Commit f9f229c1 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Add GL_NOBLOCK flag 



Add a GL_NOBLOCK flag for trying to take a glock without sleeping.  This
will be used for implementing non-blocking lookup (MAY_NOT_BLOCK in
gfs2_permission, LOOKUP_RCU in gfs2_drevalidate).

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent 95d0f625

fs/gfs2/glock.c

+38 −1
Original line number Diff line number Diff line
@@ -516,6 +516,23 @@ static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl) 
	return NULL;

}



/**

 * find_last_waiter - find the last gh that's waiting for the glock

 * @gl: the glock

 *

 * This also is a fast way of finding out if there are any waiters.

 */



static inline struct gfs2_holder *find_last_waiter(const struct gfs2_glock *gl)

{

	struct gfs2_holder *gh;



	if (list_empty(&gl->gl_holders))

		return NULL;

	gh = list_last_entry(&gl->gl_holders, struct gfs2_holder, gh_list);

	return test_bit(HIF_HOLDER, &gh->gh_iflags) ? NULL : gh;

}



/**

 * state_change - record that the glock is now in a different state

 * @gl: the glock
@@ -1555,11 +1572,30 @@ __acquires(&gl->gl_lockref.lock) 
int gfs2_glock_nq(struct gfs2_holder *gh)

{

	struct gfs2_glock *gl = gh->gh_gl;

	int error = 0;

	int error;



	if (glock_blocked_by_withdraw(gl) && !(gh->gh_flags & LM_FLAG_NOEXP))

		return -EIO;



	if (gh->gh_flags & GL_NOBLOCK) {

		struct gfs2_holder *current_gh;



		error = -ECHILD;

		spin_lock(&gl->gl_lockref.lock);

		if (find_last_waiter(gl))

			goto unlock;

		current_gh = find_first_holder(gl);

		if (!may_grant(gl, current_gh, gh))

			goto unlock;

		set_bit(HIF_HOLDER, &gh->gh_iflags);

		list_add_tail(&gh->gh_list, &gl->gl_holders);

		trace_gfs2_promote(gh);

		error = 0;

unlock:

		spin_unlock(&gl->gl_lockref.lock);

		return error;

	}



	if (test_bit(GLF_LRU, &gl->gl_flags))

		gfs2_glock_remove_from_lru(gl);
@@ -1575,6 +1611,7 @@ int gfs2_glock_nq(struct gfs2_holder *gh) 
	run_queue(gl, 1);

	spin_unlock(&gl->gl_lockref.lock);



	error = 0;

	if (!(gh->gh_flags & GL_ASYNC))

		error = gfs2_glock_wait(gh);

fs/gfs2/glock.h

+1 −0
Original line number Diff line number Diff line
@@ -84,6 +84,7 @@ enum { 
#define GL_SKIP			0x0100

#define GL_NOPID		0x0200

#define GL_NOCACHE		0x0400

#define GL_NOBLOCK		0x0800

  

/*

 * lm_async_cb return flags