From 53f79acb6ecb648afd63e0f13deba167f1a934df Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 14 Dec 2009 17:58:58 -0800 Subject: mm: mlocking in try_to_unmap_one There's contorted mlock/munlock handling in try_to_unmap_anon() and try_to_unmap_file(), which we'd prefer not to repeat for KSM swapping. Simplify it by moving it all down into try_to_unmap_one(). One thing is then lost, try_to_munlock()'s distinction between when no vma holds the page mlocked, and when a vma does mlock it, but we could not get mmap_sem to set the page flag. But its only caller takes no interest in that distinction (and is better testing SWAP_MLOCK anyway), so let's keep the code simple and return SWAP_AGAIN for both cases. 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. [kosaki.motohiro@jp.fujitsu.com: comment adding to mlocking in try_to_unmap_one] [akpm@linux-foundation.org: remove test of MLOCK_PAGES] Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Nick Piggin Cc: Rik van Riel Cc: Lee Schermerhorn Cc: Andi Kleen Cc: KAMEZAWA Hiroyuki Cc: Wu Fengguang Cc: Minchan Kim Signed-off-by: KOSAKI Motohiro Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mlock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index bd6f0e466f6..48691fb0851 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -117,7 +117,7 @@ static void munlock_vma_page(struct page *page) /* * did try_to_unlock() succeed or punt? */ - if (ret == SWAP_SUCCESS || ret == SWAP_AGAIN) + if (ret != SWAP_MLOCK) count_vm_event(UNEVICTABLE_PGMUNLOCKED); putback_lru_page(page); -- cgit v1.2.3-18-g5258 From 73848b4684e84a84cfd1555af78d41158f31e16b Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 14 Dec 2009 17:59:22 -0800 Subject: ksm: fix mlockfreed to munlocked When KSM merges an mlocked page, it has been forgetting to munlock it: that's been left to free_page_mlock(), which reports it in /proc/vmstat as unevictable_pgs_mlockfreed instead of unevictable_pgs_munlocked (and whinges "Page flag mlocked set for process" in mmotm, whereas mainline is silently forgiving). Call munlock_vma_page() to fix that. Signed-off-by: Hugh Dickins Cc: Izik Eidus Cc: Andrea Arcangeli Cc: Chris Wright Acked-by: Rik van Riel Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mlock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 48691fb0851..adcbe9032b5 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -99,14 +99,14 @@ void mlock_vma_page(struct page *page) * not get another chance to clear PageMlocked. If we successfully * isolate the page and try_to_munlock() detects other VM_LOCKED vmas * mapping the page, it will restore the PageMlocked state, unless the page - * is mapped in a non-linear vma. So, we go ahead and SetPageMlocked(), + * is mapped in a non-linear vma. So, we go ahead and ClearPageMlocked(), * perhaps redundantly. * If we lose the isolation race, and the page is mapped by other VM_LOCKED * vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap() * either of which will restore the PageMlocked state by calling * mlock_vma_page() above, if it can grab the vma's mmap sem. */ -static void munlock_vma_page(struct page *page) +void munlock_vma_page(struct page *page) { BUG_ON(!PageLocked(page)); -- cgit v1.2.3-18-g5258 From 6927c1dd93fc982140f3a3742ac4b224cd3e02b2 Mon Sep 17 00:00:00 2001 From: Lee Schermerhorn Date: Mon, 14 Dec 2009 17:59:55 -0800 Subject: mlock: replace stale comments in munlock_vma_page() Cleanup stale comments on munlock_vma_page(). Signed-off-by: Lee Schermerhorn Acked-by: Hugh Dickins Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mlock.c | 41 +++++++++++++++++++---------------------- 1 file changed, 19 insertions(+), 22 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index adcbe9032b5..2b8335a8940 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -88,23 +88,20 @@ void mlock_vma_page(struct page *page) } } -/* - * called from munlock()/munmap() path with page supposedly on the LRU. +/** + * munlock_vma_page - munlock a vma page + * @page - page to be unlocked * - * Note: unlike mlock_vma_page(), we can't just clear the PageMlocked - * [in try_to_munlock()] and then attempt to isolate the page. We must - * isolate the page to keep others from messing with its unevictable - * and mlocked state while trying to munlock. However, we pre-clear the - * mlocked state anyway as we might lose the isolation race and we might - * not get another chance to clear PageMlocked. If we successfully - * isolate the page and try_to_munlock() detects other VM_LOCKED vmas - * mapping the page, it will restore the PageMlocked state, unless the page - * is mapped in a non-linear vma. So, we go ahead and ClearPageMlocked(), - * perhaps redundantly. - * If we lose the isolation race, and the page is mapped by other VM_LOCKED - * vmas, we'll detect this in vmscan--via try_to_munlock() or try_to_unmap() - * either of which will restore the PageMlocked state by calling - * mlock_vma_page() above, if it can grab the vma's mmap sem. + * called from munlock()/munmap() path with page supposedly on the LRU. + * When we munlock a page, because the vma where we found the page is being + * munlock()ed or munmap()ed, we want to check whether other vmas hold the + * page locked so that we can leave it on the unevictable lru list and not + * bother vmscan with it. However, to walk the page's rmap list in + * try_to_munlock() we must isolate the page from the LRU. If some other + * task has removed the page from the LRU, we won't be able to do that. + * So we clear the PageMlocked as we might not get another chance. If we + * can't isolate the page, we leave it for putback_lru_page() and vmscan + * [page_referenced()/try_to_unmap()] to deal with. */ void munlock_vma_page(struct page *page) { @@ -123,12 +120,12 @@ void munlock_vma_page(struct page *page) putback_lru_page(page); } else { /* - * We lost the race. let try_to_unmap() deal - * with it. At least we get the page state and - * mlock stats right. However, page is still on - * the noreclaim list. We'll fix that up when - * the page is eventually freed or we scan the - * noreclaim list. + * Some other task has removed the page from the LRU. + * putback_lru_page() will take care of removing the + * page from the unevictable list, if necessary. + * vmscan [page_referenced()] will move the page back + * to the unevictable list if some other vma has it + * mlocked. */ if (PageUnevictable(page)) count_vm_event(UNEVICTABLE_PGSTRANDED); -- cgit v1.2.3-18-g5258