Re: [openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbsimplementation
From: Timur Tabi
Date: Thu May 05 2005 - 15:22:17 EST
Timur Tabi wrote:
When you say "older", what exactly do you mean? I have different test
that normally fails with just get_user_pages(), but it works with 2.6.9
and above. I haven't been able to get any kernel earlier than 2.6.9 to
compile or boot properly, so I'm having a hard time narrowing down the
actual point when get_user_pages() started working.
I haven't gotten a reply to this question, but I've done my own research, and I think I
found the answer. Using my own test of get_user_pages(), it appears that the fix was
placed in 2.6.7. However, I would like to know specifically what the fix is.
Unfortunately, tracking this stuff down is beyond my understanding of the Linux VM.
Assuming that the fix is in try_to_unmap_one(), the only significant change I see between
2.6.6 and 2.6.7 is the addition of this code:
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
goto out_unlock;
pmd = pmd_offset(pgd, address);
if (!pmd_present(*pmd))
goto out_unlock;
pte = pte_offset_map(pmd, address);
if (!pte_present(*pte))
goto out_unmap;
if (page_to_pfn(page) != pte_pfn(*pte))
goto out_unmap;
Can anyone tell me if this is the actual fix, or at least a major part of the actual fix?
--
Timur Tabi
Staff Software Engineer
timur.tabi@xxxxxxxxxxx
One thing a Southern boy will never say is,
"I don't think duct tape will fix it."
-- Ed Smylie, NASA engineer for Apollo 13
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