1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * This file is part of UBIFS. |
4 | * |
5 | * Copyright (C) 2006-2008 Nokia Corporation. |
6 | * |
7 | * Authors: Adrian Hunter |
8 | * Artem Bityutskiy (Битюцкий Артём) |
9 | */ |
10 | |
11 | /* |
12 | * This file implements the budgeting sub-system which is responsible for UBIFS |
13 | * space management. |
14 | * |
15 | * Factors such as compression, wasted space at the ends of LEBs, space in other |
16 | * journal heads, the effect of updates on the index, and so on, make it |
17 | * impossible to accurately predict the amount of space needed. Consequently |
18 | * approximations are used. |
19 | */ |
20 | |
21 | #include "ubifs.h" |
22 | #include <linux/writeback.h> |
23 | #include <linux/math64.h> |
24 | |
25 | /* |
26 | * When pessimistic budget calculations say that there is no enough space, |
27 | * UBIFS starts writing back dirty inodes and pages, doing garbage collection, |
28 | * or committing. The below constant defines maximum number of times UBIFS |
29 | * repeats the operations. |
30 | */ |
31 | #define MAX_MKSPC_RETRIES 3 |
32 | |
33 | /* |
34 | * The below constant defines amount of dirty pages which should be written |
35 | * back at when trying to shrink the liability. |
36 | */ |
37 | #define NR_TO_WRITE 16 |
38 | |
39 | /** |
40 | * shrink_liability - write-back some dirty pages/inodes. |
41 | * @c: UBIFS file-system description object |
42 | * @nr_to_write: how many dirty pages to write-back |
43 | * |
44 | * This function shrinks UBIFS liability by means of writing back some amount |
45 | * of dirty inodes and their pages. |
46 | * |
47 | * Note, this function synchronizes even VFS inodes which are locked |
48 | * (@i_mutex) by the caller of the budgeting function, because write-back does |
49 | * not touch @i_mutex. |
50 | */ |
51 | static void shrink_liability(struct ubifs_info *c, int nr_to_write) |
52 | { |
53 | down_read(sem: &c->vfs_sb->s_umount); |
54 | writeback_inodes_sb_nr(c->vfs_sb, nr: nr_to_write, reason: WB_REASON_FS_FREE_SPACE); |
55 | up_read(sem: &c->vfs_sb->s_umount); |
56 | } |
57 | |
58 | /** |
59 | * run_gc - run garbage collector. |
60 | * @c: UBIFS file-system description object |
61 | * |
62 | * This function runs garbage collector to make some more free space. Returns |
63 | * zero if a free LEB has been produced, %-EAGAIN if commit is required, and a |
64 | * negative error code in case of failure. |
65 | */ |
66 | static int run_gc(struct ubifs_info *c) |
67 | { |
68 | int lnum; |
69 | |
70 | /* Make some free space by garbage-collecting dirty space */ |
71 | down_read(sem: &c->commit_sem); |
72 | lnum = ubifs_garbage_collect(c, anyway: 1); |
73 | up_read(sem: &c->commit_sem); |
74 | if (lnum < 0) |
75 | return lnum; |
76 | |
77 | /* GC freed one LEB, return it to lprops */ |
78 | dbg_budg("GC freed LEB %d" , lnum); |
79 | return ubifs_return_leb(c, lnum); |
80 | } |
81 | |
82 | /** |
83 | * get_liability - calculate current liability. |
84 | * @c: UBIFS file-system description object |
85 | * |
86 | * This function calculates and returns current UBIFS liability, i.e. the |
87 | * amount of bytes UBIFS has "promised" to write to the media. |
88 | */ |
89 | static long long get_liability(struct ubifs_info *c) |
90 | { |
91 | long long liab; |
92 | |
93 | spin_lock(lock: &c->space_lock); |
94 | liab = c->bi.idx_growth + c->bi.data_growth + c->bi.dd_growth; |
95 | spin_unlock(lock: &c->space_lock); |
96 | return liab; |
97 | } |
98 | |
99 | /** |
100 | * make_free_space - make more free space on the file-system. |
