From 4a7754432bfa326d24153d0368ac6533a66bfe86 Mon Sep 17 00:00:00 2001 Message-Id: <4a7754432bfa326d24153d0368ac6533a66bfe86.1376408877.git.minovotn@redhat.com> In-Reply-To: <823d94e906b2aeecd2c60bc9f19ca8948a756f27.1376408877.git.minovotn@redhat.com> References: <823d94e906b2aeecd2c60bc9f19ca8948a756f27.1376408877.git.minovotn@redhat.com> From: Jeffrey Cody Date: Mon, 12 Aug 2013 16:20:21 +0200 Subject: [PATCH 17/18] block: add read-only support to VHDX image format. RH-Author: Jeffrey Cody Message-id: <0e760b745e2ce37a6ae7cc2d6e057e931120adc4.1376317429.git.jcody@redhat.com> Patchwork-id: 53174 O-Subject: [RHEL6.5 qemu-kvm PATCH 4/5] block: add read-only support to VHDX image format. Bugzilla: 963420 RH-Acked-by: Fam Zheng RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Kevin Wolf This adds in read-only support to the VHDX image format. This supports reads for fixed-size, and dynamic sized VHDX images. Differencing files are still unsupported. The image must be opened without BDRV_O_RDWR set, because we do not yet update the headers. I.e., pass 'readonly=on' in the drive image options from the QEMU commandline. Signed-off-by: Jeff Cody Signed-off-by: Stefan Hajnoczi (cherry picked from commit 059e2fbbca484a68ac7fd99d1d76409294551586) RHEL Notes: Changes from upstream include: * Use qemu_iovec_copy instead of qemu_iovec_concat * Argument changes to qemu_iovec_memset --- block/vhdx.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 121 insertions(+), 2 deletions(-) Signed-off-by: Michal Novotny --- block/vhdx.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 121 insertions(+), 2 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index 819121b..a05eff4 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -115,6 +115,17 @@ typedef struct VHDXMetadataEntries { } VHDXMetadataEntries; +typedef struct VHDXSectorInfo { + uint32_t bat_idx; /* BAT entry index */ + uint32_t sectors_avail; /* sectors available in payload block */ + uint32_t bytes_left; /* bytes left in the block after data to r/w */ + uint32_t bytes_avail; /* bytes available in payload block */ + uint64_t file_offset; /* absolute offset in bytes, in file */ + uint64_t block_offset; /* block offset, in bytes */ +} VHDXSectorInfo; + + + typedef struct BDRVVHDXState { CoMutex lock; @@ -793,7 +804,7 @@ static int vhdx_open(BlockDriverState *bs, int flags) goto fail; } - /* TODO: differencing files, read, write */ + /* TODO: differencing files, write */ return 0; fail: @@ -811,10 +822,118 @@ static int vhdx_reopen_prepare(BDRVReopenState *state, } +/* + * Perform sector to block offset translations, to get various + * sector and file offsets into the image. See VHDXSectorInfo + */ +static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num, + int nb_sectors, VHDXSectorInfo *sinfo) +{ + uint32_t block_offset; + + sinfo->bat_idx = sector_num >> s->sectors_per_block_bits; + /* effectively a modulo - this gives us the offset into the block + * (in sector sizes) for our sector number */ + block_offset = sector_num - (sinfo->bat_idx << s->sectors_per_block_bits); + /* the chunk ratio gives us the interleaving of the sector + * bitmaps, so we need to advance our page block index by the + * sector bitmaps entry number */ + sinfo->bat_idx += sinfo->bat_idx >> s->chunk_ratio_bits; + + /* the number of sectors we can read/write in this cycle */ + sinfo->sectors_avail = s->sectors_per_block - block_offset; + + sinfo->bytes_left = sinfo->sectors_avail << s->logical_sector_size_bits; + + if (sinfo->sectors_avail > nb_sectors) { + sinfo->sectors_avail = nb_sectors; + } + + sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits; + + sinfo->file_offset = s->bat[sinfo->bat_idx] >> VHDX_BAT_FILE_OFF_BITS; + + sinfo->block_offset = block_offset << s->logical_sector_size_bits; + + /* The file offset must be past the header section, so must be > 0 */ + if (sinfo->file_offset == 0) { + return; + } + + /* block offset is the offset in vhdx logical sectors, in + * the payload data block. Convert that to a byte offset + * in the block, and add in the payload data block offset + * in the file, in bytes, to get the final read address */ + + sinfo->file_offset <<= 20; /* now in bytes, rather than 1MB units */ + sinfo->file_offset += sinfo->block_offset; +} + + + static coroutine_fn int vhdx_co_readv(BlockDriverState *bs, int64_t sector_num, int nb_sectors, QEMUIOVector *qiov) { - return -ENOTSUP; + BDRVVHDXState *s = bs->opaque; + int ret = 0; + VHDXSectorInfo sinfo; + uint64_t bytes_done = 0; + QEMUIOVector hd_qiov; + + qemu_iovec_init(&hd_qiov, qiov->niov); + + qemu_co_mutex_lock(&s->lock); + + while (nb_sectors > 0) { + /* We are a differencing file, so we need to inspect the sector bitmap + * to see if we have the data or not */ + if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) { + /* not supported yet */ + ret = -ENOTSUP; + goto exit; + } else { + vhdx_block_translate(s, sector_num, nb_sectors, &sinfo); + + qemu_iovec_reset(&hd_qiov); + qemu_iovec_copy(&hd_qiov, qiov, bytes_done, sinfo.bytes_avail); + + /* check the payload block state */ + switch (s->bat[sinfo.bat_idx] & VHDX_BAT_STATE_BIT_MASK) { + case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */ + case PAYLOAD_BLOCK_UNDEFINED: /* fall through */ + case PAYLOAD_BLOCK_UNMAPPED: /* fall through */ + case PAYLOAD_BLOCK_ZERO: + /* return zero */ + qemu_iovec_memset(&hd_qiov, 0, sinfo.bytes_avail); + break; + case PAYLOAD_BLOCK_FULL_PRESENT: + qemu_co_mutex_unlock(&s->lock); + ret = bdrv_co_readv(bs->file, + sinfo.file_offset >> BDRV_SECTOR_BITS, + sinfo.sectors_avail, &hd_qiov); + qemu_co_mutex_lock(&s->lock); + if (ret < 0) { + goto exit; + } + break; + case PAYLOAD_BLOCK_PARTIALLY_PRESENT: + /* we don't yet support difference files, fall through + * to error */ + default: + ret = -EIO; + goto exit; + break; + } + nb_sectors -= sinfo.sectors_avail; + sector_num += sinfo.sectors_avail; + bytes_done += sinfo.bytes_avail; + } + } + ret = 0; +exit: + qemu_co_mutex_unlock(&s->lock); + qemu_iovec_destroy(&hd_qiov); + return ret; } -- 1.7.11.7