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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20220316131723.111553-1-jefflexu@linux.alibaba.com> <20220316131723.111553-4-jefflexu@linux.alibaba.com> To: Matthew Wilcox Cc: dhowells@redhat.com, Jeffle Xu , linux-cachefs@redhat.com, xiang@kernel.org, chao@kernel.org, linux-erofs@lists.ozlabs.org, torvalds@linux-foundation.org, gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.org, joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com, tao.peng@linux.alibaba.com, gerry@linux.alibaba.com, eguan@linux.alibaba.com, linux-kernel@vger.kernel.org, luodaowen.backend@bytedance.com Subject: Re: [PATCH v5 03/22] cachefiles: introduce on-demand read mode MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1029981.1647872043.1@warthog.procyon.org.uk> Date: Mon, 21 Mar 2022 14:14:03 +0000 Message-ID: <1029982.1647872043@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 X-Spam-Status: No, score=-3.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Matthew Wilcox wrote: > Why do you have a separate rwlock when the xarray already has its own > spinlock? This is usually a really bad idea. Jeffle wants to hold a lock across the CACHEFILES_DEAD check and the xarray access. However, he tells xarray to do a GFP_KERNEL alloc whilst holding the rwlock:-/ David