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Re: [Qemu-devel] [RFC PATCH 28/56] block: Widen dirty bitmap granularity
From: |
John Snow |
Subject: |
Re: [Qemu-devel] [RFC PATCH 28/56] block: Widen dirty bitmap granularity to uint64_t for safety |
Date: |
Mon, 7 Aug 2017 21:55:21 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 08/07/2017 10:45 AM, Markus Armbruster wrote:
> Block dirty bitmaps represent granularity in bytes as uint32_t. It
> must be a power of two and a multiple of BDRV_SECTOR_SIZE.
>
> The trouble with uint32_t is computations like this one in
> mirror_do_read():
>
> uint64_t max_bytes;
>
> max_bytes = s->granularity * s->max_iov;
>
> The operands of * are uint32_t and int, so the product is computed in
> uint32_t (assuming 32 bit int), then zero-extended to uint64_t.
>
> Since granularity is generally combined with 64 bit file offsets, it's
> best to make it 64 bits, too. Less opportunity to screw up.
>
> Signed-off-by: Markus Armbruster <address@hidden>
[bweeooop]
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
[buuuuweeeep]
> @@ -506,16 +506,11 @@ uint32_t
> bdrv_get_default_bitmap_granularity(BlockDriverState *bs)
> return granularity;
> }
>
> -uint32_t bdrv_dirty_bitmap_granularity(const BdrvDirtyBitmap *bitmap)
> +uint64_t bdrv_dirty_bitmap_granularity(const BdrvDirtyBitmap *bitmap)
> {
> return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->bitmap);
> }
>
> -uint32_t bdrv_dirty_bitmap_meta_granularity(BdrvDirtyBitmap *bitmap)
> -{
> - return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->meta);
> -}
Why? Unused? Not cool enough to mention?
- [Qemu-devel] [RFC PATCH 23/56] option: Fix type of qemu_opt_set_number() parameter @val, (continued)
- [Qemu-devel] [RFC PATCH 23/56] option: Fix type of qemu_opt_set_number() parameter @val, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 29/56] block: Make BlockDirtyInfo byte count unsigned in QAPI/QMP, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 43/56] blockjob: Lift speed sign conversion out of mirror_start(), Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 50/56] block: Make BLOCK_IMAGE_CORRUPTED offset, size unsigned in QAPI/QMP, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 56/56] crypto: Make QCryptoBlockInfoLUKS offsets unsigned in QAPI/QMP, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 42/56] blockjob: Lift speed sign conversion out of stream_start(), Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 28/56] block: Widen dirty bitmap granularity to uint64_t for safety, Markus Armbruster, 2017/08/07
- Re: [Qemu-devel] [RFC PATCH 28/56] block: Widen dirty bitmap granularity to uint64_t for safety,
John Snow <=
- [Qemu-devel] [RFC PATCH 20/56] block: Make ImageInfo sizes unsigned in QAPI/QMP, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 38/56] blockjob: Lift speed sign conversion out of block_job_set_speed(), Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 27/56] block/dirty-bitmap: Clean up signed vs. unsigned dirty counts, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 49/56] block: Make ImageCheck file offset unsigned in QAPI, Markus Armbruster, 2017/08/07
- [Qemu-devel] [RFC PATCH 34/56] block: Make BlockDeviceStats sizes, offsets unsigned in QAPI/QMP, Markus Armbruster, 2017/08/07