Sorry, missed add-cow-cache.c, please ignore it. I will re-send the patch.
On Thu, Mar 1, 2012 at 10:49, Dong Xu Wang <wdon...@linux.vnet.ibm.com> wrote:
> From: Dong Xu Wang <wdon...@linux.vnet.ibm.com>
>
> Provide a new file format: add-cow. The usage can be found in add-cow.txt of
> this patch.
>
> CC: Marcelo Tosatti <mtosa...@redhat.com>
> CC: Kevin Wolf <kw...@redhat.com>
> CC: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> Signed-off-by: Dong Xu Wang <wdon...@linux.vnet.ibm.com>
> ---
> Makefile.objs | 1 +
> block.c | 2 +-
> block.h | 1 +
> block/add-cow.c | 402
> ++++++++++++++++++++++++++++++++++++++++++++++++
> block_int.h | 1 +
> docs/specs/add-cow.txt | 68 ++++++++
> 6 files changed, 474 insertions(+), 1 deletions(-)
> create mode 100644 block/add-cow.c
> create mode 100644 docs/specs/add-cow.txt
>
> diff --git a/Makefile.objs b/Makefile.objs
> index 808de6a..fa9dde0 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -34,6 +34,7 @@ block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o
> dmg.o bochs.o vpc.o vv
> 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 += add-cow.o add-cow-cache.o
> block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> block-nested-y += stream.o
> block-nested-$(CONFIG_WIN32) += raw-win32.o
> diff --git a/block.c b/block.c
> index 52ffe14..581c092 100644
> --- a/block.c
> +++ b/block.c
> @@ -194,7 +194,7 @@ static void bdrv_io_limits_intercept(BlockDriverState *bs,
> }
>
> /* check if the path starts with "<protocol>:" */
> -static int path_has_protocol(const char *path)
> +int path_has_protocol(const char *path)
> {
> #ifdef _WIN32
> if (is_windows_drive(path) ||
> diff --git a/block.h b/block.h
> index 48d0bf3..3d96444 100644
> --- a/block.h
> +++ b/block.h
> @@ -310,6 +310,7 @@ char *bdrv_snapshot_dump(char *buf, int buf_size,
> QEMUSnapshotInfo *sn);
>
> char *get_human_readable_size(char *buf, int buf_size, int64_t size);
> int path_is_absolute(const char *path);
> +int path_has_protocol(const char *path);
> void path_combine(char *dest, int dest_size,
> const char *base_path,
> const char *filename);
> diff --git a/block/add-cow.c b/block/add-cow.c
> new file mode 100644
> index 0000000..6897a52
> --- /dev/null
> +++ b/block/add-cow.c
> @@ -0,0 +1,402 @@
> +/*
> + * QEMU ADD-COW Disk Format
> + *
> + * Copyright IBM, Corp. 2012
> + *
> + * Authors:
> + * Dong Xu Wang <wdon...@linux.vnet.ibm.com>
> + * This work is licensed under the terms of the GNU LGPL, version 2 or later.
> + * See the COPYING.LIB file in the top-level directory.
