From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: Re: [RFC][PATCH v3 1/6] mm: Don't unmap gup()ed page Date: Wed, 15 Apr 2009 12:46:15 +0200 Message-ID: <20090415104615.GG9809@random.random> References: <20090414143252.GE28265@random.random> <200904150042.15653.nickpiggin@yahoo.com.au> <20090415165431.AC4C.A69D9226@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nick Piggin , LKML , Linus Torvalds , Andrew Morton , Jeff Moyer , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins To: KOSAKI Motohiro Return-path: Content-Disposition: inline In-Reply-To: <20090415165431.AC4C.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Apr 15, 2009 at 05:05:54PM +0900, KOSAKI Motohiro wrote: > - /* > - * If the page is mlock()d, we cannot swap it out. > - * If it's recently referenced (perhaps page_referenced > - * skipped over this mm) then we should reactivate it. > - */ > if (!migration) { > + if (PageSwapCache(page) && > + page_count(page) != page_mapcount(page) + 2) { > + ret = SWAP_FAIL; > + goto out_unmap; > + } > + > + /* > + * If the page is mlock()d, we cannot swap it out. > + * If it's recently referenced (perhaps page_referenced > + * skipped over this mm) then we should reactivate it. > + */ > if (vma->vm_flags & VM_LOCKED) { > ret = SWAP_MLOCK; > goto out_unmap; > @@ -790,7 +796,19 @@ static int try_to_unmap_one(struct page > > /* Nuke the page table entry. */ > flush_cache_page(vma, address, page_to_pfn(page)); > - pteval = ptep_clear_flush_notify(vma, address, pte); > + pteval = ptep_clear_flush(vma, address, pte); > + > + if (!migration) { > + /* re-check */ > + if (PageSwapCache(page) && > + page_count(page) != page_mapcount(page) + 2) { > + /* We lose race against get_user_pages_fast() */ > + set_pte_at(mm, address, pte, pteval); > + ret = SWAP_FAIL; > + goto out_unmap; > + } > + } > + mmu_notifier_invalidate_page(vma->vm_mm, address); With regard to mmu notifier, this is the opposite of the right ordering. One mmu_notifier_invalidate_page must run _before_ the first check. The ptep_clear_flush_notify will then stay and there's no need of a further mmu_notifier_invalidate_page after the second check. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org