Re: [PATCH v2 2/2] mm: fix boundary judgment issues in kernel/resource.c

[Yaohui Wang]

Hi, Thomas

Thanks for your detailed reply, and your patience for a kernel newbie.

I'll carefully address the formal issues in the next version of patch.


Thanks,

        Yaohui

On 2021/6/20 06:16, Thomas Gleixner wrote:
> Yaohui!
>
> On Fri, Jun 11 2021 at 12:21, Yaohui Wang wrote:
>
> The same formal issues as with patch #1
>
> > The original boundary judgment may ignore @end if @end equals @start. For
>
> May means it can but it must not. But this is not the case here. end
> equals start is always ignored.
>
> Also 'original' is meaningless here. Before the patch is applied the
> code is that way.
>
>   find_next_iomem_res() and __walk_iomem_res_desc() require that the
>   provided end address is larger than the start address, which ...
>
>
> > example, if we call ioremap(phys, 1), then @end == @start, and the memory
> > check will not be applied on the page where @end lives, which is
> > unexpected.
>
> Please avoid 'we' and 'I':
>
>   is incorrect when ioremap() is invoked with length=1.
>
> > In kernel/resource.c:find_next_iomem_res, the mem region is a closed
>
> See the reply to #1 vs. function names. Also please write out 'memory',
> there is no shortage of space in change logs.
>
> > interval (i.e. [@start..@end]). So @start == @end should be allowed.
>
> closed interval reads strange. The usual terminology is: The end address
> is inclusive.
>
>    Resources are described with the start address and the inclusive end
>    address, which means for a resource with 1 byte length the start
>    address is the same as the end address.
>
>    find_next_iomem_res() and __walk_iomem_res_desc() ignore resources
>    with 1 byte length, which prevents that ioremap(phys, 1) is checked
>    whether it touches non ioremappable resources.
>
>    ...
>
> Thanks,
>
>          tglx