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authorTejun Heo <tj@kernel.org>2015-09-29 12:47:50 -0400
committerJens Axboe <axboe@fb.com>2015-10-12 10:31:09 -0600
commit9ad18ab938375502c03cf467abecbb77264c9475 (patch)
tree206aee6499b2e56d42de486ec4495e282ca27b61 /mm/page-writeback.c
parentdcc909d90ccdbb73226397ff6d298f7af35b0e11 (diff)
writeback: laptop_mode_timer_fn() needs rcu_read_lock() around bdi_writeback iteration
laptop_mode_timer_fn() was using bdi_for_each_wb() without the required RCU locking leading to the following warning. WARNING: CPU: 0 PID: 0 at include/linux/backing-dev.h:415 laptop_mode_timer_fn+0x106/0x170() ... Call Trace: <IRQ> [<ffffffff81480cdc>] dump_stack+0x4e/0x82 [<ffffffff81051912>] warn_slowpath_common+0x82/0xc0 [<ffffffff81051a0a>] warn_slowpath_null+0x1a/0x20 [<ffffffff8115f0e6>] laptop_mode_timer_fn+0x106/0x170 [<ffffffff810ca8e3>] call_timer_fn+0xb3/0x2f0 [<ffffffff810cad25>] run_timer_softirq+0x205/0x370 [<ffffffff81056854>] __do_softirq+0xd4/0x460 [<ffffffff81056d69>] irq_exit+0x89/0xa0 [<ffffffff8185a892>] smp_apic_timer_interrupt+0x42/0x50 [<ffffffff81858a44>] apic_timer_interrupt+0x84/0x90 ... Fix it by adding rcu_read_lock() around the iteration. Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: a06fd6b10228 ("writeback: make laptop_mode_timer_fn() handle multiple bdi_writeback's") Reviewed-by: Jan Kara <jack@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'mm/page-writeback.c')
-rw-r--r--mm/page-writeback.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0a931cdd4f6b..902e5f215e57 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1965,10 +1965,12 @@ void laptop_mode_timer_fn(unsigned long data)
if (!bdi_has_dirty_io(&q->backing_dev_info))
return;
+ rcu_read_lock();
bdi_for_each_wb(wb, &q->backing_dev_info, &iter, 0)
if (wb_has_dirty_io(wb))
wb_start_writeback(wb, nr_pages, true,
WB_REASON_LAPTOP_TIMER);
+ rcu_read_unlock();
}
/*