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Linux/fs/isofs/export.c

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  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 
 18 static struct dentry *
 19 isofs_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(). */
 43 static 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 
109 static int
110 isofs_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 
152 struct 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 
161 static 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 
173 static 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 
187 const 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 

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