From patchwork Fri Oct 10 16:17:45 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?ISO-8859-1?B?MjFH?= X-Patchwork-Id: 398721 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 43B651400AF for ; Sat, 11 Oct 2014 03:21:44 +1100 (EST) Received: from localhost ([::1]:49599 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xccwo-0002f0-9t for incoming@patchwork.ozlabs.org; Fri, 10 Oct 2014 12:21:42 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38367) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XccuC-0006fh-Ar for qemu-devel@nongnu.org; Fri, 10 Oct 2014 12:19:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xccu6-0004Qu-O8 for qemu-devel@nongnu.org; Fri, 10 Oct 2014 12:19:00 -0400 Received: from mail-pd0-x236.google.com ([2607:f8b0:400e:c02::236]:59179) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xccu6-0004Qi-8u for qemu-devel@nongnu.org; Fri, 10 Oct 2014 12:18:54 -0400 Received: by mail-pd0-f182.google.com with SMTP id y10so1927076pdj.27 for ; Fri, 10 Oct 2014 09:18:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id; bh=65VgH9hazaWEuThMZMkTRXf/vMDaa/xBxOfh7yEGU8s=; b=amynF1I4/spAvBLRke2f+LkmRseHjkuS+5RnTu2EM2MlgBagmBY1VwnUiqO2qn/nGL iGV5G9m6L8+diJb4cq6Fh+dOqSlG8LMCcp77hSC8KxbOy8UgY0VcByCLmMG921YNJRJr 55K9mLzWfCszzS8I+W8J92ZvW6nEAJzCMni60+d5m8Qa43DL7OmudTCZWTnoCefoHWly V8BzU6LOPkq3mKlsDrgVNCuEXh6G6RCSuWAYySNdI8V1uCK2N5vaupOTsUCuespOqPsa PiPMvEH+PQxz95AfwJVuelwohkgijl+vQGr+PAH4HFMP23PJPYyDqWLnPTOAGT/Z+j28 JDKA== X-Received: by 10.68.98.131 with SMTP id ei3mr6262342pbb.47.1412957933007; Fri, 10 Oct 2014 09:18:53 -0700 (PDT) Received: from localhost.localdomain ([219.145.1.180]) by mx.google.com with ESMTPSA id tu10sm3998238pab.14.2014.10.10.09.18.33 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 Oct 2014 09:18:52 -0700 (PDT) From: Xiaodong Gong X-Google-Original-From: Xiaodong Gong To: kwolf@redhat.com, stefanha@redhat.com, arei.gonglei@huawei.com, hutao@cn.fujitsu.com, rudy.zhangmin@huawei.com, cody@redhat.com, cyliu@suse.com Date: Sat, 11 Oct 2014 00:17:45 +0800 Message-Id: <1412957865-4255-1-git-send-email-gongxiaodong1@huawei.com> X-Mailer: git-send-email 1.8.3.1 X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2607:f8b0:400e:c02::236 Cc: Xiaodong Gong , qemu-devel@nongnu.org Subject: [Qemu-devel] [PATCH RESEND] Support vhd type VHD_DIFFERENCING 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 Now qemu only supports vhd type VHD_FIXED and VHD_DYNAMIC, so qemu can't read snapshot volume of vhd, and can't support other storage features of vhd file. This patch add read parent information in function "vpc_open", read bitmap in "vpc_read", and change bitmap in "vpc_write". Signed-off-by: Xiaodong Gong --- Changes since v4: - Parse the batmap only when the version of VHD > 1.2. - Add support to parent location of W2RU. Changes since v3: - Remove the PARENT_MAX_LOC. Changes since v2: - Change MACX to PLATFAORM_MACX. - Return with EINVAL to parent location is W2RU and W2KU. - Change -1 == ret to a natrual order of ret == -1. - Get rid of the get_sector_offset_diff, get_sector_offset supports VHD_DIFF. - Return code of get_sector_offset is set to, -1 for error, -2 for not allocate, -3 for in parent. - Fix un init ret of vpc_write, when nb_sector == 0. - Change if (diff == ture) to if (diff) and so on. - Add PARENT_MAX_LOC to