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Tue, 26 Nov 2024 08:47:45 +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 e2oTETGLRWeEeAAAD6G6ig (envelope-from ); Tue, 26 Nov 2024 08:47:45 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id E0897A08CA; Tue, 26 Nov 2024 09:47:44 +0100 (CET) Date: Tue, 26 Nov 2024 09:47:44 +0100 From: Jan Kara To: Ojaswin Mujoo Cc: linux-ext4@vger.kernel.org, Jan Kara , Ritesh Harjani , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Baokun Li , Disha Goel Subject: Re: [PATCH v2 1/2] quota: flush quota_release_work upon quota writeback Message-ID: <20241126084744.fjnl3mmgme2mqhh2@quack3> References: <20241121123855.645335-1-ojaswin@linux.ibm.com> <20241121123855.645335-2-ojaswin@linux.ibm.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20241121123855.645335-2-ojaswin@linux.ibm.com> X-Rspamd-Queue-Id: 50EB52115E X-Spam-Score: -2.51 X-Rspamd-Action: no action X-Spamd-Result: default: False [-2.51 / 50.00]; BAYES_HAM(-3.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_SEVEN(0.00)[8]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_CC(0.00)[vger.kernel.org,suse.com,gmail.com,huawei.com,linux.ibm.com]; DKIM_TRACE(0.00)[suse.cz:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.cz:dkim] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On Thu 21-11-24 18:08:54, Ojaswin Mujoo wrote: > One of the paths quota writeback is called from is: > > freeze_super() > sync_filesystem() > ext4_sync_fs() > dquot_writeback_dquots() > > Since we currently don't always flush the quota_release_work queue in > this path, we can end up with the following race: > > 1. dquot are added to releasing_dquots list during regular operations. > 2. FS Freeze starts, however, this does not flush the quota_release_work queue. > 3. Freeze completes. > 4. Kernel eventually tries to flush the workqueue while FS is frozen which > hits a WARN_ON since transaction gets started during frozen state: > > ext4_journal_check_start+0x28/0x110 [ext4] (unreliable) > __ext4_journal_start_sb+0x64/0x1c0 [ext4] > ext4_release_dquot+0x90/0x1d0 [ext4] > quota_release_workfn+0x43c/0x4d0 > > Which is the following line: > > WARN_ON(sb->s_writers.frozen == SB_FREEZE_COMPLETE); > > Which ultimately results in generic/390 failing due to dmesg > noise. This was detected on powerpc machine 15 cores. > > To avoid this, make sure to flush the workqueue during > dquot_writeback_dquots() so we dont have any pending workitems after > freeze. > > Reported-by: Disha Goel > Signed-off-by: Ojaswin Mujoo Thanks. Since this patch is independent, I've picked it up into my tree (will push it to Linus for rc2). Honza -- Jan Kara SUSE Labs, CR