ia64: perfmon: add d_dname method

Switch ia64/perfmon to using the d_dname() instead of relying on
__d_path() to prepend the name of the root dentry to the path.

CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/ia64/kernel/perfmon.c

@@ -2191,8 +2191,15 @@ pfmfs_delete_dentry(struct dentry *dentry)
 	return 1;
 }
 
+static char *pfmfs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	return dynamic_dname(dentry, buffer, buflen, "pfm:[%lu]",
+			     dentry->d_inode->i_ino);
+}
+
 static const struct dentry_operations pfmfs_dentry_operations = {
 	.d_delete = pfmfs_delete_dentry,
+	.d_dname = pfmfs_dname,
 };
 
 
@@ -2202,8 +2209,7 @@ pfm_alloc_file(pfm_context_t *ctx)
 	struct file *file;
 	struct inode *inode;
 	struct path path;
-	char name[32];
-	struct qstr this;
+	struct qstr this = { .name = "" };
 
 	/*
 	 * allocate a new inode
@@ -2218,11 +2224,6 @@ pfm_alloc_file(pfm_context_t *ctx)
 	inode->i_uid  = current_fsuid();
 	inode->i_gid  = current_fsgid();
 
-	sprintf(name, "[%lu]", inode->i_ino);
-	this.name = name;
-	this.len  = strlen(name);
-	this.hash = inode->i_ino;
-
 	/*
 	 * allocate a new dcache entry
 	 */