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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/efs_fs.h>
 11 #include <linux/efs_fs_sb.h>
 12 #include <linux/module.h>
 13 
 14 
 15 extern int efs_get_block(struct inode *, long, struct buffer_head *, int);
 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 int _efs_bmap(struct address_space *mapping, long block)
 21 {
 22         return generic_block_bmap(mapping,block,efs_get_block);
 23 }
 24 struct address_space_operations efs_aops = {
 25         readpage: efs_readpage,
 26         sync_page: block_sync_page,
 27         bmap: _efs_bmap
 28 };
 29 
 30 static inline void extent_copy(efs_extent *src, efs_extent *dst) {
 31         /*
 32          * this is slightly evil. it doesn't just copy
 33          * efs_extent from src to dst, it also mangles
 34          * the bits so that dst ends up in cpu byte-order.
 35          */
 36 
 37         dst->cooked.ex_magic  =  (unsigned int) src->raw[0];
 38         dst->cooked.ex_bn     = ((unsigned int) src->raw[1] << 16) |
 39                                 ((unsigned int) src->raw[2] <<  8) |
 40                                 ((unsigned int) src->raw[3] <<  0);
 41         dst->cooked.ex_length =  (unsigned int) src->raw[4];
 42         dst->cooked.ex_offset = ((unsigned int) src->raw[5] << 16) |
 43                                 ((unsigned int) src->raw[6] <<  8) |
 44                                 ((unsigned int) src->raw[7] <<  0);
 45         return;
 46 }
 47 
 48 void efs_read_inode(struct inode *inode) {
 49         int i, inode_index;
 50         dev_t device;
 51         struct buffer_head *bh;
 52         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
 53         struct efs_inode_info *in = INODE_INFO(inode);
 54         efs_block_t block, offset;
 55         struct efs_dinode *efs_inode;
 56   
 57         /*
 58         ** EFS layout:
 59         **
 60         ** |   cylinder group    |   cylinder group    |   cylinder group ..etc
 61         ** |inodes|data          |inodes|data          |inodes|data       ..etc
 62         **
 63         ** work out the inode block index, (considering initially that the
 64         ** inodes are stored as consecutive blocks). then work out the block
 65         ** number of that inode given the above layout, and finally the
 66         ** offset of the inode within that block.
 67         */
 68 
 69         inode_index = inode->i_ino /
 70                 (EFS_BLOCKSIZE / sizeof(struct efs_dinode));
 71 
 72         block = sb->fs_start + sb->first_block + 
 73                 (sb->group_size * (inode_index / sb->inode_blocks)) +
 74                 (inode_index % sb->inode_blocks);
 75 
 76         offset = (inode->i_ino %
 77                         (EFS_BLOCKSIZE / sizeof(struct efs_dinode))) *
 78                 sizeof(struct efs_dinode);
 79 
 80         bh = sb_bread(inode->i_sb, block);
 81         if (!bh) {
 82                 printk(KERN_WARNING "EFS: bread() failed at block %d\n", block);
 83                 goto read_inode_error;
 84         }
 85 
 86         efs_inode = (struct efs_dinode *) (bh->b_data + offset);
 87     
 88         inode->i_mode  = be16_to_cpu(efs_inode->di_mode);
 89         inode->i_nlink = be16_to_cpu(efs_inode->di_nlink);
 90         inode->i_uid   = (uid_t)be16_to_cpu(efs_inode->di_uid);
 91         inode->i_gid   = (gid_t)be16_to_cpu(efs_inode->di_gid);
 92         inode->i_size  = be32_to_cpu(efs_inode->di_size);
 93         inode->i_atime = be32_to_cpu(efs_inode->di_atime);
 94         inode->i_mtime = be32_to_cpu(efs_inode->di_mtime);
 95         inode->i_ctime = be32_to_cpu(efs_inode->di_ctime);
 96 
 97         /* this is the number of blocks in the file */
 98         if (inode->i_size == 0) {
 99                 inode->i_blocks = 0;
100         } else {
101                 inode->i_blocks = ((inode->i_size - 1) >> EFS_BLOCKSIZE_BITS) + 1;
102         }
103 
104         /*
105          * BUG: irix dev_t is 32-bits. linux dev_t is only 16-bits.
