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? Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
