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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * This file is part of UBIFS.4 *5 * Copyright (C) 2006-2008 Nokia Corporation.6 *7 * Authors: Adrian Hunter8 * Artem Bityutskiy (Битюцкий Артём)9 */10 11/*12 * This file implements the budgeting sub-system which is responsible for UBIFS13 * space management.14 *15 * Factors such as compression, wasted space at the ends of LEBs, space in other16 * journal heads, the effect of updates on the index, and so on, make it17 * impossible to accurately predict the amount of space needed. Consequently18 * 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 UBIFS29 * repeats the operations.30 */31#define MAX_MKSPC_RETRIES 332 33/*34 * The below constant defines amount of dirty pages which should be written35 * back at when trying to shrink the liability.36 */37#define NR_TO_WRITE 1638 39/**40 * shrink_liability - write-back some dirty pages/inodes.41 * @c: UBIFS file-system description object42 * @nr_to_write: how many dirty pages to write-back43 *44 * This function shrinks UBIFS liability by means of writing back some amount45 * of dirty inodes and their pages.46 *47 * Note, this function synchronizes even VFS inodes which are locked48 * (@i_mutex) by the caller of the budgeting function, because write-back does49 * not touch @i_mutex.50 */51static void shrink_liability(struct ubifs_info *c, int nr_to_write)52{53 down_read(&c->vfs_sb->s_umount);54 writeback_inodes_sb_nr(c->vfs_sb, nr_to_write, WB_REASON_FS_FREE_SPACE);55 up_read(&c->vfs_sb->s_umount);56}57 58/**59 * run_gc - run garbage collector.60 * @c: UBIFS file-system description object61 *62 * This function runs garbage collector to make some more free space. Returns63 * zero if a free LEB has been produced, %-EAGAIN if commit is required, and a64 * negative error code in case of failure.65 */66static 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(&c->commit_sem);72 lnum = ubifs_garbage_collect(c, 1);73 up_read(&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 object85 *86 * This function calculates and returns current UBIFS liability, i.e. the87 * amount of bytes UBIFS has "promised" to write to the media.88 */89static long long get_liability(struct ubifs_info *c)90{91 long long liab;92 93 spin_lock(&c->space_lock);94 liab = c->bi.idx_growth + c->bi.data_growth + c->bi.dd_growth;95 spin_unlock(&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 object102 *103 * This function is called when an operation cannot be budgeted because there104 * 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 actually106 * needed, so shrinking the liability is one way to make free space - the107 * 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 space109 * 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 space113 * 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 error115 * codes on failures.116 */117static 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), try126 * 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 object159 *160 * This function calculates and returns the number of LEBs which should be kept161 * for index usage.162 */163int 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 we174 * have to do this costly 64-bit division on fast-path.175 */176 idx_lebs = div_u64(idx_size + c->idx_leb_size - 1, c->idx_leb_size);177 /*178 * The index head is not available for the in-the-gaps method, so add an179 * 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 object190 * @min_idx_lebs: minimum number of LEBs reserved for the index191 *192 * This function calculates and returns amount of FS space available for use.193 */194long 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 space203 * assuming there is no index, so we have to subtract the space which204 * 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 should213 * 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 depends227 * on the data which we have on the media and which will be written. If228 * this is a lot of uncompressed or not-compressible data, the dark229 * 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 than235 * @min_idx_lebs. Those extra LEBs are assumed to be available, but236 * their dark space is not included in total_dark, so it is subtracted237 * 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 object251 *252 * UBIFS has so-called "reserved pool" which is flash space reserved253 * 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 */257static int can_use_rp(struct ubifs_info *c)258{259 if (uid_eq(current_fsuid(), c->rp_uid) || capable(CAP_SYS_RESOURCE) ||260 (!gid_eq(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 object268 *269 * This function makes sure UBIFS has enough free LEBs for index growth and270 * data.271 *272 * When budgeting index space, UBIFS reserves thrice as many LEBs as the index273 * would take if it was consolidated and written to the flash. This guarantees274 * that the "in-the-gaps" commit method always succeeds and UBIFS will always275 * be able to commit dirty index. So this function basically adds amount of276 * 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 might281 * be large, because UBIFS does not do any index consolidation as long as282 * there is free space. IOW, the index may take a lot of LEBs, but