_int(&blkdev->xendev, "feature-persistent", 1);
xenstore_write_be_int(&blkdev->xendev, "info", info);
+ blk_parse_discard(blkdev);
+
g_free(directiosafe);
return 0;
@@ -812,6 +842,9 @@ static int blk_connect(struct XenDevice *xendev)
qflags |= BDRV_O_RDWR;
readonly = false;
}
+ if (blkdev->feature_discard) {
+ qflags |= BDRV_O_UNMAP;
+ }
/* init qemu block driver */
index = (blkdev->xendev.dev - 202 * 256) / 16;
