1/*
2 * fs/isofs/export.c
3 *
4 *  (C) 2004  Paul Serice - The new inode scheme requires switching
5 *                          from iget() to iget5_locked() which means
6 *                          the NFS export operations have to be hand
7 *                          coded because the default routines rely on
8 *                          iget().
9 *
10 * The following files are helpful:
11 *
12 *     Documentation/filesystems/nfs/Exporting
13 *     fs/exportfs/expfs.c.
14 */
15
16#include "isofs.h"
17
18static struct dentry *
19isofs_export_iget(struct super_block *sb,
20		  unsigned long block,
21		  unsigned long offset,
22		  __u32 generation)
23{
24	struct inode *inode;
25
26	if (block == 0)
27		return ERR_PTR(-ESTALE);
28	inode = isofs_iget(sb, block, offset);
29	if (IS_ERR(inode))
30		return ERR_CAST(inode);
31	if (generation && inode->i_generation != generation) {
32		iput(inode);
33		return ERR_PTR(-ESTALE);
34	}
35	return d_obtain_alias(inode);
36}
37
38/* This function is surprisingly simple.  The trick is understanding
39 * that "child" is always a directory. So, to find its parent, you
40 * simply need to find its ".." entry, normalize its block and offset,
41 * and return the underlying inode.  See the comments for
42 * isofs_normalize_block_and_offset(). */
43static struct dentry *isofs_export_get_parent(struct dentry *child)
44{
45	unsigned long parent_block = 0;
46	unsigned long parent_offset = 0;
47	struct inode *child_inode = d_inode(child);
48	struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
49	struct iso_directory_record *de = NULL;
50	struct buffer_head * bh = NULL;
51	struct dentry *rv = NULL;
52
53	/* "child" must always be a directory. */
54	if (!S_ISDIR(child_inode->i_mode)) {
55		printk(KERN_ERR "isofs: isofs_export_get_parent(): "
56		       "child is not a directory!\n");
57		rv = ERR_PTR(-EACCES);
58		goto out;
59	}
60
61	/* It is an invariant that the directory offset is zero.  If
62	 * it is not zero, it means the directory failed to be
63	 * normalized for some reason. */
64	if (e_child_inode->i_iget5_offset != 0) {
65		printk(KERN_ERR "isofs: isofs_export_get_parent(): "
66		       "child directory not normalized!\n");
67		rv = ERR_PTR(-EACCES);
68		goto out;
69	}
70
71	/* The child inode has been normalized such that its
72	 * i_iget5_block value points to the "." entry.  Fortunately,
73	 * the ".." entry is located in the same block. */
74	parent_block = e_child_inode->i_iget5_block;
75
76	/* Get the block in question. */
77	bh = sb_bread(child_inode->i_sb, parent_block);
78	if (bh == NULL) {
79		rv = ERR_PTR(-EACCES);
80		goto out;
81	}
82
83	/* This is the "." entry. */
84	de = (struct iso_directory_record*)bh->b_data;
85
86	/* The ".." entry is always the second entry. */
87	parent_offset = (unsigned long)isonum_711(de->length);
88	de = (struct iso_directory_record*)(bh->b_data + parent_offset);
89
90	/* Verify it is in fact the ".." entry. */
91	if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
92		printk(KERN_ERR "isofs: Unable to find the \"..\" "
93		       "directory for NFS.\n");
94		rv = ERR_PTR(-EACCES);
95		goto out;
96	}
97
98	/* Normalize */
99	isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);
100
101	rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block,
102				     parent_offset));
103 out:
104	if (bh)
105		brelse(bh);
106	return rv;
107}
108
109static int
110isofs_export_encode_fh(struct inode *inode,
111		       __u32 *fh32,
112		       int *max_len,
113		       struct inode *parent)
114{
115	struct iso_inode_info * ei = ISOFS_I(inode);
116	int len = *max_len;
117	int type = 1;
118	__u16 *fh16 = (__u16*)fh32;
119
120	/*
121	 * WARNING: max_len is 5 for NFSv2.  Because of this
122	 * limitation, we use the lower 16 bits of fh32[1] to hold the
123	 * offset of the inode and the upper 16 bits of fh32[1] to
124	 * hold the offset of the parent.
125	 */
126	if (parent && (len < 5)) {
127		*max_len = 5;
128		return FILEID_INVALID;
129	} else if (len < 3) {
130		*max_len = 3;
131		return FILEID_INVALID;
132	}
133
134	len = 3;
135	fh32[0] = ei->i_iget5_block;
136 	fh16[2] = (__u16)ei->i_iget5_offset;  /* fh16 [sic] */
137	fh16[3] = 0;  /* avoid leaking uninitialized data */
138	fh32[2] = inode->i_generation;
139	if (parent) {
140		struct iso_inode_info *eparent;
141		eparent = ISOFS_I(parent);
142		fh32[3] = eparent->i_iget5_block;
143		fh16[3] = (__u16)eparent->i_iget5_offset;  /* fh16 [sic] */
144		fh32[4] = parent->i_generation;
145		len = 5;
146		type = 2;
147	}
148	*max_len = len;
149	return type;
150}
151
152struct isofs_fid {
153	u32 block;
154	u16 offset;
155	u16 parent_offset;
156	u32 generation;
157	u32 parent_block;
158	u32 parent_generation;
159};
160
161static struct dentry *isofs_fh_to_dentry(struct super_block *sb,
162	struct fid *fid, int fh_len, int fh_type)
163{
164	struct isofs_fid *ifid = (struct isofs_fid *)fid;
165
166	if (fh_len < 3 || fh_type > 2)
167		return NULL;
168
169	return isofs_export_iget(sb, ifid->block, ifid->offset,
170			ifid->generation);
171}
172
173static struct dentry *isofs_fh_to_parent(struct super_block *sb,
174		struct fid *fid, int fh_len, int fh_type)
175{
176	struct isofs_fid *ifid = (struct isofs_fid *)fid;
177
178	if (fh_len < 2 || fh_type != 2)
179		return NULL;
180
181	return isofs_export_iget(sb,
182			fh_len > 2 ? ifid->parent_block : 0,
183			ifid->parent_offset,
184			fh_len > 4 ? ifid->parent_generation : 0);
185}
186
187const struct export_operations isofs_export_ops = {
188	.encode_fh	= isofs_export_encode_fh,
189	.fh_to_dentry	= isofs_fh_to_dentry,
190	.fh_to_parent	= isofs_fh_to_parent,
191	.get_parent     = isofs_export_get_parent,
192};
193