JFS: flush new iag from bd_inode's mapping

This is a fix to help jfs work with grub.  A new IAG is created in
the bd_inode's mapping, but subsequently modified in a different
mapping.  We should invalidate the former page to keep grub from
using that cached page.  It isn't useful to have it cached anyway,
since jfs will never access it again through that mapping.
Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>

fs/jfs/jfs_imap.c

@@ -2604,6 +2604,12 @@ diNewIAG(struct inomap * imap, int *iagnop, int agno, struct metapage ** mpp)
 		for (i = 0; i < SMAPSZ; i++)
 			iagp->inosmap[i] = cpu_to_le32(ONES);
 
+		/*
+		 * Invalidate the page after writing and syncing it.
+		 * After it's initialized, we access it in a different
+		 * address space
+		 */
+		set_bit(META_discard, &mp->flag);
 		flush_metapage(mp);
 
 		/*

fs/jfs/jfs_metapage.c

@@ -396,14 +396,6 @@ static void __write_metapage(struct metapage * mp)
 
 	jfs_info("__write_metapage: mp = 0x%p", mp);
 
-	if (test_bit(META_discard, &mp->flag)) {
-		/*
-		 * This metadata is no longer valid
-		 */
-		clear_bit(META_dirty, &mp->flag);
-		return;
-	}
-
 	page_index = mp->page->index;
 	page_offset =
 	    (mp->index - (page_index << l2BlocksPerPage)) << l2bsize;
@@ -549,6 +541,7 @@ void __invalidate_metapages(struct inode *ip, s64 addr, int len)
 				goto again;
 			}
 
+			clear_bit(META_dirty, &mp->flag);
 			set_bit(META_discard, &mp->flag);
 			spin_unlock(&meta_lock);
 		} else {