Commit 95b19f68 authored Aug 21, 2015 by Oleg Nesterov Committed by Paul E. McKenney Oct 06, 2015

locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe



This is the temporary ugly hack which will be reverted later. We only
need it to ensure that the next patch will not break "change sb_writers
to use percpu_rw_semaphore" patches routed via the VFS tree.

The alloc_super()->destroy_super() error path assumes that it is safe
to call percpu_free_rwsem() after kzalloc() without percpu_init_rwsem(),
so let's not disappoint it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

parent 07899a6e

kernel/locking/percpu-rwsem.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,13 @@ EXPORT_SYMBOL_GPL(__percpu_init_rwsem);

		void percpu_free_rwsem(struct percpu_rw_semaphore *brw)
		{
		/*
		* XXX: temporary kludge. The error path in alloc_super()
		* assumes that percpu_free_rwsem() is safe after kzalloc().
		*/
		if (!brw->fast_read_ctr)
		return;

		free_percpu(brw->fast_read_ctr);
		brw->fast_read_ctr = NULL; /* catch use after free bugs */
		}