Commit-ID: 95b19f684c61ffc9b039e02c5d1113c2d8cd7105
Gitweb: http://git.kernel.org/tip/95b19f684c61ffc9b039e02c5d1113c2d8cd7105
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Fri, 21 Aug 2015 19:42:55 +0200
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 6 Oct 2015 11:25:26 -0700
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@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
kernel/locking/percpu-rwsem.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index e2621fb..9529a30 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -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 */
}
--
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