From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE497155300 for ; Fri, 21 Jun 2024 07:07:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718953652; cv=none; b=QLyBSBKOk6J/8p5UeoSNMpso7THTnElNqFrWtt1KZ+54kHuvnpVTvxe/a6W5IwTjEVFK7IBwcBDrYlr17BnXY3ViAO3wGi4bJoCIEJDHZEwB01WBWai7P6Owl/t4cl0Ss2T/MX8urZ9B2eRmJrvbOsYVb7WUOzDit/V3k0UfCLs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718953652; c=relaxed/simple; bh=U7O/f4ugiEkC98DWZvtW3F9cYFCOjQxaBn1Mwd+XbA8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fiul5hLKaYINUeJrf3glHbfr6rkmx747uWbsn6aRzJq9lPJm705b5dyqkWUXJlxdaK0ws6wNfRJVoJaOQ+IzBzU5HdKveTb45fGLPqpcAfXFLT5pwjv0l6g0Tfcc2RWETsyLEZhN0H8CUVceqJBGCxCD02gjnBkQ2T4lQFyuFbU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=X6dzxbMe; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="X6dzxbMe" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718953649; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pVNRr002L+NyIVSk486BNVmsI1O8j0gJ9CCkEeh4Wcg=; b=X6dzxbMemdhJJu6M2eA/eYUKCWfaLs9FXIIr5jAA/dqnK5qYVazOzoJ+sRMQ3zAxUNvFdk ySbdlbCchdJTIGWNEgf9o+Jnw/wUSruZidE3gFpef36gTomcK2g7Svt1msrXJWULoFrW0z ffzcgArXW3bfbOl0NlBN1av6KP4nQbc= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-526-FE3XjoE-MH2DRKwjKcM-DQ-1; Fri, 21 Jun 2024 03:07:24 -0400 X-MC-Unique: FE3XjoE-MH2DRKwjKcM-DQ-1 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E01451956096; Fri, 21 Jun 2024 07:07:22 +0000 (UTC) Received: from localhost (unknown [10.72.112.17]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4738F19560AF; Fri, 21 Jun 2024 07:07:20 +0000 (UTC) Date: Fri, 21 Jun 2024 15:07:16 +0800 From: Baoquan He To: Hailong Liu , Nick Bowler Cc: linux-kernel@vger.kernel.org, Linux regressions mailing list , linux-mm@kvack.org, sparclinux@vger.kernel.org, "Uladzislau Rezki (Sony)" , Andrew Morton Subject: Re: PROBLEM: kernel crashes when running xfsdump since ~6.4 Message-ID: References: <75e17b57-1178-4288-b792-4ae68b19915e@draconx.ca> <00d74f24-c49c-460e-871c-d5af64701306@draconx.ca> <20240621033005.6mccm7waduelb4m5@oppo.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240621033005.6mccm7waduelb4m5@oppo.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 On 06/21/24 at 11:30am, Hailong Liu wrote: > On Thu, 20. Jun 14:02, Nick Bowler wrote: > > On 2024-06-20 02:19, Nick Bowler wrote: > > > After upgrading my sparc to 6.9.5 I noticed that attempting to run > > > xfsdump instantly (within a couple seconds) and reliably crashes the > > > kernel. The same problem is also observed on 6.10-rc4. > > [...] > > > 062eacf57ad91b5c272f89dc964fd6dd9715ea7d is the first bad commit > > > commit 062eacf57ad91b5c272f89dc964fd6dd9715ea7d > > > Author: Uladzislau Rezki (Sony) > > > Date: Thu Mar 30 21:06:38 2023 +0200 > > > > > > mm: vmalloc: remove a global vmap_blocks xarray > > > > I think I might see what is happening here. > > > > On this machine, there are two CPUs numbered 0 and 2 (there is no CPU1). > > > +Baoquan Thanks for adding me, Hailong. > > Ahh, I thought you are right. addr_to_vb_xa assume that the CPU numbers are > contiguous. I don't have knowledge about CPU at all. > Technically change the implement addr_to_vb_xa() to > return &per_cpu(vmap_block_queue, raw_smp_processor_id()).vmap_blocks; > would also work, but it violate the load balance. Wating for > experts reply. Yeah, I think so as you explained. > > > The per-cpu variables in mm/vmalloc.c are initialized like this, in > > vmalloc_init > > > > for_each_possible_cpu(i) { > > /* ... */ > > vbq = &per_cpu(vmap_block_queue, i); > > /* initialize stuff in vbq */ > > } > > > > This loops over the set bits of cpu_possible_mask, bits 0 and 2 are set, > > so it initializes stuff with i=0 and i=2, skipping i=1 (I added prints to > > confirm this). > > > > Then, in vm_map_ram, with the problematic change it calls the new > > function addr_to_vb_xa, which does this: > > > > int index = (addr / VMAP_BLOCK_SIZE) % num_possible_cpus(); > > return &per_cpu(vmap_block_queue, index).vmap_blocks; > > > > The num_possible_cpus() function counts the number of set bits in > > cpu_possible_mask, so it returns 2. Thus, index is either 0 or 1, which > > does not correspond to what was initialized (0 or 2). The crash occurs > > when the computed index is 1 in this function. In this case, the > > returned value appears to be garbage (I added prints to confirm this). This is a great catch. > > > > If I change addr_to_vb_xa function to this: > > > > int index = ((addr / VMAP_BLOCK_SIZE) & 1) << 1; /* 0 or 2 */ > > return &per_cpu(vmap_block_queue, index).vmap_blocks; Yeah, while above change is not generic, e.g if it's CPU0 and CPU3. I think we should take the max possible CPU number as the hush bucket size. The vb->va is also got from global free_vmap_area, so no need to worry about the waste. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index be2dd281ea76..18e87cafbaf2 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2542,7 +2542,7 @@ static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue); static struct xarray * addr_to_vb_xa(unsigned long addr) { - int index = (addr / VMAP_BLOCK_SIZE) % num_possible_cpus(); + int index = (addr / VMAP_BLOCK_SIZE) % nr_cpu_ids; return &per_cpu(vmap_block_queue, index).vmap_blocks; }