JFS: Don't save agno in the inode

Resizing the file system can result in an in-memory inode being remapped
to a different aggregate group (AG). A cached AG number can cause
problems when trying to free or allocate inodes. Instead, save the IAG's
agstart address and calculate the agno when we need it.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
diff --git a/fs/jfs/file.c b/fs/jfs/file.c
index c5ce6c1..2f3f531 100644
--- a/fs/jfs/file.c
+++ b/fs/jfs/file.c
@@ -66,9 +66,9 @@
 		struct jfs_inode_info *ji = JFS_IP(inode);
 		spin_lock_irq(&ji->ag_lock);
 		if (ji->active_ag == -1) {
-			ji->active_ag = ji->agno;
-			atomic_inc(
-			    &JFS_SBI(inode->i_sb)->bmap->db_active[ji->agno]);
+			struct jfs_sb_info *jfs_sb = JFS_SBI(inode->i_sb);
+			ji->active_ag = BLKTOAG(addressPXD(&ji->ixpxd), jfs_sb);
+			atomic_inc( &jfs_sb->bmap->db_active[ji->active_ag]);
 		}
 		spin_unlock_irq(&ji->ag_lock);
 	}