On Mon, 6 Jun 2011, Marcelo Tosatti wrote:
> Mirrored writes are used by live block copy.
>
> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>
>
> Index: qemu-block-copy/block/blkmirror.c
> ===================================================================
> --- /dev/null
> +++ qemu-block-copy/block/blkmirror.c
> @@ -0,0 +1,277 @@
> +/*
> + * Block driver for mirrored writes.
> + *
> + * Copyright (C) 2011 Red Hat, Inc.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include <stdarg.h>
> +#include "block_int.h"
> +
> +typedef struct {
> + BlockDriverState *bs[2];
> +} BdrvMirrorState;
> +
> +typedef struct DupAIOCB DupAIOCB;
> +
> +typedef struct SingleAIOCB {
> + BlockDriverAIOCB *aiocb;
> + int finished;
> + DupAIOCB *parent;
> +} SingleAIOCB;
> +
> +struct DupAIOCB {
> + BlockDriverAIOCB common;
> + int count;
> +
> + BlockDriverCompletionFunc *cb;
> + SingleAIOCB aios[2];
> + int ret;
> +};
> +
> +/* Valid blkmirror filenames look like
> + * blkmirror:path/to/image1:path/to/image2 */
> +static int blkmirror_open(BlockDriverState *bs, const char *filename, int
> flags)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + int ret, escape, i, n;
> + char *raw;
> +
> + /* Parse the blkmirror: prefix */
> + if (strncmp(filename, "blkmirror:", strlen("blkmirror:"))) {
> + return -EINVAL;
> + }
> + filename += strlen("blkmirror:");
> +
> + /* Parse the raw image filename */
> + raw = malloc(strlen(filename));
> + escape = 0;
> + for (i = n = 0; i < strlen(filename); i++) {
> + if (!escape && filename[i] == ':') {
> + break;
> + }
> + if (!escape && filename[i] == '\\') {
> + escape = 1;
> + } else {
> + escape = 0;
> + }
> +
> + if (!escape) {
> + raw[n++] = filename[i];
> + }
> + }
> + raw[n] = '\0';
This potentially writes past the memory allocated for raw.
> +
> + m->bs[0] = bdrv_new("");
> + if (m->bs[0] == NULL) {
> + return -ENOMEM;
> + }
> + ret = bdrv_open(m->bs[0], raw, flags, NULL);
> + free(raw);
> + if (ret < 0) {
> + return ret;
> + }
> + filename += i + 1;
> +
> + m->bs[1] = bdrv_new("");
> + if (m->bs[1] == NULL) {
> + return -ENOMEM;
> + }
> + ret = bdrv_open(m->bs[1], filename, flags, NULL);
> + if (ret < 0) {
> + bdrv_delete(m->bs[0]);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static void blkmirror_close(BlockDriverState *bs)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + int i;
> +
> + for (i = 0; i < 2; i++) {
> + bdrv_delete(m->bs[i]);
> + m->bs[i] = NULL;
> + }
> +}
> +
> +static int blkmirror_flush(BlockDriverState *bs)
> +{
> + BdrvMirrorState *m = bs->opaque;
> +
> + bdrv_flush(m->bs[0]);
> + bdrv_flush(m->bs[1]);
> +
> + return 0;
> +}
> +
> +static int64_t blkmirror_getlength(BlockDriverState *bs)
> +{
> + BdrvMirrorState *m = bs->opaque;
> +
> + return bdrv_getlength(m->bs[0]);
> +}
> +
> +static BlockDriverAIOCB *blkmirror_aio_readv(BlockDriverState *bs,
> + int64_t sector_num,
> + QEMUIOVector *qiov,
> + int nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + return bdrv_aio_readv(m->bs[0], sector_num, qiov, nb_sectors, cb,
> opaque);
> +}
> +
> +static void dup_aio_cancel(BlockDriverAIOCB *blockacb)
> +{
> + DupAIOCB *acb = container_of(blockacb, DupAIOCB, common);
> + int i;
> +
> + for (i = 0 ; i < 2; i++) {
> + if (!acb->aios[i].finished) {
> + bdrv_aio_cancel(acb->aios[i].aiocb);
> + }
> + }
> + qemu_aio_release(acb);
> +}
> +
> +static AIOPool dup_aio_pool = {
> + .aiocb_size = sizeof(DupAIOCB),
> + .cancel = dup_aio_cancel,
> +};
> +
> +static void blkmirror_aio_cb(void *opaque, int ret)
> +{
> + SingleAIOCB *scb = opaque;
> + DupAIOCB *dcb = scb->parent;
> +
> + scb->finished = 1;
> + dcb->count--;
> + assert(dcb->count >= 0);
> + if (ret < 0) {
> + dcb->ret = ret;
> + }
> + if (dcb->count == 0) {
> + dcb->common.cb(dcb->common.opaque, dcb->ret);
> + qemu_aio_release(dcb);
