Re: [LTP] 56cbb429d9: ltp.fs_fill.fail
On Thu, Jul 25, 2019 at 07:04:28PM +0100, Al Viro wrote: > On Thu, Jul 25, 2019 at 09:32:13AM -0700, Linus Torvalds wrote: > > On Thu, Jul 25, 2019 at 6:26 AM Cyril Hrubis wrote: > > > > > > This looks like mkfs.vfat got EBUSY after the loop device was > > > succesfully umounted. > > > > Hmm. Smells like the RCU-delaying got triggered again. > > > > We have that "synchronize_rcu_expedited()" in namespace_unlock(), > > which is so that everything should be done by the time we return to > > user space. > > > > Al, maybe that RCU synchronization should be after the mntput()s? > > There are several interesting issues in there, but synchronize_rcu() > should be between zeroing ->mnt_ns and dropping the final refs. > I'm digging through that crap right now; at least one bug is dealt > with by #fixes, but there's more, unfortunately. No, it's not synchronize_rcu(). It's a bug dealt with in vfs.git #fixes, triggering the struct mount leak in mount_subtree(), which is used by btrfs. Immediately prior to vfat in their list... (oh, and AFAICS "more" in the above had been a mismerge in -next, so it might really be all there is to it) Folks, see if vfs.git #fixes solves that one.
Re: [LTP] 56cbb429d9: ltp.fs_fill.fail
On Thu, Jul 25, 2019 at 09:32:13AM -0700, Linus Torvalds wrote: > On Thu, Jul 25, 2019 at 6:26 AM Cyril Hrubis wrote: > > > > This looks like mkfs.vfat got EBUSY after the loop device was > > succesfully umounted. > > Hmm. Smells like the RCU-delaying got triggered again. > > We have that "synchronize_rcu_expedited()" in namespace_unlock(), > which is so that everything should be done by the time we return to > user space. > > Al, maybe that RCU synchronization should be after the mntput()s? There are several interesting issues in there, but synchronize_rcu() should be between zeroing ->mnt_ns and dropping the final refs. I'm digging through that crap right now; at least one bug is dealt with by #fixes, but there's more, unfortunately.
Re: [LTP] 56cbb429d9: ltp.fs_fill.fail
On Thu, Jul 25, 2019 at 6:26 AM Cyril Hrubis wrote: > > This looks like mkfs.vfat got EBUSY after the loop device was > succesfully umounted. Hmm. Smells like the RCU-delaying got triggered again. We have that "synchronize_rcu_expedited()" in namespace_unlock(), which is so that everything should be done by the time we return to user space. Al, maybe that RCU synchronization should be after the mntput()s? Linus
Re: [LTP] 56cbb429d9: ltp.fs_fill.fail
Hi! > tst_test.c:1161: INFO: Testing on vfat > tst_mkfs.c:90: INFO: Formatting /dev/loop0 with vfat opts='' extra opts='' > mkfs.vfat: unable to open /dev/loop0: Device or resource busy > tst_mkfs.c:101: BROK: mkfs.vfat:1: tst_test.c failed with 741 This looks like mkfs.vfat got EBUSY after the loop device was succesfully umounted. We do run the test in a loop for several filesystems and the loop generally does: next: mkfs mount test umount goto next; -- Cyril Hrubis chru...@suse.cz
