Hello, I'm writing a filesystem module (OBDFS - www.lustre.org) which is
trying to use a slab cache. It allocates the cache at module initialization
time using kmem_cache_create(), and tries to free it when the module is
unloaded. I have tried both kmem_cache_destroy() and kmem_cache_shrink(),
and both cause an OOPS when /proc/slabinfo is catted.
Since the module has absolutely no in-kernel memory (it interfaces only with
the VFS, and does not need a kernel patch), it is not possible for the
slab cache to keep a static cache pointer to the cache (as is indicated by
the comment before kmem_cache_shrink()). However, even kmem_cache_destroy()
seems to have a problem with the cache list - I suspect that this is because
even the "name" string for the cache is in the module memory space, and it
is not available when the module is unloaded, hence the OOPS in sprintf.
Jan 10 14:38:45 webber kernel: c01ced75
Jan 10 14:38:45 webber kernel: Oops: 0000
Jan 10 14:38:45 webber kernel: CPU: 1
Jan 10 14:38:45 webber kernel: EIP: 0010:[vsprintf+425/844]
Jan 10 14:38:45 webber kernel: EFLAGS: 00010297
Jan 10 14:38:45 webber kernel: eax: c8840f06 ebx: ffffffff ecx: c8840f06 edx: fffffffe
Jan 10 14:38:45 webber kernel: esi: c54d7038 edi: c5621f18 ebp: 00000011 esp: c5621ee4
Jan 10 14:38:45 webber kernel: ds: 0018 es: 0018 ss: 0018
Jan 10 14:38:45 webber kernel: Process cat (pid: 353, stackpage=c5621000)
Jan 10 14:38:45 webber kernel: Stack: c1265c20 00000000 00000010 00000010 0000000a c01cef2c c54d7038 c01e14ea
Jan 10 14:38:45 webber kernel: c5621f14 c0132b04 c54d7038 c01e14e6 c8840f 06 00000000 00000000 00000c00
Jan 10 14:38:45 webber kernel: 00000000 c54d7000 c54d7000 c025ca00 c54d7038 00000038 00000286 00000000
Jan 10 14:38:45 webber kernel: Call Trace: [sprintf+20/3812] [tvecs+8766/28276] [get_slabinfo+336/444] [tvecs+8762/28276] [<c8840f06>] [slabinfo_read_proc+21/72] [proc_file_read+284/532]
Jan 10 14:38:45 webber kernel: [sys_read+269/308] [system_call+52/56]
Jan 10 14:38:45 webber kernel: Code: 80 38 00 74 07 40 4a 83 fa ff 75 f4 29 c8 8b 54 24 14 89 c3
--
Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
\ would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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