Messages in this thread | | | From | KOSAKI Motohiro <> | Date | Wed, 2 May 2012 15:14:33 -0400 | Subject | Re: [PATCH] Describe race of direct read and fork for unaligned buffers |
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Hello,
>> I see what you mean. >> >> I'm not sure, though. For most apps it's bad practice I think. If you get into >> realm of sophisticated, performance critical IO/storage managers, it would >> not surprise me if such concurrent buffer modifications could be allowed. >> We allow exactly such a thing in our pagecache layer. Although probably >> those would be using shared mmaps for their buffer cache. >> >> I think it is safest to make a default policy of asking for IOs against private >> cow-able mappings to be quiesced before fork, so there are no surprises >> or reliance on COW details in the mm. Do you think? > Yes, I agree that (and MADV_DONTFORK) is probably the best thing to have > in documentation. Otherwise it's a bit too hairy...
I neglected this issue for years because Linus asked who need this and I couldn't find real world usecase.
Ah, no, not exactly correct. Fujitsu proprietary database had such usecase. But they quickly fixed it. Then I couldn't find alternative usecase.
I'm not sure why you say "hairy". Do you mean you have any use case of this?
Thank you.
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