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Tue, 13 Feb 2024 13:07:18 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id SPX0AIZpy2UoWwAAn2gu4w (envelope-from ); Tue, 13 Feb 2024 13:07:18 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 930DBA0809; Tue, 13 Feb 2024 14:07:13 +0100 (CET) Date: Tue, 13 Feb 2024 14:07:13 +0100 From: Jan Kara To: Christoph Hellwig Cc: linux-mm@kvack.org, Matthew Wilcox , Jan Kara , David Howells , Brian Foster , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/14] writeback: don't call mapping_set_error in writepage_cb Message-ID: <20240213130713.ysuxaqcwizqwjke2@quack3> References: <20240212071348.1369918-1-hch@lst.de> <20240212071348.1369918-2-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240212071348.1369918-2-hch@lst.de> X-Rspamd-Queue-Id: DE23120005 X-Rspam-User: X-Stat-Signature: 5mchf8hmz1w7azua3rkzyoiadncomgc5 X-Rspamd-Server: rspam03 X-HE-Tag: 1707829641-112533 X-HE-Meta: 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 9RONVLNu XrRhDibYICXK9gMj27yA17bg1nrIqLOirTvXaFpId0DxdbN84SCRsPa5wqBnYMYhw6OUOlBzE75CAbcy4zk7wV2c8lDEAACiLGmxNRygsgA3ST71cIfRqBzXjkIZBFZ8BP1xT1+9cKVdURQXQNFNwsGrdC1DqSXkA7iippoiVit+GUsAIxsKleZjK1CMuf8wl2XqHp+75aleFHTWp2kCYOwLe75vVulpdlc7HrGrENmo8CLmAZdmjUhVqeLdODNv3uFW+F/fh0CA9Lg5QHi/TuWPQL4W9Pj9b1X8cqgazSXQBzEhE0usPofdCsDvzcNICAf0uFa/U9puqZ9OxQbupUg73cJJAZgQh199x 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 Mon 12-02-24 08:13:35, Christoph Hellwig wrote: > writepage_cb is the iterator callback for write_cache_pages, which > already tracks all errors and returns them to the caller. There is > no need to additionally cal mapping_set_error which is intended ^^^ call > for contexts where the error can't be directly returned (e.g. the > I/O completion handlers). > > Remove the mapping_set_error call in writepage_cb which is not only > superfluous but also buggy as it can be called with the error argument > set to AOP_WRITEPAGE_ACTIVATE, which is not actually an error but a > magic return value asking the caller to unlock the page. > > Signed-off-by: Christoph Hellwig Our error handling in writeback has always been ... spotty. E.g. block_write_full_page() and iomap_writepage_map() call mapping_set_error() as well so this seems to be a common way to do things, OTOH ext4 calls mapping_set_error() only on IO completion. I guess the question is how an error in ->writepages from background writeback should propagate to eventual fsync(2) caller? Because currently such error propagates all the way up to writeback_sb_inodes() where it is silently dropped... Honza > --- > mm/page-writeback.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 3f255534986a2f..62901fa905f01e 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -2534,9 +2534,8 @@ static int writepage_cb(struct folio *folio, struct writeback_control *wbc, > void *data) > { > struct address_space *mapping = data; > - int ret = mapping->a_ops->writepage(&folio->page, wbc); > - mapping_set_error(mapping, ret); > - return ret; > + > + return mapping->a_ops->writepage(&folio->page, wbc); > } > > int do_writepages(struct address_space *mapping, struct writeback_control *wbc) > -- > 2.39.2 > -- Jan Kara SUSE Labs, CR