cfq-iosched: fix an oops caused by slab leak

I got below oops when unloading cfq-iosched. Considering scenario:
queue A merge to B, C merge to D and B will be merged to D. Before B is merged
to D, we do split B. We should put B's reference for D.

[  807.768536] =============================================================================
[  807.768539] BUG cfq_queue: Objects remaining on kmem_cache_close()
[  807.768541] -----------------------------------------------------------------------------
[  807.768543]
[  807.768546] INFO: Slab 0xffffea0003e6b4e0 objects=26 used=1 fp=0xffff88011d584fd8 flags=0x200000000004082
[  807.768550] Pid: 5946, comm: rmmod Tainted: G        W   2.6.34-07097-gf4b87de-dirty #724
[  807.768552] Call Trace:
[  807.768560]  [<ffffffff81104e8d>] slab_err+0x8f/0x9d
[  807.768564]  [<ffffffff811059e1>] ? flush_cpu_slab+0x0/0x93
[  807.768569]  [<ffffffff8164be52>] ? add_preempt_count+0xe/0xca
[  807.768572]  [<ffffffff8164bd9c>] ? sub_preempt_count+0xe/0xb6
[  807.768577]  [<ffffffff81648871>] ? _raw_spin_unlock+0x15/0x30
[  807.768580]  [<ffffffff8164bd9c>] ? sub_preempt_count+0xe/0xb6
[  807.768584]  [<ffffffff811061bc>] list_slab_objects+0x9b/0x19f
[  807.768588]  [<ffffffff8164bf0a>] ? add_preempt_count+0xc6/0xca
[  807.768591]  [<ffffffff81109e27>] kmem_cache_destroy+0x13f/0x21d
[  807.768597]  [<ffffffffa000ff13>] cfq_slab_kill+0x1a/0x43 [cfq_iosched]
[  807.768601]  [<ffffffffa000ffcf>] cfq_exit+0x93/0x9e [cfq_iosched]
[  807.768606]  [<ffffffff810973a2>] sys_delete_module+0x1b1/0x219
[  807.768612]  [<ffffffff8102fb5b>] system_call_fastpath+0x16/0x1b
[  807.768618] INFO: Object 0xffff88011d584618 @offset=1560
[  807.768622] INFO: Allocated in cfq_get_queue+0x11e/0x274 [cfq_iosched] age=7173 cpu=1 pid=5496
[  807.768626] =============================================================================

Cc: stable@kernel.org
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index c72e5ac..5ff4f48 100644 (file)
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2560,15 +2560,10 @@ static void cfq_free_io_context(struct io_context *ioc)
        __call_for_each_cic(ioc, cic_free_func);
 }
 
-static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static void cfq_put_cooperator(struct cfq_queue *cfqq)
 {
        struct cfq_queue *__cfqq, *next;
 
-       if (unlikely(cfqq == cfqd->active_queue)) {
-               __cfq_slice_expired(cfqd, cfqq, 0);
-               cfq_schedule_dispatch(cfqd);
-       }
-
        /*
         * If this queue was scheduled to merge with another queue, be
         * sure to drop the reference taken on that queue (and others in
@@ -2584,6 +2579,16 @@ static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
                cfq_put_queue(__cfqq);
                __cfqq = next;
        }
+}
+
+static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+       if (unlikely(cfqq == cfqd->active_queue)) {
+               __cfq_slice_expired(cfqd, cfqq, 0);
+               cfq_schedule_dispatch(cfqd);
+       }
+
+       cfq_put_cooperator(cfqq);
 
        cfq_put_queue(cfqq);
 }
@@ -3536,6 +3541,9 @@ split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
        }
 
        cic_set_cfqq(cic, NULL, 1);
+
+       cfq_put_cooperator(cfqq);
+
        cfq_put_queue(cfqq);
        return NULL;
 }