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Date: Mon, 18 May 2015 14:41:13 +0200 From: Vlastimil Babka <vbabka@...e.cz> To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Andrew Morton <akpm@...ux-foundation.org>, Andrea Arcangeli <aarcange@...hat.com>, Hugh Dickins <hughd@...gle.com> CC: Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>, Christoph Lameter <cl@...two.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Steve Capper <steve.capper@...aro.org>, "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...e.cz>, Jerome Marchand <jmarchan@...hat.com>, Sasha Levin <sasha.levin@...cle.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCHv5 15/28] ksm: prepare to new THP semantics On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote: > We don't need special code to stabilize THP. If you've got reference to > any subpage of THP it will not be split under you. > > New split_huge_page() also accepts tail pages: no need in special code > to get reference to head page. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> > Tested-by: Sasha Levin <sasha.levin@...cle.com> Acked-by: Vlastimil Babka <vbabka@...e.cz> > --- > mm/ksm.c | 57 ++++++++++----------------------------------------------- > 1 file changed, 10 insertions(+), 47 deletions(-) > > diff --git a/mm/ksm.c b/mm/ksm.c > index fe09f3ddc912..fb333d8188fc 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; > @@ -470,7 +456,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item) > page = follow_page(vma, addr, FOLL_GET); > 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 { > @@ -976,33 +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)) > - ret = split_huge_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 > @@ -1023,9 +982,6 @@ 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; > - BUG_ON(PageTransCompound(page)); > if (!PageAnon(page)) > goto out; > > @@ -1038,6 +994,13 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, > */ > if (!trylock_page(page)) > goto out; > + > + if (PageTransCompound(page)) { > + err = split_huge_page(page); > + if (err) > + goto out_unlock; > + } > + > /* > * If this anonymous page is mapped only here, its pte may need > * to be write-protected. If it's mapped elsewhere, all of its > @@ -1068,6 +1031,7 @@ static int try_to_merge_one_page(struct vm_area_struct *vma, > } > } > > +out_unlock: > unlock_page(page); > out: > return err; > @@ -1620,8 +1584,7 @@ next_mm: > 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, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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