From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93719C433F5 for ; Thu, 27 Jan 2022 17:33:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244654AbiA0Rdl (ORCPT ); Thu, 27 Jan 2022 12:33:41 -0500 Received: from smtp-out1.suse.de ([195.135.220.28]:56924 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238078AbiA0Rdj (ORCPT ); Thu, 27 Jan 2022 12:33:39 -0500 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id A5329218B0; Thu, 27 Jan 2022 17:33:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1643304818; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DNVZZ8sxz6PZX0hCDHOK6Gcobf083HehUDqLl9+Rksg=; b=XMU7P0JfIlcDalrwZsFfKxP7IPZWBqGSXpmRQBjcGhsrDAhUlWrcbn4CyXbX1dd43nRtCq qvMV2wL05FsJZYG6Xg8GYedzYYGM4zAc5/1hSeoBRVHwl8gxXwhH+BKuYRQ//jfkyhWGyH oOX5ROj6WW5GbIqG101hohnMJCDsjsg= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1643304818; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DNVZZ8sxz6PZX0hCDHOK6Gcobf083HehUDqLl9+Rksg=; b=0kKwYK0WXw+jSIadR30eLnysmgogtc8fYCsjS+PvzEsQYZGthkLvY/rwSTBjBs+KY4e2Xw EP3kC2EA5WPby7Bw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 5D2D213C25; Thu, 27 Jan 2022 17:33:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id nH79FXLX8mHfIgAAMHmgww (envelope-from ); Thu, 27 Jan 2022 17:33:38 +0000 Message-ID: <1bf686e4-6c22-47d9-d6e3-fd33faf59037@suse.cz> Date: Thu, 27 Jan 2022 18:33:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v4 55/66] mm/mempolicy: Use maple tree iterators instead of vma linked list Content-Language: en-US To: Liam Howlett Cc: "maple-tree@lists.infradead.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Song Liu , Davidlohr Bueso , "Paul E . McKenney" , Matthew Wilcox , Laurent Dufour , David Rientjes , Axel Rasmussen , Suren Baghdasaryan , Rik van Riel , Peter Zijlstra , Michel Lespinasse , Jerome Glisse , Minchan Kim , Joel Fernandes , Rom Lemarchand References: <20211201142918.921493-1-Liam.Howlett@oracle.com> <20211201142918.921493-56-Liam.Howlett@oracle.com> <10798a7d-e157-03c2-abf4-f005a3507cae@suse.cz> <20220126024819.i35wd6uxh463wkps@revolver> <3dc23bc9-2b0f-00af-f85b-22c270356e96@suse.cz> <20220127172516.dj7mditbishetlxv@revolver> From: Vlastimil Babka In-Reply-To: <20220127172516.dj7mditbishetlxv@revolver> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/27/22 18:25, Liam Howlett wrote: > * Vlastimil Babka [220126 04:23]: >> On 1/26/22 03:48, Liam Howlett wrote: >> > * Vlastimil Babka [220120 06:58]: >> >> On 12/1/21 15:30, Liam Howlett wrote: >> >> > From: "Liam R. Howlett" >> >> > >> >> > Signed-off-by: Matthew Wilcox (Oracle) >> >> > Signed-off-by: Liam R. Howlett >> >> > --- >> >> > mm/mempolicy.c | 53 ++++++++++++++++++++++++++------------------------ >> >> > 1 file changed, 28 insertions(+), 25 deletions(-) >> >> > >> >> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c >> >> > index 10e9c87260ed..0e2d918f4f30 100644 >> >> > --- a/mm/mempolicy.c >> >> > +++ b/mm/mempolicy.c >> >> > @@ -377,9 +377,10 @@ void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new) >> >> > void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) >> >> > { >> >> > struct vm_area_struct *vma; >> >> > + MA_STATE(mas, &mm->mm_mt, 0, 0); >> >> >> >> VMA_ITERATOR? >> > >> > Yes, I will make this change. Thanks. >> > >> >> >> >> > >> >> > mmap_write_lock(mm); >> >> > - for (vma = mm->mmap; vma; vma = vma->vm_next) >> >> > + mas_for_each(&mas, vma, ULONG_MAX) >> >> > mpol_rebind_policy(vma->vm_policy, new); >> >> > mmap_write_unlock(mm); >> >> > } >> >> > @@ -652,7 +653,7 @@ static unsigned long change_prot_numa(struct vm_area_struct *vma, >> >> > static int queue_pages_test_walk(unsigned long start, unsigned long end, >> >> > struct mm_walk *walk) >> >> > { >> >> > - struct vm_area_struct *vma = walk->vma; >> >> > + struct vm_area_struct *next, *vma = walk->vma; >> >> > struct queue_pages *qp = walk->private; >> >> > unsigned long endvma = vma->vm_end; >> >> > unsigned long flags = qp->flags; >> >> > @@ -667,9 +668,10 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, >> >> > /* hole at head side of range */ >> >> > return -EFAULT; >> >> > } >> >> > + next = find_vma(vma->vm_mm, vma->vm_end); >> >> > if (!(flags & MPOL_MF_DISCONTIG_OK) && >> >> > ((vma->vm_end < qp->end) && >> >> > - (!vma->vm_next || vma->vm_end < vma->vm_next->vm_start))) >> >> > + (!next || vma->vm_end < next->vm_start))) >> >> > /* hole at middle or tail of range */ >> >> > return -EFAULT; >> >> > >> >> > @@ -783,28 +785,24 @@ static int vma_replace_policy(struct vm_area_struct *vma, >> >> > static int mbind_range(struct mm_struct *mm, unsigned long start, >> >> > unsigned long end, struct mempolicy *new_pol) >> >> > { >> >> > - struct vm_area_struct *next; >> >> > + MA_STATE(mas, &mm->mm_mt, start - 1, start - 1); >> >> > struct vm_area_struct *prev; >> >> > struct vm_area_struct *vma; >> >> > int err = 0; >> >> > pgoff_t pgoff; >> >> > - unsigned long vmstart; >> >> > - unsigned long vmend; >> >> > - >> >> > - vma = find_vma(mm, start); >> >> > - VM_BUG_ON(!vma); >> >> > >> >> > - prev = vma->vm_prev; >> >> > - if (start > vma->vm_start) >> >> > - prev = vma; >> >> > + prev = mas_find_rev(&mas, 0); >> >> > + if (prev && (start < prev->vm_end)) >> >> > + vma = prev; >> >> > + else >> >> > + vma = mas_next(&mas, end - 1); >> >> > >> >> > - for (; vma && vma->vm_start < end; prev = vma, vma = next) { >> >> > - next = vma->vm_next; >> >> > - vmstart = max(start, vma->vm_start); >> >> > - vmend = min(end, vma->vm_end); >> >> > + do { >> >> > + unsigned long vmstart = max(start, vma->vm_start); >> >> > + unsigned long vmend = min(end, vma->vm_end); >> >> >> >> What if vma is null? Shouldn't this rather be a "for (; vma; vma = >> >> mas_next(...)" >> > >> > We have already found the vma above. >> >> AFAICS if the range intersects no vmas, we might have found a 'prev', but >> 'vma' might be NULL after the "vma = mas_next(&mas, end - 1);"? > > Yes, I agree. I was going to restore VM_BUG_ON(!vma) after mas_next(), > but that's not the same as the existing code. The VM_BUG_ON(!vma) > only catches if we search for 'start' above any VMA. It seems > mbind_range() would have returned without error if there were no VMAs > within the range but would error if the 'start' was sufficiently large. Ah I missed there was a VM_BUG_ON(!vma) previously and that the callers seem to only call mbind_range() if there's an actual vma in the range, so I guess my suggestion was misguided. > I think it is better to write it as you suggested to restore the > functionality of not failing on an empty list. I don't see a decent > way of checking if we searched for an address above any VMA to restore > the VM_BUG_ON() which existed - although I see little value in it to > begin with. I will mention this in the commit message.