Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756562AbbEVGX5 (ORCPT ); Fri, 22 May 2015 02:23:57 -0400 Received: from TYO202.gate.nec.co.jp ([210.143.35.52]:33969 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756026AbbEVGXz convert rfc822-to-8bit (ORCPT ); Fri, 22 May 2015 02:23:55 -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 v3 PATCH 03/10] mm/hugetlb: add region_del() to delete a specific range of entries Thread-Topic: [RFC v3 PATCH 03/10] mm/hugetlb: add region_del() to delete a specific range of entries Thread-Index: AQHQk92N6tPN1t9nFEGPthN+DfXy9p2G8JOA Date: Fri, 22 May 2015 06:21:52 +0000 Message-ID: <20150522062151.GA21526@hori1.linux.bs1.fc.nec.co.jp> References: <1432223264-4414-1-git-send-email-mike.kravetz@oracle.com> <1432223264-4414-4-git-send-email-mike.kravetz@oracle.com> In-Reply-To: <1432223264-4414-4-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: [10.128.101.25] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <1AE9840382DB924890F3F5DFDFB56D43@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: 6642 Lines: 196 On Thu, May 21, 2015 at 08:47:37AM -0700, Mike Kravetz wrote: > fallocate hole punch will want to remove a specific range of pages. > The existing region_truncate() routine deletes all region/reserve > map entries after a specified offset. region_del() will provide > this same functionality if the end of region is specified as -1. > Hence, region_del() can replace region_truncate(). > > Unlike region_truncate(), region_del() can return an error in the > rare case where it can not allocate memory for a region descriptor. > This ONLY happens in the case where an existing region must be split. > Current callers passing -1 as end of range will never experience > this error and do not need to deal with error handling. Future > callers of region_del() (such as fallocate hole punch) will need to > handle this error. A routine hugetlb_fix_reserve_counts() is added > to assist in cleaning up if fallocate hole punch experiences this > type of error in region_del(). > > Signed-off-by: Mike Kravetz > --- > include/linux/hugetlb.h | 1 + > mm/hugetlb.c | 99 ++++++++++++++++++++++++++++++++++++++----------- > 2 files changed, 79 insertions(+), 21 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 7b57850..fd337f2 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -81,6 +81,7 @@ bool isolate_huge_page(struct page *page, struct list_head *list); > void putback_active_hugepage(struct page *page); > bool is_hugepage_active(struct page *page); > void free_huge_page(struct page *page); > +void hugetlb_fix_reserve_counts(struct inode *inode, bool restore_reserve); This function is used in patch 6/10 for the first time, so is it better to move the definition to that patch? (this temporarily introduces "defined but not used" warning...) > #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE > pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud); > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 63f6d43..620cc9e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -261,38 +261,74 @@ out_nrg: > return chg; > } > > -static long region_truncate(struct resv_map *resv, long end) > +static long region_del(struct resv_map *resv, long f, long t) > { > struct list_head *head = &resv->regions; > struct file_region *rg, *trg; > + struct file_region *nrg = NULL; > long chg = 0; > > + /* > + * Locate segments we overlap and etiher split, remove or > + * trim the existing regions. The end of region (t) == -1 > + * indicates all remaining regions. Special case t == -1 as > + * all comparisons are signed. Also, when t == -1 it is not > + * possible to return an error (-ENOMEM) as this only happens > + * when splitting a region. Callers take advantage of this > + * when calling with -1. > + */ > + if (t == -1) > + t = LONG_MAX; > +retry: > spin_lock(&resv->lock); > - /* Locate the region we are either in or before. */ > - list_for_each_entry(rg, head, link) > - if (end <= rg->to) > + list_for_each_entry_safe(rg, trg, head, link) { > + if (rg->to <= f) > + continue; > + if (rg->from >= t) > break; > - if (&rg->link == head) > - goto out; > > - /* If we are in the middle of a region then adjust it. */ > - if (end > rg->from) { > - chg = rg->to - end; > - rg->to = end; > - rg = list_entry(rg->link.next, typeof(*rg), link); > - } > + if (f > rg->from && t < rg->to) { /* must split region */ > + if (!nrg) { > + spin_unlock(&resv->lock); > + nrg = kmalloc(sizeof(*nrg), GFP_KERNEL); > + if (!nrg) > + return -ENOMEM; > + goto retry; > + } > > - /* Drop any remaining regions. */ > - list_for_each_entry_safe(rg, trg, rg->link.prev, link) { > - if (&rg->link == head) > + chg += t - f; > + > + /* new entry for end of split region */ > + nrg->from = t; > + nrg->to = rg->to; > + INIT_LIST_HEAD(&nrg->link); > + > + /* original entry is trimmed */ > + rg->to = f; > + > + list_add(&nrg->link, &rg->link); > + nrg = NULL; > break; > - chg += rg->to - rg->from; > - list_del(&rg->link); > - kfree(rg); > + } > + > + if (f <= rg->from && t >= rg->to) { /* remove entire region */ > + chg += rg->to - rg->from; > + list_del(&rg->link); > + kfree(rg); > + continue; > + } > + > + if (f <= rg->from) { /* trim beginning of region */ > + chg += t - rg->from; > + rg->from = t; > + } else { /* trim end of region */ > + chg += rg->to - f; > + rg->to = f; Is it better to put "break" here? Thanks, Naoya Horiguchi > + } > } > > -out: > spin_unlock(&resv->lock); > + kfree(nrg); > return chg; > } > > @@ -324,6 +360,27 @@ static long region_count(struct resv_map *resv, long f, long t) > } > > /* > + * A rare out of memory error was encountered which prevented removal of > + * the reserve map region for a page. The huge page itself was free''ed > + * and removed from the page cache. This routine will adjust the global > + * reserve count if needed, and the subpool usage count. By incrementing > + * these counts, the reserve map entry which could not be deleted will > + * appear as a "reserved" entry instead of simply dangling with incorrect > + * counts. > + */ > +void hugetlb_fix_reserve_counts(struct inode *inode, bool restore_reserve) > +{ > + struct hugepage_subpool *spool = subpool_inode(inode); > + > + if (restore_reserve) { > + struct hstate *h = hstate_inode(inode); > + > + h->resv_huge_pages++; > + } > + hugepage_subpool_get_pages(spool, 1); > +} > + > +/* > * Convert the address within this vma to the page offset within > * the mapping, in pagecache page units; huge pages here. > */ > @@ -427,7 +484,7 @@ void resv_map_release(struct kref *ref) > struct resv_map *resv_map = container_of(ref, struct resv_map, refs); > > /* Clear out any active regions before we release the map. */ > - region_truncate(resv_map, 0); > + region_del(resv_map, 0, -1); > kfree(resv_map); > } > > @@ -3558,7 +3615,7 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed) > struct hugepage_subpool *spool = subpool_inode(inode); > > if (resv_map) > - chg = region_truncate(resv_map, offset); > + chg = region_del(resv_map, offset, -1); > spin_lock(&inode->i_lock); > inode->i_blocks -= (blocks_per_huge_page(h) * freed); > spin_unlock(&inode->i_lock); > -- > 2.1.0 > -- 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/