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author | 2014-07-05 18:43:21 -0400 | |
---|---|---|
committer | 2014-07-12 17:55:10 +0200 | |
commit | 0b462c89e31f7eb6789713437eb551833ee16ff3 (patch) | |
tree | 109cff096fea8247823dc8f26203c38ca5bd590c /block | |
parent | drbd: fix regression 'out of mem, failed to invoke fence-peer helper' (diff) | |
download | linux-0b462c89e31f7eb6789713437eb551833ee16ff3.tar.gz linux-0b462c89e31f7eb6789713437eb551833ee16ff3.tar.bz2 linux-0b462c89e31f7eb6789713437eb551833ee16ff3.zip |
blkcg: don't call into policy draining if root_blkg is already gone
While a queue is being destroyed, all the blkgs are destroyed and its
->root_blkg pointer is set to NULL. If someone else starts to drain
while the queue is in this state, the following oops happens.
NULL pointer dereference at 0000000000000028
IP: [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
PGD e4a1067 PUD b773067 PMD 0
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in: cfq_iosched(-) [last unloaded: cfq_iosched]
CPU: 1 PID: 537 Comm: bash Not tainted 3.16.0-rc3-work+ #2
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
task: ffff88000e222250 ti: ffff88000efd4000 task.ti: ffff88000efd4000
RIP: 0010:[<ffffffff8144e944>] [<ffffffff8144e944>] blk_throtl_drain+0x84/0x230
RSP: 0018:ffff88000efd7bf0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff880015091450 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88000efd7c10 R08: 0000000000000000 R09: 0000000000000001
R10: ffff88000e222250 R11: 0000000000000000 R12: ffff880015091450
R13: ffff880015092e00 R14: ffff880015091d70 R15: ffff88001508fc28
FS: 00007f1332650740(0000) GS:ffff88001fa80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000028 CR3: 0000000009446000 CR4: 00000000000006e0
Stack:
ffffffff8144e8f6 ffff880015091450 0000000000000000 ffff880015091d80
ffff88000efd7c28 ffffffff8144ae2f ffff880015091450 ffff88000efd7c58
ffffffff81427641 ffff880015091450 ffffffff82401f00 ffff880015091450
Call Trace:
[<ffffffff8144ae2f>] blkcg_drain_queue+0x1f/0x60
[<ffffffff81427641>] __blk_drain_queue+0x71/0x180
[<ffffffff81429b3e>] blk_queue_bypass_start+0x6e/0xb0
[<ffffffff814498b8>] blkcg_deactivate_policy+0x38/0x120
[<ffffffff8144ec44>] blk_throtl_exit+0x34/0x50
[<ffffffff8144aea5>] blkcg_exit_queue+0x35/0x40
[<ffffffff8142d476>] blk_release_queue+0x26/0xd0
[<ffffffff81454968>] kobject_cleanup+0x38/0x70
[<ffffffff81454848>] kobject_put+0x28/0x60
[<ffffffff81427505>] blk_put_queue+0x15/0x20
[<ffffffff817d07bb>] scsi_device_dev_release_usercontext+0x16b/0x1c0
[<ffffffff810bc339>] execute_in_process_context+0x89/0xa0
[<ffffffff817d064c>] scsi_device_dev_release+0x1c/0x20
[<ffffffff817930e2>] device_release+0x32/0xa0
[<ffffffff81454968>] kobject_cleanup+0x38/0x70
[<ffffffff81454848>] kobject_put+0x28/0x60
[<ffffffff817934d7>] put_device+0x17/0x20
[<ffffffff817d11b9>] __scsi_remove_device+0xa9/0xe0
[<ffffffff817d121b>] scsi_remove_device+0x2b/0x40
[<ffffffff817d1257>] sdev_store_delete+0x27/0x30
[<ffffffff81792ca8>] dev_attr_store+0x18/0x30
[<ffffffff8126f75e>] sysfs_kf_write+0x3e/0x50
[<ffffffff8126ea87>] kernfs_fop_write+0xe7/0x170
[<ffffffff811f5e9f>] vfs_write+0xaf/0x1d0
[<ffffffff811f69bd>] SyS_write+0x4d/0xc0
[<ffffffff81d24692>] system_call_fastpath+0x16/0x1b
776687bce42b ("block, blk-mq: draining can't be skipped even if
bypass_depth was non-zero") made it easier to trigger this bug by
making blk_queue_bypass_start() drain even when it loses the first
bypass test to blk_cleanup_queue(); however, the bug has always been
there even before the commit as blk_queue_bypass_start() could race
against queue destruction, win the initial bypass test but perform the
actual draining after blk_cleanup_queue() already destroyed all blkgs.
Fix it by skippping calling into policy draining if all the blkgs are
already gone.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Shirish Pargaonkar <spargaonkar@suse.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Reported-by: Jet Chen <jet.chen@intel.com>
Cc: stable@vger.kernel.org
Tested-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r-- | block/blk-cgroup.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index b9f4cc494ece..28d227c5ca77 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -872,6 +872,13 @@ void blkcg_drain_queue(struct request_queue *q) { lockdep_assert_held(q->queue_lock); + /* + * @q could be exiting and already have destroyed all blkgs as + * indicated by NULL root_blkg. If so, don't confuse policies. + */ + if (!q->root_blkg) + return; + blk_throtl_drain(q); } |