summaryrefslogtreecommitdiffstats
path: root/fs/isofs/export.c
blob: dd4687ff30d09900a14f113aec870007cfcfb7f0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
/*
 * fs/isofs/export.c
 *
 *  (C) 2004  Paul Serice - The new inode scheme requires switching
 *                          from iget() to iget5_locked() which means
 *                          the NFS export operations have to be hand
 *                          coded because the default routines rely on
 *                          iget().
 *
 * The following files are helpful:
 *
 *     Documentation/filesystems/nfs/Exporting
 *     fs/exportfs/expfs.c.
 */

#include "isofs.h"

static struct dentry *
isofs_export_iget(struct super_block *sb,
		  unsigned long block,
		  unsigned long offset,
		  __u32 generation)
{
	struct inode *inode;

	if (block == 0)
		return ERR_PTR(-ESTALE);
	inode = isofs_iget(sb, block, offset);
	if (IS_ERR(inode))
		return ERR_CAST(inode);
	if (generation && inode->i_generation != generation) {
		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	return d_obtain_alias(inode);
}

/* This function is surprisingly simple.  The trick is understanding
 * that "child" is always a directory. So, to find its parent, you
 * simply need to find its ".." entry, normalize its block and offset,
 * and return the underlying inode.  See the comments for
 * isofs_normalize_block_and_offset(). */
static struct dentry *isofs_export_get_parent(struct dentry *child)
{
	unsigned long parent_block = 0;
	unsigned long parent_offset = 0;
	struct inode *child_inode = child->d_inode;
	struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
	struct iso_directory_record *de = NULL;
	struct buffer_head * bh = NULL;
	struct dentry *rv = NULL;

	/* "child" must always be a directory. */
	if (!S_ISDIR(child_inode->i_mode)) {
		printk(KERN_ERR "isofs: isofs_export_get_parent(): "
		       "child is not a directory!\n");
		rv = ERR_PTR(-EACCES);
		goto out;
	}

	/* It is an invariant that the directory offset is zero.  If
	 * it is not zero, it means the directory failed to be
	 * normalized for some reason. */
	if (e_child_inode->i_iget5_offset != 0) {
		printk(KERN_ERR "isofs: isofs_export_get_parent(): "
		       "child directory not normalized!\n");
		rv = ERR_PTR(-EACCES);
		goto out;
	}

	/* The child inode has been normalized such that its
	 * i_iget5_block value points to the "." entry.  Fortunately,
	 * the ".." entry is located in the same block. */
	parent_block = e_child_inode->i_iget5_block;

	/* Get the block in question. */
	bh = sb_bread(child_inode->i_sb, parent_block);
	if (bh == NULL) {
		rv = ERR_PTR(-EACCES);
		goto out;
	}

	/* This is the "." entry. */
	de = (struct iso_directory_record*)bh->b_data;

	/* The ".." entry is always the second entry. */
	parent_offset = (unsigned long)isonum_711(de->length);
	de = (struct iso_directory_record*)(bh->b_data + parent_offset);

	/* Verify it is in fact the ".." entry. */
	if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
		printk(KERN_ERR "isofs: Unable to find the \"..\" "
		       "directory for NFS.\n");
		rv = ERR_PTR(-EACCES);
		goto out;
	}

	/* Normalize */
	isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);

	rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block,
				     parent_offset));
 out:
	if (bh)
		brelse(bh);
	return rv;
}

static int
isofs_export_encode_fh(struct dentry *dentry,
		       __u32 *fh32,
		       int *max_len,
		       int connectable)
{
	struct inode * inode = dentry->d_inode;
	struct iso_inode_info * ei = ISOFS_I(inode);
	int len = *max_len;
	int type = 1;
	__u16 *fh16 = (__u16*)fh32;

	/*
	 * WARNING: max_len is 5 for NFSv2.  Because of this
	 * limitation, we use the lower 16 bits of fh32[1] to hold the
	 * offset of the inode and the upper 16 bits of fh32[1] to
	 * hold the offset of the parent.
	 */
	if (connectable && (len < 5)) {
		*max_len = 5;
		return 255;
	} else if (len < 3) {
		*max_len = 3;
		return 255;
	}

	len = 3;
	fh32[0] = ei->i_iget5_block;
 	fh16[2] = (__u16)ei->i_iget5_offset;  /* fh16 [sic] */
	fh32[2] = inode->i_generation;
	if (connectable && !S_ISDIR(inode->i_mode)) {
		struct inode *parent;
		struct iso_inode_info *eparent;
		spin_lock(&dentry->d_lock);
		parent = dentry->d_parent->d_inode;
		eparent = ISOFS_I(parent);
		fh32[3] = eparent->i_iget5_block;
		fh16[3] = (__u16)eparent->i_iget5_offset;  /* fh16 [sic] */
		fh32[4] = parent->i_generation;
		spin_unlock(&dentry->d_lock);
		len = 5;
		type = 2;
	}
	*max_len = len;
	return type;
}

struct isofs_fid {
	u32 block;
	u16 offset;
	u16 parent_offset;
	u32 generation;
	u32 parent_block;
	u32 parent_generation;
};

static struct dentry *isofs_fh_to_dentry(struct super_block *sb,
	struct fid *fid, int fh_len, int fh_type)
{
	struct isofs_fid *ifid = (struct isofs_fid *)fid;

	if (fh_len < 3 || fh_type > 2)
		return NULL;

	return isofs_export_iget(sb, ifid->block, ifid->offset,
			ifid->generation);
}

static struct dentry *isofs_fh_to_parent(struct super_block *sb,
		struct fid *fid, int fh_len, int fh_type)
{
	struct isofs_fid *ifid = (struct isofs_fid *)fid;

	if (fh_type != 2)
		return NULL;

	return isofs_export_iget(sb,
			fh_len > 2 ? ifid->parent_block : 0,
			ifid->parent_offset,
			fh_len > 4 ? ifid->parent_generation : 0);
}

const struct export_operations isofs_export_ops = {
	.encode_fh	= isofs_export_encode_fh,
	.fh_to_dentry	= isofs_fh_to_dentry,
	.fh_to_parent	= isofs_fh_to_parent,
	.get_parent     = isofs_export_get_parent,
};
OpenPOWER on IntegriCloud