diff options
| author |   Steven Whitehouse <swhiteho@redhat.com> | 2007-07-23 09:54:36 +0100 |
|---|---|---|
| committer | Steven Whitehouse <swhiteho@redhat.com> | 2007-10-10 08:54:39 +0100 |
| commit | 87124e581bfeaa5864662a435b6ee2a19e91b905 (patch) | |
| tree | f9bc5d965834f1c7435123f26b9ab8f961c8848f | |
| parent | Linux 2.6.23 (diff) | |
| download | linux-dev-87124e581bfeaa5864662a435b6ee2a19e91b905.tar.xz linux-dev-87124e581bfeaa5864662a435b6ee2a19e91b905.zip | |
[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>
| -rw-r--r-- | fs/gfs2/glock.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 3f0974e1afef..6a3eeba102f9 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -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; |