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Fri, 9 Aug 2024 15:55:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id rZi+EuE7tmYrLAAAD6G6ig (envelope-from ); Fri, 09 Aug 2024 15:55:13 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id A55C4A084B; Fri, 9 Aug 2024 17:55:08 +0200 (CEST) Date: Fri, 9 Aug 2024 17:55:08 +0200 From: Jan Kara To: Stephen Zhang Cc: Jan Kara , tytso@mit.edu, jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, zhangshida@kylinos.cn, Baolin Liu Subject: Re: [RFC PATCH] jbd2: fix a potential assertion failure due to improperly dirtied buffer Message-ID: <20240809155508.taxgdkwuvsbg3i2k@quack3> References: <20240720062356.2522658-1-zhangshida@kylinos.cn> <20240806134023.rm2ggd7swopryqci@quack3> <20240807120659.y6cpxas5g3mze2rr@quack3> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Spam-Level: X-Spamd-Result: default: False [-3.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-0.998]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_TO(0.00)[gmail.com]; RCVD_VIA_SMTP_AUTH(0.00)[]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_SEVEN(0.00)[8]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_THREE(0.00)[3]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCVD_TLS_LAST(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.com:email] X-Spam-Flag: NO X-Spam-Score: -3.80 On Thu 08-08-24 11:05:26, Stephen Zhang wrote: > Jan Kara 于2024年8月7日周三 20:07写道： > > So I agree with your analysis now. But still don't like adding hacks to > > jbd2 to acommodate for this oddity of data=journal mode. Since we already > > have ext4_block_write_begin() implementation anyway, we should be able to > > tweak it to do the right thing for data=journal mode inodes... > > > > So we could replace uses of __block_write_begin() with > > ext4_block_write_begin() and then call do_journal_get_write_access() in > > ext4_block_write_begin() for inodes with journalled data after the buffer > > is mapped with get_block(). > > > > From the part: > > if (folio_test_uptodate(folio)) { > > clear_buffer_new(bh); > > set_buffer_uptodate(bh); > > mark_buffer_dirty(bh); > > continue; > > } > > > > we can actually remove the clear_buffer_new() and mark_buffer_dirty() bits > > because they will be done by block_commit_write() or > > folio_zero_new_buffers() and they are superfluous and somewhat odd here > > anyway. > > > > And the call to folio_zero_new_buffers() from ext4_block_write_begin() > > needs to call ext4_journalled_zero_new_buffers() for inodes where data is > > journalled. > > > > Will you try to implement this or should I look into it? > > > > Yeah, Thank you for giving me the opportunity to work on something truly > meaningful. All I can do until now is some small cleanups. And doing cleanups > all the time is annoyable to the maintainers and frustrating to me. I > will try my best. > > So basically, we should: > 1.Trace the user data dirting in ext4_block_write_begin(). > 2.Replace the uncontrollable __block_write_begin with ext4_block_write_begin(). > 3.Remove some superfluous things. Yes. In the first patch, I'd convert all uses of __block_write_begin() to ext4_block_write_begin(). In the second patch I'd replace folio_zero_new_buffers() with ext4_journalled_zero_new_buffers() if inode has journalled data (with explanation to avoid unexpected dirtying). In the third patch I'd remove the clear_buffer_new() and mark_buffer_dirty() mentioned above with explanation that either folio_zero_new_buffers() or block_commit_write() take care of dirtying the buffer properly. Thanks for working on this! Honza -- Jan Kara SUSE Labs, CR