Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 2/6] mm: mlocking in try_to_unmap_one | Date | Fri, 13 Nov 2009 17:26:14 +0900 (JST) |
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> > On Wed, 11 Nov 2009, KOSAKI Motohiro wrote: > > > > Though it doesn't quite answer your question, > > I'll just reinsert the last paragraph of my description here... > > > > > > try_to_unmap_file()'s TTU_MUNLOCK nonlinear handling was particularly > > > > amusing: once unravelled, it turns out to have been choosing between > > > > two different ways of doing the same nothing. Ah, no, one way was > > > > actually returning SWAP_FAIL when it meant to return SWAP_SUCCESS. > > > > ... > > > > @@ -1081,45 +1053,23 @@ static int try_to_unmap_file(struct page > > ... > > > > > > > > - if (list_empty(&mapping->i_mmap_nonlinear)) > > > > + /* We don't bother to try to find the munlocked page in nonlinears */ > > > > + if (MLOCK_PAGES && TTU_ACTION(flags) == TTU_MUNLOCK) > > > > goto out; > > > > > > I have dumb question. > > > Does this shortcut exiting code makes any behavior change? > > > > Not dumb. My intention was to make no behaviour change with any of > > this patch; but in checking back before completing the description, > > I suddenly realized that that shortcut intentionally avoids the > > > > if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */ > > ret = SWAP_FAIL; > > goto out; > > } > > > > (which doesn't show up in the patch: you'll have to look at rmap.c), > > which used to have the effect of try_to_munlock() returning SWAP_FAIL > > in the case when there were one or more VM_NONLINEAR vmas of the file, > > but none of them (and none of the covering linear vmas) VM_LOCKED. > > > > That should have been a SWAP_SUCCESS case, or with my changes > > another SWAP_AGAIN, either of which would make munlock_vma_page() > > count_vm_event(UNEVICTABLE_PGMUNLOCKED); > > which would be correct; but the SWAP_FAIL meant that count was not > > incremented in this case. > > Ah, correct. > Then, we lost the capability unevictability of non linear mapping pages, right. > if so, following additional patch makes more consistent?
[indistinct muttering]
Probably we can remove VM_NONLINEAR perfectly. I've never seen real user of it.
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