101 | * @c: UBIFS file-system description object |
102 | * |
103 | * This function is called when an operation cannot be budgeted because there |
104 | * is supposedly no free space. But in most cases there is some free space: |
105 | * o budgeting is pessimistic, so it always budgets more than it is actually |
106 | * needed, so shrinking the liability is one way to make free space - the |
107 | * cached data will take less space then it was budgeted for; |
108 | * o GC may turn some dark space into free space (budgeting treats dark space |
109 | * as not available); |
110 | * o commit may free some LEB, i.e., turn freeable LEBs into free LEBs. |
111 | * |
112 | * So this function tries to do the above. Returns %-EAGAIN if some free space |
113 | * was presumably made and the caller has to re-try budgeting the operation. |
114 | * Returns %-ENOSPC if it couldn't do more free space, and other negative error |
115 | * codes on failures. |
116 | */ |
117 | static int make_free_space(struct ubifs_info *c) |
118 | { |
119 | int err, retries = 0; |
120 | long long liab1, liab2; |
121 | |
122 | do { |
123 | liab1 = get_liability(c); |
124 | /* |
125 | * We probably have some dirty pages or inodes (liability), try |
126 | * to write them back. |
127 | */ |
128 | dbg_budg("liability %lld, run write-back" , liab1); |
129 | shrink_liability(c, NR_TO_WRITE); |
130 | |
131 | liab2 = get_liability(c); |
132 | if (liab2 < liab1) |
133 | return -EAGAIN; |
134 | |
135 | dbg_budg("new liability %lld (not shrunk)" , liab2); |
136 | |
137 | /* Liability did not shrink again, try GC */ |
138 | dbg_budg("Run GC" ); |
139 | err = run_gc(c); |
140 | if (!err) |
141 | return -EAGAIN; |
142 | |
143 | if (err != -EAGAIN && err != -ENOSPC) |
144 | /* Some real error happened */ |
145 | return err; |
146 | |
147 | dbg_budg("Run commit (retries %d)" , retries); |
148 | err = ubifs_run_commit(c); |
149 | if (err) |
150 | return err; |
151 | } while (retries++ < MAX_MKSPC_RETRIES); |
152 | |
153 | return -ENOSPC; |
154 | } |
155 | |
156 | /** |
157 | * ubifs_calc_min_idx_lebs - calculate amount of LEBs for the index. |
158 | * @c: UBIFS file-system description object |
159 | * |
160 | * This function calculates and returns the number of LEBs which should be kept |
161 | * for index usage. |
162 | */ |
163 | int ubifs_calc_min_idx_lebs(struct ubifs_info *c) |
164 | { |
165 | int idx_lebs; |
166 | long long idx_size; |
167 | |
168 | idx_size = c->bi.old_idx_sz + c->bi.idx_growth + c->bi.uncommitted_idx; |
169 | /* And make sure we have thrice the index size of space reserved */ |
170 | idx_size += idx_size << 1; |
171 | /* |
172 | * We do not maintain 'old_idx_size' as 'old_idx_lebs'/'old_idx_bytes' |
173 | * pair, nor similarly the two variables for the new index size, so we |
174 | * have to do this costly 64-bit division on fast-path. |
175 | */ |
176 | idx_lebs = div_u64(dividend: idx_size + c->idx_leb_size - 1, divisor: c->idx_leb_size); |
177 | /* |
178 | * The index head is not available for the in-the-gaps method, so add an |
179 | * extra LEB to compensate. |
180 | */ |
181 | idx_lebs += 1; |
182 | if (idx_lebs < MIN_INDEX_LEBS) |
183 | idx_lebs = MIN_INDEX_LEBS; |
184 | return idx_lebs; |
185 | } |
186 | |
187 | /** |
188 | * ubifs_calc_available - calculate available FS space. |
189 | * @c: UBIFS file-system description object |
190 | * @min_idx_lebs: minimum number of LEBs reserved for the index |
191 | * |
192 | * This function calculates and returns amount of FS space available for use. |
193 | */ |
194 | long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs) |
