switch alloc_file() to passing struct path

... and have the caller grab both mnt and dentry; kill
leak in infiniband, while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 599b233..5246285 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2200,7 +2200,7 @@
 {
 	struct file *file;
 	struct inode *inode;
-	struct dentry *dentry;
+	struct path path;
 	char name[32];
 	struct qstr this;
 
@@ -2225,18 +2225,19 @@
 	/*
 	 * allocate a new dcache entry
 	 */
-	dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
-	if (!dentry) {
+	path.dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
+	if (!path.dentry) {
 		iput(inode);
 		return ERR_PTR(-ENOMEM);
 	}
+	path.mnt = mntget(pfmfs_mnt);
 
-	dentry->d_op = &pfmfs_dentry_operations;
-	d_add(dentry, inode);
+	path.dentry->d_op = &pfmfs_dentry_operations;
+	d_add(path.dentry, inode);
 
-	file = alloc_file(pfmfs_mnt, dentry, FMODE_READ, &pfm_file_ops);
+	file = alloc_file(&path, FMODE_READ, &pfm_file_ops);
 	if (!file) {
-		dput(dentry);
+		path_put(&path);
 		return ERR_PTR(-ENFILE);
 	}