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Mon, 24 Jun 2024 23:30:41 -0400 X-MC-Unique: WvBvJypYP3eb65TvXjMe_g-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4A4E819560B1; Tue, 25 Jun 2024 03:30:39 +0000 (UTC) Received: from localhost (unknown [10.72.116.8]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CB24F19560BF; Tue, 25 Jun 2024 03:30:37 +0000 (UTC) Date: Tue, 25 Jun 2024 11:30:33 +0800 From: Baoquan He To: Uladzislau Rezki Cc: Nick Bowler , Hailong Liu , linux-kernel@vger.kernel.org, Linux regressions mailing list , linux-mm@kvack.org, sparclinux@vger.kernel.org, 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: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3A5F0120014 X-Stat-Signature: zcmc4gxe5eu1tsxgd6s7bfy43wijuupu X-Rspam-User: X-HE-Tag: 1719286245-869529 X-HE-Meta: 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 5Do2/ori 3xfdc9k6Bp35wK5IeA0ADqbv8w8C+89fy6zbLV+aDkObwflDNOhywdiGc/DynvW2P1NaYHeOBypZr34/zcFPayDhLhZXCP/KoZv2U7+E9fPG2HEO/afLK9vKQBFaKbvl1X77bknGf/QO3VLK1tB7Qx3/HaORvaLJryIsSQQbp7FFosMYVnb9lYj2l1KMpTUoA93laq2xI0UUZoAEZjqod8s1ETmvd02lofP2xSbHmgKJElP+qYU89dLBNvUg/i2gnCP7eoKjnJM/c+KTpJbcHiydxsj0pVRxD5YCAFSSfirGBskMfd3mynYzbxjjuS2AFEh5tlSmbgSMsgr0= 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 06/24/24 at 02:16pm, Uladzislau Rezki wrote: > On Fri, Jun 21, 2024 at 10:02:50PM +0800, Baoquan He wrote: > > On 06/21/24 at 11:44am, Uladzislau Rezki wrote: > > > On Fri, Jun 21, 2024 at 03:07:16PM +0800, Baoquan He wrote: > > > > 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: > > ...... > > > > 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; > > > > } > > > > > > > The problem i see is about not-initializing of the: > > > > > > for_each_possible_cpu(i) { > > > struct vmap_block_queue *vbq; > > > struct vfree_deferred *p; > > > > > > vbq = &per_cpu(vmap_block_queue, i); > > > spin_lock_init(&vbq->lock); > > > INIT_LIST_HEAD(&vbq->free); > > > p = &per_cpu(vfree_deferred, i); > > > init_llist_head(&p->list); > > > INIT_WORK(&p->wq, delayed_vfree_work); > > > xa_init(&vbq->vmap_blocks); > > > } > > > > > > > > > correctly or fully. It is my bad i did not think that CPUs in a possible mask > > > can be non sequential :-/ > > > > > > nr_cpu_ids - is not the max possible CPU. For example, in Nick case, > > > when he has two CPUs, num_possible_cpus() and nr_cpu_ids are the same. > > > > I checked the generic version of setup_nr_cpu_ids(), from codes, they > > are different with my understanding. > > > > kernel/smp.c > > void __init setup_nr_cpu_ids(void) > > { > > set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); > > } > > > I see that it is not a weak function, so it is generic, thus the > behavior can not be overwritten, which is great. This does what we > need. > > Thank you for checking this you are right! Thanks for confirming this. > > Then it is just a matter of proper initialization of the hash: > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 5d3aa2dc88a8..1733946f7a12 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -5087,7 +5087,13 @@ void __init vmalloc_init(void) > */ > vmap_area_cachep = KMEM_CACHE(vmap_area, SLAB_PANIC); > > - for_each_possible_cpu(i) { > + /* > + * We use "nr_cpu_ids" here because some architectures > + * may have "gaps" in cpu-possible-mask. It is OK for > + * per-cpu approaches but is not OK for cases where it > + * can be used as hashes also. > + */ > + for (i = 0; i < nr_cpu_ids; i++) { I was wrong about earlier comments. Percpu variables are only available on possible CPUs. For those nonexistent possible CPUs of static percpu variable vmap_block_queue, there isn't memory allocated and mapped for them. So accessing into them will cause problem. In Nick's case, there are only CPU0, CPU2. If you access &per_cpu(vmap_block_queue, 1), problem occurs. So I think we may need to change to take other way for vbq. E.g: 1) Storing the vb in the nearest neighbouring vbq on possible CPU as below draft patch; 2) create an normal array to store vbq of size nr_cpu_ids, then we can store/fetch each vbq on non-possible CPU? The way 1) is simpler, the existing code can be adapted a little just as below. diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 633363997dec..59a8951cc6c0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2542,7 +2542,10 @@ 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; + + if (!cpu_possible(idex)) + index = cpumask_next(index, cpu_possible_mask); return &per_cpu(vmap_block_queue, index).vmap_blocks; } @@ -2556,9 +2559,15 @@ addr_to_vb_xa(unsigned long addr) static unsigned long addr_to_vb_idx(unsigned long addr) { + int id = (addr / VMAP_BLOCK_SIZE) % nr_cpu_ids; + int id_dest = id; + + if (!cpu_possible(id)) + id_dest = cpumask_next(id, cpu_possible_mask); + addr -= VMALLOC_START & ~(VMAP_BLOCK_SIZE-1); addr /= VMAP_BLOCK_SIZE; - return addr; + return addr + (id_dest - id); }