[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: S. Wendy Cheng <wcheng@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
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@ -567,7 +567,10 @@ static int rq_demote(struct gfs2_glock *gl)
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gfs2_demote_wake(gl);
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gfs2_demote_wake(gl);
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return 0;
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return 0;
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}
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}
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set_bit(GLF_LOCK, &gl->gl_flags);
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set_bit(GLF_LOCK, &gl->gl_flags);
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set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
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if (gl->gl_demote_state == LM_ST_UNLOCKED ||
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if (gl->gl_demote_state == LM_ST_UNLOCKED ||
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gl->gl_state != LM_ST_EXCLUSIVE) {
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gl->gl_state != LM_ST_EXCLUSIVE) {
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spin_unlock(&gl->gl_spin);
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spin_unlock(&gl->gl_spin);
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@ -576,7 +579,9 @@ static int rq_demote(struct gfs2_glock *gl)
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spin_unlock(&gl->gl_spin);
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spin_unlock(&gl->gl_spin);
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gfs2_glock_xmote_th(gl, NULL);
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gfs2_glock_xmote_th(gl, NULL);
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}
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}
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spin_lock(&gl->gl_spin);
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spin_lock(&gl->gl_spin);
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clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
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return 0;
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return 0;
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}
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}
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@ -606,6 +611,11 @@ static void run_queue(struct gfs2_glock *gl)
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} else if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {
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} else if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {
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blocked = rq_demote(gl);
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blocked = rq_demote(gl);
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if (gl->gl_waiters2 && !blocked) {
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set_bit(GLF_DEMOTE, &gl->gl_flags);
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gl->gl_demote_state = LM_ST_UNLOCKED;
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}
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gl->gl_waiters2 = 0;
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} else if (!list_empty(&gl->gl_waiters3)) {
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} else if (!list_empty(&gl->gl_waiters3)) {
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gh = list_entry(gl->gl_waiters3.next,
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gh = list_entry(gl->gl_waiters3.next,
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struct gfs2_holder, gh_list);
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struct gfs2_holder, gh_list);
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@ -722,6 +732,9 @@ static void handle_callback(struct gfs2_glock *gl, unsigned int state,
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}
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}
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} else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
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} else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
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gl->gl_demote_state != state) {
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gl->gl_demote_state != state) {
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if (test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags))
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gl->gl_waiters2 = 1;
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else
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gl->gl_demote_state = LM_ST_UNLOCKED;
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gl->gl_demote_state = LM_ST_UNLOCKED;
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}
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}
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spin_unlock(&gl->gl_spin);
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spin_unlock(&gl->gl_spin);
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@ -171,6 +171,7 @@ enum {
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GLF_DEMOTE = 3,
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GLF_DEMOTE = 3,
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GLF_PENDING_DEMOTE = 4,
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GLF_PENDING_DEMOTE = 4,
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GLF_DIRTY = 5,
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GLF_DIRTY = 5,
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GLF_DEMOTE_IN_PROGRESS = 6,
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};
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};
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struct gfs2_glock {
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struct gfs2_glock {
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@ -190,6 +191,7 @@ struct gfs2_glock {
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struct list_head gl_holders;
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struct list_head gl_holders;
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struct list_head gl_waiters1; /* HIF_MUTEX */
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struct list_head gl_waiters1; /* HIF_MUTEX */
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struct list_head gl_waiters3; /* HIF_PROMOTE */
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struct list_head gl_waiters3; /* HIF_PROMOTE */
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int gl_waiters2; /* GIF_DEMOTE */
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const struct gfs2_glock_operations *gl_ops;
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const struct gfs2_glock_operations *gl_ops;
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