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 720B4EB64D8 for ; Sun, 18 Jun 2023 05:28:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229533AbjFRFZf (ORCPT ); Sun, 18 Jun 2023 01:25:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbjFRFZd (ORCPT ); Sun, 18 Jun 2023 01:25:33 -0400 Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 137B7DA for ; Sat, 17 Jun 2023 22:25:32 -0700 (PDT) Received: by mail-pf1-x435.google.com with SMTP id d2e1a72fcca58-66869feb7d1so355590b3a.3 for ; Sat, 17 Jun 2023 22:25:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1687065931; x=1689657931; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=2lEqHyxGtCRDjYgsfTX1nfcI5nfmX6OULc3IM+psge4=; b=LCRM+gXkewTc7CVIoPzQl0RbPysH9hV3npvzPDDnu1asWxNE0iZNHZbckrm4KnsB+A QDy0VZaR8WOZgfYsYi8yueNybrOfR0ys8QEtBzclC4JOwyS346ECW/qIBqYqhe41/l0f ZrJuWg1lBFpq1Vd58dOAnP8TmL5SZtGw5cRsI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687065931; x=1689657931; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=2lEqHyxGtCRDjYgsfTX1nfcI5nfmX6OULc3IM+psge4=; b=TZ14q7KsOaNyVoUBpGFeD3UV4pjGofi0diVb4ramcqF6+JdHPWgZLtK5dU6bLp3cl7 gN3x8YUf2iUNwMrUP9WybxukqtRgiKparYKhSyZ+nc7ADm/aT/Ygt6ScQYQ4co0ltzph 9+vXommntsNSNJ4o59epOBI3v02XHqyurHSiadf8Ozw9GAZCJhO8dk/tyhPd3Ss4uE5K /KZXH8rqw/3wtSKJGc4BPUVLooTUnMXwegjX0kEwOsCX/OpO1/bF0vS9ZroX91zx1awQ rpvRdN5qftHKz+pU0teUtKLniZGQ/FoqKs3xPQFrf/ezCkZg7pzEpwNSfdXa81NcpE7h Uxug== X-Gm-Message-State: AC+VfDzPtPYbyDdiYlKbDl49bT3n6chvawY84vQsjGe/AZyga7CjSsHx KMblM7libZQbwjjOHlAgYeBMTQ== X-Google-Smtp-Source: ACHHUZ7+beLKa/0zxEEmwU6sXe49M0T5XlPdzQxQmP/BaTPYunD89PVhR+uQkdbx9fTT5GdIFGAy7Q== X-Received: by 2002:a17:902:d483:b0:1b4:fe23:1eaa with SMTP id c3-20020a170902d48300b001b4fe231eaamr5350017plg.28.1687065931541; Sat, 17 Jun 2023 22:25:31 -0700 (PDT) Received: from google.com (KD124209188001.ppp-bb.dion.ne.jp. [124.209.188.1]) by smtp.gmail.com with ESMTPSA id jk17-20020a170903331100b001b54a88e6adsm1739188plb.309.2023.06.17.22.25.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 17 Jun 2023 22:25:30 -0700 (PDT) Date: Sun, 18 Jun 2023 14:25:26 +0900 From: Sergey Senozhatsky To: Yosry Ahmed Cc: Sergey Senozhatsky , Domenico Cerasuolo , vitaly.wool@konsulko.com, minchan@kernel.org, linux-mm@kvack.org, ddstreet@ieee.org, sjenning@redhat.com, nphamcs@gmail.com, hannes@cmpxchg.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v3 1/7] mm: zswap: add pool shrinking mechanism Message-ID: <20230618052526.GB2417524@google.com> References: <20230612093815.133504-1-cerasuolodomenico@gmail.com> <20230612093815.133504-2-cerasuolodomenico@gmail.com> <20230618043857.GA2417524@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (23/06/17 21:48), Yosry Ahmed wrote: > > On (23/06/12 11:38), Domenico Cerasuolo wrote: > > > +static int zswap_reclaim_entry(struct zswap_pool *pool) > > > +{ > > > + struct zswap_header *zhdr; > > > + struct zswap_entry *entry; > > > + struct zswap_tree *tree; > > > + pgoff_t swpoffset; > > > + int ret; > > > + > > > + /* Get an entry off the LRU */ > > > + spin_lock(&pool->lru_lock); > > > + if (list_empty(&pool->lru)) { > > > + spin_unlock(&pool->lru_lock); > > > + return -EINVAL; > > > + } > > > + entry = list_last_entry(&pool->lru, struct zswap_entry, lru); > > > + list_del_init(&entry->lru); > > > > A quick question: should we zswap_entry_get() here? > > We need to hold the tree lock for that, and the lock ordering is tree > lock -> lru lock. If we try to grab the tree lock here we may > deadlock. We can deadlock doing this? lock tree_lock lock lru_lock list_del_init unlock lru_lock entry_get unlock tree_lock writeback