From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f174.google.com (mail-pd0-f174.google.com [209.85.192.174]) by kanga.kvack.org (Postfix) with ESMTP id A6E9E6B00DF for ; Tue, 4 Nov 2014 01:04:34 -0500 (EST) Received: by mail-pd0-f174.google.com with SMTP id p10so13038023pdj.33 for ; Mon, 03 Nov 2014 22:04:34 -0800 (PST) Received: from mail-pa0-x232.google.com (mail-pa0-x232.google.com. [2607:f8b0:400e:c03::232]) by mx.google.com with ESMTPS id fl13si3389912pdb.111.2014.11.03.22.04.32 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 03 Nov 2014 22:04:33 -0800 (PST) Received: by mail-pa0-f50.google.com with SMTP id eu11so13874252pac.9 for ; Mon, 03 Nov 2014 22:04:32 -0800 (PST) Date: Mon, 3 Nov 2014 22:04:24 -0800 (PST) From: Hugh Dickins Subject: Re: [PATCH 08/10] mm/mremap: share the i_mmap_rwsem In-Reply-To: <1414697657-1678-9-git-send-email-dave@stgolabs.net> Message-ID: References: <1414697657-1678-1-git-send-email-dave@stgolabs.net> <1414697657-1678-9-git-send-email-dave@stgolabs.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Davidlohr Bueso Cc: "Kirill A. Shutemov" , Michel Lespinasse , akpm@linux-foundation.org, hughd@google.com, riel@redhat.com, mgorman@suse.de, peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, dbueso@suse.de, linux-mm@kvack.org I'm glad to see this series back, and nicely presented: thank you. Not worth respinning them, but consider 1,2,3,4,5,6,7 and 9 as Acked-by: Hugh Dickins On Thu, 30 Oct 2014, Davidlohr Bueso wrote: > As per the comment in move_ptes(), we only require taking the > anon vma and i_mmap locks to ensure that rmap will always observe > either the old or new ptes, in the case of need_rmap_lock=true. > No modifications to the tree itself, thus share the i_mmap_rwsem. > > Signed-off-by: Davidlohr Bueso > Acked-by: Kirill A. Shutemov But this one is Nacked by me. I don't understand how you and Kirill could read Michel's painstaking comment on need_rmap_locks, then go go ahead and remove the exclusion of rmap_walk(). I agree the code here does not modify the interval tree, but the comment explains how we're moving a pte from one place in the tree to another, and in some cases there's a danger that the rmap walk might miss the pte from both places (which doesn't matter much to most of its uses, but is critical in page migration). Or am I the one missing something? Hugh > --- > mm/mremap.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index c929324..09bd644 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -119,7 +119,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, > if (need_rmap_locks) { > if (vma->vm_file) { > mapping = vma->vm_file->f_mapping; > - i_mmap_lock_write(mapping); > + i_mmap_lock_read(mapping); > } > if (vma->anon_vma) { > anon_vma = vma->anon_vma; > @@ -156,7 +156,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, > if (anon_vma) > anon_vma_unlock_read(anon_vma); > if (mapping) > - i_mmap_unlock_write(mapping); > + i_mmap_unlock_read(mapping); > } > > #define LATENCY_LIMIT (64 * PAGE_SIZE) > -- > 1.8.4.5 -- 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