On Mon, 07 Feb 2011 15:14:40 +0200, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > On 02/05/2011 11:01 AM, Tao Ma wrote: > > From: Tao Ma <boyu.mt@xxxxxxxxxx> > > > > In fa0d7e3, we use rcu free inode instead of freeing the inode > > directly. It causes a problem when we rmmod immediately after > > we umount the volume[1]. > > > > So we need to call synchronize_rcu after we kill_sb so that > > the inode is freed before we do rmmod. The idea is inspired > > by Chris Mason[2]. I tested with ext4 by umount+rmmod and it > > doesn't show any error by now. > > > > 1. http://marc.info/?l=linux-fsdevel&m=129680863330185&w=2 > > 2. http://marc.info/?l=linux-fsdevel&m=129684698713709&w=2 > > > > Cc: Nick Piggin <npiggin@xxxxxxxxx> > > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: Chris Mason <chris.mason@xxxxxxxxxx> > > Cc: Boaz Harrosh <bharrosh@xxxxxxxxxxx> > > Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx> > > --- > > fs/super.c | 7 +++++++ > > 1 files changed, 7 insertions(+), 0 deletions(-) > > > > diff --git a/fs/super.c b/fs/super.c > > index 74e149e..315bce9 100644 > > --- a/fs/super.c > > +++ b/fs/super.c > > @@ -177,6 +177,13 @@ void deactivate_locked_super(struct super_block *s) > > struct file_system_type *fs = s->s_type; > > if (atomic_dec_and_test(&s->s_active)) { > > fs->kill_sb(s); > > + /* > > + * We need to synchronize rcu here so that > > + * the delayed rcu inode free can be executed > > + * before we put_super. > > + * https://bugzilla.kernel.org/show_bug.cgi?id=27652 > > + */ > > + synchronize_rcu(); > > put_filesystem(fs); > > put_super(s); > > } else { > > > Sorry for not testing sooner. > > The above does not work I still get the exact same crash!! > > Looking at the code for synchronize_rcu() it looks like it might not be > enough. It looks like all it does is a memory barrier. But we need > something that will actually pump these pending releases. > (I might be way off here) > > BTW after I get the Warning from the kmem_cache_destroy: > slab error in kmem_cache_destroy(): cache `exofs_inode_cache': Can't free all objects > Call Trace: > 754efe08: [<6007e9a6>] kmem_cache_destroy+0x82/0xca > 754efe38: [<7a9296ba>] exit_exofs+0x1a/0x1c [exofs] > 754efe48: [<60054c10>] sys_delete_module+0x1b9/0x217 > 754efee8: [<60014d60>] handle_syscall+0x58/0x70 > 754eff08: [<60024163>] userspace+0x2dd/0x38a > 754effc8: [<600126af>] fork_handler+0x62/0x69 > > > I also get a Kernel crash. I suspect it's when finally these > free_rcu come and the module (and kmem_cache) are no longer there. > > What to do? Nick? http://lwn.net/Articles/217484/ explains how to wait for rcu callback to finish -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
