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Commit 8d67c821 authored by Jinshan Xiong's avatar Jinshan Xiong Committed by Greg Kroah-Hartman
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staging/lustre/clio: Solve a race in cl_lock_put 



It's not atomic to check the last reference and state of cl_lock
in cl_lock_put(). This can cause a problem that an using lock is
freed, if the process is preempted between atomic_dec_and_test()
and (lock->cll_state == CLS_FREEING).

This problem can be solved by holding a refcount by coh_locks. In
this case, it can be sure that if the lock refcount reaches zero,
nobody else can have any chance to use it again.

Signed-off-by: default avatarJinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/9881
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4558


Reviewed-by: default avatarBobi Jam <bobijam@gmail.com>
Reviewed-by: default avatarLai Siyao <lai.siyao@intel.com>
Signed-off-by: default avatarOleg Drokin <oleg.drokin@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 4de665c1

drivers/staging/lustre/lustre/obdclass/cl_lock.c

+9 −1
Original line number Original line Diff line number Diff line
@@ -533,6 +533,7 @@ static struct cl_lock *cl_lock_find(const struct lu_env *env, 
			spin_lock(&head->coh_lock_guard);

			spin_lock(&head->coh_lock_guard);

			ghost = cl_lock_lookup(env, obj, io, need);

			ghost = cl_lock_lookup(env, obj, io, need);

			if (ghost == NULL) {

			if (ghost == NULL) {

				cl_lock_get_trust(lock);

				list_add_tail(&lock->cll_linkage,

				list_add_tail(&lock->cll_linkage,

						  &head->coh_locks);

						  &head->coh_locks);

				spin_unlock(&head->coh_lock_guard);

				spin_unlock(&head->coh_lock_guard);
@@ -791,15 +792,22 @@ static void cl_lock_delete0(const struct lu_env *env, struct cl_lock *lock) 
	LINVRNT(cl_lock_invariant(env, lock));

	LINVRNT(cl_lock_invariant(env, lock));





	if (lock->cll_state < CLS_FREEING) {

	if (lock->cll_state < CLS_FREEING) {

		bool in_cache;



		LASSERT(lock->cll_state != CLS_INTRANSIT);

		LASSERT(lock->cll_state != CLS_INTRANSIT);

		cl_lock_state_set(env, lock, CLS_FREEING);

		cl_lock_state_set(env, lock, CLS_FREEING);





		head = cl_object_header(lock->cll_descr.cld_obj);

		head = cl_object_header(lock->cll_descr.cld_obj);





		spin_lock(&head->coh_lock_guard);

		spin_lock(&head->coh_lock_guard);

		in_cache = !list_empty(&lock->cll_linkage);

		if (in_cache)

			list_del_init(&lock->cll_linkage);

			list_del_init(&lock->cll_linkage);

		spin_unlock(&head->coh_lock_guard);

		spin_unlock(&head->coh_lock_guard);





		if (in_cache) /* coh_locks cache holds a refcount. */

			cl_lock_put(env, lock);



		/*

		/*

		 * From now on, no new references to this lock can be acquired

		 * From now on, no new references to this lock can be acquired

		 * by cl_lock_lookup().

		 * by cl_lock_lookup().