Il giorno gio, 12/12/2019 alle 05.33 +0800, Ming Lei ha scritto: > On Wed, Dec 11, 2019 at 11:07:45AM -0500, Theodore Y. Ts'o wrote: > > On Wed, Dec 11, 2019 at 12:00:58PM +0800, Ming Lei wrote: > > > I didn't reproduce the issue in my test environment, and follows > > > Andrea's test commands[1]: > > > > > > mount UUID=$uuid /mnt/pendrive 2>&1 |tee -a $logfile > > > SECONDS=0 > > > cp $testfile /mnt/pendrive 2>&1 |tee -a $logfile > > > umount /mnt/pendrive 2>&1 |tee -a $logfile > > > > > > The 'cp' command supposes to open/close the file just once, > however > > > ext4_release_file() & write pages is observed to run for 4358 > times > > > when executing the above 'cp' test. > > > > Why are we sure the ext4_release_file() / _fput() is coming from > the > > cp command, as opposed to something else that might be running on > the > > system under test? _fput() is called by the kernel when the last > > Please see the log: > > https://lore.kernel.org/linux-scsi/3af3666920e7d46f8f0c6d88612f143ffabc743c.camel@xxxxxxxx/2-log_ming.zip > > Which is collected by: > > #!/bin/sh > MAJ=$1 > MIN=$2 > MAJ=$(( $MAJ << 20 )) > DEV=$(( $MAJ | $MIN )) > > /usr/share/bcc/tools/trace -t -C \ > 't:block:block_rq_issue (args->dev == '$DEV') "%s %d %d", args- > >rwbs, args->sector, args->nr_sector' \ > 't:block:block_rq_insert (args->dev == '$DEV') "%s %d %d", args- > >rwbs, args->sector, args->nr_sector' > > $MAJ:$MIN points to the USB storage disk. > > From the above IO trace, there are two write paths, one is from cp, > another is from writeback wq. > > The stackcount trace[1] is consistent with the IO trace log since it > only shows two IO paths, that is why I concluded that the write done > via > ext4_release_file() is from 'cp'. > > [1] > https://lore.kernel.org/linux-scsi/320b315b9c87543d4fb919ecbdf841596c8fbcea.camel@xxxxxxxx/2-log_ming_20191129_150609.zip > > > reference to a struct file is released. (Specifically, if you > have a > > fd which is dup'ed, it's only when the last fd corresponding to > the > > struct file is closed, and the struct file is about to be > released, > > does the file system's f_ops->release function get called.) > > > > So the first question I'd ask is whether there is anything else > going > > on the system, and whether the writes are happening to the USB > thumb > > drive, or to some other storage device. And if there is something > > else which is writing to the pendrive, maybe that's why no one > else > > has been able to reproduce the OP's complaint.... > > OK, we can ask Andrea to confirm that via the following trace, which > will add pid/comm info in the stack trace: > > /usr/share/bcc/tools/stackcount blk_mq_sched_request_inserted > > Andrea, could you collect the above log again when running new/bad > kernel for confirming if the write done by ext4_release_file() is > from > the 'cp' process? Yes, I will try to do it as soon as possible and let you know. I will also try xfs or btrfs, as you suggested in another message. Thanks, and bye Andrea
