CIFS: Make cifsFileInfo_put work with strict cache mode

On strict cache mode when we close the last file handle of the inode we
should set invalid_mapping flag on this inode to prevent data coherency
problem when we open it again but it has been modified on the server.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifs_fs_sb.h

@@ -40,6 +40,7 @@
 #define CIFS_MOUNT_FSCACHE	0x8000 /* local caching enabled */
 #define CIFS_MOUNT_MF_SYMLINKS	0x10000 /* Minshall+French Symlinks enabled */
 #define CIFS_MOUNT_MULTIUSER	0x20000 /* multiuser mount */
+#define CIFS_MOUNT_STRICT_IO	0x40000 /* strict cache mode */
 
 struct cifs_sb_info {
 	struct rb_root tlink_tree;

fs/cifs/file.c

@@ -287,6 +287,7 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 	struct inode *inode = cifs_file->dentry->d_inode;
 	struct cifsTconInfo *tcon = tlink_tcon(cifs_file->tlink);
 	struct cifsInodeInfo *cifsi = CIFS_I(inode);
+	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 	struct cifsLockInfo *li, *tmp;
 
 	spin_lock(&cifs_file_list_lock);
@@ -302,6 +303,13 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 	if (list_empty(&cifsi->openFileList)) {
 		cFYI(1, "closing last open instance for inode %p",
 			cifs_file->dentry->d_inode);
+
+		/* in strict cache mode we need invalidate mapping on the last
+		   close  because it may cause a error when we open this file
+		   again and get at least level II oplock */
+		if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO)
+			CIFS_I(inode)->invalid_mapping = true;
+
 		cifs_set_oplock_level(cifsi, 0);
 	}
 	spin_unlock(&cifs_file_list_lock);