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1 | /* Generic part */ |
2 | |
3 | typedef struct { |
4 | block_t *p; |
5 | block_t key; |
6 | struct buffer_head *bh; |
7 | } Indirect; |
8 | |
9 | static DEFINE_RWLOCK(pointers_lock); |
10 | |
11 | static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v) |
12 | { |
13 | p->key = *(p->p = v); |
14 | p->bh = bh; |
15 | } |
16 | |
17 | static inline int verify_chain(Indirect *from, Indirect *to) |
18 | { |
19 | while (from <= to && from->key == *from->p) |
20 | from++; |
21 | return (from > to); |
22 | } |
23 | |
24 | static inline block_t *block_end(struct buffer_head *bh) |
25 | { |
26 | return (block_t *)((char*)bh->b_data + bh->b_size); |
27 | } |
28 | |
29 | static inline Indirect *get_branch(struct inode *inode, |
30 | int depth, |
31 | int *offsets, |
32 | Indirect chain[DEPTH], |
33 | int *err) |
34 | { |
35 | struct super_block *sb = inode->i_sb; |
36 | Indirect *p = chain; |
37 | struct buffer_head *bh; |
38 | |
39 | *err = 0; |
40 | /* i_data is not going away, no lock needed */ |
41 | add_chain (chain, NULL, i_data(inode) + *offsets); |
42 | if (!p->key) |
43 | goto no_block; |
44 | while (--depth) { |
45 | bh = sb_bread(sb, block_to_cpu(p->key)); |
46 | if (!bh) |
47 | goto failure; |
48 | read_lock(&pointers_lock); |
49 | if (!verify_chain(chain, p)) |
50 | goto changed; |
51 | add_chain(++p, bh, (block_t *)bh->b_data + *++offsets); |
52 | read_unlock(&pointers_lock); |
53 | if (!p->key) |
54 | goto no_block; |
55 | } |
56 | return NULL; |
57 | |
58 | changed: |
59 | read_unlock(&pointers_lock); |
60 | brelse(bh); |
61 | *err = -EAGAIN; |
62 | goto no_block; |
63 | failure: |
64 | *err = -EIO; |
65 | no_block: |
66 | return p; |
67 | } |
68 | |
69 | static int alloc_branch(struct inode *inode, |
70 | int num, |
71 | int *offsets, |
72 | Indirect *branch) |
73 | { |
74 | int n = 0; |
75 | int i; |
76 | int parent = minix_new_block(inode); |
77 | |
78 | branch[0].key = cpu_to_block(parent); |
79 | if (parent) for (n = 1; n < num; n++) { |
80 | struct buffer_head *bh; |
81 | /* Allocate the next block */ |
82 | int nr = minix_new_block(inode); |
83 | if (!nr) |
84 | break; |
85 | branch[n].key = cpu_to_block(nr); |
86 | bh = sb_getblk(inode->i_sb, parent); |
87 | lock_buffer(bh); |
88 | memset(bh->b_data, 0, bh->b_size); |
89 | branch[n].bh = bh; |
90 | branch[n].p = (block_t*) bh->b_data + offsets[n]; |
91 | *branch[n].p = branch[n].key; |
92 | set_buffer_uptodate(bh); |
93 | unlock_buffer(bh); |
94 | mark_buffer_dirty_inode(bh, inode); |
95 | parent = nr; |
96 | } |
97 | if (n == num) |
98 | return 0; |
99 | |
100 | /* Allocation failed, free what we already allocated */ |
101 | for (i = 1; i < n; i++) |
102 | bforget(branch[i].bh); |
103 | for (i = 0; i < n; i++) |
104 | minix_free_block(inode, block_to_cpu(branch[i].key)); |
105 | return -ENOSPC; |
106 | } |
107 | |
108 | static inline int splice_branch(struct inode *inode, |
109 | Indirect chain[DEPTH], |
110 | Indirect *where, |
111 | int num) |
112 | { |
113 | int i; |
114 | |
115 | write_lock(&pointers_lock); |
116 | |
117 | /* Verify that place we are splicing to is still there and vacant */ |
118 | if (!verify_chain(chain, where-1) || *where->p) |
119 | goto changed; |
120 | |
121 | *where->p = where->key; |
122 | |
123 | write_unlock(&pointers_lock); |
124 | |
125 | /* We are done with atomic stuff, now do the rest of housekeeping */ |
