Commit f3135204 authored by Olaf Hering's avatar Olaf Hering Committed by Stefano Stabellini
Browse files

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: default avatarOlaf Hering <olaf@aepfle.de>
Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
parent 8b6bb0ad

hw/block/xen_blkif.h

+12 −0
Original line number Diff line number Diff line
@@ -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++)

hw/block/xen_disk.c

+33 −0
Original line number Diff line number Diff line
@@ -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;

include/hw/xen/xen_common.h

+7 −0
Original line number Diff line number Diff line
@@ -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)