106          *
107          * apparently linux will change to 32-bit dev_t sometime during
108          * linux 2.3.
109          *
110          * as is, this code maps devices that can't be represented in
111          * 16-bits (ie major > 255 or minor > 255) to major = minor = 255.
112          *
113          * during 2.3 when 32-bit dev_t become available, we should test
114          * to see whether odev contains 65535. if this is the case then we
115          * should then do device = be32_to_cpu(efs_inode->di_u.di_dev.ndev).
116          */
117         device = be16_to_cpu(efs_inode->di_u.di_dev.odev);
118 
119         /* get the number of extents for this object */
120         in->numextents = be16_to_cpu(efs_inode->di_numextents);
121         in->lastextent = 0;
122 
123         /* copy the extents contained within the inode to memory */
124         for(i = 0; i < EFS_DIRECTEXTENTS; i++) {
125                 extent_copy(&(efs_inode->di_u.di_extents[i]), &(in->extents[i]));
126                 if (i < in->numextents && in->extents[i].cooked.ex_magic != 0) {
127                         printk(KERN_WARNING "EFS: extent %d has bad magic number in inode %lu\n", i, inode->i_ino);
128                         brelse(bh);
129                         goto read_inode_error;
130                 }
131         }
132 
133         brelse(bh);
134    
135 #ifdef DEBUG
136         printk(KERN_DEBUG "EFS: read_inode(): inode %lu, extents %d, mode %o\n",
137                 inode->i_ino, in->numextents, inode->i_mode);
138 #endif
139 
140         switch (inode->i_mode & S_IFMT) {
141                 case S_IFDIR: 
142                         inode->i_op = &efs_dir_inode_operations; 
143                         inode->i_fop = &efs_dir_operations; 
144                         break;
145                 case S_IFREG:
146                         inode->i_fop = &generic_ro_fops;
147                         inode->i_data.a_ops = &efs_aops;
148                         break;
149                 case S_IFLNK:
150                         inode->i_op = &page_symlink_inode_operations;
151                         inode->i_data.a_ops = &efs_symlink_aops;
152                         break;
153                 case S_IFCHR:
154                 case S_IFBLK:
155                 case S_IFIFO:
156                         init_special_inode(inode, inode->i_mode, device);
157                         break;
158                 default:
159                         printk(KERN_WARNING "EFS: unsupported inode mode %o\n", inode->i_mode);
160                         goto read_inode_error;
161                         break;
162         }
163 
164         return;
165         
166 read_inode_error:
167         printk(KERN_WARNING "EFS: failed to read inode %lu\n", inode->i_ino);
168         make_bad_inode(inode);
169 
170         return;
171 }
172 
173 static inline efs_block_t
174 efs_extent_check(efs_extent *ptr, efs_block_t block, struct efs_sb_info *sb) {
175         efs_block_t start;
176         efs_block_t length;
177         efs_block_t offset;
178 
179         /*
180          * given an extent and a logical block within a file,
181          * can this block be found within this extent ?
