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TOMOYO Linux Cross Reference
Linux/fs/efs/inode.c

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  1 /*
  2  * inode.c
  3  *
  4  * Copyright (c) 1999 Al Smith
  5  *
  6  * Portions derived from work (c) 1995,1996 Christian Vogelgsang,
  7  *              and from work (c) 1998 Mike Shaver.
  8  */
  9 
 10 #include <linux/buffer_head.h>
 11 #include <linux/module.h>
 12 #include <linux/fs.h>
 13 #include "efs.h"
 14 #include <linux/efs_fs_sb.h>
 15 
 16 static int efs_readpage(struct file *file, struct page *page)
 17 {
 18         return block_read_full_page(page,efs_get_block);
 19 }
 20 static sector_t _efs_bmap(struct address_space *mapping, sector_t block)
 21 {
 22         return generic_block_bmap(mapping,block,efs_get_block);
 23 }
 24 static const struct address_space_operations efs_aops = {
 25         .readpage = efs_readpage,
 26         .bmap = _efs_bmap
 27 };
 28 
 29 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
 30         /*
 31          * this is slightly evil. it doesn't just copy
 32          * efs_extent from src to dst, it also mangles
 33          * the bits so that dst ends up in cpu byte-order.
 34          */
 35 
 36         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
 37         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
 38                                 ((unsigned int) src->raw[2] <<  8) |
 39                                 ((unsigned int) src->raw[3] <<  0);
 40         dst->cooked.ex_length =  (unsigned int) src->raw[4];
 41         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
 42                                 ((unsigned int) src->raw[6] <<  8) |
 43                                 ((unsigned int) src->raw[7] <<  0);
 44         return;
 45 }
 46 
 47 struct inode *efs_iget(struct super_block *super, unsigned long ino)
 48 {
 49         int i, inode_index;
 50         dev_t device;
 51         u32 rdev;
 52         struct buffer_head *bh;
 53         struct efs_sb_info    *sb = SUPER_INFO(super);
 54         struct efs_inode_info *in;
 55         efs_block_t block, offset;
 56         struct efs_dinode *efs_inode;
 57         struct inode *inode;
 58 
 59         inode = iget_locked(super, ino);
 60         if (!inode)
 61                 return ERR_PTR(-ENOMEM);
 62         if (!(inode->i_state & I_NEW))
 63                 return inode;
 64 
 65         in = INODE_INFO(inode);
 66 
 67         /*
 68         ** EFS layout:
 69         **
 70         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
 71         ** |inodes|data          |inodes|data          |inodes|data       ..etc
 72         **
 73         ** work out the inode block index, (considering initially that the
 74         ** inodes are stored as consecutive blocks). then work out the block
 75         ** number of that inode given the above layout, and finally the
 76         ** offset of the inode within that block.
 77         */
 78 
 79         inode_index = inode->i_ino /
 80                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
 81 
 82         block = sb->fs_start + sb->first_block + 
 83                 (sb->group_size * (inode_index / sb->inode_blocks)) +
 84                 (inode_index % sb->inode_blocks);
 85 
 86         offset = (inode->i_ino %
 87                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
 88                 sizeof(struct efs_dinode);
 89 
 90         bh = sb_bread(inode->i_sb, block);
 91         if (!bh) {
 92                 pr_warn("%s() failed at block %d\n", __func__, block);
 93                 goto read_inode_error;
 94         }
 95 
 96         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
 97     
 98         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
 99         set_nlink(inode, be16_to_cpu(efs_inode->di_nlink));
100         i_uid_write(inode, (uid_t)be16_to_cpu(efs_inode->di_uid));
101         i_gid_write(inode, (gid_t)be16_to_cpu(efs_inode->di_gid));
102         inode->i_size  = be32_to_cpu(efs_inode->di_size);
103         inode->i_atime.tv_sec = be32_to_cpu(efs_inode->di_atime);
104         inode->i_mtime.tv_sec = be32_to_cpu(efs_inode->di_mtime);
105         inode->i_ctime.tv_sec = be32_to_cpu(efs_inode->di_ctime);
106         inode->i_atime.tv_nsec = inode->i_mtime.tv_nsec = inode->i_ctime.tv_nsec = 0;
107 
108         /* this is the number of blocks in the file */
109         if (inode->i_size == 0) {
110                 inode->i_blocks = 0;
111         } else {
112                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
113         }
114 
115         rdev = be16_to_cpu(efs_inode->di_u.di_dev.odev);
116         if (rdev == 0xffff) {
117                 rdev = be32_to_cpu(efs_inode->di_u.di_dev.ndev);
118                 if (sysv_major(rdev) > 0xfff)
119                         device = 0;
120                 else
121                         device = MKDEV(sysv_major(rdev), sysv_minor(rdev));
122         } else
123                 device = old_decode_dev(rdev);
124 
125         /* get the number of extents for this object */
126         in->numextents = be16_to_cpu(efs_inode->di_numextents);
127         in->lastextent = 0;
128 
129         /* copy the extents contained within the inode to memory */
130         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
131                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
132                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
133                         pr_warn("extent %d has bad magic number in inode %lu\n",
134                                 i, inode->i_ino);
135                         brelse(bh);
136                         goto read_inode_error;
137                 }
138         }
139 
140         brelse(bh);
141         pr_debug("efs_iget(): inode %lu, extents %d, mode %o\n",
142                  inode->i_ino, in->numextents, inode->i_mode);
143         switch (inode->i_mode & S_IFMT) {
144                 case S_IFDIR: 
145                         inode->i_op = &efs_dir_inode_operations; 
146                         inode->i_fop = &efs_dir_operations; 
147                         break;
148                 case S_IFREG:
149                         inode->i_fop = &generic_ro_fops;
150                         inode->i_data.a_ops = &efs_aops;
151                         break;
152                 case S_IFLNK:
153                         inode->i_op = &page_symlink_inode_operations;
154                         inode_nohighmem(inode);
155                         inode->i_data.a_ops = &efs_symlink_aops;
156                         break;
157                 case S_IFCHR:
158                 case S_IFBLK:
159                 case S_IFIFO:
160                         init_special_inode(inode, inode->i_mode, device);
161                         break;
162                 default:
163                         pr_warn("unsupported inode mode %o\n", inode->i_mode);
164                         goto read_inode_error;
165                         break;
166         }
167 
168         unlock_new_inode(inode);
169         return inode;
170         
171 read_inode_error:
172         pr_warn("failed to read inode %lu\n", inode->i_ino);
173         iget_failed(inode);
174         return ERR_PTR(-EIO);
175 }
176 
177 static inline efs_block_t
178 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
179         efs_block_t start;
180         efs_block_t length;
181         efs_block_t offset;
182 
183         /*
184          * given an extent and a logical block within a file,
185          * can this block be found within this extent ?