126 | |
127 | inode->i_ctime = CURRENT_TIME_SEC; |
128 | |
129 | /* had we spliced it onto indirect block? */ |
130 | if (where->bh) |
131 | mark_buffer_dirty_inode(where->bh, inode); |
132 | |
133 | mark_inode_dirty(inode); |
134 | return 0; |
135 | |
136 | changed: |
137 | write_unlock(&pointers_lock); |
138 | for (i = 1; i < num; i++) |
139 | bforget(where[i].bh); |
140 | for (i = 0; i < num; i++) |
141 | minix_free_block(inode, block_to_cpu(where[i].key)); |
142 | return -EAGAIN; |
143 | } |
144 | |
145 | static inline int get_block(struct inode * inode, sector_t block, |
146 | struct buffer_head *bh, int create) |
147 | { |
148 | int err = -EIO; |
149 | int offsets[DEPTH]; |
150 | Indirect chain[DEPTH]; |
151 | Indirect *partial; |
152 | int left; |
153 | int depth = block_to_path(inode, block, offsets); |
154 | |
155 | if (depth == 0) |
156 | goto out; |
157 | |
158 | reread: |
159 | partial = get_branch(inode, depth, offsets, chain, &err); |
160 | |
161 | /* Simplest case - block found, no allocation needed */ |
162 | if (!partial) { |
163 | got_it: |
164 | map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key)); |
165 | /* Clean up and exit */ |
166 | partial = chain+depth-1; /* the whole chain */ |
167 | goto cleanup; |
168 | } |
169 | |
170 | /* Next simple case - plain lookup or failed read of indirect block */ |
171 | if (!create || err == -EIO) { |
172 | cleanup: |
173 | while (partial > chain) { |
174 | brelse(partial->bh); |
175 | partial--; |
176 | } |
177 | out: |
178 | return err; |
179 | } |
180 | |
181 | /* |
182 | * Indirect block might be removed by truncate while we were |
183 | * reading it. Handling of that case (forget what we've got and |
184 | * reread) is taken out of the main path. |
185 | */ |
186 | if (err == -EAGAIN) |
187 | goto changed; |
188 | |
189 | left = (chain + depth) - partial; |
190 | err = alloc_branch(inode, left, offsets+(partial-chain), partial); |
191 | if (err) |
192 | goto cleanup; |
193 | |
194 | if (splice_branch(inode, chain, partial, left) < 0) |
195 | goto changed; |
196 | |
197 | set_buffer_new(bh); |
198 | goto got_it; |
199 | |
200 | changed: |
201 | while (partial > chain) { |
202 | brelse(partial->bh); |
203 | partial--; |
204 | } |
205 | goto reread; |
206 | } |
207 | |
208 | static inline int all_zeroes(block_t *p, block_t *q) |
209 | { |
210 | while (p < q) |
211 | if (*p++) |
212 | return 0; |
213 | return 1; |
214 | } |
215 | |
216 | static Indirect *find_shared(struct inode *inode, |
217 | int depth, |
218 | int offsets[DEPTH], |
219 | Indirect chain[DEPTH], |
220 | block_t *top) |
221 | { |
222 | Indirect *partial, *p; |
223 | int k, err; |
224 | |
225 | *top = 0; |
226 | for (k = depth; k > 1 && !offsets[k-1]; k--) |
227 | ; |
228 | partial = get_branch(inode, k, offsets, chain, &err); |
229 | |
230 | write_lock(&pointers_lock); |
231 | if (!partial) |
232 | partial = chain + k-1; |
233 | if (!partial->key && *partial->p) { |
234 | write_unlock(&pointers_lock); |
235 | goto no_top; |
236 | } |
237 | for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--) |
238 | ; |
239 | if (p == chain + k - 1 && p > chain) { |
240 | p->p--; |
241 | } else { |
242 | *top = *p->p; |
243 | *p->p = 0; |
244 | } |
245 | write_unlock(&pointers_lock); |
246 | |
247 | while(partial > p) |
248 | { |
249 | brelse(partial->bh); |
250 | partial--; |