195 | { |
196 | int subtract_lebs; |
197 | long long available; |
198 | |
199 | available = c->main_bytes - c->lst.total_used; |
200 | |
201 | /* |
202 | * Now 'available' contains theoretically available flash space |
203 | * assuming there is no index, so we have to subtract the space which |
204 | * is reserved for the index. |
205 | */ |
206 | subtract_lebs = min_idx_lebs; |
207 | |
208 | /* Take into account that GC reserves one LEB for its own needs */ |
209 | subtract_lebs += 1; |
210 | |
211 | /* |
212 | * Since different write types go to different heads, we should |
213 | * reserve one leb for each head. |
214 | */ |
215 | subtract_lebs += c->jhead_cnt; |
216 | |
217 | /* We also reserve one LEB for deletions, which bypass budgeting */ |
218 | subtract_lebs += 1; |
219 | |
220 | available -= (long long)subtract_lebs * c->leb_size; |
221 | |
222 | /* Subtract the dead space which is not available for use */ |
223 | available -= c->lst.total_dead; |
224 | |
225 | /* |
226 | * Subtract dark space, which might or might not be usable - it depends |
227 | * on the data which we have on the media and which will be written. If |
228 | * this is a lot of uncompressed or not-compressible data, the dark |
229 | * space cannot be used. |
230 | */ |
231 | available -= c->lst.total_dark; |
232 | |
233 | /* |
234 | * However, there is more dark space. The index may be bigger than |
235 | * @min_idx_lebs. Those extra LEBs are assumed to be available, but |
236 | * their dark space is not included in total_dark, so it is subtracted |
237 | * here. |
238 | */ |
239 | if (c->lst.idx_lebs > min_idx_lebs) { |
240 | subtract_lebs = c->lst.idx_lebs - min_idx_lebs; |
241 | available -= subtract_lebs * c->dark_wm; |
242 | } |
243 | |
244 | /* The calculations are rough and may end up with a negative number */ |
245 | return available > 0 ? available : 0; |
246 | } |
247 | |
248 | /** |
249 | * can_use_rp - check whether the user is allowed to use reserved pool. |
250 | * @c: UBIFS file-system description object |
251 | * |
252 | * UBIFS has so-called "reserved pool" which is flash space reserved |
253 | * for the superuser and for uses whose UID/GID is recorded in UBIFS superblock. |
254 | * This function checks whether current user is allowed to use reserved pool. |
255 | * Returns %1 current user is allowed to use reserved pool and %0 otherwise. |
256 | */ |
257 | static int can_use_rp(struct ubifs_info *c) |
258 | { |
259 | if (uid_eq(current_fsuid(), right: c->rp_uid) || capable(CAP_SYS_RESOURCE) || |
260 | (!gid_eq(left: c->rp_gid, GLOBAL_ROOT_GID) && in_group_p(c->rp_gid))) |
261 | return 1; |
262 | return 0; |
263 | } |
264 | |
265 | /** |
266 | * do_budget_space - reserve flash space for index and data growth. |
267 | * @c: UBIFS file-system description object |
268 | * |
269 | * This function makes sure UBIFS has enough free LEBs for index growth and |
270 | * data. |
271 | * |
272 | * When budgeting index space, UBIFS reserves thrice as many LEBs as the index |
273 | * would take if it was consolidated and written to the flash. This guarantees |
274 | * that the "in-the-gaps" commit method always succeeds and UBIFS will always |
275 | * be able to commit dirty index. So this function basically adds amount of |
276 | * budgeted index space to the size of the current index, multiplies this by 3, |
277 | * and makes sure this does not exceed the amount of free LEBs. |
278 | * |
279 | * Notes about @c->bi.min_idx_lebs and @c->lst.idx_lebs variables: |
280 | * o @c->lst.idx_lebs is the number of LEBs the index currently uses. It might |
