From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 497BA6B0062 for ; Sat, 9 Jun 2012 09:03:26 -0400 (EDT) Received: from /spool/local by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 9 Jun 2012 12:42:51 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q59D3FLb60751892 for ; Sat, 9 Jun 2012 23:03:16 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q59D3EsV000801 for ; Sat, 9 Jun 2012 23:03:14 +1000 From: "Aneesh Kumar K.V" Subject: Re: [PATCH -V8 05/16] hugetlb: avoid taking i_mmap_mutex in unmap_single_vma() for hugetlb In-Reply-To: <20120609094444.GG1761@cmpxchg.org> References: <1339232401-14392-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1339232401-14392-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20120609094444.GG1761@cmpxchg.org>User-Agent: Notmuch/0.11.1+346~g13d19c3 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) Date: Sat, 09 Jun 2012 18:33:05 +0530 Message-ID: <87sje4ljsm.fsf@skywalker.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: linux-mm@kvack.org, kamezawa.hiroyu@jp.fujitsu.com, dhillf@gmail.com, rientjes@google.com, mhocko@suse.cz, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Johannes Weiner writes: > On Sat, Jun 09, 2012 at 02:29:50PM +0530, Aneesh Kumar K.V wrote: >> From: "Aneesh Kumar K.V" >> >> i_mmap_mutex lock was added in unmap_single_vma by 502717f4e ("hugetlb: >> fix linked list corruption in unmap_hugepage_range()") but we don't use >> page->lru in unmap_hugepage_range any more. Also the lock was taken >> higher up in the stack in some code path. That would result in deadlock. >> >> unmap_mapping_range (i_mmap_mutex) >> -> unmap_mapping_range_tree >> -> unmap_mapping_range_vma >> -> zap_page_range_single >> -> unmap_single_vma >> -> unmap_hugepage_range (i_mmap_mutex) >> >> For shared pagetable support for huge pages, since pagetable pages are ref >> counted we don't need any lock during huge_pmd_unshare. We do take >> i_mmap_mutex in huge_pmd_share while walking the vma_prio_tree in mapping. >> (39dde65c9940c97f ("shared page table for hugetlb page")). >> >> Signed-off-by: Aneesh Kumar K.V > > This patch (together with the previous one) seems like a bugfix that's > not really related to the hugetlb controller, unless I miss something. > > Could you please submit the fix separately? Patches upto 6 can really got in a separate series. I was not sure whether I should split them. I will post that as a separate series now > > Maybe also fold the two patches into one and make it a single bugfix > change that gets rid of the lock by switching away from page->lru. I wanted to make sure the patch that drop i_mmap_mutex is a separate one so that we understand and document the locking details separately -aneesh -- 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