Messages in this thread | | | Date | Thu, 5 Jan 2023 09:47:10 +0100 | Subject | Re: [PATCH 3/3] mm/uffd: Detect pgtable allocation failures | From | David Hildenbrand <> |
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On 04.01.23 23:52, Peter Xu wrote: > Before this patch, when there's any pgtable allocation issues happened > during change_protection(), the error will be ignored from the syscall. > For shmem, there will be an error dumped into the host dmesg. Two issues > with that: > > (1) Doing a trace dump when allocation fails is not anything close to > grace..
s/..//
> > (2) The user should be notified with any kind of such error, so the user > can trap it and decide what to do next, either by retrying, or stop > the process properly, or anything else. > > For userfault users, this will change the API of UFFDIO_WRITEPROTECT when > pgtable allocation failure happened. It should not normally break anyone, > though. If it breaks, then in good ways. > > One man-page update will be on the way to introduce the new -ENOMEM for > UFFDIO_WRITEPROTECT. Not marking stable so we keep the old behavior on the > 5.19-till-now kernels.
We'd now fail after already having modified some state (protected some PTEs). I assume that can already happen when protecting across multiple VMAs and is expected, right?
-- Thanks,
David / dhildenb
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