281 | * be large, because UBIFS does not do any index consolidation as long as |
282 | * there is free space. IOW, the index may take a lot of LEBs, but the LEBs |
283 | * will contain a lot of dirt. |
284 | * o @c->bi.min_idx_lebs is the number of LEBS the index presumably takes. IOW, |
285 | * the index may be consolidated to take up to @c->bi.min_idx_lebs LEBs. |
286 | * |
287 | * This function returns zero in case of success, and %-ENOSPC in case of |
288 | * failure. |
289 | */ |
290 | static int do_budget_space(struct ubifs_info *c) |
291 | { |
292 | long long outstanding, available; |
293 | int lebs, rsvd_idx_lebs, min_idx_lebs; |
294 | |
295 | /* First budget index space */ |
296 | min_idx_lebs = ubifs_calc_min_idx_lebs(c); |
297 | |
298 | /* Now 'min_idx_lebs' contains number of LEBs to reserve */ |
299 | if (min_idx_lebs > c->lst.idx_lebs) |
300 | rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs; |
301 | else |
302 | rsvd_idx_lebs = 0; |
303 | |
304 | /* |
305 | * The number of LEBs that are available to be used by the index is: |
306 | * |
307 | * @c->lst.empty_lebs + @c->freeable_cnt + @c->idx_gc_cnt - |
308 | * @c->lst.taken_empty_lebs |
309 | * |
310 | * @c->lst.empty_lebs are available because they are empty. |
311 | * @c->freeable_cnt are available because they contain only free and |
312 | * dirty space, @c->idx_gc_cnt are available because they are index |
313 | * LEBs that have been garbage collected and are awaiting the commit |
314 | * before they can be used. And the in-the-gaps method will grab these |
315 | * if it needs them. @c->lst.taken_empty_lebs are empty LEBs that have |
316 | * already been allocated for some purpose. |
317 | * |
318 | * Note, @c->idx_gc_cnt is included to both @c->lst.empty_lebs (because |
319 | * these LEBs are empty) and to @c->lst.taken_empty_lebs (because they |
320 | * are taken until after the commit). |
321 | * |
322 | * Note, @c->lst.taken_empty_lebs may temporarily be higher by one |
323 | * because of the way we serialize LEB allocations and budgeting. See a |
324 | * comment in 'ubifs_find_free_space()'. |
325 | */ |
326 | lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt - |
327 | c->lst.taken_empty_lebs; |
328 | if (unlikely(rsvd_idx_lebs > lebs)) { |
329 | dbg_budg("out of indexing space: min_idx_lebs %d (old %d), rsvd_idx_lebs %d" , |
330 | min_idx_lebs, c->bi.min_idx_lebs, rsvd_idx_lebs); |
331 | return -ENOSPC; |
332 | } |
333 | |
334 | available = ubifs_calc_available(c, min_idx_lebs); |
335 | outstanding = c->bi.data_growth + c->bi.dd_growth; |
336 | |
337 | if (unlikely(available < outstanding)) { |
338 | dbg_budg("out of data space: available %lld, outstanding %lld" , |
339 | available, outstanding); |
340 | return -ENOSPC; |
341 | } |
342 | |
343 | if (available - outstanding <= c->rp_size && !can_use_rp(c)) |
344 | return -ENOSPC; |
345 | |
346 | c->bi.min_idx_lebs = min_idx_lebs; |
347 | return 0; |
348 | } |
349 | |
350 | /** |
351 | * calc_idx_growth - calculate approximate index growth from budgeting request. |
352 | * @c: UBIFS file-system description object |
353 | * @req: budgeting request |
354 | * |
355 | * For now we assume each new node adds one znode. But this is rather poor |
356 | * approximation, though. |
357 | */ |
358 | static int calc_idx_growth(const struct ubifs_info *c, |
359 | const struct ubifs_budget_req *req) |
360 | { |
361 | int znodes; |
362 | |
363 | znodes = req->new_ino + (req->new_page << UBIFS_BLOCKS_PER_PAGE_SHIFT) + |
364 | req->new_dent; |
