fs/9p: Add support for marking inode attribute invalid

With cached mode some of the file system operation result
in updating inode attributes (ctime). Add support for
marking inode attribute invalid in such cases so that
we fetch the updated inode attribute on dentry revalidation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index 71cab8e..cfdc055 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -116,12 +116,16 @@
 	struct p9_fid *root_fid; /* Used for file system sync */
 };
 
+/* cache_validity flags */
+#define V9FS_INO_INVALID_ATTR 0x01
+
 struct v9fs_inode {
 #ifdef CONFIG_9P_FSCACHE
 	spinlock_t fscache_lock;
 	struct fscache_cookie *fscache;
 	struct p9_qid *fscache_key;
 #endif
+	unsigned int cache_validity;
 	struct p9_fid *writeback_fid;
 	struct inode vfs_inode;
 };