releases/3.18.3/blk-mq-fix-uninitialized-kobject-at-cpu-hotplugging.patch

   1 From 06a41a99d13d8e919e9a00a4849e6b85ae492592 Mon Sep 17 00:00:00 2001
   2 From: Takashi Iwai <tiwai@suse.de>
   3 Date: Wed, 10 Dec 2014 16:38:30 +0100
   4 Subject: blk-mq: Fix uninitialized kobject at CPU hotplugging
   5
   6 From: Takashi Iwai <tiwai@suse.de>
   7
   8 commit 06a41a99d13d8e919e9a00a4849e6b85ae492592 upstream.
   9
  10 When a CPU is hotplugged, the current blk-mq spews a warning like:
  11
  12   kobject '(null)' (ffffe8ffffc8b5d8): tried to add an uninitialized object, something is seriously wrong.
  13   CPU: 1 PID: 1386 Comm: systemd-udevd Not tainted 3.18.0-rc7-2.g088d59b-default #1
  14   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_171129-lamiak 04/01/2014
  15    0000000000000000 0000000000000002 ffffffff81605f07 ffffe8ffffc8b5d8
  16    ffffffff8132c7a0 ffff88023341d370 0000000000000020 ffff8800bb05bd58
  17    ffff8800bb05bd08 000000000000a0a0 000000003f441940 0000000000000007
  18   Call Trace:
  19    [<ffffffff81005306>] dump_trace+0x86/0x330
  20    [<ffffffff81005644>] show_stack_log_lvl+0x94/0x170
  21    [<ffffffff81006d21>] show_stack+0x21/0x50
  22    [<ffffffff81605f07>] dump_stack+0x41/0x51
  23    [<ffffffff8132c7a0>] kobject_add+0xa0/0xb0
  24    [<ffffffff8130aee1>] blk_mq_register_hctx+0x91/0xb0
  25    [<ffffffff8130b82e>] blk_mq_sysfs_register+0x3e/0x60
  26    [<ffffffff81309298>] blk_mq_queue_reinit_notify+0xf8/0x190
  27    [<ffffffff8107cfdc>] notifier_call_chain+0x4c/0x70
  28    [<ffffffff8105fd23>] cpu_notify+0x23/0x50
  29    [<ffffffff81060037>] _cpu_up+0x157/0x170
  30    [<ffffffff810600d9>] cpu_up+0x89/0xb0
  31    [<ffffffff815fa5b5>] cpu_subsys_online+0x35/0x80
  32    [<ffffffff814323cd>] device_online+0x5d/0xa0
  33    [<ffffffff81432485>] online_store+0x75/0x80
  34    [<ffffffff81236a5a>] kernfs_fop_write+0xda/0x150
  35    [<ffffffff811c5532>] vfs_write+0xb2/0x1f0
  36    [<ffffffff811c5f42>] SyS_write+0x42/0xb0
  37    [<ffffffff8160c4ed>] system_call_fastpath+0x16/0x1b
  38    [<00007f0132fb24e0>] 0x7f0132fb24e0
  39
  40 This is indeed because of an uninitialized kobject for blk_mq_ctx.
  41 The blk_mq_ctx kobjects are initialized in blk_mq_sysfs_init(), but it
  42 goes loop over hctx_for_each_ctx(), i.e. it initializes only for
  43 online CPUs.  Thus, when a CPU is hotplugged, the ctx for the newly
  44 onlined CPU is registered without initialization.
  45
  46 This patch fixes the issue by initializing the all ctx kobjects
  47 belonging to each queue.
  48
  49 Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=908794
  50 Signed-off-by: Takashi Iwai <tiwai@suse.de>
  51 Signed-off-by: Jens Axboe <axboe@fb.com>
  52 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  53
  54 ---
  55  block/blk-mq-sysfs.c |    9 ++++-----
  56  1 file changed, 4 insertions(+), 5 deletions(-)
  57
  58 --- a/block/blk-mq-sysfs.c
  59 +++ b/block/blk-mq-sysfs.c
  60 @@ -390,16 +390,15 @@ static void blk_mq_sysfs_init(struct req
  61  {
  62         struct blk_mq_hw_ctx *hctx;
  63         struct blk_mq_ctx *ctx;
  64 -       int i, j;
  65 +       int i;
  66
  67         kobject_init(&q->mq_kobj, &blk_mq_ktype);
  68
  69 -       queue_for_each_hw_ctx(q, hctx, i) {
  70 +       queue_for_each_hw_ctx(q, hctx, i)
  71                 kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
  72
  73 -               hctx_for_each_ctx(hctx, ctx, j)
  74 -                       kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
  75 -       }
  76 +       queue_for_each_ctx(q, ctx, i)
  77 +               kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
  78  }
  79
  80  /* see blk_register_queue() */