365 | return znodes * c->max_idx_node_sz; |
366 | } |
367 | |
368 | /** |
369 | * calc_data_growth - calculate approximate amount of new data from budgeting |
370 | * request. |
371 | * @c: UBIFS file-system description object |
372 | * @req: budgeting request |
373 | */ |
374 | static int calc_data_growth(const struct ubifs_info *c, |
375 | const struct ubifs_budget_req *req) |
376 | { |
377 | int data_growth; |
378 | |
379 | data_growth = req->new_ino ? c->bi.inode_budget : 0; |
380 | if (req->new_page) |
381 | data_growth += c->bi.page_budget; |
382 | if (req->new_dent) |
383 | data_growth += c->bi.dent_budget; |
384 | data_growth += req->new_ino_d; |
385 | return data_growth; |
386 | } |
387 | |
388 | /** |
389 | * calc_dd_growth - calculate approximate amount of data which makes other data |
390 | * dirty from budgeting request. |
391 | * @c: UBIFS file-system description object |
392 | * @req: budgeting request |
393 | */ |
394 | static int calc_dd_growth(const struct ubifs_info *c, |
395 | const struct ubifs_budget_req *req) |
396 | { |
397 | int dd_growth; |
398 | |
399 | dd_growth = req->dirtied_page ? c->bi.page_budget : 0; |
400 | |
401 | if (req->dirtied_ino) |
402 | dd_growth += c->bi.inode_budget * req->dirtied_ino; |
403 | if (req->mod_dent) |
404 | dd_growth += c->bi.dent_budget; |
405 | dd_growth += req->dirtied_ino_d; |
406 | return dd_growth; |
407 | } |
408 | |
409 | /** |
410 | * ubifs_budget_space - ensure there is enough space to complete an operation. |
411 | * @c: UBIFS file-system description object |
412 | * @req: budget request |
413 | * |
414 | * This function allocates budget for an operation. It uses pessimistic |
415 | * approximation of how much flash space the operation needs. The goal of this |
416 | * function is to make sure UBIFS always has flash space to flush all dirty |
417 | * pages, dirty inodes, and dirty znodes (liability). This function may force |
418 | * commit, garbage-collection or write-back. Returns zero in case of success, |
419 | * %-ENOSPC if there is no free space and other negative error codes in case of |
420 | * failures. |
421 | */ |
422 | int ubifs_budget_space(struct ubifs_info *c, struct ubifs_budget_req *req) |
423 | { |
424 | int err, idx_growth, data_growth, dd_growth, retried = 0; |
425 | |
426 | ubifs_assert(c, req->new_page <= 1); |
427 | ubifs_assert(c, req->dirtied_page <= 1); |
428 | ubifs_assert(c, req->new_dent <= 1); |
429 | ubifs_assert(c, req->mod_dent <= 1); |
430 | ubifs_assert(c, req->new_ino <= 1); |
431 | ubifs_assert(c, req->new_ino_d <= UBIFS_MAX_INO_DATA); |
432 | ubifs_assert(c, req->dirtied_ino <= 4); |
433 | ubifs_assert(c, req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); |
434 | ubifs_assert(c, !(req->new_ino_d & 7)); |
435 | ubifs_assert(c, !(req->dirtied_ino_d & 7)); |
436 | |
437 | data_growth = calc_data_growth(c, req); |
438 | dd_growth = calc_dd_growth(c, req); |
439 | if (!data_growth && !dd_growth) |
440 | return 0; |
441 | idx_growth = calc_idx_growth(c, req); |
442 | |
443 | again: |
444 | spin_lock(lock: &c->space_lock); |
445 | ubifs_assert(c, c->bi.idx_growth >= 0); |
446 | ubifs_assert(c, c->bi.data_growth >= 0); |
447 | ubifs_assert(c, c->bi.dd_growth >= 0); |
448 | |
449 | if (unlikely(c->bi.nospace) && (c->bi.nospace_rp || !can_use_rp(c))) { |
450 | dbg_budg("no space" ); |
451 | spin_unlock(lock: &c->space_lock); |
452 | return -ENOSPC; |
453 | } |
454 | |
455 | c->bi.idx_growth += idx_growth; |
456 | c->bi.data_growth += data_growth; |
457 | c->bi.dd_growth += dd_growth; |
458 | |
459 | err = do_budget_space(c); |
