Hi Boaz,
On 02/08/2011 10:45 PM, Boaz Harrosh wrote:
On 02/04/2011 09:15 PM, Chris Mason wrote:
Excerpts from Tao Ma's message of 2011-02-04 03:36:59 -0500:
On 02/04/2011 02:51 AM, Boaz Harrosh wrote:
Last good Kernel was 2.6.37
I'm doing a "mount" then "unmount". I think root is the only created inode.
rmmod is called immediately after "unmount" within a script
if I only do unmount and manually call "modprobe --remove exofs" after a small while
all is fine.
I get:
slab error in kmem_cache_destroy(): cache `exofs_inode_cache': Can't free all objects
Call Trace:
77dfde08: [<6007e9a6>] kmem_cache_destroy+0x82/0xca
77dfde38: [<7c1fa3da>] exit_exofs+0x1a/0x1c [exofs]
77dfde48: [<60054c10>] sys_delete_module+0x1b9/0x217
77dfdee8: [<60014d60>] handle_syscall+0x58/0x70
77dfdf08: [<60024163>] userspace+0x2dd/0x38a
77dfdfc8: [<600126af>] fork_handler+0x62/0x69
I also get a similar error when testing ext4 and a bug is opened there.
https://bugzilla.kernel.org/show_bug.cgi?id=27652
And I have done some simple investigation for ext4 and It looks as if now with the new *fs_i_callback doesn't free the inode to *fs_inode_cache immediately. So the old logic will destroy the inode cache before we free all the inode object.
Since there are more than one fs affected by this, we may need to find a way in the VFS.
Sounds like we just need a synchronize_rcu call before we delete the
cache?
-chris
Hi Al, Nick.
Al please look into this issue. Absolutely all filesystems should be affected.
Tao Ma has attempted the below fix, but it does not help. Exact same trace
with his patch applied.
I am in vacation so I could't reach my test box today. I have done some
simple tracing yesterday, and it looked that although synchronize_rcu is
called, I can still get ext4_i_callback after it.
So the reason may be:
1. synchronize_rcu doesn't work as we expected.
2. the inode free rcu doesn't work as Nick expected.
I will go to the office tomorrow and do more test and debug there. Hope
to find something more.
If you unmount and immediately rmmod the filesystem it will crash because of
those RCU freed objects at umount, like the root inode. Nick is not responding,
I'd try to fix it, but I don't know how.
I raised the error to Nick on Jan. 19, about 3 weeks ago.
http://marc.info/?l=linux-ext4&m=129542001031750&w=2
But it seems that he is quite busy these days. It is still rc3 and we
have a lot of time before the final release. So no panic here. ;)
Finally, I just tried to fix it recently. But it doesn't work. :( I will
continue to work on it before Al or Nick respond with a perfect patch. :)
Regards,
Tao
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