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[Qemu-devel] [PATCH v6] block:add-cow file format
From: |
Dong Xu Wang |
Subject: |
[Qemu-devel] [PATCH v6] block:add-cow file format |
Date: |
Thu, 29 Dec 2011 17:36:59 +0800 |
From: Dong Xu Wang <address@hidden>
Introduce a new file format: add-cow. The usage can be found in add-cow.txt of
this patch.
CC: Kevin Wolf <address@hidden>
CC: Stefan Hajnoczi <address@hidden>
Signed-off-by: Dong Xu Wang <address@hidden>
---
After applying this patch, qemu might can not compile, need apply this patch
first:
http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg02527.html
Makefile.objs | 1 +
block.c | 2 +-
block.h | 1 +
block/add-cow.c | 429 ++++++++++++++++++++++++++++++++++++++++++++++++
block_int.h | 1 +
docs/specs/add-cow.txt | 72 ++++++++
6 files changed, 505 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 f753d83..23fab70 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 aa9d142..0f52a67 100644
--- a/block.c
+++ b/block.c
@@ -187,7 +187,7 @@ 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 0e3ff9f..f5bf078 100644
--- a/block.h
+++ b/block.h
@@ -289,6 +289,7 @@ 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..95af5b7
--- /dev/null
+++ b/block/add-cow.c
@@ -0,0 +1,429 @@
+#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;
+ char reserved[492];
+} 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];
+ BlockDriver *image_drv = NULL;
+ int ret;
+ BDRVAddCowState *s = bs->opaque;
+ BlockDriverState *backing_bs = NULL;
+
+ 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;
+ }
+
+ size = be64_to_cpu(header.size);
+ bs->total_sectors = size / BDRV_SECTOR_SIZE;
+
+ QEMU_BUILD_BUG_ON(sizeof(bs->backing_file) != sizeof(header.backing_file));
+ QEMU_BUILD_BUG_ON(sizeof(s->image_file) != sizeof(header.image_file));
+ pstrcpy(bs->backing_file, sizeof(bs->backing_file),
+ header.backing_file);
+ pstrcpy(s->image_file, sizeof(s->image_file),
+ header.image_file);
+
+ s->bitmap_size = ((bs->total_sectors + 7) >> 3);
+ s->bitmap = qemu_blockalign(bs, s->bitmap_size);
+
+ ret = bdrv_pread(bs->file, sizeof(header), s->bitmap,
+ s->bitmap_size);
+ if (ret != s->bitmap_size) {
+ goto fail;
+ }
+
+ if (s->image_file[0] == '\0') {
+ ret = -ENOENT;
+ goto fail;
+ }
+
+ ret = bdrv_file_open(&backing_bs, bs->backing_file, 0);
+ if (ret < 0) {
+ return ret;
+ }
+ bdrv_delete(backing_bs);
+
+ s->image_hd = bdrv_new("");
+
+ if (path_has_protocol(s->image_file)) {
+ pstrcpy(image_filename, sizeof(image_filename),
+ s->image_file);
+ } else {
+ path_combine(image_filename, sizeof(image_filename),
+ bs->filename, s->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);
+ s->image_hd = NULL;
+ goto fail;
+ }
+
+ qemu_co_mutex_init(&s->lock);
+ return 0;
+ fail:
+ g_free(s->bitmap);
+ return ret;
+}
+
+static inline void add_cow_set_bit(BlockDriverState *bs, int64_t bitnum)
+{
+ uint64_t offset = bitnum >> 3;
+ BDRVAddCowState *s = bs->opaque;
+ s->bitmap[offset] |= (1 << (bitnum % 8));
+}
+
+static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
+{
+ BDRVAddCowState *s = bs->opaque;
+ uint64_t offset = bitnum >> 3;
+ return !!(s->bitmap[offset] & (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;
+ BDRVAddCowState *s = bs->opaque;
+
+ /* Beyond the end of bitmap, return error or read from backing_file? */
+ if (((sector_num + nb_sectors + 7) >> 3) > s->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 *s = bs->opaque;
+ uint64_t start_pos = (sector_num >> 3) & (~511);
+ uint64_t end_pos = (((sector_num + nb_sectors - 1) >> 3) + 511) & (~511);
+ uint64_t sectors_to_write = MIN(end_pos - start_pos,
+ s->bitmap_size - start_pos);
+
+ if (start_pos > s->bitmap_size) {
+ return 0;
+ }
+
+ for (i = 0; i < nb_sectors; i++) {
+ if (!changed) {
+ changed = true;
+ }
+ add_cow_set_bit(bs, sector_num + i);
+ }
+
+ if (changed) {
+ ret = bdrv_pwrite(bs->file, sizeof(AddCowHeader) + start_pos,
+ s->bitmap + start_pos, sectors_to_write);
+ }
+ return ret;
+}
+
+static void add_cow_close(BlockDriverState *bs)
+{
+ BDRVAddCowState *s = bs->opaque;
+ g_free(s->bitmap);
+}
+
+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;
+ }
+ 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);
+ 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);
+ }
+ }
+ 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 *s = bs->opaque;
+ int64_t old_image_sector = s->image_hd->total_sectors;
+
+ ret = bdrv_truncate(s->image_hd, offset);
+ if (ret < 0) {
+ return ret;
+ }
+
+ ret = bdrv_truncate(bs->file, ((image_sectors + 7) >> 3)
+ + sizeof(AddCowHeader));
+ if (ret < 0) {
+ bdrv_truncate(s->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(s->image_hd, old_image_sector * BDRV_SECTOR_SIZE);
+ }
+
+ 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;
+ }
+
+ 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_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 311bd2a..2384e76 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..33f358e
--- /dev/null
+++ b/docs/specs/add-cow.txt
@@ -0,0 +1,72 @@
+== 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 |
+ +---------------+--------------------------+
+
+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. All
+ unused bytes are padded with zeros.
+
+ 1036 - 2059: image_file
+ image_file is a raw file, While using image_file, must
+ together with image_file. All unused bytes are padded
+ with zeros.
+
+ 2060 - 2067: size
+ Virtual disk size of image_file in bytes.
+
+ 2068 - 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.
--
1.7.5.4
- [Qemu-devel] [PATCH v6] block:add-cow file format,
Dong Xu Wang <=