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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: S. Wendy Cheng <wcheng@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Wendy Cheng 2007-10-05 00:27:58 -04:00 committed by Steven Whitehouse
parent 49914084e7
commit cc7e79b168
2 changed files with 16 additions and 1 deletions
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15
fs/gfs2/glock.c
View File

@ -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);
@ -722,7 +732,10 @@ 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) {
gl->gl_demote_state = LM_ST_UNLOCKED;
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);
}

2
fs/gfs2/incore.h
View File

@ -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;