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Date: Tue, 21 Jun 2016 16:05:10 +0200
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20160621140510.GH4520@noname.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 15/17] block: Switch discard length
 bounds to byte-based
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To: Eric Blake <eblake@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Fam Zheng <famz@redhat.com>, Max Reitz <mreitz@redhat.com>, Ronnie Sahlberg <ronniesahlberg@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, Peter Lieven <pl@kamp.de>

Am 14.06.2016 um 23:30 hat Eric Blake geschrieben:
> Sector-based limits are awkward to think about; in our on-going
> quest to move to byte-based interfaces, convert max_discard and
> discard_alignment.  Rename them, using 'pdiscard' as an aid to
> track which remaining discard interfaces need conversion, and so
> that the compiler will help us catch the change in semantics
> across any rebased code.  In iscsi.c, sector_limits_lun2qemu()
> is no longer needed; and the BlockLimits type is now completely
> byte-based.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>

>      /* maximum number of bytes that can zeroized at once (since it is
> -     * signed, it must be < 2G, if set) */
> +     * signed, it must be < 2G, if set), should be multiple of
> +     * pwrite_zeroes_alignment. May be 0 if no inherent 32-bit limit */
>      int32_t max_pwrite_zeroes;
> 
>      /* optimal alignment for write zeroes requests in bytes, must be
> -     * power of 2, and less than max_pwrite_zeroes if that is set */
> +     * power of 2, less than max_pwrite_zeroes if that is set, and
> +     * multiple of bs->request_alignment. May be 0 if
> +     * bs->request_alignment is good enough */
>      uint32_t pwrite_zeroes_alignment;

I think you intended to have these as part of some earlier patch, they
are not related to discard.

Kevin