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xen_disk: add discard support 

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 <olaf@aepfle.de>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
This commit is contained in:
Olaf Hering 2014-05-07 13:40:04 +00:00 committed by Stefano Stabellini
parent 8b6bb0ad17
commit f31352041b
3 changed files with 52 additions and 0 deletions
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12
hw/block/xen_blkif.h
View File

@ -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++)

33
hw/block/xen_disk.c
View File

@ -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;

7
include/hw/xen/xen_common.h
View File

@ -144,6 +144,13 @@ static inline int xen_xc_hvm_inject_msi(XenXC xen_xc, domid_t dom,
{
return -ENOSYS;
}
/* The followings are only to compile op_discard related code on older
* Xen releases. */
#define BLKIF_OP_DISCARD 5
struct blkif_request_discard {
uint64_t nr_sectors;
uint64_t sector_number;
};
#else
static inline int xen_xc_hvm_inject_msi(XenXC xen_xc, domid_t dom,
uint64_t addr, uint32_t data)