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Commit cc7e79b1 authored by Wendy Cheng's avatar Wendy Cheng Committed by Steven Whitehouse
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[GFS2] Handle multiple glock demote requests 



Fix a race condition where multiple glock demote requests are sent to
a node back-to-back. This patch does a check inside handle_callback()
to see whether a demote request is in progress. If true, it sets a flag
to make sure run_queue() will loop again to handle the new request,
instead of erronously setting gl_demote_state to a different state.

Signed-off-by: default avatarS. Wendy Cheng <wcheng@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent 49914084

fs/gfs2/glock.c

+14 −1
Original line number Diff line number Diff line
@@ -567,7 +567,10 @@ static int rq_demote(struct gfs2_glock *gl) 
		gfs2_demote_wake(gl);

		return 0;

	}



	set_bit(GLF_LOCK, &gl->gl_flags);

	set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);



	if (gl->gl_demote_state == LM_ST_UNLOCKED ||

	    gl->gl_state != LM_ST_EXCLUSIVE) {

		spin_unlock(&gl->gl_spin);
@@ -576,7 +579,9 @@ static int rq_demote(struct gfs2_glock *gl) 
		spin_unlock(&gl->gl_spin);

		gfs2_glock_xmote_th(gl, NULL);

	}



	spin_lock(&gl->gl_spin);

	clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);



	return 0;

}
@@ -606,6 +611,11 @@ static void run_queue(struct gfs2_glock *gl) 


		} else if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {

			blocked = rq_demote(gl);

			if (gl->gl_waiters2 && !blocked) {

				set_bit(GLF_DEMOTE, &gl->gl_flags);

				gl->gl_demote_state = LM_ST_UNLOCKED;

			}

			gl->gl_waiters2 = 0;

		} else if (!list_empty(&gl->gl_waiters3)) {

			gh = list_entry(gl->gl_waiters3.next,

					struct gfs2_holder, gh_list);
@@ -722,6 +732,9 @@ static void handle_callback(struct gfs2_glock *gl, unsigned int state, 
		}

	} else if (gl->gl_demote_state != LM_ST_UNLOCKED &&

			gl->gl_demote_state != state) {

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

			gl->gl_waiters2 = 1;

		else 

			gl->gl_demote_state = LM_ST_UNLOCKED;

	}

	spin_unlock(&gl->gl_spin);

fs/gfs2/incore.h

+2 −0
Original line number Diff line number Diff line
@@ -171,6 +171,7 @@ enum { 
	GLF_DEMOTE		= 3,

	GLF_PENDING_DEMOTE	= 4,

	GLF_DIRTY		= 5,

	GLF_DEMOTE_IN_PROGRESS	= 6,

};



struct gfs2_glock {
@@ -190,6 +191,7 @@ struct gfs2_glock { 
	struct list_head gl_holders;

	struct list_head gl_waiters1;	/* HIF_MUTEX */

	struct list_head gl_waiters3;	/* HIF_PROMOTE */

	int gl_waiters2;		/* GIF_DEMOTE */



	const struct gfs2_glock_operations *gl_ops;