Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756456AbbBLQT3 (ORCPT ); Thu, 12 Feb 2015 11:19:29 -0500 Received: from mga01.intel.com ([192.55.52.88]:23990 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756433AbbBLQT0 (ORCPT ); Thu, 12 Feb 2015 11:19:26 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.09,565,1418112000"; d="scan'208";a="684838356" 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 , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A. Shutemov" Subject: [PATCHv3 23/24] ksm: split huge pages on follow_page() Date: Thu, 12 Feb 2015 18:18:37 +0200 Message-Id: <1423757918-197669-24-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1423757918-197669-1-git-send-email-kirill.shutemov@linux.intel.com> References: <1423757918-197669-1-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 Content-Length: 3467 Lines: 121 Let's split THP with FOLL_SPLIT. Attempting to split them laterk would always fail bacause we take references on tail pages. Signed-off-by: Kirill A. Shutemov --- mm/ksm.c | 58 ++++++++-------------------------------------------------- 1 file changed, 8 insertions(+), 50 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index a8a88b0f6f62..8d977f074a74 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -441,20 +441,6 @@ static void break_cow(struct rmap_item *rmap_item) up_read(&mm->mmap_sem); } -static struct page *page_trans_compound_anon(struct page *page) -{ - if (PageTransCompound(page)) { - struct page *head = compound_head(page); - /* - * head may actually be splitted and freed from under - * us but it's ok here. - */ - if (PageAnon(head)) - return head; - } - return NULL; -} - static struct page *get_mergeable_page(struct rmap_item *rmap_item) { struct mm_struct *mm = rmap_item->mm; @@ -467,10 +453,10 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item) if (!vma) goto out; - page = follow_page(vma, addr, FOLL_GET); + page = follow_page(vma, addr, FOLL_GET | FOLL_SPLIT); if (IS_ERR_OR_NULL(page)) goto out; - if (PageAnon(page) || page_trans_compound_anon(page)) { + if (PageAnon(page)) { flush_anon_page(vma, page, addr); flush_dcache_page(page); } else { @@ -976,35 +962,6 @@ out: return err; } -static int page_trans_compound_anon_split(struct page *page) -{ - int ret = 0; - struct page *transhuge_head = page_trans_compound_anon(page); - if (transhuge_head) { - /* Get the reference on the head to split it. */ - if (get_page_unless_zero(transhuge_head)) { - /* - * Recheck we got the reference while the head - * was still anonymous. - */ - if (PageAnon(transhuge_head)) { - lock_page(transhuge_head); - ret = split_huge_page(transhuge_head); - unlock_page(transhuge_head); - } else - /* - * Retry later if split_huge_page run - * from under us. - */ - ret = 1; - put_page(transhuge_head); - } else - /* Retry later if split_huge_page run from under us. */ - ret = 1; - } - return ret; -} - /* * try_to_merge_one_page - take two pages and merge them into one * @vma: the vma that holds the pte pointing to page @@ -1025,9 +982,10 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, if (!(vma->vm_flags & VM_MERGEABLE)) goto out; - if (PageTransCompound(page) && page_trans_compound_anon_split(page)) - goto out; + + /* huge pages must be split by this time */ BUG_ON(PageTransCompound(page)); + if (!PageAnon(page)) goto out; @@ -1616,14 +1574,14 @@ next_mm: while (ksm_scan.address < vma->vm_end) { if (ksm_test_exit(mm)) break; - *page = follow_page(vma, ksm_scan.address, FOLL_GET); + *page = follow_page(vma, ksm_scan.address, + FOLL_GET | FOLL_SPLIT); if (IS_ERR_OR_NULL(*page)) { ksm_scan.address += PAGE_SIZE; cond_resched(); continue; } - if (PageAnon(*page) || - page_trans_compound_anon(*page)) { + if (PageAnon(*page)) { flush_anon_page(vma, *page, ksm_scan.address); flush_dcache_page(*page); rmap_item = get_next_rmap_item(slot, -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/