more understand. - Restore the boundary check to write on dynamic type in get_sector_offset. Changes since v1: - Add Boundary check to any input. - Clean the code no used after in vpc_open. - Change bdrv_co_readv() to bdrv_preadv in vpc_read. - Added some code to make it easy to understand. --- block/vpc.c | 428 ++++++++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 357 insertions(+), 71 deletions(-) diff --git a/block/vpc.c b/block/vpc.c index 4947369..1210542 100644 --- a/block/vpc.c +++ b/block/vpc.c @@ -29,17 +29,27 @@ #if defined(CONFIG_UUID) #include #endif +#include /**************************************************************/ #define HEADER_SIZE 512 +#define DYNAMIC_HEADER_SIZE 1024 +#define PARENT_LOCATOR_NUM 8 +#define MACX_PREFIX_LEN 7 /* file:// */ +#define TBBATMAP_HEAD_SIZE 28 + +#define PLATFORM_MACX 0x5863614d /* big endian */ +#define PLATFORM_W2RU 0x75723257 + +#define VHD_VERSION(major, minor) (((major) << 16) | ((minor) & 0x0000FFFF)) //#define CACHE enum vhd_type { VHD_FIXED = 2, VHD_DYNAMIC = 3, - VHD_DIFFERENCING = 4, + VHD_DIFF = 4, }; // Seconds since Jan 1, 2000 0:00:00 (UTC) @@ -138,6 +148,15 @@ typedef struct BDRVVPCState { Error *migration_blocker; } BDRVVPCState; +typedef struct vhd_tdbatmap_header { + char magic[8]; /* always "tdbatmap" */ + + uint64_t batmap_offset; + uint32_t batmap_size; + uint32_t batmap_version; + uint32_t checksum; +} QEMU_PACKED VHDTdBatmapHeader; + static uint32_t vpc_checksum(uint8_t* buf, size_t size) { uint32_t res = 0; @@ -153,10 +172,107 @@ static uint32_t vpc_checksum(uint8_t* buf, size_t size) static int vpc_probe(const uint8_t *buf, int buf_size, const char *filename) { if (buf_size >= 8 && !strncmp((char *)buf, "conectix", 8)) - return 100; + return 100; return 0; } +static int vpc_read_backing_loc(VHDDynDiskHeader *dyndisk_header, + BlockDriverState *bs, + Error **errp) +{ + BDRVVPCState *s = bs->opaque; + int64_t data_offset = 0; + int data_length = 0; + uint32_t platform; + bool done = false; + int parent_locator_offset = 0; + int i; + int ret = 0; + + for (i = 0; i < PARENT_LOCATOR_NUM; i++) { + data_offset = + be64_to_cpu(dyndisk_header->parent_locator[i].data_offset); + data_length = + be32_to_cpu(dyndisk_header->parent_locator[i].data_length); + platform = dyndisk_header->parent_locator[i].platform; + + /* Extend the location offset */ + if (parent_locator_offset < data_offset) { + parent_locator_offset = data_offset; + } + + if (done) { + continue; + } + + /* Skip "file://" in MacX platform */ + if (platform == PLATFORM_MACX) { + data_offset += MACX_PREFIX_LEN; + data_length -= MACX_PREFIX_LEN; + } + + /* Read location of backing file */ + if (platform == PLATFORM_MACX || platform == PLATFORM_W2RU) { + if (data_offset > s->max_table_entries * s->block_size) { + return -1; + } + if (data_length > BDRV_SECTOR_SIZE) { + return -1; + } + ret = bdrv_pread(bs->file, data_offset, bs->backing_file, + data_length); + if (ret < 0) { + return ret; + } + bs->backing_file[data_length] = '\0'; + } + + /* Convert location to ACSII string */ + if (platform == PLATFORM_MACX) { + done = true; + + } else if (platform == PLATFORM_W2RU) { + /* Must be UTF16-LE to ASCII */ + char *out, *optr; + int j; + + optr = out = (char *) malloc(data_length + 1); + if (out == NULL) { + ret = -1; + return ret; + } + memset(out, 