drm/sysfs lifetime interaction fixes

[Fengguang Wu]

> >[   97.260371] BUG: Bad page map in process killall5  pte:4f426de0 pmd:0f4f4067
> >[   97.261114] addr:3fc00000 vm_flags:00100173 anon_vma:4f4066c0 mapping:  (null) index:3ffe6
> >[   97.261912] CPU: 0 PID: 334 Comm: killall5 Not tainted 3.12.0-rc3-00156-gdaeb5e3 #1
> >[   97.262633] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> >[   97.263192]  3fc00000 4f4c1e14 4212e45c 4fbff9a0 4f4c1e4c 411a9c4b 4262ade0 3fc00000
> >[   97.264051]  00100173 4f4066c0 00000000 0003ffe6 4f426de0 0003ffe6 00000000 4fbff9a0
> >[   97.264906]  3fc00000 3fc00000 4f4c1e60 411ab50e 00000000 4f464000 00000000 4f4c1ed0
> >[   97.265751] Call Trace:
> >[   97.266022]  [<4212e45c>] dump_stack+0xbb/0x14b
> >[   97.266456]  [<411a9c4b>] print_bad_pte+0x28b/0x2c0
> >[   97.266931]  [<411ab50e>] vm_normal_page+0xae/0xe0
> >[   97.267388]  [<411b37f3>] munlock_vma_pages_range+0x143/0x320
> >[   97.267950]  [<410d30fd>] ? sched_clock_cpu+0x20d/0x250
> >[   97.268451]  [<411bacee>] exit_mmap+0x7e/0x200

> Yes, this should have been fixed by commit eadb41ae82f80210
> "mm/mlock.c: prevent walking off the end of a pagetable in no-pmd
> configuration", merged between rc3 and rc4.

Great, thanks! This explains why only v3.12-rc4 is free from the bug
in the below config.

/kernel/i386-randconfig-i003-1011/daeb5e37165e2ad745d1d2d5d7ab32ad9cb08f1a

+-------------------------------------------------+-----------+-----------+--------------+--------------+
|                                                 | v3.12-rc3 | v3.12-rc4 | 6aba5b6cf098 | daeb5e37165e |
+-------------------------------------------------+-----------+-----------+--------------+--------------+
| good_boots                                      | 1088      | 1092      | 1070         | 1043         |
| has_kernel_error_warning                        | 42        | 71        | 40           | 67           |
| BUG:kernel_early_hang_without_any_printk_output | 37        | 71        | 36           | 59           |
| BUG:Bad_page_map_in_process_killall5_pte:pmd    | 5         | 0         | 4            | 8            |
+-------------------------------------------------+-----------+-----------+--------------+--------------+

Thanks,
Fengguang