On 2019/07/30 18:29, Jan Kara wrote: >> This patch introduced a regression [1]. >> A reproducer can be found at [2]. >> >> [1] https://bugs.launchpad.net/bugs/1836914 >> [2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1836914/comments/4 > > Thanks for the notice and the references. What's your version of > util-linux? What your test script does is indeed racy. You have there: > > echo Running: > for i in {a..z}{a..z}; do > mount $i.squash /mnt/$i & > done > > So all mount(8) commands will run in parallel and race to setup loop > devices with LOOP_SET_FD and mount them. However util-linux (at least in > the current version) seems to handle EBUSY from LOOP_SET_FD just fine and > retries with the new loop device. So at this point I don't see why the patch > makes difference... I guess I'll need to reproduce and see what's going on > in detail. Firstly, why not to check the return value of blkdev_get() ? EBUSY is not the only error code blkdev_get() might return. /* * If we don't hold exclusive handle for the device, upgrade to it * here to avoid changing device under exclusive owner. */ if (!(mode & FMODE_EXCL)) { bdgrab(bdev); error = blkdev_get(bdev, mode | FMODE_EXCL, loop_set_fd); - if (error) + if (error) { + printk("loop_set_fd: %d\n", error); goto out_putf; + } } And try finding which line is returning an error (like https://marc.info/?l=linux-xfs&m=156437221703110 does).