0, data_length + 1); + + for (j = 0; j < data_length + 1; j++) { + out[j] = bs->backing_file[2*j]; + } + out[data_length + 1] = '\0'; + + while (*optr != '\0') { + if (*optr == '\\') { + *optr = '/'; + } + optr++; + } + + strncpy(bs->backing_file, out, data_length + 1); + + out = NULL; + free(out); + + done = true; + } + } + + if (bs->backing_file[0] == '\0') { + error_setg(errp, "block-vpc: differencing is not support in w2ku"); + ret = -EINVAL; + return ret; + } + + return parent_locator_offset; +} + static int vpc_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { @@ -164,11 +280,14 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags, int i; VHDFooter *footer; VHDDynDiskHeader *dyndisk_header; - uint8_t buf[HEADER_SIZE]; + uint8_t buf[DYNAMIC_HEADER_SIZE]; + uint8_t tdbatmap_header_buf[TBBATMAP_HEAD_SIZE]; uint32_t checksum; uint64_t computed_size; - int disk_type = VHD_DYNAMIC; + uint32_t disk_type; int ret; + VHDTdBatmapHeader *tdbatmap_header; + int parent_locator_offset = 0; ret = bdrv_pread(bs->file, 0, s->footer_buf, HEADER_SIZE); if (ret < 0) { @@ -176,6 +295,8 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags, } footer = (VHDFooter *) s->footer_buf; + disk_type = be32_to_cpu(footer->type); + if (strncmp(footer->creator, "conectix", 8)) { int64_t offset = bdrv_getlength(bs->file); if (offset < 0) { @@ -230,9 +351,9 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } - if (disk_type == VHD_DYNAMIC) { + if (disk_type == VHD_DYNAMIC || disk_type == VHD_DIFF) { ret = bdrv_pread(bs->file, be64_to_cpu(footer->data_offset), buf, - HEADER_SIZE); + DYNAMIC_HEADER_SIZE); if (ret < 0) { goto fail; } @@ -286,6 +407,37 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags, s->free_data_block_offset = (s->bat_offset + (s->max_table_entries * 4) + 511) & ~511; + /* Read tdbatmap header by offset */ + if (footer->version >= VHD_VERSION(1, 2)) { + ret = bdrv_pread(bs->file, s->free_data_block_offset, + tdbatmap_header_buf, TBBATMAP_HEAD_SIZE); + if (ret < 0) { + goto fail; + } + + tdbatmap_header = (VHDTdBatmapHeader *) tdbatmap_header_buf; + if (!strncmp(tdbatmap_header->magic, "tdbatmap", 8)) { + s->free_data_block_offset = + be32_to_cpu(tdbatmap_header->batmap_size) * 512 + + be64_to_cpu(tdbatmap_header->batmap_offset); + } + } + + /* Read backing file location from dyn header table */ + if (dyndisk_header->parent_name[0] || dyndisk_header->parent_name[1]) { + ret = parent_locator_offset = vpc_read_backing_loc(dyndisk_header, + bs, errp); + if (ret < 0) { + goto fail; + } + } + + if (s->free_data_block_offset < parent_locator_offset + + BDRV_SECTOR_SIZE) { + s->free_data_block_offset = parent_locator_offset + + BDRV_SECTOR_SIZE; + } + for (i = 0; i < s->max_table_entries; i++) { be32_to_cpus(&s->pagetable[i]); if (s->pagetable[i] != 0xFFFFFFFF) { @@ -340,35 +492,76 @@ static int vpc_reopen_prepare(BDRVReopenState *state, } /* - * Returns the absolute byte offset of the given sector in the image file. - * If the sector is not allocated, -1 is returned instead. + * Returns the absolute byte offset of the given sector in the differencing + * image file. + * + * If error happened, -1 is returned. + * + * When write all type or read dynamic, if the sector is not allocated, -2 + * is returned instead. If the sector is allocated in current file, the block + * offset is returned. * - * The parameter write must be 1 if the offset will be used for a write - * operation (the block bitmaps is updated then), 0 otherwise. + * When read diff. If the sector is not allocated, -2 is returned instead. + * If the sector is allocated in the backing file, -3 is returned. If the + * sector is allocated in current file, the block offset is returned. */ static inline int64_t get_sector_offset(BlockDriverState *bs, - int64_t sector_num, int write) + int64_t sector_num, bool write, bool diff) { BDRVVPCState *s = bs->opaque; - uint64_t offset = sector_num * 512; - uint64_t bitmap_offset, block_offset; + uint64_t offset = sector_num << BDRV_SECTOR_BITS; + uint64_t bitmap_offset; uint32_t pagetable_index, pageentry_index; + int64_t block_offset = LONG_MIN; + int ret; pagetable_index = offset / s->block_size; - pageentry_index = (offset % s->block_size) / 512; + pageentry_index = (offset % s->block_size) >> BDRV_SECTOR_BITS; - if (pagetable_index >= s->max_table_entries || s->pagetable[pagetable_index] == 0xffffffff) - return -1; // not allocated + if (pagetable_index >= s->max_table_entries) { + return -2; + } + if (s->pagetable[pagetable_index] == 0xffffffff) { + if (!write && diff) { + return -3; /* parent allocated */ + } else { + return -2; /* not allocated */ + } + } - bitmap_offset = 512 * (uint64_t) s->pagetable[pagetable_index]; - block_offset = bitmap_offset + s->bitmap_size + (512 * pageentry_index); + bitmap_offset = (uint64_t) s->pagetable[pagetable_index] + << BDRV_SECTOR_BITS; + + if (!diff || write) { + block_offset = bitmap_offset + s->bitmap_size + + (pageentry_index << BDRV_SECTOR_BITS); + } else { + uint32_t bitmap_index, bitmapentry_index; + uint8_t bitmap[s->bitmap_size]; + if (bitmap_offset > s->max_table_entries * s->block_size) { + return -1; + } + ret = bdrv_pread(bs->file, bitmap_offset, bitmap, s->bitmap_size); + if (ret < 0) { + return -1; + } + + bitmap_index = pageentry_index / 8; + bitmapentry_index = 7 - pageentry_index % 8; + if (bitmap[bitmap_index] & 0x1 << bitmapentry_index) { + block_offset = bitmap_offset + s->bitmap_size + + (pageentry_index << BDRV_SECTOR_BITS); + } else { + return -3; + } + } // We must ensure that we don't write to any sectors which are marked as // unused in the bitmap. We get away with setting all bits in the block // bitmap each time we write to a new block. This might cause Virtual PC to // miss sparse read optimization, but it's not a problem in terms of // correctness. - if (write && (s->last_bitmap_offset != bitmap_offset)) { + if (!diff && write && (s->last_bitmap_offset != bitmap_offset)) { uint8_t bitmap[s->bitmap_size]; s->last_bitmap_offset = bitmap_offset; @@ -376,7 +569,7 @@ static inline int64_t get_sector_offset(BlockDriverState *bs, bdrv_pwrite_sync(bs->file, bitmap_offset, bitmap, s->bitmap_size); } -// printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n", +// printf("sector: %" PRIx64 ", index: %x, offset: %x, bioff: %" PRIx64 ", bloff: %" PRIx64 "\n", // sector_num, pagetable_index, pageentry_index, // bitmap_offset, block_offset); @@ -437,7 +630,8 @@ static int rewrite_footer(BlockDriverState* bs) * * Returns the sectors' offset in the image file on success and < 0 on error */ -static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num) +static int64_t