JFS: Add d_hash and d_compare operations for case-insensitive names

JFS supports OS/2-compatibility with case-insensitive file names.
To avoid multiple dentries for these names, jfs needs to provide
the d_hash and d_compare dentry_operations.  The operations are
only used when the volume was created in OS/2 or with the -O flag.

fs/jfs/namei.c

 /*
- *   Copyright (C) International Business Machines Corp., 2000-2003
+ *   Copyright (C) International Business Machines Corp., 2000-2004
  *   Portions Copyright (C) Christoph Hellwig, 2001-2002
  *
  *   This program is free software;  you can redistribute it and/or modify
@@ -18,6 +18,7 @@
  */
 
 #include <linux/fs.h>
+#include <linux/ctype.h>
 #include "jfs_incore.h"
 #include "jfs_superblock.h"
 #include "jfs_inode.h"
@@ -43,6 +44,7 @@ extern int jfs_init_acl(struct inode *, struct inode *);
  */
 struct inode_operations jfs_dir_inode_operations;
 struct file_operations jfs_dir_operations;
+struct dentry_operations jfs_ci_dentry_operations;
 
 static s64 commitZeroLink(tid_t, struct inode *);
 
@@ -1422,7 +1424,15 @@ static struct dentry *jfs_lookup(struct inode *dip, struct dentry *dentry, struc
 		return ERR_PTR(-EACCES);
 	}
 
-	return d_splice_alias(ip, dentry);
+	if (JFS_SBI(dip->i_sb)->mntflag & JFS_OS2)
+		dentry->d_op = &jfs_ci_dentry_operations;
+
+	dentry = d_splice_alias(ip, dentry);
+
+	if (dentry && (JFS_SBI(dip->i_sb)->mntflag & JFS_OS2))
+		dentry->d_op = &jfs_ci_dentry_operations;
+
+	return dentry;
 }
 
 struct dentry *jfs_get_parent(struct dentry *dentry)
@@ -1476,3 +1486,46 @@ struct file_operations jfs_dir_operations = {
 	.readdir	= jfs_readdir,
 	.fsync		= jfs_fsync,
 };
+
+static int jfs_ci_hash(struct dentry *dir, struct qstr *this)
+{
+	unsigned long hash;
+	int i;
+
+	hash = init_name_hash();
+	for (i=0; i < this->len; i++)
+		hash = partial_name_hash(tolower(this->name[i]), hash);
+	this->hash = end_name_hash(hash);
+
+	return 0;
+}
+
+static int jfs_ci_compare(struct dentry *dir, struct qstr *a, struct qstr *b)
+{
+	int i, result = 1;
+
+	if (a->len != b->len)
+		goto out;
+	for (i=0; i < a->len; i++) {
+		if (tolower(a->name[i]) != tolower(b->name[i]))
+			goto out;
+	}
+	result = 0;
+
+	/*
+	 * We want creates to preserve case.  A negative dentry, a, that
+	 * has a different case than b may cause a new entry to be created
+	 * with the wrong case.  Since we can't tell if a comes from a negative
+	 * dentry, we blindly replace it with b.  This should be harmless if
+	 * a is not a negative dentry.
+	 */
+	memcpy((unsigned char *)a->name, b->name, a->len);
+out:
+	return result;
+}
+
+struct dentry_operations jfs_ci_dentry_operations =
+{
+	.d_hash = jfs_ci_hash,
+	.d_compare = jfs_ci_compare,
+};

fs/jfs/super.c

@@ -82,6 +82,8 @@ extern void jfs_write_inode(struct inode *inode, int wait);
 extern struct dentry *jfs_get_parent(struct dentry *dentry);
 extern int jfs_extendfs(struct super_block *, s64, int);
 
+extern struct dentry_operations jfs_ci_dentry_operations;
+
 #ifdef PROC_FS_JFS		/* see jfs_debug.h */
 extern void jfs_proc_init(void);
 extern void jfs_proc_clean(void);
@@ -446,6 +448,9 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 	if (!sb->s_root)
 		goto out_no_root;
 
+	if (sbi->mntflag & JFS_OS2)
+		sb->s_root->d_op = &jfs_ci_dentry_operations;
+
 	/* logical blocks are represented by 40 bits in pxd_t, etc. */
 	sb->s_maxbytes = ((u64) sb->s_blocksize) << 40;
 #if BITS_PER_LONG == 32