[kernel/f21] Fix blk-mq crash on CPU hotplug (rhbz 1175261)

[Josh Boyer]

commit 303b0b72c0075f329312e1abd9107af2b63d8cf2
Author: Josh Boyer <jwboyer at fedoraproject.org>
Date:   Thu Dec 18 08:49:08 2014 -0500

    Fix blk-mq crash on CPU hotplug (rhbz 1175261)

 ...-uninitialized-kobject-at-CPU-hotplugging.patch |   79 ++++++++++++++++++++
 kernel.spec                                        |    9 ++
 2 files changed, 88 insertions(+), 0 deletions(-)
---
diff --git a/blk-mq-Fix-uninitialized-kobject-at-CPU-hotplugging.patch b/blk-mq-Fix-uninitialized-kobject-at-CPU-hotplugging.patch
new file mode 100644
index 0000000..af3ba39
--- /dev/null
+++ b/blk-mq-Fix-uninitialized-kobject-at-CPU-hotplugging.patch
@@ -0,0 +1,79 @@
+From: Takashi Iwai <tiwai at suse.de>
+Date: Wed, 10 Dec 2014 16:38:30 +0100
+Subject: [PATCH] blk-mq: Fix uninitialized kobject at CPU hotplugging
+
+When a CPU is hotplugged, the current blk-mq spews a warning like:
+
+  kobject '(null)' (ffffe8ffffc8b5d8): tried to add an uninitialized object, something is seriously wrong.
+  CPU: 1 PID: 1386 Comm: systemd-udevd Not tainted 3.18.0-rc7-2.g088d59b-default #1
+  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_171129-lamiak 04/01/2014
+   0000000000000000 0000000000000002 ffffffff81605f07 ffffe8ffffc8b5d8
+   ffffffff8132c7a0 ffff88023341d370 0000000000000020 ffff8800bb05bd58
+   ffff8800bb05bd08 000000000000a0a0 000000003f441940 0000000000000007
+  Call Trace:
+   [<ffffffff81005306>] dump_trace+0x86/0x330
+   [<ffffffff81005644>] show_stack_log_lvl+0x94/0x170
+   [<ffffffff81006d21>] show_stack+0x21/0x50
+   [<ffffffff81605f07>] dump_stack+0x41/0x51
+   [<ffffffff8132c7a0>] kobject_add+0xa0/0xb0
+   [<ffffffff8130aee1>] blk_mq_register_hctx+0x91/0xb0
+   [<ffffffff8130b82e>] blk_mq_sysfs_register+0x3e/0x60
+   [<ffffffff81309298>] blk_mq_queue_reinit_notify+0xf8/0x190
+   [<ffffffff8107cfdc>] notifier_call_chain+0x4c/0x70
+   [<ffffffff8105fd23>] cpu_notify+0x23/0x50
+   [<ffffffff81060037>] _cpu_up+0x157/0x170
+   [<ffffffff810600d9>] cpu_up+0x89/0xb0
+   [<ffffffff815fa5b5>] cpu_subsys_online+0x35/0x80
+   [<ffffffff814323cd>] device_online+0x5d/0xa0
+   [<ffffffff81432485>] online_store+0x75/0x80
+   [<ffffffff81236a5a>] kernfs_fop_write+0xda/0x150
+   [<ffffffff811c5532>] vfs_write+0xb2/0x1f0
+   [<ffffffff811c5f42>] SyS_write+0x42/0xb0
+   [<ffffffff8160c4ed>] system_call_fastpath+0x16/0x1b
+   [<00007f0132fb24e0>] 0x7f0132fb24e0
+
+This is indeed because of an uninitialized kobject for blk_mq_ctx.
+The blk_mq_ctx kobjects are initialized in blk_mq_sysfs_init(), but it
+goes loop over hctx_for_each_ctx(), i.e. it initializes only for
+online CPUs.  Thus, when a CPU is hotplugged, the ctx for the newly
+onlined CPU is registered without initialization.
+
+This patch fixes the issue by initializing the all ctx kobjects
+belonging to each queue.
+
+Bugzilla: https://bugzilla.novell.com/show_bug.cgi?id=908794
+Cc: <stable at vger.kernel.org>
+Signed-off-by: Takashi Iwai <tiwai at suse.de>
+Signed-off-by: Jens Axboe <axboe at fb.com>
+---
+ block/blk-mq-sysfs.c | 9 ++++-----
+ 1 file changed, 4 insertions(+), 5 deletions(-)
+
+diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
+index ed5217867555..e0fb3f4a628f 100644
+--- a/block/blk-mq-sysfs.c
++++ b/block/blk-mq-sysfs.c
+@@ -390,16 +390,15 @@ static void blk_mq_sysfs_init(struct request_queue *q)
+ {
+ 	struct blk_mq_hw_ctx *hctx;
+ 	struct blk_mq_ctx *ctx;
+-	int i, j;
++	int i;
+ 
+ 	kobject_init(&q->mq_kobj, &blk_mq_ktype);
+ 
+-	queue_for_each_hw_ctx(q, hctx, i) {
++	queue_for_each_hw_ctx(q, hctx, i)
+ 		kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
+ 
+-		hctx_for_each_ctx(hctx, ctx, j)
+-			kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
+-	}
++	queue_for_each_ctx(q, ctx, i)
++		kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
+ }
+ 
+ int blk_mq_register_disk(struct gendisk *disk)
+-- 
+2.1.0
+
diff --git a/kernel.spec b/kernel.spec
index 0fab762..830bac2 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -648,6 +648,9 @@ Patch26099: deal-with-deadlock-in-d_walk.patch
 #CVE-2014-XXXX rhbz 1175235 1175250
 Patch26102: isofs-Fix-infinite-looping-over-CE-entries.patch
 
+#rhbz 1175261
+Patch26103: blk-mq-Fix-uninitialized-kobject-at-CPU-hotplugging.patch
+
 # git clone ssh://git.fedorahosted.org/git/kernel-arm64.git, git diff master...devel
 Patch30000: kernel-arm64.patch
 
@@ -1405,6 +1408,9 @@ ApplyPatch deal-with-deadlock-in-d_walk.patch
 #CVE-2014-XXXX rhbz 1175235 1175250
 ApplyPatch isofs-Fix-infinite-looping-over-CE-entries.patch
 
+#rhbz 1175261
+ApplyPatch blk-mq-Fix-uninitialized-kobject-at-CPU-hotplugging.patch
+
 %if 0%{?aarch64patches}
 ApplyPatch kernel-arm64.patch
 %ifnarch aarch64 # this is stupid, but i want to notice before secondary koji does.
@@ -2279,6 +2285,9 @@ fi
 #                                    ||----w |
 #                                    ||     ||
 %changelog
+* Thu Dec 18 2014 Josh Boyer <jwboyer at fedoraproject.org>
+- Fix blk-mq crash on CPU hotplug (rhbz 1175261)
+
 * Wed Dec 17 2014 Josh Boyer <jwboyer at fedoraproject.org>
 - Enable USBIP in modules-extra from Johnathan Dieter (rhbz 1169478)
 - CVE-2014-XXXX isofs: infinite loop in CE record entries (rhbz 1175235 1175250)