[kernel] Add patch to prevent scheduling while atomic error in blkcg

[Josh Boyer]

commit 6c6f27531fdde64e62b1a94c261cdcea8ca22f72
Author: Josh Boyer <jwboyer at redhat.com>
Date:   Fri Apr 26 08:45:12 2013 -0400

    Add patch to prevent scheduling while atomic error in blkcg

 ...ng-while-atomic-in-blk_queue_bypass_start.patch |   79 ++++++++++++++++++++
 kernel.spec                                        |    7 ++
 2 files changed, 86 insertions(+), 0 deletions(-)
---
diff --git a/blkcg-fix-scheduling-while-atomic-in-blk_queue_bypass_start.patch b/blkcg-fix-scheduling-while-atomic-in-blk_queue_bypass_start.patch
new file mode 100644
index 0000000..615d755
--- /dev/null
+++ b/blkcg-fix-scheduling-while-atomic-in-blk_queue_bypass_start.patch
@@ -0,0 +1,79 @@
+From e5072664f8237cf53b0bd68a51aa1a7bc69061c5 Mon Sep 17 00:00:00 2001
+From: Jun'ichi Nomura <j-nomura at ce.jp.nec.com>
+Date: Tue, 09 Apr 2013 13:01:21 +0000
+Subject: blkcg: fix "scheduling while atomic" in blk_queue_bypass_start
+
+Since 749fefe677 in v3.7 ("block: lift the initial queue bypass mode
+on blk_register_queue() instead of blk_init_allocated_queue()"),
+the following warning appears when multipath is used with CONFIG_PREEMPT=y.
+
+This patch moves blk_queue_bypass_start() before radix_tree_preload()
+to avoid the sleeping call while preemption is disabled.
+
+  BUG: scheduling while atomic: multipath/2460/0x00000002
+  1 lock held by multipath/2460:
+   #0:  (&md->type_lock){......}, at: [<ffffffffa019fb05>] dm_lock_md_type+0x17/0x19 [dm_mod]
+  Modules linked in: ...
+  Pid: 2460, comm: multipath Tainted: G        W    3.7.0-rc2 #1
+  Call Trace:
+   [<ffffffff810723ae>] __schedule_bug+0x6a/0x78
+   [<ffffffff81428ba2>] __schedule+0xb4/0x5e0
+   [<ffffffff814291e6>] schedule+0x64/0x66
+   [<ffffffff8142773a>] schedule_timeout+0x39/0xf8
+   [<ffffffff8108ad5f>] ? put_lock_stats+0xe/0x29
+   [<ffffffff8108ae30>] ? lock_release_holdtime+0xb6/0xbb
+   [<ffffffff814289e3>] wait_for_common+0x9d/0xee
+   [<ffffffff8107526c>] ? try_to_wake_up+0x206/0x206
+   [<ffffffff810c0eb8>] ? kfree_call_rcu+0x1c/0x1c
+   [<ffffffff81428aec>] wait_for_completion+0x1d/0x1f
+   [<ffffffff810611f9>] wait_rcu_gp+0x5d/0x7a
+   [<ffffffff81061216>] ? wait_rcu_gp+0x7a/0x7a
+   [<ffffffff8106fb18>] ? complete+0x21/0x53
+   [<ffffffff810c0556>] synchronize_rcu+0x1e/0x20
+   [<ffffffff811dd903>] blk_queue_bypass_start+0x5d/0x62
+   [<ffffffff811ee109>] blkcg_activate_policy+0x73/0x270
+   [<ffffffff81130521>] ? kmem_cache_alloc_node_trace+0xc7/0x108
+   [<ffffffff811f04b3>] cfq_init_queue+0x80/0x28e
+   [<ffffffffa01a1600>] ? dm_blk_ioctl+0xa7/0xa7 [dm_mod]
+   [<ffffffff811d8c41>] elevator_init+0xe1/0x115
+   [<ffffffff811e229f>] ? blk_queue_make_request+0x54/0x59
+   [<ffffffff811dd743>] blk_init_allocated_queue+0x8c/0x9e
+   [<ffffffffa019ffcd>] dm_setup_md_queue+0x36/0xaa [dm_mod]
+   [<ffffffffa01a60e6>] table_load+0x1bd/0x2c8 [dm_mod]
+   [<ffffffffa01a7026>] ctl_ioctl+0x1d6/0x236 [dm_mod]
+   [<ffffffffa01a5f29>] ? table_clear+0xaa/0xaa [dm_mod]
+   [<ffffffffa01a7099>] dm_ctl_ioctl+0x13/0x17 [dm_mod]
+   [<ffffffff811479fc>] do_vfs_ioctl+0x3fb/0x441
+   [<ffffffff811b643c>] ? file_has_perm+0x8a/0x99
+   [<ffffffff81147aa0>] sys_ioctl+0x5e/0x82
+   [<ffffffff812010be>] ? trace_hardirqs_on_thunk+0x3a/0x3f
+   [<ffffffff814310d9>] system_call_fastpath+0x16/0x1b
+
+Signed-off-by: Jun'ichi Nomura <j-nomura at ce.jp.nec.com>
+Acked-by: Vivek Goyal <vgoyal at redhat.com>
+Acked-by: Tejun Heo <tj at kernel.org>
+Cc: Alasdair G Kergon <agk at redhat.com>
+Cc: stable at kernel.org
+Signed-off-by: Jens Axboe <axboe at kernel.dk>
+---
+(limited to 'block/blk-cgroup.c')
+
+diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
+index b2b9837..e8918ff 100644
+--- a/block/blk-cgroup.c
++++ b/block/blk-cgroup.c
+@@ -972,10 +972,10 @@ int blkcg_activate_policy(struct request_queue *q,
+ 	if (!new_blkg)
+ 		return -ENOMEM;
+ 
+-	preloaded = !radix_tree_preload(GFP_KERNEL);
+-
+ 	blk_queue_bypass_start(q);
+ 
++	preloaded = !radix_tree_preload(GFP_KERNEL);
++
+ 	/*
+ 	 * Make sure the root blkg exists and count the existing blkgs.  As
+ 	 * @q is bypassing at this point, blkg_lookup_create() can't be
+--
+cgit v0.9.1
diff --git a/kernel.spec b/kernel.spec
index 7ea5d79..84f186f 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -758,6 +758,8 @@ Patch25012: events-protect-access-via-task-subsys-state-check.patch
 #rhbz 953447
 Patch25013: efi-Check-EFI-revision-in-setup_efi_vars.patch
 
+Patch25014: blkcg-fix-scheduling-while-atomic-in-blk_queue_bypass_start.patch
+
 # END OF PATCH DEFINITIONS
 
 %endif
@@ -1465,6 +1467,8 @@ ApplyPatch events-protect-access-via-task-subsys-state-check.patch
 #rhbz 953447
 ApplyPatch efi-Check-EFI-revision-in-setup_efi_vars.patch
 
+ApplyPatch blkcg-fix-scheduling-while-atomic-in-blk_queue_bypass_start.patch
+
 # END OF PATCH APPLICATIONS
 
 %endif
@@ -2298,6 +2302,9 @@ fi
 #                 ||----w |
 #                 ||     ||
 %changelog
+* Fri Apr 26 2013 Josh Boyer <jwboyer at redhat.com>
+- Add patch to prevent scheduling while atomic error in blkcg
+
 * Wed Apr 24 2013 Josh Boyer <jwboyer at redhat.com>
 - Add patch to fix EFI boot on Macs (rhbz 953447)