> + }
> +}
> +
> +static DupAIOCB *dup_aio_get(BlockDriverState *bs,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + DupAIOCB *dcb;
> + int i;
> +
> + dcb = qemu_aio_get(&dup_aio_pool, bs, cb, opaque);
> + if (!dcb) {
> + return NULL;
> + }
> + dcb->count = 2;
> + for (i = 0; i < 2; i++) {
> + dcb->aios[i].parent = dcb;
> + dcb->aios[i].finished = 0;
> + }
> + dcb->ret = 0;
> +
> + return dcb;
> +}
> +
> +static BlockDriverAIOCB *blkmirror_aio_writev(BlockDriverState *bs,
> + int64_t sector_num,
> + QEMUIOVector *qiov,
> + int nb_sectors,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + DupAIOCB *dcb = dup_aio_get(bs, cb, opaque);
> + int i;
> +
> + for (i = 0; i < 2; i++) {
> + dcb->aios[i].aiocb = bdrv_aio_writev(m->bs[i], sector_num, qiov,
> + nb_sectors, &blkmirror_aio_cb,
> + &dcb->aios[i]);
> + if (!dcb->aios[i].aiocb) {
> + int a;
> +
> + for (a = 0; a < i; a++) {
> + bdrv_aio_cancel(dcb->aios[i].aiocb);
> + }
> + qemu_aio_release(dcb);
> + return NULL;
> + }
> + }
> +
> + return &dcb->common;
> +}
> +
> +static BlockDriverAIOCB *blkmirror_aio_flush(BlockDriverState *bs,
> + BlockDriverCompletionFunc *cb,
> + void *opaque)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + DupAIOCB *dcb = dup_aio_get(bs, cb, opaque);
> + int i;
> +
> + for (i = 0; i < 2; i++) {
> + dcb->aios[i].aiocb = bdrv_aio_flush(m->bs[i], &blkmirror_aio_cb,
> + &dcb->aios[i]);
> + if (!dcb->aios[i].aiocb) {
> + int a;
> +
> + for (a = 0; a < i; a++) {
> + bdrv_aio_cancel(dcb->aios[i].aiocb);
> + }
> + qemu_aio_release(dcb);
> + return NULL;
> + }
> + }
> +
> + return &dcb->common;
> +}
> +
> +static int blkmirror_discard(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors)
> +{
> + BdrvMirrorState *m = bs->opaque;
> + int ret;
> +
> + ret = bdrv_discard(m->bs[0], sector_num, nb_sectors);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + return bdrv_discard(m->bs[1], sector_num, nb_sectors);
> +}
> +
> +
> +static BlockDriver bdrv_blkmirror = {
> + .format_name = "blkmirror",
> + .protocol_name = "blkmirror",
> + .instance_size = sizeof(BdrvMirrorState),
> +
> + .bdrv_getlength = blkmirror_getlength,
> +
> + .bdrv_file_open = blkmirror_open,
> + .bdrv_close = blkmirror_close,
> + .bdrv_flush = blkmirror_flush,
> + .bdrv_discard = blkmirror_discard,
> +
> + .bdrv_aio_readv = blkmirror_aio_readv,
> + .bdrv_aio_writev = blkmirror_aio_writev,
> + .bdrv_aio_flush = blkmirror_aio_flush,
> +};
> +
> +static void bdrv_blkmirror_init(void)
> +{
> + bdrv_register(&bdrv_blkmirror);
> +}
> +
> +block_init(bdrv_blkmirror_init);
> Index: qemu-block-copy/Makefile.objs
> ===================================================================
> --- qemu-block-copy.orig/Makefile.objs
> +++ qemu-block-copy/Makefile.objs
> @@ -22,7 +22,7 @@ block-nested-y += raw.o cow.o qcow.o vdi
> block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
> qcow2-cache.o
> block-nested-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
> block-nested-y += qed-check.o
> -block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> +block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> blkmirror.o
> block-nested-$(CONFIG_WIN32) += raw-win32.o
> block-nested-$(CONFIG_POSIX) += raw-posix.o
> block-nested-$(CONFIG_CURL) += curl.o
> Index: qemu-block-copy/docs/blkmirror.txt
> ===================================================================
> --- /dev/null
> +++ qemu-block-copy/docs/blkmirror.txt
> @@ -0,0 +1,15 @@
> +Block mirror driver
> +-------------------
> +
> +This driver will mirror writes to two distinct images.
> +Its used internally by live block copy.
> +
> +Format
> +------
> +
> +blkmirror:/image1.img:/image2.img
> +
> +'\' (backslash) can be used to escape colon processing
> +as a separator.
> +
> +
>
>
>
--
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