Messages in this thread |  | | Date | Wed, 19 Sep 2001 23:15:47 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: pre12 VM doubts and patch |
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On Thu, 20 Sep 2001, Andrea Arcangeli wrote: > > hmm, the stuff inside #if 0 doesn't seem to be correct either there, > write_access doesn't mean we have the right to write to it, it just mean > we're trying to.
No, write_access means not only that we are trying to write to it, but it (by implication) means that we have the right too - otherwise we would have SIGSEGV'd.
Anyway, I'm not at all sure that the write_access test is worth it, we could just never do it (like your patch), or we could test if we allow COW and do early COW (which the write-access kind of means).
However, your patch isn't right for another reason: if we do delete it from the swap cache, we'd better mark it dirty so that it gets re-allocated a swap entry if it later on needs it.
That's why the old code went to such extremes: it marked it dirty and writable if it was a write access (and exclusive), and it marked it _just_ dirty and removed it from the swap cache if it went over the swap limit.
Whether that complexity is worth it, I don't know.
Linus
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