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Date: Fri, 5 Jul 2013 11:09:10 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130705090910.GA11252@stefanha-thinkpad.redhat.com>
References: <1372862071-28225-1-git-send-email-pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 01/17] cow: make reads go at a decent speed
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, pl@kamp.de, qemu-devel@nongnu.org, stefanha@redhat.com

On Wed, Jul 03, 2013 at 04:34:15PM +0200, Paolo Bonzini wrote:
> @@ -146,23 +159,20 @@ static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
>  static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
>          int64_t sector_num, int nb_sectors, int *num_same)
>  {
> +    int64_t bitnum = sector_num + sizeof(struct cow_header_v2) * 8;
> +    uint64_t offset = (bitnum / 8) & -BDRV_SECTOR_SIZE;
> +    uint8_t bitmap[512];

Please use BDRV_SECTOR_SIZE, you used it one line above but then
switched to literal 512.