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SubjectRe: [PATCH v8 04/22] Change direct_access calling convention
On Thu, Jul 31, 2014 at 01:11:42PM +0300, Boaz Harrosh wrote:
> >>> + if (size < 0)
> >>
> >> if(size < PAGE_SIZE), No?
> >
> > No, absolutely not. PAGE_SIZE is unsigned long, which (if I understand
> > my C integer promotions correctly) means that 'size' gets promoted to
> > an unsigned long, and we compare them unsigned, so errors will never be
> > caught by this check.
>
> Good point I agree that you need a cast ie.
>
> if(size < (long)PAGE_SIZE)
>
> The reason I'm saying this is because of a bug I actually hit when
> playing with partitioning and fdisk, it came out that the last partition's
> size was not page aligned, and code that checked for (< 0) crashed because
> prd returned the last two sectors of the partition, since your API is sector
> based this can happen for you here, before you are memseting a PAGE_SIZE
> you need to test there is space, No?

Not in ext2/ext4. It requires block size == PAGE_SIZE, so it's never
going to request the last partial block in a partition.


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