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[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: X-Rspamd-Queue-Id: A3B7CA0004 X-Rspam-User: X-Stat-Signature: iotrir9hgyd3ueaonuaou7ho395xuoot X-Rspamd-Server: rspam03 X-HE-Tag: 1687065932-678270 X-HE-Meta: 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 bEssh+X7 pj2ORaw4rL10WEOoU4VnuAx3ID/DpoNApT8ESmIZKHgusSDVQWsS/+iLcSKPS0GCdX5n4AHMc+JPgiFIocUOoe7nlvfc1mW9tqzgNXAqieDhRaZRG8u1oht7P2molJOkxPVsiqEqzRDaACIzdnuetTJTBBypA3ZtU49t68dAt6ixt3yOWlgK/jty+EpYT4cvmWADhLFVFgy30uB9ZW6H7hIAemhTJTVTOTa8fY0EvbxdT3sZnA93Iug8klG/0OmUF//4r+XxIaasGB+vtqnT6NYKBSueSB05CpC+fFt4nMZp5izm0mZRQP0qLE2oEmhOsFYSG0c4nBu2RVzecfiOtFFemDI8laC1Z9yI+ 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 (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