> + *
> + */
> +
> +#include "qemu-common.h"
> +#include "block_int.h"
> +#include "module.h"
> +#include "add-cow.h"
> +
> +static int add_cow_probe(const uint8_t *buf, int buf_size, const char
> *filename)
> +{
> + const AddCowHeader *header = (const void *)buf;
> +
> + if (be64_to_cpu(header->magic) == ADD_COW_MAGIC &&
> + be32_to_cpu(header->version) == ADD_COW_VERSION) {
> + return 100;
> + } else {
> + return 0;
> + }
> +}
> +
> +static int add_cow_open(BlockDriverState *bs, int flags)
> +{
> + AddCowHeader header;
> + char image_filename[ADD_COW_FILE_LEN];
> + BlockDriver *image_drv = NULL;
> + int ret;
> + BDRVAddCowState *s = bs->opaque;
> +
> + ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
> + if (ret != sizeof(header)) {
> + goto fail;
> + }
> +
> + if (be64_to_cpu(header.magic) != ADD_COW_MAGIC) {
> + ret = -EINVAL;
> + goto fail;
> + }
> + if (be32_to_cpu(header.version) != ADD_COW_VERSION) {
> + char version[64];
> + snprintf(version, sizeof(version), "ADD-COW version %d",
> header.version);
> + qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
> + bs->device_name, "add-cow", version);
> + ret = -ENOTSUP;
> + goto fail;
> + }
> +
> + QEMU_BUILD_BUG_ON(sizeof(bs->backing_file) !=
> sizeof(header.backing_file));
> + strncpy(bs->backing_file, header.backing_file,
> + sizeof(bs->backing_file));
> +
> + if (header.image_file[0] == '\0') {
> + ret = -ENOENT;
> + goto fail;
> + }
> + s->image_hd = bdrv_new("");
> + if (path_has_protocol(header.image_file)) {
> + strncpy(image_filename, header.image_file, sizeof(image_filename));
> + } else {
> + path_combine(image_filename, sizeof(image_filename),
> + bs->filename, header.image_file);
> + }
> +
> + image_drv = bdrv_find_format("raw");
> + ret = bdrv_open(s->image_hd, image_filename, flags, image_drv);
> + if (ret < 0) {
> + bdrv_delete(s->image_hd);
> + goto fail;
> + }
> + bs->total_sectors = s->image_hd->total_sectors;
> + s->cluster_size = ADD_COW_CLUSTER_SIZE;
> + s->bitmap_cache = add_cow_cache_create(bs, ADD_COW_CACHE_SIZE);
> + qemu_co_mutex_init(&s->lock);
> + return 0;
> + fail:
> + return ret;
> +}
> +
> +static inline bool is_bit_set(BlockDriverState *bs, int64_t bitnum)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + uint64_t offset = bitnum >> 3;
> + uint8_t *bitmap;
> + int ret = add_cow_cache_get(bs, s->bitmap_cache,
> + offset & ~(ADD_COW_CLUSTER_SIZE - 1), (void **)&bitmap);
> + if (ret < 0) {
> + abort();
> + }
> +
> + return *(bitmap + (offset & (ADD_COW_CLUSTER_SIZE - 1))) & (1 << (bitnum
> % 8));
> +}
> +
> +static coroutine_fn int add_cow_is_allocated(BlockDriverState *bs,
> + int64_t sector_num, int nb_sectors, int *num_same)
> +{
> + int changed;
> +
> + if (nb_sectors == 0) {
> + *num_same = nb_sectors;
> + return 0;
> + }
> +
> + changed = is_bit_set(bs, sector_num);
> + for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
> + if (is_bit_set(bs, sector_num + *num_same) != changed) {
> + break;
> + }
> + }
> +
> + return changed;
> +}
> +
> +static int add_cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + uint8_t *bitmap;
> +
> + int i, ret = 0;
> + for (i = 0; i < nb_sectors; i++) {
> + int ret = add_cow_cache_get(bs, s->bitmap_cache,
> + (sector_num + i) / 8 & ~(ADD_COW_CLUSTER_SIZE - 1), (void
> **)&bitmap);
> + if (ret < 0) {
> + abort();
> + }
> + *(bitmap + ((sector_num + i) / 8 & (ADD_COW_CLUSTER_SIZE - 1))) |=
> + (1 << ((sector_num + i) % 8));
> + add_cow_cache_entry_mark_dirty(s->bitmap_cache, bitmap);
> +
> + }
