From patchwork Thu Dec 29 09:36:59 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robert Wang X-Patchwork-Id: 133534 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [140.186.70.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id AD76CB6F74 for ; Thu, 29 Dec 2011 20:37:35 +1100 (EST) Received: from localhost ([::1]:38481 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RgCQU-0007wU-VE for incoming@patchwork.ozlabs.org; Thu, 29 Dec 2011 04:37:30 -0500 Received: from eggs.gnu.org ([140.186.70.92]:57967) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RgCQL-0007vz-Bt for qemu-devel@nongnu.org; Thu, 29 Dec 2011 04:37:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RgCQI-00012k-Ul for qemu-devel@nongnu.org; Thu, 29 Dec 2011 04:37:21 -0500 Received: from e28smtp07.in.ibm.com ([122.248.162.7]:37213) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RgCQH-00011b-Gc for qemu-devel@nongnu.org; Thu, 29 Dec 2011 04:37:18 -0500 Received: from /spool/local by e28smtp07.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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X-Received-From: 122.248.162.7 Cc: Kevin Wolf , Dong Xu Wang , Stefan Hajnoczi Subject: [Qemu-devel] [PATCH v6] block:add-cow file format X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Dong Xu Wang Introduce a new file format: add-cow. The usage can be found in add-cow.txt of this patch. CC: Kevin Wolf CC: Stefan Hajnoczi Signed-off-by: Dong Xu Wang --- 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 ":" */ -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.