Re: [Qemu-devel] [Qemu-block] [PATCH] block: Swap request limit definitions

[Kevin Wolf <kwolf@redhat.com>]

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Am 15.02.2017 um 14:42 hat Max Reitz geschrieben:
> On 14.02.2017 10:52, Alberto Garcia wrote:
> > On Mon 13 Feb 2017 06:13:38 PM CET, Max Reitz wrote:
> > 
> >>>> -#define BDRV_REQUEST_MAX_SECTORS MIN(SIZE_MAX >> BDRV_SECTOR_BITS, \
> >>>> -                                     INT_MAX >> BDRV_SECTOR_BITS)
> >>>> -#define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS)
> >>>> +#define BDRV_REQUEST_MAX_BYTES      MIN(SIZE_MAX, INT_MAX)
> >>>> +#define BDRV_REQUEST_MAX_SECTORS    (BDRV_REQUEST_MAX_BYTES >> BDRV_SECTOR_BITS)
> >>>
> >>> I'm just pointing it out because I don't know if this can cause
> >>> problems, but this patch would make BDRV_REQUEST_MAX_BYTES not a
> >>> multiple of the sector size (INT_MAX is actually a prime number).
> >>
> >> Very good point. I don't think this could be an issue, though. For one
> >> thing, the use of BDRV_REQUEST_MAX_BYTES is very limited.
> > 
> > Ok, but then I wonder what's the benefit of increasing
> > BDRV_REQUEST_MAX_BYTES.
> 
> The benefit is that the definition looks cleaner.

Whatever way we want to write it, I think MAX_BYTES = MAX_SECTORS * 512
should be a given. Everything else is bound to confuse people and
introduce bugs sooner or later.

Kevin

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