Re: [RFC Patch] use MTRR for write combining if PAT is not available

["H. Peter Anvin" <hpa@zytor.com>]

On 10/22/2009 09:08 PM, Thomas Schlichter wrote:
>>
>> I have couple of issues with this patchset still. pci_mmap_page_range()
>> doesn't get called for each fork(). So, we won't be ref counting the
>> mtrr usage properly.
>
> When forking, what happens with the "struct file"? If it is being copied, then the
> processes share the same private data which would be freed during the first
> release(). I think this would be a problem whereever file-private data are used.
>
> So I think it must be shared between the forked processes and some reference
> counting must exist. This reference counting must ensure that release() is only
> called when all processes did close() their file.
>
> And in that case (shared "struct file", one single release() call in the end) this
> implementation should be completely safe...
>

struct file is shared between forked processes.

	-hpa