Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753961AbbFOGg3 (ORCPT ); Mon, 15 Jun 2015 02:36:29 -0400 Received: from TYO202.gate.nec.co.jp ([210.143.35.52]:61018 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751515AbbFOGgY convert rfc822-to-8bit (ORCPT ); Mon, 15 Jun 2015 02:36:24 -0400 From: Naoya Horiguchi To: Mike Kravetz CC: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Dave Hansen , David Rientjes , Hugh Dickins , Davidlohr Bueso , Aneesh Kumar , Hillf Danton , Christoph Hellwig Subject: Re: [RFC v4 PATCH 6/9] mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate Thread-Topic: [RFC v4 PATCH 6/9] mm/hugetlb: alloc_huge_page handle areas hole punched by fallocate Thread-Index: AQHQpInhx0q/yuSNNkOucNwpvfSQOp2siscA Date: Mon, 15 Jun 2015 06:34:44 +0000 Message-ID: <20150615063444.GA26050@hori1.linux.bs1.fc.nec.co.jp> References: <1434056500-2434-1-git-send-email-mike.kravetz@oracle.com> <1434056500-2434-7-git-send-email-mike.kravetz@oracle.com> In-Reply-To: <1434056500-2434-7-git-send-email-mike.kravetz@oracle.com> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.128.101.17] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <0973F4C9DF3D014497DE3B4EE258431B@gisp.nec.co.jp> Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4445 Lines: 115 On Thu, Jun 11, 2015 at 02:01:37PM -0700, Mike Kravetz wrote: > Areas hole punched by fallocate will not have entries in the > region/reserve map. However, shared mappings with min_size subpool > reservations may still have reserved pages. alloc_huge_page needs > to handle this special case and do the proper accounting. > > Signed-off-by: Mike Kravetz > --- > mm/hugetlb.c | 48 +++++++++++++++++++++++++++--------------------- > 1 file changed, 27 insertions(+), 21 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index ecbaffe..9c295c9 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -692,19 +692,9 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg) > return 0; > } > > - if (vma->vm_flags & VM_MAYSHARE) { > - /* > - * We know VM_NORESERVE is not set. Therefore, there SHOULD > - * be a region map for all pages. The only situation where > - * there is no region map is if a hole was punched via > - * fallocate. In this case, there really are no reverves to > - * use. This situation is indicated if chg != 0. > - */ > - if (chg) > - return 0; > - else > - return 1; > - } > + /* Shared mappings always use reserves */ > + if (vma->vm_flags & VM_MAYSHARE) > + return 1; This change completely reverts 5/9, so can you omit 5/9? > > /* > * Only the process that called mmap() has reserves for > @@ -1601,6 +1591,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, > struct hstate *h = hstate_vma(vma); > struct page *page; > long chg, commit; > + long gbl_chg; > int ret, idx; > struct hugetlb_cgroup *h_cg; > > @@ -1608,24 +1599,39 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma, > /* > * Processes that did not create the mapping will have no > * reserves and will not have accounted against subpool > - * limit. Check that the subpool limit can be made before > - * satisfying the allocation MAP_NORESERVE mappings may also > - * need pages and subpool limit allocated allocated if no reserve > - * mapping overlaps. > + * limit. Check that the subpool limit will not be exceeded > + * before performing the allocation. Allocations for > + * MAP_NORESERVE mappings also need to be checked against > + * any subpool limit. > + * > + * NOTE: Shared mappings with holes punched via fallocate > + * may still have reservations, even without entries in the > + * reserve map as indicated by vma_needs_reservation. This > + * would be the case if hugepage_subpool_get_pages returns > + * zero to indicate no changes to the global reservation count > + * are necessary. In this case, pass the output of > + * hugepage_subpool_get_pages (zero) to dequeue_huge_page_vma > + * so that the page is not counted against the global limit. > + * For MAP_NORESERVE mappings always pass the output of > + * vma_needs_reservation. For race detection and error cleanup > + * use output of vma_needs_reservation as well. > */ > - chg = vma_needs_reservation(h, vma, addr); > + chg = gbl_chg = vma_needs_reservation(h, vma, addr); > if (chg < 0) > return ERR_PTR(-ENOMEM); > - if (chg || avoid_reserve) > - if (hugepage_subpool_get_pages(spool, 1) < 0) > + if (chg || avoid_reserve) { > + gbl_chg = hugepage_subpool_get_pages(spool, 1); > + if (gbl_chg < 0) > return ERR_PTR(-ENOSPC); > + } > > ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg); > if (ret) > goto out_subpool_put; > > spin_lock(&hugetlb_lock); > - page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg); > + page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, > + avoid_reserve ? chg : gbl_chg); You use chg or gbl_chg depending on avoid_reserve here, and below this line there's code like below commit = vma_commit_reservation(h, vma, addr); if (unlikely(chg > commit)) { ... } This also need to be changed to use chg or gbl_chg depending on avoid_reserve? # I feel that this reserve-handling code in alloc_huge_page() is too complicated # and hard to understand, so some cleanup like separating reserve parts into # other new routine(s) might be helpful... Thanks, Naoya Horiguchi-- 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/