251 | } |
252 | no_top: |
253 | return partial; |
254 | } |
255 | |
256 | static inline void free_data(struct inode *inode, block_t *p, block_t *q) |
257 | { |
258 | unsigned long nr; |
259 | |
260 | for ( ; p < q ; p++) { |
261 | nr = block_to_cpu(*p); |
262 | if (nr) { |
263 | *p = 0; |
264 | minix_free_block(inode, nr); |
265 | } |
266 | } |
267 | } |
268 | |
269 | static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth) |
270 | { |
271 | struct buffer_head * bh; |
272 | unsigned long nr; |
273 | |
274 | if (depth--) { |
275 | for ( ; p < q ; p++) { |
276 | nr = block_to_cpu(*p); |
277 | if (!nr) |
278 | continue; |
279 | *p = 0; |
280 | bh = sb_bread(inode->i_sb, nr); |
281 | if (!bh) |
282 | continue; |
283 | free_branches(inode, (block_t*)bh->b_data, |
284 | block_end(bh), depth); |
285 | bforget(bh); |
286 | minix_free_block(inode, nr); |
287 | mark_inode_dirty(inode); |
288 | } |
289 | } else |
290 | free_data(inode, p, q); |
291 | } |
292 | |
293 | static inline void truncate (struct inode * inode) |
294 | { |
295 | struct super_block *sb = inode->i_sb; |
296 | block_t *idata = i_data(inode); |
297 | int offsets[DEPTH]; |
298 | Indirect chain[DEPTH]; |
299 | Indirect *partial; |
300 | block_t nr = 0; |
301 | int n; |
302 | int first_whole; |
303 | long iblock; |
304 | |
305 | iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits; |
306 | block_truncate_page(inode->i_mapping, inode->i_size, get_block); |
307 | |
308 | n = block_to_path(inode, iblock, offsets); |
309 | if (!n) |
310 | return; |
311 | |
312 | if (n == 1) { |
313 | free_data(inode, idata+offsets[0], idata + DIRECT); |
314 | first_whole = 0; |
315 | goto do_indirects; |
316 | } |
317 | |
318 | first_whole = offsets[0] + 1 - DIRECT; |
319 | partial = find_shared(inode, n, offsets, chain, &nr); |
320 | if (nr) { |
321 | if (partial == chain) |
322 | mark_inode_dirty(inode); |
323 | else |
324 | mark_buffer_dirty_inode(partial->bh, inode); |
325 | free_branches(inode, &nr, &nr+1, (chain+n-1) - partial); |
326 | } |
327 | /* Clear the ends of indirect blocks on the shared branch */ |
328 | while (partial > chain) { |
329 | free_branches(inode, partial->p + 1, block_end(partial->bh), |
330 | (chain+n-1) - partial); |
331 | mark_buffer_dirty_inode(partial->bh, inode); |
332 | brelse (partial->bh); |
333 | partial--; |
334 | } |
335 | do_indirects: |
336 | /* Kill the remaining (whole) subtrees */ |
337 | while (first_whole < DEPTH-1) { |
338 | nr = idata[DIRECT+first_whole]; |
339 | if (nr) { |
340 | idata[DIRECT+first_whole] = 0; |
341 | mark_inode_dirty(inode); |
342 | free_branches(inode, &nr, &nr+1, first_whole+1); |
343 | } |
344 | first_whole++; |
345 | } |
346 | inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC; |
347 | mark_inode_dirty(inode); |
348 | } |
349 | |
350 | static inline unsigned nblocks(loff_t size, struct super_block *sb) |
351 | { |
352 | int k = sb->s_blocksize_bits - 10; |
353 | unsigned blocks, res, direct = DIRECT, i = DEPTH; |
354 | blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k); |
355 | res = blocks; |
356 | while (--i && blocks > direct) { |
357 | blocks -= direct; |
358 | blocks += sb->s_blocksize/sizeof(block_t) - 1; |
359 | blocks /= sb->s_blocksize/sizeof(block_t); |
360 | res += blocks; |
361 | direct = 1; |
362 | } |
363 | return res; |
364 | } |
365 |
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