182          */
183         start  = ptr->cooked.ex_bn;
184         length = ptr->cooked.ex_length;
185         offset = ptr->cooked.ex_offset;
186 
187         if ((block >= offset) && (block < offset+length)) {
188                 return(sb->fs_start + start + block - offset);
189         } else {
190                 return 0;
191         }
192 }
193 
194 efs_block_t efs_map_block(struct inode *inode, efs_block_t block) {
195         struct efs_sb_info    *sb = SUPER_INFO(inode->i_sb);
196         struct efs_inode_info *in = INODE_INFO(inode);
197         struct buffer_head    *bh = NULL;
198 
199         int cur, last, first = 1;
200         int ibase, ioffset, dirext, direxts, indext, indexts;
201         efs_block_t iblock, result = 0, lastblock = 0;
202         efs_extent ext, *exts;
203 
204         last = in->lastextent;
205 
206         if (in->numextents <= EFS_DIRECTEXTENTS) {
207                 /* first check the last extent we returned */
208                 if ((result = efs_extent_check(&in->extents[last], block, sb)))
209                         return result;
210     
211                 /* if we only have one extent then nothing can be found */
212                 if (in->numextents == 1) {
213                         printk(KERN_ERR "EFS: map_block() failed to map (1 extent)\n");
214                         return 0;
215                 }
216 
217                 direxts = in->numextents;
218 
219                 /*
220                  * check the stored extents in the inode
221                  * start with next extent and check forwards
222                  */
223                 for(dirext = 1; dirext < direxts; dirext++) {
224                         cur = (last + dirext) % in->numextents;
225                         if ((result = efs_extent_check(&in->extents[cur], block, sb))) {
226                                 in->lastextent = cur;
227                                 return result;
228                         }
229                 }
230 
231                 printk(KERN_ERR "EFS: map_block() failed to map block %u (dir)\n", block);
232                 return 0;
233         }
234 
235 #ifdef DEBUG
236         printk(KERN_DEBUG "EFS: map_block(): indirect search for logical block %u\n", block);
237 #endif
238         direxts = in->extents[0].cooked.ex_offset;
239         indexts = in->numextents;
240 
241         for(indext = 0; indext < indexts; indext++) {
242                 cur = (last + indext) % indexts;
243 
244                 /*
245                  * work out which direct extent contains `cur'.
246                  *
247                  * also compute ibase: i.e. the number of the first
248                  * indirect extent contained within direct extent `cur'.
249                  *
250                  */
251                 ibase = 0;
252                 for(dirext = 0; cur < ibase && dirext < direxts; dirext++) {
253                         ibase += in->extents[dirext].cooked.ex_length *
254                                 (EFS_BLOCKSIZE / sizeof(efs_extent));
255                 }
256 
257                 if (dirext == direxts) {
258                         /* should never happen */
259                         printk(KERN_ERR "EFS: couldn't find direct extent for indirect extent %d (block %u)\n", cur, block);
260                         if (bh) brelse(bh);
261                         return 0;
262                 }
263                 
264                 /* work out block number and offset of this indirect extent */
265                 iblock = sb->fs_start + in->extents[dirext].cooked.ex_bn +
266                         (cur - ibase) /
267                         (EFS_BLOCKSIZE / sizeof(efs_extent));
268                 ioffset = (cur - ibase) %
269                         (EFS_BLOCKSIZE / sizeof(efs_extent));
270 
271                 if (first || lastblock != iblock) {
272                         if (bh) brelse(bh);
273 
274                         bh = sb_bread(inode->i_sb, iblock);
275                         if (!bh) {
276                                 printk(KERN_ERR "EFS: bread() failed at block %d\n", iblock);
277                                 return 0;
278                         }
279 #ifdef DEBUG
280                         printk(KERN_DEBUG "EFS: map_block(): read indirect extent block %d\n", iblock);
281 #endif
282                         first = 0;
283                         lastblock = iblock;
284                 }
285 
286                 exts = (efs_extent *) bh->b_data;
287 
288                 extent_copy(&(exts[ioffset]), &ext);
289 
290                 if (ext.cooked.ex_magic != 0) {
291                         printk(KERN_ERR "EFS: extent %d has bad magic number in block %d\n", cur, iblock);
292                         if (bh) brelse(bh);
293                         return 0;
294                 }
295 
296                 if ((result = efs_extent_check(&ext, block, sb))) {
297                         if (bh) brelse(bh);
298                         in->lastextent = cur;
299                         return result;
300                 }
301         }
302         if (bh) brelse(bh);
303         printk(KERN_ERR "EFS: map_block() failed to map block %u (indir)\n", block);
304         return 0;
305 }  
306 
307 MODULE_LICENSE("GPL");
308 

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