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bh=MGYgQ5Bh2P8Cc6or0I+ZKDCXT0ChcvmEjyPmkuyY6ZM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gk0Oo0mSm++qDOHDzArLm/6KLAml4dXxc378kuLNpp6WlwW34I9ux+4rdH+D3wGfI /dsm74lRZT89ok+cPVq1VZ/vXmLAeBHXBn+WSwv1LlwPrDNwZZYPAYhtORxC4tmSWF BhRGjlOi6THsS1hSj5RHhhvb9gQLNciLUwiCKZBY= Date: Tue, 4 Apr 2023 12:26:00 -0700 From: Andrew Morton To: Rongwei Wang Cc: bagasdotme@gmail.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Aaron Lu Subject: Re: [PATCH v2] mm/swap: fix swap_info_struct race between swapoff and get_swap_pages() Message-Id: <20230404122600.88257a623c7f72e078dcf705@linux-foundation.org> In-Reply-To: <20230404154716.23058-1-rongwei.wang@linux.alibaba.com> References: <20230401221920.57986-1-rongwei.wang@linux.alibaba.com> <20230404154716.23058-1-rongwei.wang@linux.alibaba.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 0FF24180007 X-Rspam-User: X-Stat-Signature: omuidis797kpmkwsrqancquzh3dnooo1 X-HE-Tag: 1680636362-113964 X-HE-Meta: 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 JlT0b9Sr b4lbUFt2hsrdYqNWfUKwLn0svi+sFUyY0NfWcV3x8d25AkvixYVnMs4/wdcnLAMb/YMsRZIRlyDR50fuaIJpkrhJa4GhcFl0FOZv/ueb5Jx7n/lax7WEQ7puAsc0/Hpmj38qO+hnkDuVjsdEfZFK1kYcND/K0WSXTaaztE8EjygKsm+RRYa1LtQD/kKa7fgzlPsjGsx982riqBPMoFLBlpAAJ/Ck7N+hFxMxCKICr+bKsRVAK4ewpcUPvPcV3afpaSuZpsUe6/w9MmdKpOUe0zLJxSC2WdGS8UsOIIn5ZZ2riCP6xiYr2bZhPB4kJl/4CaPUEwG5nvVzj2uvmu5B5YvZOnZrsWS3kA/iCJbuuNE5FiLmaDh1xbaDDG6OGSAUTcmxJ1/8R7q9+ban146EJ/dJ1qIb/aSyMjpkX 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: On Tue, 4 Apr 2023 23:47:16 +0800 Rongwei Wang wrote: > The si->lock must be held when deleting the si from > the available list. > > ... > > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -679,6 +679,7 @@ static void __del_from_avail_list(struct swap_info_struct *p) > { > int nid; > > + assert_spin_locked(&p->lock); > for_each_node(nid) > plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]); > } > @@ -2434,8 +2435,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) > spin_unlock(&swap_lock); > goto out_dput; > } > - del_from_avail_list(p); > spin_lock(&p->lock); > + del_from_avail_list(p); > if (p->prio < 0) { > struct swap_info_struct *si = p; > int nid; So we have swap_avail_lock swap_info_struct.lock swap_cluster_info.lock Is the ranking of these three clearly documented somewhere? Did you test this with lockdep fully enabled? I'm thinking that Aaron's a2468cc9bfdff ("swap: choose swap device according to numa node") is the appropriate Fixes: target - do you agree? These functions use identifier `p' for the swap_info_struct*, whereas most other code uses the much more sensible `si'. That's just rude. But we shouldn't change that within this fix.