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[148.163.156.1]) by mx.google.com with ESMTPS id w187si9193832pgb.130.2017.03.03.03.45.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Mar 2017 03:45:36 -0800 (PST) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v23BjR31001268 for ; Fri, 3 Mar 2017 06:45:36 -0500 Received: from e23smtp05.au.ibm.com (e23smtp05.au.ibm.com [202.81.31.147]) by mx0a-001b2d01.pphosted.com with ESMTP id 28xs8ekmeg-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 03 Mar 2017 06:45:31 -0500 Received: from localhost by e23smtp05.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 3 Mar 2017 21:45:00 +1000 Received: from d23relay10.au.ibm.com (d23relay10.au.ibm.com [9.190.26.77]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 5135A3578053 for ; Fri, 3 Mar 2017 22:44:59 +1100 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay10.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v23Biphm40501380 for ; Fri, 3 Mar 2017 22:44:59 +1100 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v23BiQdQ030006 for ; Fri, 3 Mar 2017 22:44:26 +1100 Subject: Re: [RFC 05/11] mm: make the try_to_munlock void function References: <1488436765-32350-1-git-send-email-minchan@kernel.org> <1488436765-32350-6-git-send-email-minchan@kernel.org> From: Anshuman Khandual Date: Fri, 3 Mar 2017 17:13:54 +0530 MIME-Version: 1.0 In-Reply-To: <1488436765-32350-6-git-send-email-minchan@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Message-Id: <98488e1a-0202-b88b-ca9c-1dc0d6c27ae5@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim , Andrew Morton Cc: kernel-team@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Michal Hocko , Vlastimil Babka , "Kirill A . Shutemov" On 03/02/2017 12:09 PM, Minchan Kim wrote: > try_to_munlock returns SWAP_MLOCK if the one of VMAs mapped > the page has VM_LOCKED flag. In that time, VM set PG_mlocked to > the page if the page is not pte-mapped THP which cannot be > mlocked, either. Right. > > With that, __munlock_isolated_page can use PageMlocked to check > whether try_to_munlock is successful or not without relying on > try_to_munlock's retval. It helps to make ttu/ttuo simple with > upcoming patches. Right. > > Cc: Vlastimil Babka > Cc: Kirill A. Shutemov > Signed-off-by: Minchan Kim > --- > include/linux/rmap.h | 2 +- > mm/mlock.c | 6 ++---- > mm/rmap.c | 16 ++++------------ > 3 files changed, 7 insertions(+), 17 deletions(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index b556eef..1b0cd4c 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -235,7 +235,7 @@ int page_mkclean(struct page *); > * called in munlock()/munmap() path to check for other vmas holding > * the page mlocked. > */ > -int try_to_munlock(struct page *); > +void try_to_munlock(struct page *); > > void remove_migration_ptes(struct page *old, struct page *new, bool locked); > > diff --git a/mm/mlock.c b/mm/mlock.c > index cdbed8a..d34a540 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -122,17 +122,15 @@ static bool __munlock_isolate_lru_page(struct page *page, bool getpage) > */ > static void __munlock_isolated_page(struct page *page) > { > - int ret = SWAP_AGAIN; > - > /* > * Optimization: if the page was mapped just once, that's our mapping > * and we don't need to check all the other vmas. > */ > if (page_mapcount(page) > 1) > - ret = try_to_munlock(page); > + try_to_munlock(page); > > /* Did try_to_unlock() succeed or punt? */ > - if (ret != SWAP_MLOCK) > + if (!PageMlocked(page)) Checks if the page is still mlocked or not. > count_vm_event(UNEVICTABLE_PGMUNLOCKED); > > putback_lru_page(page); > diff --git a/mm/rmap.c b/mm/rmap.c > index 0a48958..61ae694 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1540,18 +1540,10 @@ static int page_not_mapped(struct page *page) > * Called from munlock code. Checks all of the VMAs mapping the page > * to make sure nobody else has this page mlocked. The page will be > * returned with PG_mlocked cleared if no other vmas have it mlocked. > - * > - * Return values are: > - * > - * SWAP_AGAIN - no vma is holding page mlocked, or, > - * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem > - * SWAP_FAIL - page cannot be located at present > - * SWAP_MLOCK - page is now mlocked. > */ > -int try_to_munlock(struct page *page) > -{ > - int ret; > > +void try_to_munlock(struct page *page) > +{ > struct rmap_walk_control rwc = { > .rmap_one = try_to_unmap_one, > .arg = (void *)TTU_MUNLOCK, > @@ -1561,9 +1553,9 @@ int try_to_munlock(struct page *page) > }; > > VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); > + VM_BUG_ON_PAGE(PageMlocked(page), page); We are calling on the page to see if its mlocked from any of it's mapping VMAs. Then it is a possibility that the page is mlocked and the above condition is true and we print VM BUG report there. The point is if its a valid possibility why we have added the above check ? -- 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