> + ret = add_cow_cache_flush(bs, s->bitmap_cache);
> + if (ret < 0) {
> + abort();
> + }
> + return ret;
> +}
> +
> +static void add_cow_close(BlockDriverState *bs)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + add_cow_cache_destroy(bs, s->bitmap_cache);
> + bdrv_delete(s->image_hd);
> +}
> +static int add_cow_create(const char *filename, QEMUOptionParameter *options)
> +{
> + AddCowHeader header;
> + int64_t image_sectors = 0;
> + const char *backing_filename = NULL;
> + const char *image_filename = NULL;
> + int ret;
> + BlockDriverState *bs, *image_bs = NULL, *backing_bs = NULL;
> +
> + while (options && options->name) {
> + if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
> + image_sectors = options->value.n / BDRV_SECTOR_SIZE;
> + } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
> + backing_filename = options->value.s;
> + } else if (!strcmp(options->name, BLOCK_OPT_IMAGE_FILE)) {
> + image_filename = options->value.s;
> + }
> + options++;
> + }
> +
> + if (!backing_filename || !image_filename) {
> + error_report("Both backing_file and image_file should be given.");
> + return -EINVAL;
> + }
> +
> + ret = bdrv_file_open(&image_bs, image_filename, BDRV_O_RDWR
> + | BDRV_O_CACHE_WB);
> + if (ret < 0) {
> + return ret;
> + }
> + image_sectors = image_bs->total_sectors;
> + bdrv_delete(image_bs);
> +
> + ret = bdrv_file_open(&backing_bs, backing_filename, BDRV_O_RDWR
> + | BDRV_O_CACHE_WB);
> + if (ret < 0) {
> + return ret;
> + }
> + bdrv_delete(backing_bs);
> +
> + ret = bdrv_create_file(filename, NULL);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + ret = bdrv_file_open(&bs, filename, BDRV_O_RDWR);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + memset(&header, 0, sizeof(header));
> + header.magic = cpu_to_be64(ADD_COW_MAGIC);
> + header.version = cpu_to_be32(ADD_COW_VERSION);
> + strncpy(header.backing_file, backing_filename,
> sizeof(header.backing_file));
> + strncpy(header.image_file, image_filename, sizeof(header.image_file));
> +
> + ret = bdrv_pwrite(bs, 0, &header, sizeof(header));
> + if (ret < 0) {
> + bdrv_delete(bs);
> + return ret;
> + }
> +
> + BlockDriver *drv = bdrv_find_format("add-cow");
> + assert(drv != NULL);
> + ret = bdrv_open(bs, filename, BDRV_O_RDWR | BDRV_O_NO_FLUSH, drv);
> + if (ret < 0) {
> + bdrv_delete(bs);
> + return ret;
> + }
> +
> + ret = bdrv_truncate(bs, image_sectors * BDRV_SECTOR_SIZE);
> + bdrv_delete(bs);
> + return ret;
> +}
> +
> +static int add_cow_backing_read(BlockDriverState *bs, QEMUIOVector *qiov,
> + int64_t sector_num, int nb_sectors)
> +{
> + int n1;
> + if ((sector_num + nb_sectors) <= bs->total_sectors) {
> + return nb_sectors;
> + }
> + if (sector_num >= bs->total_sectors) {
> + n1 = 0;
> + } else {
> + n1 = bs->total_sectors - sector_num;
> + }
> +
> + qemu_iovec_memset_skip(qiov, 0, BDRV_SECTOR_SIZE * (nb_sectors - n1),
> + BDRV_SECTOR_SIZE * n1);
> + return n1;
> +}
> +
> +static coroutine_fn int add_cow_co_readv(BlockDriverState *bs, int64_t
> sector_num,
> + int remaining_sectors, QEMUIOVector *qiov)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + int cur_nr_sectors;
> + uint64_t bytes_done = 0;
> + QEMUIOVector hd_qiov;
> + int n, n1, ret = 0;
> +
> + qemu_iovec_init(&hd_qiov, qiov->niov);
> + qemu_co_mutex_lock(&s->lock);
> + while (remaining_sectors != 0) {
> + cur_nr_sectors = remaining_sectors;
> + if (add_cow_is_allocated(bs, sector_num, cur_nr_sectors, &n)) {
> + cur_nr_sectors = n;
> + qemu_iovec_reset(&hd_qiov);
> + qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
> + cur_nr_sectors * BDRV_SECTOR_SIZE);
> + ret = bdrv_co_readv(s->image_hd, sector_num, n, &hd_qiov);
> + if (ret < 0) {
> + goto fail;
> + }
> + } else {
> + cur_nr_sectors = n;
> + if (bs->backing_hd) {
> + n1 = add_cow_backing_read(bs->backing_hd, &hd_qiov,
> + sector_num, cur_nr_sectors);
> + if (n1 > 0) {
> + qemu_iovec_reset(&hd_qiov);
> + qemu_iovec_copy(&hd_qiov, qiov, bytes_done,
> + cur_nr_sectors * BDRV_SECTOR_SIZE);
> + ret = bdrv_co_readv(bs->backing_hd, sector_num,
> + n, &hd_qiov);
> + if (ret < 0) {
> + goto fail;
> + }
> + }
> + } else {
> + qemu_iovec_reset(&hd_qiov);
> + }
> + }
> + remaining_sectors -= cur_nr_sectors;
> + sector_num += cur_nr_sectors;
> + bytes_done += cur_nr_sectors * BDRV_SECTOR_SIZE;
> + }
> +fail:
> + qemu_co_mutex_unlock(&s->lock);
> + qemu_iovec_destroy(&hd_qiov);
> + return ret;
> +}
> +
> +static coroutine_fn int add_cow_co_writev(BlockDriverState *bs, int64_t
> sector_num,
> + int remaining_sectors, QEMUIOVector *qiov)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + int ret = 0;
> + QEMUIOVector hd_qiov;
> + qemu_iovec_init(&hd_qiov, qiov->niov);
> + qemu_co_mutex_lock(&s->lock);
> + qemu_iovec_reset(&hd_qiov);
> + qemu_iovec_copy(&hd_qiov, qiov, 0, remaining_sectors * BDRV_SECTOR_SIZE);
> + ret = bdrv_co_writev(s->image_hd,
> + sector_num,
> + remaining_sectors, &hd_qiov);
> + if (ret < 0) {
> + goto fail;
> + }
> +
> + ret = add_cow_update_bitmap(bs, sector_num, remaining_sectors);
> + if (ret < 0) {
> + goto fail;
> + }
> +fail:
> + qemu_co_mutex_unlock(&s->lock);
> + qemu_iovec_destroy(&hd_qiov);
> + return ret;
> +}
> +
> +static int bdrv_add_cow_truncate(BlockDriverState *bs, int64_t offset)
> +{
> + int ret = 0;
> + int64_t image_sectors = offset / BDRV_SECTOR_SIZE;
> + BDRVAddCowState *s = bs->opaque;
> + int64_t old_image_sector = s->image_hd->total_sectors;
> +
> + ret = bdrv_truncate(bs->file, sizeof(AddCowHeader) + ((image_sectors +
> 7) >> 3));
> + if (ret < 0) {
> + bdrv_truncate(s->image_hd, old_image_sector * BDRV_SECTOR_SIZE);
> + return ret;
> + }
> + return ret;
> +}
> +
> +static coroutine_fn int add_cow_co_flush(BlockDriverState *bs)
> +{
> + BDRVAddCowState *s = bs->opaque;
> + int ret = bdrv_co_flush(s->image_hd);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + qemu_co_mutex_lock(&s->lock);
> + ret = add_cow_cache_flush(bs, s->bitmap_cache);
> + if (ret < 0) {
> + qemu_co_mutex_unlock(&s->lock);
> + return ret;
> + }
> + qemu_co_mutex_unlock(&s->lock);
> + return bdrv_co_flush(bs->file);
> +}
> +
> +static QEMUOptionParameter add_cow_create_options[] = {
> + {
> + .name = BLOCK_OPT_SIZE,
> + .type = OPT_SIZE,
> + .help = "Virtual disk size"
> + },
> + {
> + .name = BLOCK_OPT_BACKING_FILE,
> + .type = OPT_STRING,
> + .help = "File name of a base image"
> + },
> + {
> + .name = BLOCK_OPT_IMAGE_FILE,
> + .type = OPT_STRING,
> + .help = "File name of a image file"
> + },
> + {
> + .name = BLOCK_OPT_BACKING_FMT,
> + .type = OPT_STRING,
> + .help = "Image format of the base image"
> + },
> + { NULL }
> +};
> +
> +static BlockDriver bdrv_add_cow = {
> + .format_name = "add-cow",
> + .instance_size = sizeof(BDRVAddCowState),
> + .bdrv_probe = add_cow_probe,
> + .bdrv_open = add_cow_open,
> + .bdrv_close = add_cow_close,
> + .bdrv_create = add_cow_create,
> + .bdrv_co_is_allocated = add_cow_is_allocated,
> +
> + .bdrv_co_readv = add_cow_co_readv,
> + .bdrv_co_writev = add_cow_co_writev,
> + .bdrv_truncate = bdrv_add_cow_truncate,
