From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933740AbbFWNww (ORCPT ); Tue, 23 Jun 2015 09:52:52 -0400 Received: from mga03.intel.com ([134.134.136.65]:34979 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933171AbbFWNrb (ORCPT ); Tue, 23 Jun 2015 09:47:31 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.13,665,1427785200"; d="scan'208";a="751734625" From: "Kirill A. Shutemov" To: Andrew Morton , Andrea Arcangeli , Hugh Dickins Cc: Dave Hansen , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , Sasha Levin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" Subject: [PATCHv7 14/36] futex, thp: remove special case for THP in get_futex_key Date: Tue, 23 Jun 2015 16:46:24 +0300 Message-Id: <1435067206-92901-15-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1435067206-92901-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1435067206-92901-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With new THP refcounting, we don't need tricks to stabilize huge page. If we've got reference to tail page, it can't split under us. This patch effectively reverts a5b338f2b0b1. Signed-off-by: Kirill A. Shutemov Tested-by: Sasha Levin --- kernel/futex.c | 61 ++++++++++++---------------------------------------------- 1 file changed, 12 insertions(+), 49 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 2a5e3830e953..1809371ebef8 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -399,7 +399,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; - struct page *page, *page_head; + struct page *page; int err, ro = 0; /* @@ -442,46 +442,9 @@ again: else err = 0; -#ifdef CONFIG_TRANSPARENT_HUGEPAGE - page_head = page; - if (unlikely(PageTail(page))) { - put_page(page); - /* serialize against __split_huge_page_splitting() */ - local_irq_disable(); - if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { - page_head = compound_head(page); - /* - * page_head is valid pointer but we must pin - * it before taking the PG_lock and/or - * PG_compound_lock. The moment we re-enable - * irqs __split_huge_page_splitting() can - * return and the head page can be freed from - * under us. We can't take the PG_lock and/or - * PG_compound_lock on a page that could be - * freed from under us. - */ - if (page != page_head) { - get_page(page_head); - put_page(page); - } - local_irq_enable(); - } else { - local_irq_enable(); - goto again; - } - } -#else - page_head = compound_head(page); - if (page != page_head) { - get_page(page_head); - put_page(page); - } -#endif - - lock_page(page_head); - + lock_page(page); /* - * If page_head->mapping is NULL, then it cannot be a PageAnon + * If page->mapping is NULL, then it cannot be a PageAnon * page; but it might be the ZERO_PAGE or in the gate area or * in a special mapping (all cases which we are happy to fail); * or it may have been a good file page when get_user_pages_fast @@ -493,12 +456,12 @@ again: * * The case we do have to guard against is when memory pressure made * shmem_writepage move it from filecache to swapcache beneath us: - * an unlikely race, but we do need to retry for page_head->mapping. + * an unlikely race, but we do need to retry for page->mapping. */ - if (!page_head->mapping) { - int shmem_swizzled = PageSwapCache(page_head); - unlock_page(page_head); - put_page(page_head); + if (!page->mapping) { + int shmem_swizzled = PageSwapCache(page); + unlock_page(page); + put_page(page); if (shmem_swizzled) goto again; return -EFAULT; @@ -511,7 +474,7 @@ again: * it's a read-only handle, it's expected that futexes attach to * the object not the particular process. */ - if (PageAnon(page_head)) { + if (PageAnon(page)) { /* * A RO anonymous page will never change and thus doesn't make * sense for futex operations. @@ -526,15 +489,15 @@ again: key->private.address = address; } else { key->both.offset |= FUT_OFF_INODE; /* inode-based key */ - key->shared.inode = page_head->mapping->host; + key->shared.inode = page->mapping->host; key->shared.pgoff = basepage_index(page); } get_futex_key_refs(key); /* implies MB (B) */ out: - unlock_page(page_head); - put_page(page_head); + unlock_page(page); + put_page(page); return err; } -- 2.1.