Any comment?
Thanks.
2011/11/15 Dong Xu Wang <wdon...@linux.vnet.ibm.com>
> 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.
>
> Signed-off-by: Dong Xu Wang <wdon...@linux.vnet.ibm.com>
> ---
> Makefile.objs | 1 +
> block.c | 2 +-
> block.h | 1 +
> block/add-cow.c | 417
> ++++++++++++++++++++++++++++++++++++++++++++++++
> block_int.h | 1 +
> docs/specs/add-cow.txt | 57 +++++++
> 6 files changed, 478 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 d7a6539..ad99243 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -31,6 +31,7 @@ block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
>
> block-nested-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o
> vpc.o vvfat.o
> block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o
> qcow2-snapshot.o qcow2-cache.o
> +block-nested-y += add-cow.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
> diff --git a/block.c b/block.c
> index 86910b0..a2be27b 100644
> --- a/block.c
> +++ b/block.c
> @@ -106,7 +106,7 @@ int is_windows_drive(const char *filename)
> #endif
>
> /* 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 051a25d..836284f 100644
> --- a/block.h
> +++ b/block.h
> @@ -276,6 +276,7 @@ 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..54d30a9
> --- /dev/null
> +++ b/block/add-cow.c
> @@ -0,0 +1,417 @@
> +#include "qemu-common.h"
> +#include "block_int.h"
> +#include "module.h"
> +
> +#define ADD_COW_MAGIC (((uint64_t)'A' << 56) | ((uint64_t)'D' <<
> 48) | \
> + ((uint64_t)'D' << 40) | ((uint64_t)'_' << 32)
> | \
> + ((uint64_t)'C' << 24) | ((uint64_t)'O' << 16)
> | \
> + ((uint64_t)'W' << 8) | 0xFF)
> +#define ADD_COW_VERSION 1
> +#define ADD_COW_FILE_LEN 1024
> +
> +typedef struct AddCowHeader {
> + uint64_t magic;
> + uint32_t version;
> + char backing_file[ADD_COW_FILE_LEN];
> + char image_file[ADD_COW_FILE_LEN];
> + uint64_t size;
> +} QEMU_PACKED AddCowHeader;
> +
> +typedef struct BDRVAddCowState {
> + char image_file[ADD_COW_FILE_LEN];
> + BlockDriverState *image_hd;
> + uint8_t *bitmap;
> + uint64_t bitmap_size;
> + CoMutex lock;
> +} BDRVAddCowState;
> +
> +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;
> + int64_t size;
> + char image_filename[ADD_COW_FILE_LEN];
> + int image_flags;
> + BlockDriver *image_drv = NULL;
> + int ret;
> + BDRVAddCowState *state = (BDRVAddCowState *)(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 ||
> + be32_to_cpu(header.version) != ADD_COW_VERSION) {
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + size = be64_to_cpu(header.size);
> + bs->total_sectors = size / BDRV_SECTOR_SIZE;
> +
> + QEMU_BUILD_BUG_ON(sizeof(state->image_file) !=
> sizeof(header.image_file));
> + pstrcpy(bs->backing_file, sizeof(bs->backing_file),
> + header.backing_file);
> + pstrcpy(state->image_file, sizeof(state->image_file),
> + header.image_file);
> +
> + state->bitmap_size = ((bs->total_sectors + 7) >> 3);
> + state->bitmap = g_malloc0(state->bitmap_size);
> +
> + ret = bdrv_pread(bs->file, sizeof(header), state->bitmap,
> + state->bitmap_size);
> + if (ret != state->bitmap_size) {
> + goto fail;
> + }
> + /* If there is a image_file, must be together with backing_file */
> + if (state->image_file[0] != '\0') {
> + state->image_hd = bdrv_new("");
> +
> + if (path_has_protocol(state->image_file)) {
> + pstrcpy(image_filename, sizeof(image_filename),
> + state->image_file);
> + } else {
> + path_combine(image_filename, sizeof(image_filename),
> + bs->filename, state->image_file);
> + }
> +
> + image_drv = bdrv_find_format("raw");
> + image_flags =
> + (flags & (~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING))) |
> BDRV_O_RDWR;
> + state->image_hd->keep_read_only = 0;
> +
> + ret = bdrv_open(state->image_hd, image_filename, image_flags,
> + image_drv);
> + if (ret < 0) {
> + bdrv_delete(state->image_hd);
> + state->image_hd = NULL;
> + goto fail;
> + }
> + }
> + if (state->image_file[0] == '\0') {
> + ret = -ENOENT;
> + goto fail;
> + }
> +
> + qemu_co_mutex_init(&state->lock);
> + return 0;
> + fail:
> + g_free(state->bitmap);
> + state->bitmap = NULL;
> + return ret;
> +}
> +
> +static inline void add_cow_set_bit(BlockDriverState *bs, int64_t bitnum)
> +{
> + uint64_t offset = bitnum / 8;
> + BDRVAddCowState *state = (BDRVAddCowState *)(bs->opaque);
> + state->bitmap[offset] |= (1 << (bitnum % 8));
> +}
> +
> +static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
> +{
> + BDRVAddCowState *state = (BDRVAddCowState *)(bs->opaque);
> + uint64_t offset = bitnum / 8;
> + return !!(state->bitmap[offset] & (1 << (bitnum % 8)));
> +}
> +
> +static int add_cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, int *num_same)
> +{
> + int changed;
> + uint64_t bitmap_size = ((BDRVAddCowState *)(bs->opaque))->bitmap_size;
> +
> + /* Beyond the end of bitmap, return error or read from backing_file?
