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[174.109.172.136]) by smtp.gmail.com with ESMTPSA id a11sm4399564qkn.12.2021.04.16.08.36.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Apr 2021 08:36:20 -0700 (PDT) Subject: Re: [PATCH 21/42] btrfs: make process_one_page() to handle subpage locking To: Qu Wenruo , linux-btrfs@vger.kernel.org References: <20210415050448.267306-1-wqu@suse.com> <20210415050448.267306-22-wqu@suse.com> From: Josef Bacik Message-ID: <2740fee0-5fcd-ac5d-01e2-c4411f229958@toxicpanda.com> Date: Fri, 16 Apr 2021 11:36:19 -0400 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20210415050448.267306-22-wqu@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 4/15/21 1:04 AM, Qu Wenruo wrote: > Introduce a new data inodes specific subpage member, writers, to record > how many sectors are under page lock for delalloc writing. > > This member acts pretty much the same as readers, except it's only for > delalloc writes. > > This is important for delalloc code to trace which page can really be > freed, as we have cases like run_delalloc_nocow() where we may exit > processing nocow range inside a page, but need to exit to do cow half > way. > In that case, we need a way to determine if we can really unlock a full > page. > > With the new btrfs_subpage::writers, there is a new requirement: > - Page locked by process_one_page() must be unlocked by > process_one_page() > There are still tons of call sites manually lock and unlock a page, > without updating btrfs_subpage::writers. > So if we lock a page through process_one_page() then it must be > unlocked by process_one_page() to keep btrfs_subpage::writers > consistent. > > This will be handled in next patch. > > Signed-off-by: Qu Wenruo Reviewed-by: Josef Bacik Thanks, Josef