[GFS2] Journaled file write/unstuff bug

This patch is for bugzilla bug 283162, which uncovered a number of
bugs pertaining to writing to files that have the journaled bit on.
These bugs happen most often when writing to the meta_fs because
the files are always journaled.  So operations like gfs2_grow were
particularly vulnerable, although many of the problems could be
recreated with normal files after setting the journaled bit on.
The problems fixed are:

-GFS2 wasn't ever writing unstuffed journaled data blocks to their
 in-place location on disk. Now it does.

-If you unmounted too quickly after doing IO to a journaled file,
 GFS2 was crashing because you would discard a buffer whose bufdata
 was still on the active items list.  GFS2 now deals with this
 gracefully.

-GFS2 was losing track of the bufdata for journaled data blocks,
 and it wasn't getting freed, causing an error when you tried to
 unmount the module.  GFS2 now frees all the bufdata structures.

-There was a memory corruption occurring because GFS2 wrote
 twice as many log entries for journaled buffers.

-It was occasionally trying to write journal headers in buffers
 that weren't currently mapped.

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

fs/gfs2/lops.c

@@ -607,7 +607,8 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp)
 				if (unlikely(magic != 0))
 					set_buffer_escaped(bh1);
 				gfs2_log_lock(sdp);
-				if (n++ > num)
+				n += 2;
+				if (n >= num)
 					break;
 			} else if (!bh1) {
 				total_dbuf--;
@@ -624,6 +625,7 @@ static void databuf_lo_before_commit(struct gfs2_sbd *sdp)
 		}
 		gfs2_log_unlock(sdp);
 		if (bh) {
+			set_buffer_mapped(bh);
 			set_buffer_dirty(bh);
 			ll_rw_block(WRITE, 1, &bh);
 			bh = NULL;