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Fri, 15 Dec 2023 14:14:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id T8eYAl5ffGXRZwAAn2gu4w (envelope-from ); Fri, 15 Dec 2023 14:14:54 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 63C54A07E0; Fri, 15 Dec 2023 15:14:45 +0100 (CET) Date: Fri, 15 Dec 2023 15:14:45 +0100 From: Jan Kara To: Christoph Hellwig Cc: linux-mm@kvack.org, "Matthew Wilcox (Oracle)" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jan Kara , David Howells Subject: Re: [PATCH 02/11] writeback: Factor writeback_get_batch() out of write_cache_pages() Message-ID: <20231215141445.rnt34v6emxulezde@quack3> References: <20231214132544.376574-1-hch@lst.de> <20231214132544.376574-3-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231214132544.376574-3-hch@lst.de> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 60CF310000A X-Stat-Signature: a535k86iess8h4uf5ughwk4gkbabcydj X-Rspam-User: X-HE-Tag: 1702649696-242162 X-HE-Meta: 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 0mNR6jte jNF45h51IGK24Yey1tbanL8gZngxdMy58yMqKQQgO5GAgZyqGRi8Ik0BIoqM3d6wubnZdQnEEMHGmq+ozfB+6Szf9IiAjBUlWL9HlP8EcVZ4ffJEAEeZ4836omtdLyZG4JumwXZLB5K3lxbiPVsC7H4vvaOQ71fJxCQWZPd1wXU6g5Mocit6iA6GHJvPEi+ZCcv7tqkck5t/310rfsFDANUybFFmyehSssg7DHQ75fzFpYMGuw2XuGJvwJpdgwZ1+sLRC+fsM0MaeoyDTBp8LCPa/GxmDRVHEmfr+sgyJZhM4E+t0clewpx8xmWZ5V3a8mzDqZB2QLJyBU56wFXZ0J81Nf6zEMy7sgKgt7krQI4Mdl0I7lXkyA/E0X7BzKQIvbSWV 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: List-Subscribe: List-Unsubscribe: On Thu 14-12-23 14:25:35, Christoph Hellwig wrote: > From: "Matthew Wilcox (Oracle)" > > This simple helper will be the basis of the writeback iterator. > To make this work, we need to remember the current index > and end positions in writeback_control. > > Signed-off-by: Matthew Wilcox (Oracle) > Signed-off-by: Christoph Hellwig Just some nits: > --- a/include/linux/writeback.h > +++ b/include/linux/writeback.h > @@ -81,6 +81,8 @@ struct writeback_control { > > /* internal fields used by the ->writepages implementation: */ > struct folio_batch fbatch; > + pgoff_t index; > + pgoff_t end; /* inclusive */ > pgoff_t done_index; I don't think we need to cache 'end' since it isn't used that much. In writeback_get_batch() we can just compute it locally as: if (wbc->range_cyclic) end = -1; else end = wbc->range_end >> PAGE_SHIFT; and in the termination condition of the loop we can have it like: while (wbc->range_cyclic || index <= wbc->range_end >> PAGE_SHIFT) Also I don't think we need both done_index and index since they are closely related and when spread over several functions it gets a bit confusing what's for what. So I'd just remove done_index, use index instead for setting writeback_index and just reset 'index' to the desired value in those two cases where we break out of the loop early and thus index != done_index. I'm sorry for nitpicking about these state variables but IMO reducing their amount actually makes things easier to verify (and thus maintain) when they are spread over several functions. Honza -- Jan Kara SUSE Labs, CR