lkml.org 
[lkml]   [2012]   [Aug]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectIs iommu_num_pages() broken ?
From
Date
Hi folks !

I stumbled upon this today:

static inline unsigned long iommu_num_pages(unsigned long addr,
unsigned long len,
unsigned long io_page_size)
{
unsigned long size = (addr & (io_page_size - 1)) + len;

return DIV_ROUND_UP(size, io_page_size);
}


That doesn't look right to me...

The powerpc iommu code at least uses that with an addr which may not be
page aligned (ie, result of sg_virt() which include the offset).

The above code will align the start before adding the len which is wrong
and will result in potentially missing a page or am I missing
something ?

Shouldn't it be something like

static inline unsigned long iommu_num_pages(unsigned long addr,
unsigned long len,
unsigned long io_page_size)
{
unsigned long start = addr & (io_page_size - 1);
unsigned long end = addr + len;

return DIV_ROUND_UP(end - start, io_page_size);
}

?

Cheers,
Ben.




\
 
 \ /
  Last update: 2012-08-05 03:02    [W:0.043 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site