Messages in this thread | | | Subject | Re: [RFC v3 PATCH 5/5] x86: check VM_DEAD flag in page fault | From | Yang Shi <> | Date | Mon, 2 Jul 2018 10:24:27 -0700 |
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On 7/2/18 6:37 AM, Michal Hocko wrote: > On Mon 02-07-18 15:33:11, Laurent Dufour wrote: >> >> On 02/07/2018 14:45, Michal Hocko wrote: >>> On Mon 02-07-18 14:26:09, Laurent Dufour wrote: >>>> On 02/07/2018 14:15, Michal Hocko wrote: > [...] >>>>> We already do have a model for that. Have a look at MMF_UNSTABLE. >>>> MMF_UNSTABLE is a mm's flag, here this is a VMA's flag which is checked. >>> Yeah, and we have the VMA ready for all places where we do check the >>> flag. check_stable_address_space can be made to get vma rather than mm. >> Yeah, this would have been more efficient to check that flag at the beginning >> of the page fault handler rather than the end, but this way it will be easier >> to handle the speculative page fault too ;) > The thing is that it doesn't really need to be called earlier. You are > not risking data corruption on file backed mappings.
OK, I just think it could save a few cycles to check the flag earlier.
If nobody think it is necessary, we definitely could re-use check_stable_address_space(), just return VM_FAULT_SIGSEGV for VM_DEAD vma, and check for both shared and non-shared.
Thanks, Yang
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