ocfs2: fix the la space leak when unmounting an ocfs2 volume

This bug has existed since the initial OCFS2 code. The code logic in
ocfs2_sync_local_to_main() is wrong, as it ignores the last contiguous
free bits, which causes an OCFS2 volume to lose the last free clusters of
LA window on each umount command.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Heming Zhao <[e-mail]>
Reviewed-by: Su Yue <[e-mail]>
Reviewed-by: Joseph Qi <[e-mail]>
Cc: Mark Fasheh <[e-mail]>
Cc: Joel Becker <[e-mail]>
Cc: Junxiao Bi <[e-mail]>
Cc: Changwei Ge <[e-mail]>
Cc: Gang He <[e-mail]>
Cc: Jun Piao <[e-mail]>
Cc: Heming Zhao <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/ocfs2/localalloc.c

···
 		start = bit_off + 1;
 	}
 
+	/* clear the contiguous bits until the end boundary */
+	if (count) {
+		blkno = la_start_blk +
+			ocfs2_clusters_to_blocks(osb->sb,
+					start - count);
+
+		trace_ocfs2_sync_local_to_main_free(
+				count, start - count,
+				(unsigned long long)la_start_blk,
+				(unsigned long long)blkno);
+
+		status = ocfs2_release_clusters(handle,
+				main_bm_inode,
+				main_bm_bh, blkno,
+				count);
+		if (status < 0)
+			mlog_errno(status);
+	}
+
 bail:
 	if (status)
 		mlog_errno(status);