Jens Axboe 430c62fb29 elevator: fix oops on early call to elevator_change() ... 2.6.36 introduces an API for drivers to switch the IO scheduler instead of manually calling the elevator exit and init functions. This API was added since q->elevator must be cleared in between those two calls. And since we already have this functionality directly from use by the sysfs interface to switch schedulers online, it was prudent to reuse it internally too. But this API needs the queue to be in a fully initialized state before it is called, or it will attempt to unregister elevator kobjects before they have been added. This results in an oops like this: BUG: unable to handle kernel NULL pointer dereference at 0000000000000051 IP: [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0 PGD 47ddfc067 PUD 47c6a1067 PMD 0 Oops: 0000 [#1] PREEMPT SMP last sysfs file: /sys/devices/pci0000:00/0000:00:02.0/0000:04:00.1/irq CPU 2 Modules linked in: t(+) loop hid_apple usbhid ahci ehci_hcd uhci_hcd libahci usbcore nls_base igb Pid: 7319, comm: modprobe Not tainted 2.6.36-rc6+ #132 QSSC-S4R/QSSC-S4R RIP: 0010:[<ffffffff8116f15e>] [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0 RSP: 0018:ffff88027da25d08 EFLAGS: 00010246 RAX: ffff88047c68c528 RBX: 00000000fffffffe RCX: 0000000000000000 RDX: 000000000000002f RSI: 000000000000002f RDI: ffff88047e196c88 RBP: ffff88027da25d38 R08: 0000000000000000 R09: d84156c5635688c0 R10: d84156c5635688c0 R11: 0000000000000000 R12: ffff88047e196c88 R13: 0000000000000000 R14: 0000000000000000 R15: ffff88047c68c528 FS: 00007fcb0b26f6e0(0000) GS:ffff880287400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000051 CR3: 000000047e76e000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process modprobe (pid: 7319, threadinfo ffff88027da24000, task ffff88027d377090) Stack: ffff88027da25d58 ffff88047c68c528 00000000fffffffe ffff88047e196c88 <0> ffff88047c68c528 ffff88047e05bd90 ffff88027da25d78 ffffffff8123fb77 <0> ffff88047e05bd90 0000000000000000 ffff88047e196c88 ffff88047c68c528 Call Trace: [<ffffffff8123fb77>] kobject_add_internal+0xe7/0x1f0 [<ffffffff8123fd98>] kobject_add_varg+0x38/0x60 [<ffffffff8123feb9>] kobject_add+0x69/0x90 [<ffffffff8116efe0>] ? sysfs_remove_dir+0x20/0xa0 [<ffffffff8103d48d>] ? sub_preempt_count+0x9d/0xe0 [<ffffffff8143de20>] ? _raw_spin_unlock+0x30/0x50 [<ffffffff8116efe0>] ? sysfs_remove_dir+0x20/0xa0 [<ffffffff8116eff4>] ? sysfs_remove_dir+0x34/0xa0 [<ffffffff81224204>] elv_register_queue+0x34/0xa0 [<ffffffff81224aad>] elevator_change+0xfd/0x250 [<ffffffffa007e000>] ? t_init+0x0/0x361 [t] [<ffffffffa007e000>] ? t_init+0x0/0x361 [t] [<ffffffffa007e0a8>] t_init+0xa8/0x361 [t] [<ffffffff810001de>] do_one_initcall+0x3e/0x170 [<ffffffff8108c3fd>] sys_init_module+0xbd/0x220 [<ffffffff81002f2b>] system_call_fastpath+0x16/0x1b Code: e5 41 56 41 55 41 54 49 89 fc 53 48 83 ec 10 48 85 ff 74 52 48 8b 47 18 49 c7 c5 00 46 61 81 48 85 c0 74 04 4c 8b 68 30 45 31 f6 <41> 80 7d 51 00 74 0e 49 8b 44 24 28 4c 89 e7 ff 50 20 49 89 c6 RIP [<ffffffff8116f15e>] sysfs_create_dir+0x2e/0xc0 RSP <ffff88027da25d08> CR2: 0000000000000051 ---[ end trace a6541d3bf07945df ]--- Fix this by adding a registered bit to the elevator queue, which is set when the sysfs kobjects have been registered. Signed-off-by: Jens Axboe <jaxboe@fusionio.com>		2010-10-07 09:35:16 +02:00
..
blk-barrier.c	block: set up rq->rq_disk properly for flush requests	2010-08-07 18:52:41 +02:00
blk-cgroup.c	blkio: Fix return code for mkdir calls	2010-08-23 10:56:30 +02:00
blk-cgroup.h	blk-cgroup: config options re-arrangement	2010-04-26 19:27:56 +02:00
blk-core.c	BLOCK: fix bio.bi_rw handling	2010-08-23 12:33:10 +02:00
blk-exec.c	block: remove wrappers for request type/flags	2010-08-07 18:17:56 +02:00
blk-integrity.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
blk-ioc.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
blk-iopoll.c	tree-wide: fix assorted typos all over the place	2009-12-04 15:39:55 +01:00
blk-lib.c	block: add secure discard	2010-08-12 08:43:30 -07:00
blk-map.c	block: fix blk_rq_map_kern bio direction flag	2010-09-21 11:49:17 +02:00
blk-merge.c	block: prevent merges of discard and write requests	2010-09-25 12:42:55 +02:00
blk-settings.c	block: implement an unprep function corresponding directly to prep	2010-08-07 18:23:47 +02:00
blk-softirq.c	generic-ipi: remove CSD_FLAG_WAIT	2009-02-25 14:13:44 +01:00
blk-sysfs.c	block: put dev->kobj in blk_register_queue fail path	2010-08-23 12:30:29 +02:00
blk-tag.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
blk-timeout.c	block: ensure jiffies wrap is handled correctly in blk_rq_timed_out_timer	2010-04-21 17:42:08 +02:00
blk.h	block: Range check cpu in blk_cpu_to_group	2010-09-10 09:03:21 +02:00
bsg.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
cfq-iosched.c	cfq-iosched: fix a kernel OOPs when usb key is inserted	2010-09-21 11:49:17 +02:00
cfq.h	cfq: fix recursive call in cfq_blkiocg_update_completion_stats()	2010-06-21 09:10:55 +02:00
compat_ioctl.c	block: add secure discard	2010-08-12 08:43:30 -07:00
deadline-iosched.c	block: convert to pos and nr_sectors accessors	2009-05-11 09:50:54 +02:00
elevator.c	elevator: fix oops on early call to elevator_change()	2010-10-07 09:35:16 +02:00
genhd.c	block: remove all rcu head initializations	2010-05-21 20:01:02 +02:00
ioctl.c	block: add secure discard	2010-08-12 08:43:30 -07:00
Kconfig	blk-cgroup: config options re-arrangement	2010-04-26 19:27:56 +02:00
Kconfig.iosched	blk-cgroup: config options re-arrangement	2010-04-26 19:27:56 +02:00
Makefile	blkdev: move blkdev_issue helper functions to separate file	2010-04-28 19:47:36 +02:00
noop-iosched.c	include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h	2010-03-30 22:02:32 +09:00
scsi_ioctl.c	block/scsi_ioctl.c: quiet sparse noise	2009-11-04 09:10:33 +01:00