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id 289E56B00AB for ; Tue, 23 Jun 2015 09:53:20 -0400 (EDT) Received: by pdbki1 with SMTP id ki1so7876337pdb.1 for ; Tue, 23 Jun 2015 06:53:19 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id b1si31539348pat.26.2015.06.23.06.47.18 for ; Tue, 23 Jun 2015 06:47:18 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv7 14/36] futex, thp: remove special case for THP in get_futex_key Date: Tue, 23 Jun 2015 16:46:24 +0300 Message-Id: <1435067206-92901-15-git-send-email-kirill.shutemov@linux.intel.com> In-Reply-To: <1435067206-92901-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1435067206-92901-1-git-send-email-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Andrea Arcangeli , Hugh Dickins Cc: Dave Hansen , Mel Gorman , Rik van Riel , Vlastimil Babka , Christoph Lameter , Naoya Horiguchi , Steve Capper , "Aneesh Kumar K.V" , Johannes Weiner , Michal Hocko , Jerome Marchand , Sasha Levin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" With new THP refcounting, we don't need tricks to stabilize huge page. If we've got reference to tail page, it can't split under us. This patch effectively reverts a5b338f2b0b1. Signed-off-by: Kirill A. Shutemov Tested-by: Sasha Levin --- kernel/futex.c | 61 ++++++++++++---------------------------------------------- 1 file changed, 12 insertions(+), 49 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 2a5e3830e953..1809371ebef8 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -399,7 +399,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) { unsigned long address = (unsigned long)uaddr; struct mm_struct *mm = current->mm; - struct page *page, *page_head; + struct page *page; int err, ro = 0; /* @@ -442,46 +442,9 @@ again: else err = 0; -#ifdef CONFIG_TRANSPARENT_HUGEPAGE - page_head = page; - if (unlikely(PageTail(page))) { - put_page(page); - /* serialize against __split_huge_page_splitting() */ - local_irq_disable(); - if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { - page_head = compound_head(page); - /* - * page_head is valid pointer but we must pin - * it before taking the PG_lock and/or - * PG_compound_lock. The moment we re-enable - * irqs __split_huge_page_splitting() can - * return and the head page can be freed from - * under us. We can't take the PG_lock and/or - * PG_compound_lock on a page that could be - * freed from under us. - */ - if (page != page_head) { - get_page(page_head); - put_page(page); - } - local_irq_enable(); - } else { - local_irq_enable(); - goto again; - } - } -#else - page_head = compound_head(page); - if (page != page_head) { - get_page(page_head); - put_page(page); - } -#endif - - lock_page(page_head); - + lock_page(page); /* - * If page_head->mapping is NULL, then it cannot be a PageAnon + * If page->mapping is NULL, then it cannot be a PageAnon * page; but it might be the ZERO_PAGE or in the gate area or * in a special mapping (all cases which we are happy to fail); * or it may have been a good file page when get_user_pages_fast @@ -493,12 +456,12 @@ again: * * The case we do have to guard against is when memory pressure made * shmem_writepage move it from filecache to swapcache beneath us: - * an unlikely race, but we do need to retry for page_head->mapping. + * an unlikely race, but we do need to retry for page->mapping. */ - if (!page_head->mapping) { - int shmem_swizzled = PageSwapCache(page_head); - unlock_page(page_head); - put_page(page_head); + if (!page->mapping) { + int shmem_swizzled = PageSwapCache(page); + unlock_page(page); + put_page(page); if (shmem_swizzled) goto again; return -EFAULT; @@ -511,7 +474,7 @@ again: * it's a read-only handle, it's expected that futexes attach to * the object not the particular process. */ - if (PageAnon(page_head)) { + if (PageAnon(page)) { /* * A RO anonymous page will never change and thus doesn't make * sense for futex operations. @@ -526,15 +489,15 @@ again: key->private.address = address; } else { key->both.offset |= FUT_OFF_INODE; /* inode-based key */ - key->shared.inode = page_head->mapping->host; + key->shared.inode = page->mapping->host; key->shared.pgoff = basepage_index(page); } get_futex_key_refs(key); /* implies MB (B) */ out: - unlock_page(page_head); - put_page(page_head); + unlock_page(page); + put_page(page); return err; } -- 2.1.4 -- 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