Re: [Qemu-devel] [PATCH 04/17] qcow2: Dirty Bitmaps Ext: structs and consts

[John Snow <jsnow@redhat.com>]

On 09/05/2015 12:43 PM, Vladimir Sementsov-Ogievskiy wrote:
> Add data structures and constraints accordingly to docs/specs/qcow2.txt
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/Makefile.objs        |  2 +-
>  block/qcow2-dirty-bitmap.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>  block/qcow2.h              | 28 ++++++++++++++++++++++++++++
>  3 files changed, 71 insertions(+), 1 deletion(-)
>  create mode 100644 block/qcow2-dirty-bitmap.c
> 
> diff --git a/block/Makefile.objs b/block/Makefile.objs
> index 58ef2ef..c6e1f4b 100644
> --- a/block/Makefile.objs
> +++ b/block/Makefile.objs
> @@ -1,5 +1,5 @@
>  block-obj-y += raw_bsd.o qcow.o vdi.o vmdk.o cloop.o bochs.o vpc.o vvfat.o
> -block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
> +block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o qcow2-dirty-bitmap.o
>  block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
>  block-obj-y += qed-check.o
>  block-obj-$(CONFIG_VHDX) += vhdx.o vhdx-endian.o vhdx-log.o
> diff --git a/block/qcow2-dirty-bitmap.c b/block/qcow2-dirty-bitmap.c
> new file mode 100644
> index 0000000..fd4e0ef
> --- /dev/null
> +++ b/block/qcow2-dirty-bitmap.c
> @@ -0,0 +1,42 @@
> +/*
> + * Dirty bitmaps for the QCOW version 2 format
> + *
> + * Copyright (c) 2014-2015 Vladimir Sementsov-Ogievskiy
> + *
> + * This file is derived from qcow2-snapshot.c, original copyright:
> + * Copyright (c) 2004-2006 Fabrice Bellard
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +/* NOTICE: DBM here means Dirty Bitmap and used as a namespace for _internal_
> + * constants. Please do not use this _internal_ abbreviation for other needs
> + * and/or outside of this file. */
> +
> +/* Dirty Bitmap Directory Enrty constraints */
> +#define DBM_MAX_TABLE_SIZE 0x8000000
> +#define DBM_MAX_PHYS_SIZE 0x20000000 /* 512 mb */
> +#define DBM_MAX_GRANULARITY_BITS 63
> +#define DBM_MAX_NAME_SIZE 1023
> +
> +/* Dirty Bitmap Directory Enrty flags */
> +#define DBM_RESERVED_FLAGS 0xffffffff
> +
> +/* bits [0, 8] U [56, 63] are reserved */
> +#define DBM_TABLE_ENTRY_RESERVED_MASK 0xff000000000001ff
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 72e1328..a2a5d4a 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -52,6 +52,10 @@
>   * space for snapshot names and IDs */
>  #define QCOW_MAX_SNAPSHOTS_SIZE (1024 * QCOW_MAX_SNAPSHOTS)
>  
> +/* Dirty Bitmap Header Extension constraints */
> +#define QCOW_MAX_DIRTY_BITMAPS 65536
> +#define QCOW_MAX_DIRTY_BITMAP_DIRECTORY_SIZE (1024 * QCOW_MAX_DIRTY_BITMAPS)
> +
>  /* indicate that the refcount of the referenced cluster is exactly one. */
>  #define QCOW_OFLAG_COPIED     (1ULL << 63)
>  /* indicate that the cluster is compressed (they never have the copied flag) */
> @@ -141,6 +145,19 @@ typedef struct QEMU_PACKED QCowSnapshotHeader {
>      /* name follows  */
>  } QCowSnapshotHeader;
>  
> +typedef struct QEMU_PACKED QCowDirtyBitmapHeader {
> +    /* header is 8 byte aligned */
> +    uint64_t dirty_bitmap_table_offset;
> +    uint64_t nb_virtual_bits;
> +
> +    uint32_t dirty_bitmap_table_size;
> +    uint32_t granularity_bits;
> +
> +    uint32_t flags;

looks like DBM_RESERVED_FLAGS was meant to apply to this field, but I
think the mask is incorrect and should be 0xfffffff0.

> +    uint16_t name_size;
> +    /* name follows  */
> +} QCowDirtyBitmapHeader;
> +
>  typedef struct QEMU_PACKED QCowSnapshotExtraData {
>      uint64_t vm_state_size_large;
>      uint64_t disk_size;
> @@ -159,6 +176,11 @@ typedef struct QCowSnapshot {
>      uint64_t vm_clock_nsec;
>  } QCowSnapshot;
>  
> +typedef struct QCowDirtyBitmap {
> +    uint64_t offset;
> +    char *name;
> +} QCowDirtyBitmap;
> +
>  struct Qcow2Cache;
>  typedef struct Qcow2Cache Qcow2Cache;
>  
> @@ -221,6 +243,12 @@ typedef uint64_t Qcow2GetRefcountFunc(const void *refcount_array,
>  typedef void Qcow2SetRefcountFunc(void *refcount_array,
>                                    uint64_t index, uint64_t value);
>  
> +typedef struct Qcow2DirtyBitmapHeaderExt {
> +    uint32_t nb_dirty_bitmaps;
> +    uint32_t dirty_bitmap_directory_size;
> +    uint64_t dirty_bitmap_directory_offset;
> +} QEMU_PACKED Qcow2DirtyBitmapHeaderExt;
> +
>  typedef struct BDRVQcowState {
>      int cluster_bits;
>      int cluster_size;
>