460 | if (likely(!err)) { |
461 | req->idx_growth = idx_growth; |
462 | req->data_growth = data_growth; |
463 | req->dd_growth = dd_growth; |
464 | spin_unlock(lock: &c->space_lock); |
465 | return 0; |
466 | } |
467 | |
468 | /* Restore the old values */ |
469 | c->bi.idx_growth -= idx_growth; |
470 | c->bi.data_growth -= data_growth; |
471 | c->bi.dd_growth -= dd_growth; |
472 | spin_unlock(lock: &c->space_lock); |
473 | |
474 | if (req->fast) { |
475 | dbg_budg("no space for fast budgeting" ); |
476 | return err; |
477 | } |
478 | |
479 | err = make_free_space(c); |
480 | cond_resched(); |
481 | if (err == -EAGAIN) { |
482 | dbg_budg("try again" ); |
483 | goto again; |
484 | } else if (err == -ENOSPC) { |
485 | if (!retried) { |
486 | retried = 1; |
487 | dbg_budg("-ENOSPC, but anyway try once again" ); |
488 | goto again; |
489 | } |
490 | dbg_budg("FS is full, -ENOSPC" ); |
491 | c->bi.nospace = 1; |
492 | if (can_use_rp(c) || c->rp_size == 0) |
493 | c->bi.nospace_rp = 1; |
494 | smp_wmb(); |
495 | } else |
496 | ubifs_err(c, fmt: "cannot budget space, error %d" , err); |
497 | return err; |
498 | } |
499 | |
500 | /** |
501 | * ubifs_release_budget - release budgeted free space. |
502 | * @c: UBIFS file-system description object |
503 | * @req: budget request |
504 | * |
505 | * This function releases the space budgeted by 'ubifs_budget_space()'. Note, |
506 | * since the index changes (which were budgeted for in @req->idx_growth) will |
507 | * only be written to the media on commit, this function moves the index budget |
508 | * from @c->bi.idx_growth to @c->bi.uncommitted_idx. The latter will be zeroed |
509 | * by the commit operation. |
510 | */ |
511 | void ubifs_release_budget(struct ubifs_info *c, struct ubifs_budget_req *req) |
512 | { |
513 | ubifs_assert(c, req->new_page <= 1); |
514 | ubifs_assert(c, req->dirtied_page <= 1); |
515 | ubifs_assert(c, req->new_dent <= 1); |
516 | ubifs_assert(c, req->mod_dent <= 1); |
517 | ubifs_assert(c, req->new_ino <= 1); |
518 | ubifs_assert(c, req->new_ino_d <= UBIFS_MAX_INO_DATA); |
519 | ubifs_assert(c, req->dirtied_ino <= 4); |
520 | ubifs_assert(c, req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); |
521 | ubifs_assert(c, !(req->new_ino_d & 7)); |
522 | ubifs_assert(c, !(req->dirtied_ino_d & 7)); |
523 | if (!req->recalculate) { |
524 | ubifs_assert(c, req->idx_growth >= 0); |
525 | ubifs_assert(c, req->data_growth >= 0); |
526 | ubifs_assert(c, req->dd_growth >= 0); |
527 | } |
528 | |
529 | if (req->recalculate) { |
530 | req->data_growth = calc_data_growth(c, req); |
531 | req->dd_growth = calc_dd_growth(c, req); |
532 | req->idx_growth = calc_idx_growth(c, req); |
533 | } |
534 | |
535 | if (!req->data_growth && !req->dd_growth) |
536 | return; |
537 | |
538 | c->bi.nospace = c->bi.nospace_rp = 0; |
539 | smp_wmb(); |
540 | |
541 | spin_lock(lock: &c->space_lock); |
542 | c->bi.idx_growth -= req->idx_growth; |
543 | c->bi.uncommitted_idx += req->idx_growth; |
544 | c->bi.data_growth -= req->data_growth; |
545 | c->bi.dd_growth -= req->dd_growth; |
546 | c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c); |
547 | |
548 | ubifs_assert(c, c->bi.idx_growth >= 0); |
549 | ubifs_assert(c, c->bi.data_growth >= 0); |
550 | ubifs_assert(c, c->bi.dd_growth >= 0); |
551 | ubifs_assert(c, c->bi.min_idx_lebs < c->main_lebs); |
552 | ubifs_assert(c, !(c->bi.idx_growth & 7)); |
553 | ubifs_assert(c, !(c->bi.data_growth & 7)); |
554 | ubifs_assert(c, !(c->bi.dd_growth & 7)); |
555 | spin_unlock(lock: &c->space_lock); |
556 | } |
557 | |
558 | /** |
