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authorVivek Goyal <vgoyal@redhat.com>2010-09-14 08:47:11 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-09-21 11:49:17 +0200
commit180be2a0420a0d680285e9352c0db85016b9ed2a (patch)
tree455f9f890a52bf728c4d8ab96f8773ff41347a5c /block
parenta45dc2d2b8d1afa57c91dcfac224e50ffcd3f805 (diff)
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cfq-iosched: fix a kernel OOPs when usb key is inserted
Mike reported a kernel crash when a usb key hotplug is performed while all kernel thrads are not in a root cgroup and are running in one of the child cgroups of blkio controller. BUG: unable to handle kernel NULL pointer dereference at 0000002c IP: [<c11c7b08>] cfq_get_queue+0x232/0x412 *pde = 00000000 Oops: 0000 [#1] PREEMPT last sysfs file: /sys/devices/pci0000:00/0000:00:1d.7/usb2/2-1/2-1:1.0/host3/scsi_host/host3/uevent [..] Pid: 30039, comm: scsi_scan_3 Not tainted 2.6.35.2-fg.roam #1 Volvi2 /Aspire 4315 EIP: 0060:[<c11c7b08>] EFLAGS: 00010086 CPU: 0 EIP is at cfq_get_queue+0x232/0x412 EAX: f705f9c0 EBX: e977abac ECX: 00000000 EDX: 00000000 ESI: f00da400 EDI: f00da4ec EBP: e977a800 ESP: dff8fd00 DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 Process scsi_scan_3 (pid: 30039, ti=dff8e000 task=f6b6c9a0 task.ti=dff8e000) Stack: 00000000 00000000 00000001 01ff0000 f00da508 00000000 f00da524 f00da540 <0> e7994940 dd631750 f705f9c0 e977a820 e977ac44 f00da4d0 00000001 f6b6c9a0 <0> 00000010 00008010 0000000b 00000000 00000001 e977a800 dd76fac0 00000246 Call Trace: [<c11c7f10>] ? cfq_set_request+0x228/0x34c [<c11c7ce8>] ? cfq_set_request+0x0/0x34c [<c11bb3b9>] ? elv_set_request+0xf/0x1c [<c11bdd51>] ? get_request+0x1ad/0x22f [<c11bddf2>] ? get_request_wait+0x1f/0x11a [<c11d013b>] ? kvasprintf+0x33/0x3b [<c127b537>] ? scsi_execute+0x1d/0x103 [<c127b675>] ? scsi_execute_req+0x58/0x83 [<c127c391>] ? scsi_probe_and_add_lun+0x188/0x7c2 [<c12718c6>] ? attribute_container_add_device+0x15/0xfa [<c11c95d1>] ? kobject_get+0xf/0x13 [<c126d1db>] ? get_device+0x10/0x14 [<c127be93>] ? scsi_alloc_target+0x217/0x24d [<c127cbd8>] ? __scsi_scan_target+0x95/0x480 [<c10204eb>] ? dequeue_entity+0x14/0x1fe [<c1020491>] ? update_curr+0x165/0x1ab [<c1020491>] ? update_curr+0x165/0x1ab [<c127d00d>] ? scsi_scan_channel+0x4a/0x76 [<c127d0b0>] ? scsi_scan_host_selected+0x77/0xad [<c127d13c>] ? do_scan_async+0x0/0x11a [<c127d137>] ? do_scsi_scan_host+0x51/0x56 [<c127d13c>] ? do_scan_async+0x0/0x11a [<c127d14a>] ? do_scan_async+0xe/0x11a [<c127d13c>] ? do_scan_async+0x0/0x11a [<c10354c5>] ? kthread+0x5e/0x63 [<c1035467>] ? kthread+0x0/0x63 [<c1002af6>] ? kernel_thread_helper+0x6/0x10 Code: 44 24 1c 54 83 44 24 18 54 83 fa 03 75 94 8b 06 c7 86 64 02 00 00 01 00 00 00 83 e0 03 09 f0 89 06 8b 44 24 28 8b 90 58 01 00 00 <8b> 42 2c 85 c0 75 03 8b 42 08 8d 54 24 48 52 8d 4c 24 50 51 68 EIP: [<c11c7b08>] cfq_get_queue+0x232/0x412 SS:ESP 0068:dff8fd00 CR2: 000000000000002c ---[ end trace 9a88306573f69b12 ]--- The problem here is that we don't have bdi->dev information available when thread does some IO. Hence when dev_name() tries to access bdi->dev, it crashes. This problem does not happen if kernel threads are in root group as root group is statically allocated at device initialization time and we don't hit this piece of code. Fix it by delaying the filling of major and minor number information of device in blk_group. Initially a blk_group is created with 0 as device information and this information is filled later once some more IO comes in from same group. Reported-by: Mike Kazantsev <mk.fraggod@gmail.com> Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-rw-r--r--block/cfq-iosched.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f65c6f01c47..9eba291eb6f 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1019,10 +1019,20 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
*/
atomic_set(&cfqg->ref, 1);
- /* Add group onto cgroup list */
- sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
- cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+ /*
+ * Add group onto cgroup list. It might happen that bdi->dev is
+ * not initiliazed yet. Initialize this new group without major
+ * and minor info and this info will be filled in once a new thread
+ * comes for IO. See code above.
+ */
+ if (bdi->dev) {
+ sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+ cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
MKDEV(major, minor));
+ } else
+ cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+ 0);
+
cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
/* Add group on cfqd list */