> */
> + if (((sector_num + nb_sectors + 7) / 8) > bitmap_size) {
> + return 0;
> + }
> +
> + 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)
> +{
> + int i, ret = 0;
> + bool changed = false;
> + BDRVAddCowState *state = (BDRVAddCowState *)(bs->opaque);
> + uint64_t start_pos = sector_num / 8;
> + uint64_t end_pos = (sector_num + nb_sectors - 1) / 8;
> +
> + if (start_pos > state->bitmap_size) {
> + return -1;
> + }
> +
> + for (i = 0; i < nb_sectors; i++) {
> + if (changed || !is_bit_set(bs, sector_num + i)) {
> + changed = true;
> + }
> + add_cow_set_bit(bs, sector_num + i);
> + }
> +
> + if (changed) {
> + ret = bdrv_pwrite(bs->file, sizeof(AddCowHeader) + start_pos,
> + state->bitmap + start_pos,
> + MIN(((end_pos - start_pos) & (~512)) + 512,
> + state->bitmap_size - start_pos));
> + }
> + return ret;
> +}
> +
> +static void add_cow_close(BlockDriverState *bs)
> +{
> + BDRVAddCowState *state = (BDRVAddCowState *)(bs->opaque);
> + g_free(state->bitmap);
> + state->bitmap = NULL;
> +}
> +
> +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;
> +
> + 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;
> + }
> + /* Make sure image file exists */
> + ret = bdrv_file_open(&image_bs, image_filename, BDRV_O_RDWR
> + | BDRV_O_CACHE_WB);
> + if (ret < 0) {
> + return ret;
> + }
> + bdrv_delete(image_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);
> + pstrcpy(header.backing_file, sizeof(header.backing_file),
> backing_filename);
> + pstrcpy(header.image_file, sizeof(header.image_file), image_filename);
> + header.size = cpu_to_be64(image_sectors * BDRV_SECTOR_SIZE);
> +
> + 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 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, 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) {
> + 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);
> + qemu_iovec_memset(&hd_qiov, 0,
> + BDRV_SECTOR_SIZE * cur_nr_sectors);
> + }
> + }
> + 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;
> + int64_t be_offset = cpu_to_be64(offset);
> + BDRVAddCowState *state = bs->opaque;
> + int64_t old_image_sector = state->image_hd->total_sectors;
> +
> + ret = bdrv_truncate(state->image_hd, offset);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + ret = bdrv_truncate(bs->file, ((image_sectors + 7) >> 3)
> + + sizeof(AddCowHeader));
> + if (ret < 0) {
> + bdrv_truncate(state->image_hd, old_image_sector *
> BDRV_SECTOR_SIZE);
> + return ret;
> + }
> +
> + ret = bdrv_pwrite_sync(bs->file, offsetof(AddCowHeader, size),
> + &be_offset, sizeof(uint64_t));
> + if (ret < 0) {
> + bdrv_truncate(state->image_hd, old_image_sector *
> BDRV_SECTOR_SIZE);
> + }
> +
> + return ret;
> +}
> +
> +static coroutine_fn int add_cow_co_flush(BlockDriverState *bs)
> +{
> + BDRVAddCowState *state = bs->opaque;
> + int ret = bdrv_co_flush(state->image_hd);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + 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"
> + },
> + { 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_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 1ec4921..d6e8337 100644
> --- a/block_int.h
> +++ b/block_int.h
> @@ -43,6 +43,7 @@
> #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 AIOPool {
> void (*cancel)(BlockDriverAIOCB *acb);
> diff --git a/docs/specs/add-cow.txt b/docs/specs/add-cow.txt
> new file mode 100644
> index 0000000..e403c84
> --- /dev/null
> +++ b/docs/specs/add-cow.txt
> @@ -0,0 +1,57 @@
> +== General ==
> +
> +Raw file format does not support backing_file and copy on write feature.
> Then
> +you can use add-cow file to implement these features.
> +
> +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
> +
> +While QEMU is running, virtual size of image_file and backing_file must
> be the
> +same. So if image_file does not have the same virtual size as
> backing_file's in
> +step 2), qemu-img will truncate it.
> +
> +=Specification=
> +
> +The file format looks like this:
> +
> + +----------+----------+----------+-----+
> + | Header | Data | 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.
> While
> + using backing_file, must together with image_file.
> +
> + 1036 - 2059: image_file
> + image_file is a raw file, While using image_file,
> must
> + together with image_file.
> +
> + 2060 - 2067: size
> + Virtual disk size of image_file in bytes.
> +
> +== Data ==
> +
> +The Data field stores a bitmap related to backing_file and image_file.
> The bitmap
> +will track whether the cluster in backing_file is dirty or not.
> +
> +Each bit in the bitmap indicates one cluster. So the size of bitmap is
> calculated
> +according to virtual size of backing_file.
> --
> 1.7.5.4
>
>
>
