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Commit 26bb7505 authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

GFS2: Fix glock refcount issues 



This patch fixes some ref counting issues. Firstly by moving
the point at which we drop the ref count after a dlm lock
operation has completed we ensure that we never call
gfs2_glock_hold() on a lock with a zero ref count.

Secondly, by using atomic_dec_and_lock() in gfs2_glock_put()
we ensure that at no time will a glock with zero ref count
appear on the lru_list. That means that we can remove the
check for this in our shrinker (which was racy).

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent c29cd900

fs/gfs2/glock.c

+8 −13
Original line number Diff line number Diff line
@@ -241,15 +241,14 @@ int gfs2_glock_put(struct gfs2_glock *gl) 
	int rv = 0;



	write_lock(gl_lock_addr(gl->gl_hash));

	if (atomic_dec_and_test(&gl->gl_ref)) {

	if (atomic_dec_and_lock(&gl->gl_ref, &lru_lock)) {

		hlist_del(&gl->gl_list);

		write_unlock(gl_lock_addr(gl->gl_hash));

		spin_lock(&lru_lock);

		if (!list_empty(&gl->gl_lru)) {

			list_del_init(&gl->gl_lru);

			atomic_dec(&lru_count);

		}

		spin_unlock(&lru_lock);

		write_unlock(gl_lock_addr(gl->gl_hash));

		GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));

		glock_free(gl);

		rv = 1;
@@ -513,7 +512,6 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret) 
			GLOCK_BUG_ON(gl, 1);

		}

		spin_unlock(&gl->gl_spin);

		gfs2_glock_put(gl);

		return;

	}
@@ -524,8 +522,6 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret) 
		if (glops->go_xmote_bh) {

			spin_unlock(&gl->gl_spin);

			rv = glops->go_xmote_bh(gl, gh);

			if (rv == -EAGAIN)

				return;

			spin_lock(&gl->gl_spin);

			if (rv) {

				do_error(gl, rv);
@@ -540,7 +536,6 @@ static void finish_xmote(struct gfs2_glock *gl, unsigned int ret) 
	clear_bit(GLF_LOCK, &gl->gl_flags);

out_locked:

	spin_unlock(&gl->gl_spin);

	gfs2_glock_put(gl);

}



static unsigned int gfs2_lm_lock(struct gfs2_sbd *sdp, void *lock,
@@ -600,7 +595,6 @@ __acquires(&gl->gl_spin) 


	if (!(ret & LM_OUT_ASYNC)) {

		finish_xmote(gl, ret);

		gfs2_glock_hold(gl);

		if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)

			gfs2_glock_put(gl);

	} else {
@@ -712,9 +706,12 @@ static void glock_work_func(struct work_struct *work) 
{

	unsigned long delay = 0;

	struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work);

	int drop_ref = 0;



	if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags))

	if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) {

		finish_xmote(gl, gl->gl_reply);

		drop_ref = 1;

	}

	down_read(&gfs2_umount_flush_sem);

	spin_lock(&gl->gl_spin);

	if (test_and_clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
@@ -732,6 +729,8 @@ static void glock_work_func(struct work_struct *work) 
	if (!delay ||

	    queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)

		gfs2_glock_put(gl);

	if (drop_ref)

		gfs2_glock_put(gl);

}



/**
@@ -1366,10 +1365,6 @@ static int gfs2_shrink_glock_memory(int nr, gfp_t gfp_mask) 
		list_del_init(&gl->gl_lru);

		atomic_dec(&lru_count);



		/* Check if glock is about to be freed */

		if (atomic_read(&gl->gl_ref) == 0)

			continue;



		/* Test for being demotable */

		if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {

			gfs2_glock_hold(gl);