Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 02 Apr 2003 17:23:07 -0600 | From | Dave McCracken <> | Subject | Re: [PATCH 2.5.66-mm2] Fix page_convert_anon locking issues |
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--On Wednesday, April 02, 2003 15:09:03 -0800 Andrew Morton <akpm@digeo.com> wrote:
> i_shared_sem won't stop that. The pte points into thin air, and may now > point at a value which looks like our page.
Once we find a match in the pte entry, we have the additional protection of the pte_chain lock. The pte entry is never cleared without a call to page_remove_rmap, which will block on the pte_chain lock.
>> Because the page is in transition from !PageAnon to PageAnon. > > These are file-backed pages. So what does PageAnon really mean?
I suppose PageAnon should be renamed to PageChain, to mean it's using pte_chains. It did mean anon pages until I used it for nonlinear pages.
>> We have to >> hold the pte_chain lock during the entire transition in case someone else >> tries to do something like page_remove_rmap, which would break. > > How about setting PageAnon at the _start_ of the operation? > page_remove_rmap() will cope with that OK.
Hmm... I was gonna say that page_remove_rmap will BUG() if it doesn't find the entry, but it's only under DEBUG and could easily be changed. Lemme think on this one a bit. I need to assure myself it's safe to go unlocked in the middle.
Dave
====================================================================== Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059 dmccr@us.ibm.com T/L 678-3059
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