> +
> + .create_options = add_cow_create_options,
> + .bdrv_co_flush_to_disk = add_cow_co_flush,
> +};
> +
> +static void bdrv_add_cow_init(void)
> +{
> + bdrv_register(&bdrv_add_cow);
> +}
> +
> +block_init(bdrv_add_cow_init);
> diff --git a/block_int.h b/block_int.h
> index b460c36..8126f27 100644
> --- a/block_int.h
> +++ b/block_int.h
> @@ -50,6 +50,7 @@
> #define BLOCK_OPT_TABLE_SIZE "table_size"
> #define BLOCK_OPT_PREALLOC "preallocation"
> #define BLOCK_OPT_SUBFMT "subformat"
> +#define BLOCK_OPT_IMAGE_FILE "image_file"
>
> typedef struct BdrvTrackedRequest BdrvTrackedRequest;
>
> diff --git a/docs/specs/add-cow.txt b/docs/specs/add-cow.txt
> new file mode 100644
> index 0000000..db992a4
> --- /dev/null
> +++ b/docs/specs/add-cow.txt
> @@ -0,0 +1,68 @@
> +== General ==
> +
> +Raw file format does not support backing_file and copy on write feature.
> +The add-cow image format makes it possible to use backing files with raw
> +image by keeping a separate .add-cow metadata file. Once all sectors
> +have been written to in the raw image it is safe to discard the .add-cow
> +and backing files and instead use the raw image directly.
> +
> +When using add-cow, procedures may like this:
> +(ubuntu.img is a disk image which has been installed OS.)
> + 1) Create a raw image with the same size of ubuntu.img
> + qemu-img create -f raw test.raw 8G
> + 2) Create a add-cow image which will store dirty bitmap
> + qemu-img create -f add-cow test.add-cow -o
> backing_file=ubuntu.img,image_file=test.raw
> + 3) Run qemu with add-cow image
> + qemu -drive if=virtio,file=test.add-cow
> +
> +=Specification=
> +
> +The file format looks like this:
> +
> + +---------------+--------------------------+
> + | Header | Data |
> + +---------------+--------------------------+
> +
> +All numbers in add-cow are stored in Big Endian byte order.
> +
> +== Header ==
> +
> +The Header is included in the first bytes:
> +
> + Byte 0 - 7: magic
> + add-cow magic string ("ADD_COW\xff")
> +
> + 8 - 11: version
> + Version number (only valid value is 1 now)
> +
> + 12 - 1035: backing_file
> + backing_file file name related to add-cow file. All
> + unused bytes are padded with zeros. Must not be
> longer
> + than 1023 bytes.
> +
> + 1036 - 2059: image_file
> + image_file is a raw file. All unused bytes are padded
> + with zeros. Must not be longer than 1023 bytes.
> +
> + 2060 - 2559: The Reserved field is used to make sure Data field
> starts
> + at the multiple of 512, not used currently. All
> bytes are
> + filled with 0.
> +
> +== Data ==
> +
> +The Data field starts at the 2560th byte, stores a bitmap related to
> backing_file
> +and image_file. The bitmap will track whether the sector in backing_file is
> dirty
> +or not.
> +
> +
> +Each bit in the bitmap indicates one sector's status. So the size of bitmap
> is
> +calculated according to virtual size of backing_file. In each byte, bit 0 to
> 7
> +will track the 1st to 7th sector in sequence, bit orders in one byte look
> like:
> + +----+----+----+----+----+----+----+----+
> + | b7 | b6 | b5 | b4 | b3 | b2 | b1 | b0 |
> + +----+----+----+----+----+----+----+----+
> +
> +If the bit is 0, indicates the sector has not been allocated in image_file,
> data
> +should be loaded from backing_file while reading; if the bit is 1,
> indicates the
> +related sector has been dirty, should be loaded from image_file while
> reading.
> +Writing to a sector causes the corresponding bit to be set to 1.
> --
> 1.7.5.4
>
>
