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[GFS2] Fix two races relating to glock callbacks 

One of the races relates to referencing a variable while not holding
its protecting spinlock. The patch simply moves the test inside the
spin lock. The other races occurs when a demote to unlocked request
occurs during the time a demote to shared request is already running.
This of course only happens in the case that the lock was in the
exclusive mode to start with. The patch adds a check to see if another
demote request has occurred in the mean time and if it has, then it
performs a second demote.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
This commit is contained in:
Steven Whitehouse 2007-07-23 09:54:36 +01:00
parent bbf25010f1
commit 87124e581b
1 changed files with 18 additions and 6 deletions
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24
fs/gfs2/glock.c
View File

@ -545,12 +545,14 @@ static int rq_demote(struct gfs2_glock *gl)
return 0;
}
set_bit(GLF_LOCK, &gl->gl_flags);
spin_unlock(&gl->gl_spin);
if (gl->gl_demote_state == LM_ST_UNLOCKED ||
gl->gl_state != LM_ST_EXCLUSIVE)
gl->gl_state != LM_ST_EXCLUSIVE) {
spin_unlock(&gl->gl_spin);
gfs2_glock_drop_th(gl);
else
} else {
spin_unlock(&gl->gl_spin);
gfs2_glock_xmote_th(gl, NULL);
}
spin_lock(&gl->gl_spin);
return 0;
@ -760,10 +762,20 @@ static void xmote_bh(struct gfs2_glock *gl, unsigned int ret)
if (!gh) {
gl->gl_stamp = jiffies;
if (ret & LM_OUT_CANCELED)
if (ret & LM_OUT_CANCELED) {
op_done = 0;
else
} else {
spin_lock(&gl->gl_spin);
if (gl->gl_state != gl->gl_demote_state) {
gl->gl_req_bh = NULL;
spin_unlock(&gl->gl_spin);
gfs2_glock_drop_th(gl);
gfs2_glock_put(gl);
return;
}
gfs2_demote_wake(gl);
spin_unlock(&gl->gl_spin);
}
} else {
spin_lock(&gl->gl_spin);
list_del_init(&gh->gh_list);
@ -817,7 +829,7 @@ out:
*
*/
void gfs2_glock_xmote_th(struct gfs2_glock *gl, struct gfs2_holder *gh)
static void gfs2_glock_xmote_th(struct gfs2_glock *gl, struct gfs2_holder *gh)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
int flags = gh ? gh->gh_flags : 0;