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Mon, 08 Feb 2021 15:21:53 -0800 (PST) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id s21sm19428323pga.12.2021.02.08.15.21.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Feb 2021 15:21:53 -0800 (PST) Subject: Re: [PATCH 1/3] mm: provide filemap_range_needs_writeback() helper To: Matthew Wilcox Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, hch@infradead.org, akpm@linux-foundation.org References: <20210208221829.17247-1-axboe@kernel.dk> <20210208221829.17247-2-axboe@kernel.dk> <20210208230205.GV308988@casper.infradead.org> From: Jens Axboe Message-ID: Date: Mon, 8 Feb 2021 16:21:50 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210208230205.GV308988@casper.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Stat-Signature: y5tgmipm1hkbxq9ga7pm4uiqoqm3jqhs X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4141F40001FD Received-SPF: none (kernel.dk>: No applicable sender policy available) receiver=imf02; identity=mailfrom; envelope-from=""; helo=mail-pf1-f169.google.com; client-ip=209.85.210.169 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1612826514-11842 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 2/8/21 4:02 PM, Matthew Wilcox wrote: > On Mon, Feb 08, 2021 at 03:18:27PM -0700, Jens Axboe wrote: >> + rcu_read_lock(); >> + xas_for_each(&xas, head, max) { >> + if (xas_retry(&xas, head)) >> + continue; >> + if (xa_is_value(head)) >> + continue; >> + page = find_subpage(head, xas.xa_index); >> + if (PageDirty(page) || PageLocked(page) || PageWriteback(page)) >> + break; >> + page = NULL; >> + } >> + rcu_read_unlock(); > > There's no need to find the sub-page for any of these three conditions -- > the bit will be set on the head page. Gotcha, that makes it simpler. I'll make the edit. -- Jens Axboe