Ping...
2011/11/28 Dong Xu Wang <wdon...@linux.vnet.ibm.com>
> 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
>>
>>
>>
>