alloc_block(BlockDriverState *bs, int64_t sector_num, + bool diff) { BDRVVPCState *s = bs->opaque; int64_t bat_offset; @@ -457,7 +651,11 @@ static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num) s->pagetable[index] = s->free_data_block_offset / 512; // Initialize the block's bitmap - memset(bitmap, 0xff, s->bitmap_size); + if (diff) { + memset(bitmap, 0x0, s->bitmap_size); + } else { + memset(bitmap, 0xff, s->bitmap_size); + } ret = bdrv_pwrite_sync(bs->file, s->free_data_block_offset, bitmap, s->bitmap_size); if (ret < 0) { @@ -477,7 +675,7 @@ static int64_t alloc_block(BlockDriverState* bs, int64_t sector_num) if (ret < 0) goto fail; - return get_sector_offset(bs, sector_num, 0); + return get_sector_offset(bs, sector_num, false, diff); fail: s->free_data_block_offset -= (s->block_size + s->bitmap_size); @@ -501,36 +699,66 @@ static int vpc_read(BlockDriverState *bs, int64_t sector_num, uint8_t *buf, int nb_sectors) { BDRVVPCState *s = bs->opaque; - int ret; - int64_t offset; - int64_t sectors, sectors_per_block; VHDFooter *footer = (VHDFooter *) s->footer_buf; + int64_t sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; + int64_t offset, sectors; + int ret; - if (be32_to_cpu(footer->type) == VHD_FIXED) { + switch (be32_to_cpu(footer->type)) { + case VHD_FIXED: return bdrv_read(bs->file, sector_num, buf, nb_sectors); - } - while (nb_sectors > 0) { - offset = get_sector_offset(bs, sector_num, 0); - - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; - sectors = sectors_per_block - (sector_num % sectors_per_block); - if (sectors > nb_sectors) { - sectors = nb_sectors; - } + case VHD_DYNAMIC: + while (nb_sectors > 0) { + sectors = sectors_per_block - (sector_num % sectors_per_block); + if (sectors > nb_sectors) { + sectors = nb_sectors; + } - if (offset == -1) { - memset(buf, 0, sectors * BDRV_SECTOR_SIZE); - } else { - ret = bdrv_pread(bs->file, offset, buf, - sectors * BDRV_SECTOR_SIZE); - if (ret != sectors * BDRV_SECTOR_SIZE) { + offset = get_sector_offset(bs, sector_num, false, false); + if (offset == -1) { return -1; + } else if (offset == -2) { + memset(buf, 0, sectors * BDRV_SECTOR_SIZE); + } else { + ret = bdrv_pread(bs->file, offset, buf, + sectors * BDRV_SECTOR_SIZE); + if (ret != sectors * BDRV_SECTOR_SIZE) { + return -1; + } } + + nb_sectors -= sectors; + sector_num += sectors; + buf += sectors * BDRV_SECTOR_SIZE; } + break; + case VHD_DIFF: + while (nb_sectors > 0) { + offset = get_sector_offset(bs, sector_num, false, true); + if (offset == -1) { + return -1; + } else if (offset == -2) { + memset(buf, 0, BDRV_SECTOR_SIZE); + } else if (offset == -3) { + ret = bdrv_pread(bs->backing_hd, sector_num << BDRV_SECTOR_BITS + , buf, BDRV_SECTOR_SIZE); + if (ret < 0) { + return -1; + } + } else { + ret = bdrv_pread(bs->file, offset, buf, BDRV_SECTOR_SIZE); + if (ret != BDRV_SECTOR_SIZE) { + return -1; + } + } - nb_sectors -= sectors; - sector_num += sectors; - buf += sectors * BDRV_SECTOR_SIZE; + nb_sectors--; + sector_num++; + buf += BDRV_SECTOR_SIZE; + } + break; + default: + return -1; } return 0; } @@ -546,44 +774,101 @@ static coroutine_fn int vpc_co_read(BlockDriverState *bs, int64_t sector_num, return ret; } -static int vpc_write(BlockDriverState *bs, int64_t sector_num, - const uint8_t *buf, int nb_sectors) +static inline int64_t write_bitmap(BlockDriverState *bs, int64_t sector_num, + int64_t sectors) { BDRVVPCState *s = bs->opaque; - int64_t offset; - int64_t sectors, sectors_per_block; + uint64_t offset = sector_num << BDRV_SECTOR_BITS; + uint64_t bitmap_offset; + uint32_t pagetable_index, pageentry_index; + uint8_t bitmap[s->bitmap_size]; + uint32_t bitmap_index, bitmapbit_index; + int i; int ret; - VHDFooter *footer = (VHDFooter *) s->footer_buf; - if (be32_to_cpu(footer->type) == VHD_FIXED) { - return bdrv_write(bs->file, sector_num, buf, nb_sectors); + pagetable_index = offset / s->block_size; + pageentry_index = (offset % s->block_size) / 512; + bitmap_offset = 512 * (uint64_t) s->pagetable[pagetable_index]; + + if (bitmap_offset > s->max_table_entries * s->block_size) { + return -1; + } + ret = bdrv_pread(bs->file, bitmap_offset, bitmap, s->bitmap_size); + if (ret < 0) { + return -1; } - while (nb_sectors > 0) { - offset = get_sector_offset(bs, sector_num, 1); - sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; - sectors = sectors_per_block - (sector_num % sectors_per_block); - if (sectors > nb_sectors) { - sectors = nb_sectors; + for (i = 0; i < sectors; i++) { + bitmap_index = pageentry_index / 8; + bitmapbit_index = 7 - pageentry_index % 8; + bitmap[bitmap_index] |= (0x1 << bitmapbit_index); + pageentry_index++; + } + ret = bdrv_pwrite(bs->file, bitmap_offset, bitmap, s->bitmap_size); + if (ret < 0) { + return -1; + } + + return 0; +} + +static int vpc_write(BlockDriverState *bs, int64_t sector_num, + const uint8_t *buf, int nb_sectors) +{ + BDRVVPCState *s = bs->opaque; + VHDFooter *footer = (VHDFooter *) s->footer_buf; + int64_t sectors_per_block = s->block_size >> BDRV_SECTOR_BITS; + int64_t offset, sectors; + bool diff = true; + int ret = 0; + + switch (be32_to_cpu(footer->type)) { + case VHD_FIXED: + return bdrv_write(bs->file, sector_num, buf, nb_sectors); + case VHD_DYNAMIC: + case VHD_DIFF: + if (be32_to_cpu(footer->type) == VHD_DYNAMIC) { + diff = false; } - if (offset == -1) { - offset = alloc_block(bs, sector_num); - if (offset < 0) + while (nb_sectors > 0) { + sectors = sectors_per_block - (sector_num % sectors_per_block); + if (sectors > nb_sectors) { + sectors = nb_sectors; + } + + offset = get_sector_offset(bs, sector_num, true, diff); + if (offset == -1) { return -1; - } + } else if (offset == -2) { + offset = alloc_block(bs, sector_num, diff); + if (offset < 0) { + return -1; + } + } - ret = bdrv_pwrite(bs->file, offset, buf, sectors * BDRV_SECTOR_SIZE); - if (ret != sectors * BDRV_SECTOR_SIZE) { - return -1; - } + ret = bdrv_pwrite(bs->file, offset, buf, + sectors * BDRV_SECTOR_SIZE); + if (ret != sectors * BDRV_SECTOR_SIZE) { + return -1; + } - nb_sectors -= sectors; - sector_num += sectors; - buf += sectors * BDRV_SECTOR_SIZE; - } + if (diff) { + ret = write_bitmap(bs, sector_num, sectors); + if (ret < 0) { + return -1; + } + } - return 0; + nb_sectors -= sectors; + sector_num += sectors; + buf += sectors * BDRV_SECTOR_SIZE; + } + break; + default: + return -1; + } + return ret; } static coroutine_fn int vpc_co_write(BlockDriverState *bs, int64_t sector_num, @@ -911,6 +1196,7 @@ static BlockDriver bdrv_vpc = { .bdrv_close = vpc_close, .bdrv_reopen_prepare = vpc_reopen_prepare, .bdrv_create = vpc_create, + .supports_backing = true, .bdrv_read = vpc_co_read, .bdrv_write = vpc_co_write,