559 | * ubifs_convert_page_budget - convert budget of a new page. |
560 | * @c: UBIFS file-system description object |
561 | * |
562 | * This function converts budget which was allocated for a new page of data to |
563 | * the budget of changing an existing page of data. The latter is smaller than |
564 | * the former, so this function only does simple re-calculation and does not |
565 | * involve any write-back. |
566 | */ |
567 | void ubifs_convert_page_budget(struct ubifs_info *c) |
568 | { |
569 | spin_lock(lock: &c->space_lock); |
570 | /* Release the index growth reservation */ |
571 | c->bi.idx_growth -= c->max_idx_node_sz << UBIFS_BLOCKS_PER_PAGE_SHIFT; |
572 | /* Release the data growth reservation */ |
573 | c->bi.data_growth -= c->bi.page_budget; |
574 | /* Increase the dirty data growth reservation instead */ |
575 | c->bi.dd_growth += c->bi.page_budget; |
576 | /* And re-calculate the indexing space reservation */ |
577 | c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c); |
578 | spin_unlock(lock: &c->space_lock); |
579 | } |
580 | |
581 | /** |
582 | * ubifs_release_dirty_inode_budget - release dirty inode budget. |
583 | * @c: UBIFS file-system description object |
584 | * @ui: UBIFS inode to release the budget for |
585 | * |
586 | * This function releases budget corresponding to a dirty inode. It is usually |
587 | * called when after the inode has been written to the media and marked as |
588 | * clean. It also causes the "no space" flags to be cleared. |
589 | */ |
590 | void ubifs_release_dirty_inode_budget(struct ubifs_info *c, |
591 | struct ubifs_inode *ui) |
592 | { |
593 | struct ubifs_budget_req req; |
594 | |
595 | memset(&req, 0, sizeof(struct ubifs_budget_req)); |
596 | /* The "no space" flags will be cleared because dd_growth is > 0 */ |
597 | req.dd_growth = c->bi.inode_budget + ALIGN(ui->data_len, 8); |
598 | ubifs_release_budget(c, req: &req); |
599 | } |
600 | |
601 | /** |
602 | * ubifs_reported_space - calculate reported free space. |
603 | * @c: the UBIFS file-system description object |
604 | * @free: amount of free space |
605 | * |
606 | * This function calculates amount of free space which will be reported to |
607 | * user-space. User-space application tend to expect that if the file-system |
608 | * (e.g., via the 'statfs()' call) reports that it has N bytes available, they |
609 | * are able to write a file of size N. UBIFS attaches node headers to each data |
610 | * node and it has to write indexing nodes as well. This introduces additional |
611 | * overhead, and UBIFS has to report slightly less free space to meet the above |
612 | * expectations. |
613 | * |
614 | * This function assumes free space is made up of uncompressed data nodes and |
615 | * full index nodes (one per data node, tripled because we always allow enough |
616 | * space to write the index thrice). |
617 | * |
618 | * Note, the calculation is pessimistic, which means that most of the time |
619 | * UBIFS reports less space than it actually has. |
620 | */ |
621 | long long ubifs_reported_space(const struct ubifs_info *c, long long free) |
622 | { |
623 | int divisor, factor, f; |
624 | |
625 | /* |
626 | * Reported space size is @free * X, where X is UBIFS block size |
627 | * divided by UBIFS block size + all overhead one data block |
628 | * introduces. The overhead is the node header + indexing overhead. |
629 | * |
630 | * Indexing overhead calculations are based on the following formula: |
631 | * I = N/(f - 1) + 1, where I - number of indexing nodes, N - number |