186          */
187         start  = ptr->cooked.ex_bn;
188         length = ptr->cooked.ex_length;
189         offset = ptr->cooked.ex_offset;
190 
191         if ((block >= offset) && (block < offset+length)) {
192                 return(sb->fs_start + start + block - offset);
193         } else {
194                 return 0;
195         }
196 }
197 
198 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
199         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
200         struct efs_inode_info *in = INODE_INFO(inode);
201         struct buffer_head    *bh = NULL;
202 
203         int cur, last, first = 1;
204         int ibase, ioffset, dirext, direxts, indext, indexts;
205         efs_block_t iblock, result = 0, lastblock = 0;
206         efs_extent ext, *exts;
207 
208         last = in->lastextent;
209 
210         if (in->numextents <= EFS_DIRECTEXTENTS) {
211                 /* first check the last extent we returned */
212                 if ((result = efs_extent_check(&in->extents[last], block, sb)))
213                         return result;
214     
215                 /* if we only have one extent then nothing can be found */
216                 if (in->numextents == 1) {
217                         pr_err("%s() failed to map (1 extent)\n", __func__);
218                         return 0;
219                 }
220 
221                 direxts = in->numextents;
222 
223                 /*
224                  * check the stored extents in the inode
225                  * start with next extent and check forwards
226                  */
227                 for(dirext = 1; dirext < direxts; dirext++) {
228                         cur = (last + dirext) % in->numextents;
229                         if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
230                                 in->lastextent = cur;
231                                 return result;
232                         }
233                 }
234 
235                 pr_err("%s() failed to map block %u (dir)\n", __func__, block);
236                 return 0;
237         }
238 
239         pr_debug("%s(): indirect search for logical block %u\n",
240                  __func__, block);
241         direxts = in->extents[0].cooked.ex_offset;
242         indexts = in->numextents;
243 
244         for(indext = 0; indext < indexts; indext++) {
245                 cur = (last + indext) % indexts;
246 
247                 /*
248                  * work out which direct extent contains `cur'.
249                  *
250                  * also compute ibase: i.e. the number of the first
251                  * indirect extent contained within direct extent `cur'.
252                  *
253                  */
254                 ibase = 0;
255                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
256                         ibase += in->extents[dirext].cooked.ex_length *
257                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
258                 }
259 
260                 if (dirext == direxts) {
261                         /* should never happen */
262                         pr_err("couldn't find direct extent for indirect extent %d (block %u)\n",
263                                cur, block);
264                         if (bh) brelse(bh);
265                         return 0;
266                 }
267                 
268                 /* work out block number and offset of this indirect extent */
269                 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
270                         (cur - ibase) /
271                         (EFS_BLOCKSIZE / sizeof(efs_extent));
272                 ioffset = (cur - ibase) %
273                         (EFS_BLOCKSIZE / sizeof(efs_extent));
274 
275                 if (first || lastblock != iblock) {
276                         if (bh) brelse(bh);
277 
278                         bh = sb_bread(inode->i_sb, iblock);
279                         if (!bh) {
280                                 pr_err("%s() failed at block %d\n",
281                                        __func__, iblock);
282                                 return 0;
283                         }
284                         pr_debug("%s(): read indirect extent block %d\n",
285                                  __func__, iblock);
286                         first = 0;
287                         lastblock = iblock;
288                 }
289 
290                 exts = (efs_extent *) bh->b_data;
291 
292                 extent_copy(&(exts[ioffset]), &ext);
293 
294                 if (ext.cooked.ex_magic != 0) {
295                         pr_err("extent %d has bad magic number in block %d\n",
296                                cur, iblock);
297                         if (bh) brelse(bh);
298                         return 0;
299                 }
300 
301                 if ((result = efs_extent_check(&ext, block, sb))) {
302                         if (bh) brelse(bh);
303                         in->lastextent = cur;
304                         return result;
305                 }
306         }
307         if (bh) brelse(bh);
308         pr_err("%s() failed to map block %u (indir)\n", __func__, block);
309         return 0;
310 }  
311 
312 MODULE_LICENSE("GPL");
313 

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