CIFS: Implement cifs_file_strict_mmap (try #2)

Invalidate inode mapping if we don't have at least Level II oplock.
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/cifsfs.c

@@ -743,7 +743,7 @@ const struct file_operations cifs_file_strict_ops = {
 	.lock = cifs_lock,
 	.fsync = cifs_strict_fsync,
 	.flush = cifs_flush,
-	.mmap = cifs_file_mmap,
+	.mmap = cifs_file_strict_mmap,
 	.splice_read = generic_file_splice_read,
 	.llseek = cifs_llseek,
 #ifdef CONFIG_CIFS_POSIX
@@ -798,7 +798,7 @@ const struct file_operations cifs_file_strict_nobrl_ops = {
 	.release = cifs_close,
 	.fsync = cifs_strict_fsync,
 	.flush = cifs_flush,
-	.mmap = cifs_file_mmap,
+	.mmap = cifs_file_strict_mmap,
 	.splice_read = generic_file_splice_read,
 	.llseek = cifs_llseek,
 #ifdef CONFIG_CIFS_POSIX

fs/cifs/cifsfs.h

@@ -89,6 +89,7 @@ extern int cifs_fsync(struct file *, int);
 extern int cifs_strict_fsync(struct file *, int);
 extern int cifs_flush(struct file *, fl_owner_t id);
 extern int cifs_file_mmap(struct file * , struct vm_area_struct *);
+extern int cifs_file_strict_mmap(struct file * , struct vm_area_struct *);
 extern const struct file_operations cifs_dir_ops;
 extern int cifs_dir_open(struct inode *inode, struct file *file);
 extern int cifs_readdir(struct file *file, void *direntry, filldir_t filldir);

fs/cifs/file.c

@@ -1769,6 +1769,21 @@ static ssize_t cifs_read(struct file *file, char *read_data, size_t read_size,
 	return total_read;
 }
 
+int cifs_file_strict_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	int rc, xid;
+	struct inode *inode = file->f_path.dentry->d_inode;
+
+	xid = GetXid();
+
+	if (!CIFS_I(inode)->clientCanCacheRead)
+		cifs_invalidate_mapping(inode);
+
+	rc = generic_file_mmap(file, vma);
+	FreeXid(xid);
+	return rc;
+}
+
 int cifs_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	int rc, xid;