632 | * of data nodes, f - fanout. Because effective UBIFS fanout is twice |
633 | * as less than maximum fanout, we assume that each data node |
634 | * introduces 3 * @c->max_idx_node_sz / (@c->fanout/2 - 1) bytes. |
635 | * Note, the multiplier 3 is because UBIFS reserves thrice as more space |
636 | * for the index. |
637 | */ |
638 | f = c->fanout > 3 ? c->fanout >> 1 : 2; |
639 | factor = UBIFS_BLOCK_SIZE; |
640 | divisor = UBIFS_MAX_DATA_NODE_SZ; |
641 | divisor += (c->max_idx_node_sz * 3) / (f - 1); |
642 | free *= factor; |
643 | return div_u64(dividend: free, divisor); |
644 | } |
645 | |
646 | /** |
647 | * ubifs_get_free_space_nolock - return amount of free space. |
648 | * @c: UBIFS file-system description object |
649 | * |
650 | * This function calculates amount of free space to report to user-space. |
651 | * |
652 | * Because UBIFS may introduce substantial overhead (the index, node headers, |
653 | * alignment, wastage at the end of LEBs, etc), it cannot report real amount of |
654 | * free flash space it has (well, because not all dirty space is reclaimable, |
655 | * UBIFS does not actually know the real amount). If UBIFS did so, it would |
656 | * bread user expectations about what free space is. Users seem to accustomed |
657 | * to assume that if the file-system reports N bytes of free space, they would |
658 | * be able to fit a file of N bytes to the FS. This almost works for |
659 | * traditional file-systems, because they have way less overhead than UBIFS. |
660 | * So, to keep users happy, UBIFS tries to take the overhead into account. |
661 | */ |
662 | long long ubifs_get_free_space_nolock(struct ubifs_info *c) |
663 | { |
664 | int rsvd_idx_lebs, lebs; |
665 | long long available, outstanding, free; |
666 | |
667 | ubifs_assert(c, c->bi.min_idx_lebs == ubifs_calc_min_idx_lebs(c)); |
668 | outstanding = c->bi.data_growth + c->bi.dd_growth; |
669 | available = ubifs_calc_available(c, min_idx_lebs: c->bi.min_idx_lebs); |
670 | |
671 | /* |
672 | * When reporting free space to user-space, UBIFS guarantees that it is |
673 | * possible to write a file of free space size. This means that for |
674 | * empty LEBs we may use more precise calculations than |
675 | * 'ubifs_calc_available()' is using. Namely, we know that in empty |
676 | * LEBs we would waste only @c->leb_overhead bytes, not @c->dark_wm. |
677 | * Thus, amend the available space. |
678 | * |
679 | * Note, the calculations below are similar to what we have in |
680 | * 'do_budget_space()', so refer there for comments. |
681 | */ |
682 | if (c->bi.min_idx_lebs > c->lst.idx_lebs) |
683 | rsvd_idx_lebs = c->bi.min_idx_lebs - c->lst.idx_lebs; |
684 | else |
685 | rsvd_idx_lebs = 0; |
686 | lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt - |
687 | c->lst.taken_empty_lebs; |
688 | lebs -= rsvd_idx_lebs; |
689 | available += lebs * (c->dark_wm - c->leb_overhead); |
690 | |
691 | if (available > outstanding) |
692 | free = ubifs_reported_space(c, free: available - outstanding); |
693 | else |
694 | free = 0; |
695 | return free; |
696 | } |
697 | |
698 | /** |
699 | * ubifs_get_free_space - return amount of free space. |
700 | * @c: UBIFS file-system description object |
701 | * |
702 | * This function calculates and returns amount of free space to report to |
703 | * user-space. |
704 | */ |
705 | long long ubifs_get_free_space(struct ubifs_info *c) |
706 | { |
707 | long long free; |
708 | |
709 | spin_lock(lock: &c->space_lock); |
710 | free = ubifs_get_free_space_nolock(c); |
711 | spin_unlock(lock: &c->space_lock); |
712 | |
713 | return free; |
714 | } |
715 | |