[XFS] Add a chunk of tracing code to diagnose truncate related issues.

SGI-PV: 938410
SGI-Modid: xfs-linux:xfs-kern:22966a

Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/linux-2.6/xfs_aops.c

@@ -1202,6 +1202,16 @@ linvfs_writepage(
 	return error;
 }
 
+STATIC int
+linvfs_invalidate_page(
+	struct page		*page,
+	unsigned long		offset)
+{
+	xfs_page_trace(XFS_INVALIDPAGE_ENTER,
+			page->mapping->host, page, offset);
+	return block_invalidatepage(page, offset);
+}
+
 /*
  * Called to move a page into cleanable state - and from there
  * to be released. Possibly the page is already clean. We always
@@ -1279,6 +1289,7 @@ struct address_space_operations linvfs_aops = {
 	.writepage		= linvfs_writepage,
 	.sync_page		= block_sync_page,
 	.releasepage		= linvfs_release_page,
+	.invalidatepage		= linvfs_invalidate_page,
 	.prepare_write		= linvfs_prepare_write,
 	.commit_write		= generic_commit_write,
 	.bmap			= linvfs_bmap,

fs/xfs/linux-2.6/xfs_lrw.h

@@ -70,9 +70,10 @@ struct xfs_iomap;
 #define	XFS_SENDFILE_ENTER	21
 #define	XFS_WRITEPAGE_ENTER	22
 #define	XFS_RELEASEPAGE_ENTER	23
-#define	XFS_IOMAP_ALLOC_ENTER	24
-#define	XFS_IOMAP_ALLOC_MAP	25
-#define	XFS_IOMAP_UNWRITTEN	26
+#define	XFS_INVALIDPAGE_ENTER	24
+#define	XFS_IOMAP_ALLOC_ENTER	25
+#define	XFS_IOMAP_ALLOC_MAP	26
+#define	XFS_IOMAP_UNWRITTEN	27
 extern void xfs_rw_enter_trace(int, struct xfs_iocore *,
 				void *, size_t, loff_t, int);
 extern void xfs_inval_cached_trace(struct xfs_iocore *,