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Re: [Qemu-devel] [PATCH v3] add add-cow file format
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From: |
shu ming |
|
Subject: |
Re: [Qemu-devel] [PATCH v3] add add-cow file format |
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Date: |
Sun, 23 Oct 2011 23:28:54 +0800 |
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User-agent: |
Mozilla/5.0 (Windows NT 5.1; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 |
On 2011-10-13 0:23, Dong Xu Wang wrote:
Add add-cow file format
Signed-off-by: Dong Xu Wang<address@hidden>
---
Makefile.objs | 1 +
block.c | 2 +-
block.h | 1 +
block/add-cow.c | 412 ++++++++++++++++++++++++++++++++++++++++++++++++
block_int.h | 1 +
docs/specs/add-cow.txt | 45 ++++++
6 files changed, 461 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 c849e51..624c04c 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 e865fab..c25241d 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 16bfa0a..8b09f12 100644
--- a/block.h
+++ b/block.h
@@ -256,6 +256,7 @@ 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..d2538a2
--- /dev/null
+++ b/block/add-cow.c
@@ -0,0 +1,412 @@
+#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
+
+typedef struct AddCowHeader {
+ uint64_t magic;
+ uint32_t version;
+ char backing_file[1024];
+ char image_file[1024];
1024 is a magic number for me. Can we have a meaningful macro?
+ uint64_t size;
+} QEMU_PACKED AddCowHeader;
+
+typedef struct BDRVAddCowState {
+ char image_file[1024];
+ BlockDriverState *image_hd;
+ uint8_t *bitmap;
+ uint64_t bitmap_size;
+} 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[1024];
+ 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 = -1;
+ 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("");
+ /* Relative to image or working dir, need discussion */
+ 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) {
+ goto fail;
+ }
+ } else {
+ ret = -ENOENT;
+ goto fail;
+ }
+ return 0;
+ fail:
+ if (state->bitmap) {
+ 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);
+ if (changed< 0) {
+ return 0;
+ }
+
+ 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;
+ 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++) {
+ add_cow_set_bit(bs, sector_num + i);
+ }
+ ret = bdrv_pwrite_sync(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);
+ if (state->bitmap) {
+ 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) {
+ 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_close(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_close(bs);
+ return ret;
+ }
+ bdrv_close(bs);
+
+ 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) {
+ return ret;
+ }
+
+ ret = bdrv_truncate(bs, image_sectors * BDRV_SECTOR_SIZE);
+fail:
"fail" label is not used in this function.
+ bdrv_close(bs);
+ return ret;
+}
+
+static 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);
+ 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_iovec_destroy(&hd_qiov);
+ return ret;
+}
+
+static 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);
+
It looks like that the memory where "bs" is pointing to should be
protected by a lock. Because "bs"
was passed to several BlockDriver entries like ".bdrv_co_writev',
'bdrv_co_readv'&etc which can be executed
in parallel to access the memory where "bs" is pointing to.
+ 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_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;
+ ret = bdrv_truncate(bs->file, ((image_sectors + 7)>> 3)
+ + sizeof(AddCowHeader));
+ if (ret< 0) {
+ return ret;
+ }
+
+ ret = bdrv_pwrite_sync(bs->file, offsetof(AddCowHeader, size),
+&be_offset, sizeof(uint64_t));
+ if (ret< 0) {
+ return ret;
+ }
+
+ ret = bdrv_truncate(state->image_hd, offset);
+ return ret;
+}
+
+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 int add_cow_flush(BlockDriverState *bs)
+{
+ BDRVAddCowState *state = bs->opaque;
+ int ret = bdrv_flush(state->image_hd);
+ if (ret< 0) {
+ return ret;
+ }
+ return bdrv_flush(bs->file);
+}
+
+static BlockDriverAIOCB *add_cow_aio_flush(BlockDriverState *bs,
+ BlockDriverCompletionFunc *cb, void *opaque)
+{
+ BDRVAddCowState *state = bs->opaque;
+ int ret = bdrv_flush(state->image_hd);
+ if (ret< 0) {
+ return NULL;
+ }
+
+ return bdrv_aio_flush(bs->file, cb, opaque);
+}
+
+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_flush = add_cow_flush,
+ .bdrv_aio_flush = add_cow_aio_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 8c3b863..2b26fdc 100644
--- a/block_int.h
+++ b/block_int.h
@@ -42,6 +42,7 @@
#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..0443c6c
--- /dev/null
+++ b/docs/specs/add-cow.txt
@@ -0,0 +1,45 @@
+== General ==
+
+Raw file format does not support backing_file and copy on write feature. Then
+you can use add-cow file realize 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
+
+=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.