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charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 X-Rspamd-Queue-Id: 3296040020 X-Stat-Signature: eis7ptunrkbmo5ete1ft4mnjdkiih7io X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1682589707-420613 X-HE-Meta: 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 7tXakxFh AiAli68vQgo6JFClLrhjPJ9TV/O99Yw2TDrOGTZeZ6YQih3/vp/Q1rBBZe140O8T21m9bfPI+QGcJIVO4QdJxWa1kTjktidwpqGbXTgOcey+1vnjXyOfqidzfYe2+SsaHqLoKAY0KqkdpsH4Fvo9nmDP83GjzyNGCE2vBuLn8RnExBMng2cClbNyvVduqxXL3WGaYd9zto617pYNEbXhlUdGxOQ== 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 Thu, Apr 27, 2023 at 02:36:51PM +0800, Baokun Li wrote: > On 2023/4/27 12:50, Ming Lei wrote: > > Hello Matthew, > > > > On Thu, Apr 27, 2023 at 04:58:36AM +0100, Matthew Wilcox wrote: > > > On Thu, Apr 27, 2023 at 10:20:28AM +0800, Ming Lei wrote: > > > > Hello Guys, > > > > > > > > I got one report in which buffered write IO hangs in balance_dirty_pages, > > > > after one nvme block device is unplugged physically, then umount can't > > > > succeed. > > > That's a feature, not a bug ... the dd should continue indefinitely? > > Can you explain what the feature is? And not see such 'issue' or 'feature' > > on xfs. > > > > The device has been gone, so IMO it is reasonable to see FS buffered write IO > > failed. Actually dmesg has shown that 'EXT4-fs (nvme0n1): Remounting > > filesystem read-only'. Seems these things may confuse user. > > > The reason for this difference is that ext4 and xfs handle errors > differently. > > ext4 remounts the filesystem as read-only or even just continues, vfs_write > does not check for these. vfs_write may not find anything wrong, but ext4 remount could see that disk is gone, which might happen during or after remount, however. > > xfs shuts down the filesystem, so it returns a failure at > xfs_file_write_iter when it finds an error. > > > ``` ext4 > ksys_write >  vfs_write >   ext4_file_write_iter >    ext4_buffered_write_iter >     ext4_write_checks >      file_modified >       file_modified_flags >        __file_update_time >         inode_update_time >          generic_update_time >           __mark_inode_dirty >            ext4_dirty_inode ---> 2. void func, No propagating errors out >             __ext4_journal_start_sb >              ext4_journal_check_start ---> 1. Error found, remount-ro >     generic_perform_write ---> 3. No error sensed, continue >      balance_dirty_pages_ratelimited >       balance_dirty_pages_ratelimited_flags >        balance_dirty_pages >         // 4. Sleeping waiting for dirty pages to be freed >         __set_current_state(TASK_KILLABLE) >         io_schedule_timeout(pause); > ``` > > ``` xfs > ksys_write >  vfs_write >   xfs_file_write_iter >    if (xfs_is_shutdown(ip->i_mount)) >      return -EIO;    ---> dd fail > ``` Thanks for the info which is really helpful for me to understand the problem. > > > balance_dirty_pages() is sleeping in KILLABLE state, so kill -9 of > > > the dd process should succeed. > > Yeah, dd can be killed, however it may be any application(s), :-) > > > > Fortunately it won't cause trouble during reboot/power off, given > > userspace will be killed at that time. > > > > > > > > Thanks, > > Ming > > > Don't worry about that, we always set the current thread to TASK_KILLABLE > > while waiting in balance_dirty_pages(). I have another concern, if 'dd' isn't killed, dirty pages won't be cleaned, and these (big amount)memory becomes not usable, and typical scenario could be USB HDD unplugged. thanks, Ming