Commit 166f66d0 authored Aug 06, 2015 by Zhaolei Committed by Chris Mason Aug 09, 2015

btrfs: Add WARN_ON() for double lock in btrfs_tree_lock()



When a task trying to double lock a extent buffer, there are no
lockdep warning about it because this lock may be in "blocking_lock"
state, and make us hard to debug.

This patch add a WARN_ON() for above condition, it can not report
all deadlock cases(as lock between tasks), but at least helps us
some.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 9ed0dea0

fs/btrfs/locking.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -241,6 +241,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
		*/
		void btrfs_tree_lock(struct extent_buffer *eb)
		{
		WARN_ON(eb->lock_owner == current->pid);
		again:
		wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
		wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);

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