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Linux/fs/isofs/export.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * fs/isofs/export.c
  4  *
  5  *  (C) 2004  Paul Serice - The new inode scheme requires switching
  6  *                          from iget() to iget5_locked() which means
  7  *                          the NFS export operations have to be hand
  8  *                          coded because the default routines rely on
  9  *                          iget().
 10  *
 11  * The following files are helpful:
 12  *
 13  *     Documentation/filesystems/nfs/Exporting
 14  *     fs/exportfs/expfs.c.
 15  */
 16 
 17 #include "isofs.h"
 18 
 19 static struct dentry *
 20 isofs_export_iget(struct super_block *sb,
 21                   unsigned long block,
 22                   unsigned long offset,
 23                   __u32 generation)
 24 {
 25         struct inode *inode;
 26 
 27         if (block == 0)
 28                 return ERR_PTR(-ESTALE);
 29         inode = isofs_iget(sb, block, offset);
 30         if (IS_ERR(inode))
 31                 return ERR_CAST(inode);
 32         if (generation && inode->i_generation != generation) {
 33                 iput(inode);
 34                 return ERR_PTR(-ESTALE);
 35         }
 36         return d_obtain_alias(inode);
 37 }
 38 
 39 /* This function is surprisingly simple.  The trick is understanding
 40  * that "child" is always a directory. So, to find its parent, you
 41  * simply need to find its ".." entry, normalize its block and offset,
 42  * and return the underlying inode.  See the comments for
 43  * isofs_normalize_block_and_offset(). */
 44 static struct dentry *isofs_export_get_parent(struct dentry *child)
 45 {
 46         unsigned long parent_block = 0;
 47         unsigned long parent_offset = 0;
 48         struct inode *child_inode = d_inode(child);
 49         struct iso_inode_info *e_child_inode = ISOFS_I(child_inode);
 50         struct iso_directory_record *de = NULL;
 51         struct buffer_head * bh = NULL;
 52         struct dentry *rv = NULL;
 53 
 54         /* "child" must always be a directory. */
 55         if (!S_ISDIR(child_inode->i_mode)) {
 56                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
 57                        "child is not a directory!\n");
 58                 rv = ERR_PTR(-EACCES);
 59                 goto out;
 60         }
 61 
 62         /* It is an invariant that the directory offset is zero.  If
 63          * it is not zero, it means the directory failed to be
 64          * normalized for some reason. */
 65         if (e_child_inode->i_iget5_offset != 0) {
 66                 printk(KERN_ERR "isofs: isofs_export_get_parent(): "
 67                        "child directory not normalized!\n");
 68                 rv = ERR_PTR(-EACCES);
 69                 goto out;
 70         }
 71 
 72         /* The child inode has been normalized such that its
 73          * i_iget5_block value points to the "." entry.  Fortunately,
 74          * the ".." entry is located in the same block. */
 75         parent_block = e_child_inode->i_iget5_block;
 76 
 77         /* Get the block in question. */
 78         bh = sb_bread(child_inode->i_sb, parent_block);
 79         if (bh == NULL) {
 80                 rv = ERR_PTR(-EACCES);
 81                 goto out;
 82         }
 83 
 84         /* This is the "." entry. */
 85         de = (struct iso_directory_record*)bh->b_data;
 86 
 87         /* The ".." entry is always the second entry. */
 88         parent_offset = (unsigned long)isonum_711(de->length);
 89         de = (struct iso_directory_record*)(bh->b_data + parent_offset);
 90 
 91         /* Verify it is in fact the ".." entry. */
 92         if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) {
 93                 printk(KERN_ERR "isofs: Unable to find the \"..\" "
 94                        "directory for NFS.\n");
 95                 rv = ERR_PTR(-EACCES);
 96                 goto out;
 97         }
 98 
 99         /* Normalize */
100         isofs_normalize_block_and_offset(de, &parent_block, &parent_offset);
101 
102         rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block,
103                                      parent_offset));
104  out:
105         if (bh)
106                 brelse(bh);
107         return rv;
108 }
109 
110 static int
111 isofs_export_encode_fh(struct inode *inode,
112                        __u32 *fh32,
113                        int *max_len,
114                        struct inode *parent)
115 {
116         struct iso_inode_info * ei = ISOFS_I(inode);
117         int len = *max_len;
118         int type = 1;
119         __u16 *fh16 = (__u16*)fh32;
120 
121         /*
122          * WARNING: max_len is 5 for NFSv2.  Because of this
123          * limitation, we use the lower 16 bits of fh32[1] to hold the
124          * offset of the inode and the upper 16 bits of fh32[1] to
125          * hold the offset of the parent.
126          */
127         if (parent && (len < 5)) {
128                 *max_len = 5;
129                 return FILEID_INVALID;
130         } else if (len < 3) {
131                 *max_len = 3;
132                 return FILEID_INVALID;
133         }
134 
135         len = 3;
136         fh32[0] = ei->i_iget5_block;
137         fh16[2] = (__u16)ei->i_iget5_offset;  /* fh16 [sic] */
138         fh16[3] = 0;  /* avoid leaking uninitialized data */
139         fh32[2] = inode->i_generation;
140         if (parent) {
141                 struct iso_inode_info *eparent;
142                 eparent = ISOFS_I(parent);
143                 fh32[3] = eparent->i_iget5_block;
144                 fh16[3] = (__u16)eparent->i_iget5_offset;  /* fh16 [sic] */
145                 fh32[4] = parent->i_generation;
146                 len = 5;
147                 type = 2;
148         }
149         *max_len = len;
150         return type;
151 }
152 
153 struct isofs_fid {
154         u32 block;
155         u16 offset;
156         u16 parent_offset;
157         u32 generation;
158         u32 parent_block;
159         u32 parent_generation;
160 };
161 
162 static struct dentry *isofs_fh_to_dentry(struct super_block *sb,
163         struct fid *fid, int fh_len, int fh_type)
164 {
165         struct isofs_fid *ifid = (struct isofs_fid *)fid;
166 
167         if (fh_len < 3 || fh_type > 2)
168                 return NULL;
169 
170         return isofs_export_iget(sb, ifid->block, ifid->offset,
171                         ifid->generation);
172 }
173 
174 static struct dentry *isofs_fh_to_parent(struct super_block *sb,
175                 struct fid *fid, int fh_len, int fh_type)
176 {
177         struct isofs_fid *ifid = (struct isofs_fid *)fid;
178 
179         if (fh_len < 2 || fh_type != 2)
180                 return NULL;
181 
182         return isofs_export_iget(sb,
183                         fh_len > 2 ? ifid->parent_block : 0,
184                         ifid->parent_offset,
185                         fh_len > 4 ? ifid->parent_generation : 0);
186 }
187 
188 const struct export_operations isofs_export_ops = {
189         .encode_fh      = isofs_export_encode_fh,
190         .fh_to_dentry   = isofs_fh_to_dentry,
191         .fh_to_parent   = isofs_fh_to_parent,
192         .get_parent     = isofs_export_get_parent,
193 };
194 

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