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AJvYcCXLOiwxTc6myTiO4KYnCJ0O82A5oZsfD4s3CRBlWs7GEocvi/jLd2XAT9gI3irgGwLhfkxXELfq5Sx2cIfRRGzL3jr6XrS1SCw+v/qC X-Gm-Message-State: AOJu0YwxCJh2Q/AS8gk/e9FkztPp9f//57KXsKdxf+9tkKIRH3ReYO5r GsCVee+eS6Wr6Psm7tJn9Tqyc/MKTKH+HpzlWMfoLwM/ue7wbsQgCxdZu3dleUg= X-Google-Smtp-Source: AGHT+IGXNptk+olxPRJcLAW0W9h984MMeb0Lybawe6fqDXiy7gt7eKH1E3YmxBnctdni7giQ3i6BUw== X-Received: by 2002:a05:6808:170e:b0:3c6:6e1:b166 with SMTP id bc14-20020a056808170e00b003c606e1b166mr1792336oib.28.1713937615179; Tue, 23 Apr 2024 22:46:55 -0700 (PDT) Received: from [10.3.132.118] ([61.213.176.6]) by smtp.gmail.com with ESMTPSA id j9-20020a056a00130900b006eae2d9298esm10560634pfu.194.2024.04.23.22.46.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Apr 2024 22:46:54 -0700 (PDT) Message-ID: Date: Wed, 24 Apr 2024 13:46:47 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5/5] cachefiles: add missing lock protection when polling To: libaokun@huaweicloud.com, netfs@lists.linux.dev Cc: dhowells@redhat.com, jlayton@kernel.org, jefflexu@linux.alibaba.com, linux-cachefs@redhat.com, linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Joseph Qi , Gao Xiang , Baokun Li References: <20240424033409.2735257-1-libaokun@huaweicloud.com> <20240424033409.2735257-6-libaokun@huaweicloud.com> From: Jia Zhu In-Reply-To: <20240424033409.2735257-6-libaokun@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2024/4/24 11:34, libaokun@huaweicloud.com 写道: > From: Jingbo Xu > > Add missing lock protection in poll routine when iterating xarray, > otherwise: > > Even with RCU read lock held, only the slot of the radix tree is > ensured to be pinned there, while the data structure (e.g. struct > cachefiles_req) stored in the slot has no such guarantee. The poll > routine will iterate the radix tree and dereference cachefiles_req > accordingly. Thus RCU read lock is not adequate in this case and > spinlock is needed here. > > Fixes: b817e22b2e91 ("cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode") > Signed-off-by: Jingbo Xu > Reviewed-by: Joseph Qi > Reviewed-by: Gao Xiang > Signed-off-by: Baokun Li Thanks for catching this. Reviewed-by: Jia Zhu > --- > fs/cachefiles/daemon.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c > index 6465e2574230..73ed2323282a 100644 > --- a/fs/cachefiles/daemon.c > +++ b/fs/cachefiles/daemon.c > @@ -365,14 +365,14 @@ static __poll_t cachefiles_daemon_poll(struct file *file, > > if (cachefiles_in_ondemand_mode(cache)) { > if (!xa_empty(&cache->reqs)) { > - rcu_read_lock(); > + xas_lock(&xas); > xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) { > if (!cachefiles_ondemand_is_reopening_read(req)) { > mask |= EPOLLIN; > break; > } > } > - rcu_read_unlock(); > + xas_unlock(&xas); > } > } else { > if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))