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staging/lustre/clio: Solve a race in cl_lock_put

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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: Jinshan 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: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jinshan Xiong 2014-04-27 13:07:03 -04:00 committed by Greg Kroah-Hartman
parent 4de665c1b3
commit 8d67c821d9
1 changed files with 9 additions and 1 deletions
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10
drivers/staging/lustre/lustre/obdclass/cl_lock.c
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@ -533,6 +533,7 @@ static struct cl_lock *cl_lock_find(const struct lu_env *env,
spin_lock(&head->coh_lock_guard);
ghost = cl_lock_lookup(env, obj, io, need);
if (ghost == NULL) {
cl_lock_get_trust(lock);
list_add_tail(&lock->cll_linkage,
&head->coh_locks);
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));
if (lock->cll_state < CLS_FREEING) {
bool in_cache;
LASSERT(lock->cll_state != CLS_INTRANSIT);
cl_lock_state_set(env, lock, CLS_FREEING);
head = cl_object_header(lock->cll_descr.cld_obj);
spin_lock(&head->coh_lock_guard);
list_del_init(&lock->cll_linkage);
in_cache = !list_empty(&lock->cll_linkage);
if (in_cache)
list_del_init(&lock->cll_linkage);
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
* by cl_lock_lookup().