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| author | Steven Whitehouse <swhiteho@redhat.com> | 2013-08-20 09:35:09 +0100 |
|---|---|---|
| committer | Steven Whitehouse <swhiteho@redhat.com> | 2013-08-20 09:35:09 +0100 |
| commit | 7286b31eaba6404fa92f68d04626da1f395b3916 (patch) | |
| tree | 1576b582aae540bb0069654b2c2d8171692dce73 /fs/gfs2/glock.c | |
| parent | 7c0ef28a2c9a768ffb63c1c3d9542b6e175ab260 (diff) | |
| download | linux-7286b31eaba6404fa92f68d04626da1f395b3916.tar.gz linux-7286b31eaba6404fa92f68d04626da1f395b3916.tar.bz2 linux-7286b31eaba6404fa92f68d04626da1f395b3916.zip | |
GFS2: Take glock reference in examine_bucket()
We need to check the glock ref counter in a race free way
in order to ensure that the gfs2_glock_hold() call will
succeed. The easiest way to do that is to simply take the
reference count early in the common code of examine_bucket,
skipping any glocks with zero ref count.
That means that the examiner functions all need to put their
reference on the glock once they've performed their function.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reported-by: David Teigland <teigland@redhat.com>
Tested-by: David Teigland <teigland@redhat.com>
Diffstat (limited to 'fs/gfs2/glock.c')
| -rw-r--r-- | fs/gfs2/glock.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 544a809819c3..ce7078d5aa97 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -1488,7 +1488,7 @@ static void examine_bucket(glock_examiner examiner, const struct gfs2_sbd *sdp, rcu_read_lock(); hlist_bl_for_each_entry_rcu(gl, pos, head, gl_list) { - if ((gl->gl_sbd == sdp) && atomic_read(&gl->gl_ref)) + if ((gl->gl_sbd == sdp) && atomic_inc_not_zero(&gl->gl_ref)) examiner(gl); } rcu_read_unlock(); @@ -1508,18 +1508,17 @@ static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp) * thaw_glock - thaw out a glock which has an unprocessed reply waiting * @gl: The glock to thaw * - * N.B. When we freeze a glock, we leave a ref to the glock outstanding, - * so this has to result in the ref count being dropped by one. */ static void thaw_glock(struct gfs2_glock *gl) { if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) - return; + goto out; set_bit(GLF_REPLY_PENDING, &gl->gl_flags); - gfs2_glock_hold(gl); - if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) + if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) { +out: gfs2_glock_put(gl); + } } /** @@ -1536,7 +1535,6 @@ static void clear_glock(struct gfs2_glock *gl) if (gl->gl_state != LM_ST_UNLOCKED) handle_callback(gl, LM_ST_UNLOCKED, 0, false); spin_unlock(&gl->gl_spin); - gfs2_glock_hold(gl); if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0) gfs2_glock_put(gl); } |