Re: [Xen-devel] [PATCH mini-os enhancements for vtpm 2/8] add posix io to blkfront

[Matthew Fioravante <matthew.fioravante@xxxxxxxxxx>]

The math done by blkfront doesn't always work if your use
BLKIF_MAX_SEGMENTS_PER_REQUEST (11).

Where you do:
ASSERT(n <= BLKIF_MAX_SEGMENTS_PER_REQUEST);

Sometimes n comes out to be BLKIF_MAX_SEGEMENTS_PER_REQUEST +1. This
happens when your buffer address is sector aligned (512k), but not page
aligned (4096k). So we can either optimize yet again if address is page
aligned or use BLKIF_MAX_SEGMENTS_PER_REQUEST-1;

Is the page math being done above that assertion correct?


On 10/08/2012 04:05 AM, Samuel Thibault wrote:
> Matthew Fioravante, le Fri 05 Oct 2012 14:02:06 -0400, a écrit :
>> See latest v2 patch
> It looks good, except why BLKIF_MAX_SEGMENTS_PER_REQUEST-1 and not
> BLKIF_MAX_SEGMENTS_PER_REQUEST?
>
> Samuel

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