GFS2: Merge glock state fields into a bitfield

We can only merge the fields into a bitfield if the locking
rules for them are the same. In this case gl_spin covers all
of the fields (write side) but a couple of them are used
with GLF_LOCK as the read side lock, which should be ok
since we know that the field in question won't be changing
at the time.

The gl_req setting has to be done earlier (in glock.c) in order
to place it under gl_spin. The gl_reply setting also has to be
brought under gl_spin in order to comply with the new rules.

This saves 4*sizeof(unsigned int) per glock.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Bob Peterson <rpeterso@redhat.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 764fbb49efc..8d3d2b4a0a7 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -207,12 +207,14 @@ struct gfs2_glock {
 
 	spinlock_t gl_spin;
 
-	unsigned int gl_state;
-	unsigned int gl_target;
-	unsigned int gl_reply;
+	/* State fields protected by gl_spin */
+	unsigned int gl_state:2,	/* Current state */
+		     gl_target:2,	/* Target state */
+		     gl_demote_state:2,	/* State requested by remote node */
+		     gl_req:2,		/* State in last dlm request */
+		     gl_reply:8;	/* Last reply from the dlm */
+
 	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;