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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> 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 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9C1F9A0015 X-Stat-Signature: oz47uon7ajxkos5to5ats5w41zeu7pzy X-HE-Tag: 1718953648-581885 X-HE-Meta: U2FsdGVkX199xPpoi4V5z/n7wzOtsTfrxTvffO9BRuHFSeXK3mYEq34FmQQybYpXJMfZK7rM9jXWODKWYoKvSEmPpEvdg5JKED3Ore00KAkkgEFCN+uj6cPGzccGDjTegKB9uH7M8wtm18hi7av+SCxevvuyeEEYdNu/iPuAkjquBNqOwX61EQBVX8GOJmSr5tMuarWvPF+hhBIJBOsn+xtEA16ahySdt+vjc+T6OqNIgRuJamgpv86tmGzZeWYLe9TQHdUvTx7+aKhmfxYVZVxEjiU0yRMhwl0MCAQ68Id5eteJAdRywX7Y1kFl8fBxgdWUibdh4lnC3ixgl+ea6kRr93gC+l0dRmXmum4YjZGIClYsXR36bbxJ9KxQ6GMLipf71FYM0JxxrjlakQ4k5aNmPnvNiIZawDkja4HT9J2qIqvcC1uUWvxs1vzg+V3YbnZOXHWxshOpuL8uOV8hZxog+cNpl94aMkVzJQLrOG3hq3AvrTrY1cUmnpw09Z7ZWQomfOO3EogFNdSob1giKrFerEvZROt3RpMfAAg66mnBRTMu4RDKNP9tMr3wgQLrP8mPKhMhNnwU0xq3R/z3z3iqS8kmQ3GT+MRzvrsODSJeNbg4sBHya/awTBy9F1Dtdae9zvLKuMFdqKQt/7qup8jjIhaLJDS+Es+G/Qz0ttWJi+ET8ZjYfvqVkgdeaLz/F1PueNV/7l29ngsJVNkmEb3jXon4mPZgZIESRP75TlDsBx1GbQ+SZ14jCvS8KVcLJ1hKng1zlVrgKfyWpNuJkWMEauGeODCMpgwlMHch5X5UxQbQLx+E3HUo3FDuSOwvNouOYmnuy/vwmJdfJP3mfcyms9OSksaUB0Vb3GNZWVTGpXJ/8O6/emN8fjlqkNGrlBGJRP2Aiq0rR0w6uKCIb3jkrKXZ/N2JfVA8CHHJ1TEbHLyAiBd1XReYd+leQ0v7UA+vaU65MvlSeBox8NJ 2IyRRCPR uZwH3nKBQJOc3jQyHxgU5iuihGvitiLZ9X871By5UTke1dndK1zAfHhZywhHKJj+8IwfHXR62wcPQ1Bk5iUspnBYdyvYFHGo5itPvVE4UkP9XnAqcjX6Fm4jauAhAeKFId29Rt4OFWM9FyTItEOLoKFdRQDxKgYLFzKt6uijZ6fdK3AxeyIFBLXivj53/392OTL0KaU4GDA71m52f8i0FwrIQtO2KDRVUWUF8NYjS/drWNfsA0rN6DtwQ/5OVKhCeL6TtlYbXHzZTwkhDiHZaHfgizLDdzCtf5imZCVVaRELUS5RvmwlhrVs7xUcN4b+sPPu/6rya1mgSJ9LOwztlkTRyi/xbKl5IDm5m X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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; }