GFS2: Fix locking bug in failed shared to exclusive conversion

After calling out to the dlm, GFS2 sets the new state of a glock to
gl_target in gdlm_ast().  However, gl_target is not always the lock
state that was requested. If a conversion from shared to exclusive
fails, finish_xmote() will call do_xmote() with LM_ST_UNLOCKED, instead
of gl->gl_target, so that it can reacquire the lock in exlusive the next
time around.  In this case, setting the lock to gl_target in gdlm_ast()
will make GFS2 think that it has the glock in exclusive mode, when
really, it doesn't have the glock locked at all.  This patch adds a new
field to the gfs2_glock structure, gl_req, to track the mode that was
requested.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

2 files changed, 5 insertions, 3 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 980a0864ca6c..399d1b978049 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -203,6 +203,7 @@ struct gfs2_glock {
         unsigned int gl_target;
         unsigned int gl_reply;
         unsigned int gl_hash;
+        unsigned int gl_req;
         unsigned int gl_demote_state; /* state requested by remote node */
         unsigned long gl_demote_time; /* time of first demote request */
         struct list_head gl_holders;
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index a0bb7d2251a0..46df988323bc 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -46,11 +46,11 @@ static void gdlm_ast(void *arg)
                 BUG();
         }
 
-        ret = gl->gl_target;
+        ret = gl->gl_req;
         if (gl->gl_lksb.sb_flags & DLM_SBF_ALTMODE) {
-                if (gl->gl_target == LM_ST_SHARED)
+                if (gl->gl_req == LM_ST_SHARED)
                         ret = LM_ST_DEFERRED;
-                else if (gl->gl_target == LM_ST_DEFERRED)
+                else if (gl->gl_req == LM_ST_DEFERRED)
                         ret = LM_ST_SHARED;
                 else
                         BUG();
@@ -147,6 +147,7 @@ static unsigned int gdlm_lock(struct gfs2_glock *gl,
         int req;
         u32 lkf;
 
+        gl->gl_req = req_state;
         req = make_mode(req_state);
         lkf = make_flags(gl->gl_lksb.sb_lkid, flags, req);