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lib/radix-tree.c: swapoff tmpfs radix_tree: remember to rcu_read_unlock 

Running fsx on tmpfs with concurrent memhog-swapoff-swapon, lots of

  BUG: sleeping function called from invalid context at kernel/fork.c:606
  in_atomic(): 0, irqs_disabled(): 0, pid: 1394, name: swapoff
  1 lock held by swapoff/1394:
   #0:  (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6

followed by

  ================================================
  [ BUG: lock held when returning to user space! ]
  3.14.0-rc1 #3 Not tainted
  ------------------------------------------------
  swapoff/1394 is leaving the kernel with locks still held!
  1 lock held by swapoff/1394:
   #0:  (rcu_read_lock){.+.+.+}, at: [<ffffffff812520a1>] radix_tree_locate_item+0x1f/0x2b6

after which the system recovered nicely.

Whoops, I long ago forgot the rcu_read_unlock() on one unlikely branch.

Fixes e504f3fdd6 ("tmpfs radix_tree: locate_item to speed up swapoff")

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2014-03-03 15:38:23 -08:00 committed by Linus Torvalds
parent 3b7a6418c7
commit 5f30fc94ca
1 changed files with 3 additions and 1 deletions
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4
lib/radix-tree.c
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@ -1253,8 +1253,10 @@ unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
node = indirect_to_ptr(node); node = indirect_to_ptr(node);
max_index = radix_tree_maxindex(node->height); max_index = radix_tree_maxindex(node->height);
if (cur_index > max_index) if (cur_index > max_index) {
rcu_read_unlock();
break; break;
}
cur_index = __locate(node, item, cur_index, &found_index); cur_index = __locate(node, item, cur_index, &found_index);
rcu_read_unlock(); rcu_read_unlock();