the LEBs283 * 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 of288 * failure.289 */290static 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 else302 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_lebs309 *310 * @c->lst.empty_lebs are available because they are empty.311 * @c->freeable_cnt are available because they contain only free and312 * dirty space, @c->idx_gc_cnt are available because they are index313 * LEBs that have been garbage collected and are awaiting the commit314 * before they can be used. And the in-the-gaps method will grab these315 * if it needs them. @c->lst.taken_empty_lebs are empty LEBs that have316 * already been allocated for some purpose.317 *318 * Note, @c->idx_gc_cnt is included to both @c->lst.empty_lebs (because319 * these LEBs are empty) and to @c->lst.taken_empty_lebs (because they320 * are taken until after the commit).321 *322 * Note, @c->lst.taken_empty_lebs may temporarily be higher by one323 * because of the way we serialize LEB allocations and budgeting. See a324 * 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 object353 * @req: budgeting request354 *355 * For now we assume each new node adds one znode. But this is rather poor356 * approximation, though.357 */358static 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 budgeting370 * request.371 * @c: UBIFS file-system description object372 * @req: budgeting request373 */374static 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 data390 * dirty from budgeting request.391 * @c: UBIFS file-system description object392 * @req: budgeting request393 */394static 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 object412 * @req: budget request413 *414 * This function allocates budget for an operation. It uses pessimistic415 * approximation of how much flash space the operation needs. The goal of this416 * function is to make sure UBIFS always has flash space to flush all dirty417 * pages, dirty inodes, and dirty znodes (liability). This function may force418 * 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 of420 * failures.421 */422int 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 443again:444 spin_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(&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(&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(&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 } else496 ubifs_err(c, "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 object503 * @req: budget request504 *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) will507 * only be written to the media on commit, this function moves the index budget508 * from @c->bi.idx_growth to @c->bi.uncommitted_idx. The latter will be zeroed509 * by the commit operation.510 */511void 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(&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(&c->space_lock);556}557 558/**559 * ubifs_convert_page_budget - convert budget of a new page.560 * @c: UBIFS file-system description object561 *562 * This function converts budget which was allocated for a new page of data to563 * the budget of changing an existing page of data. The latter is smaller than564 * the former, so this function only does simple re-calculation and does not565 * involve any write-back.566 */567void ubifs_convert_page_budget(struct ubifs_info *c)568{569 spin_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(&c->space_lock);579}580 581/**582 * ubifs_release_dirty_inode_budget - release dirty inode budget.583 * @c: UBIFS file-system description object584 * @ui: UBIFS inode to release the budget for585 *586 * This function releases budget corresponding to a dirty inode. It is usually587 * called when after the inode has been written to the media and marked as588 * clean. It also causes the "no space" flags to be cleared.589 */590void 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);599}600 601/**602 * ubifs_reported_space - calculate reported free space.603 * @c: the UBIFS file-system description object604 * @free: amount of free space605 *606 * This function calculates amount of free space which will be reported to607 * user-space. User-space application tend to expect that if the file-system608 * (e.g., via the 'statfs()' call) reports that it has N bytes available, they609 * are able to write a file of size N. UBIFS attaches node headers to each data610 * node and it has to write indexing nodes as well. This introduces additional611 * overhead, and UBIFS has to report slightly less free space to meet the above612 * expectations.613 *614 * This function assumes free space is made up of uncompressed data nodes and615 * full index nodes (one per data node, tripled because we always allow enough616 * space to write the index thrice).617 *618 * Note, the calculation is pessimistic, which means that most of the time619 * UBIFS reports less space than it actually has.620 */621long 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 size627 * divided by UBIFS block size + all overhead one data block628 * 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 - number632 * of data nodes, f - fanout. Because effective UBIFS fanout is twice633 * as less than maximum fanout, we assume that each data node634 * introduces 3 * @c->max_idx_node_sz / (@c->fanout/2 - 1) bytes.635 * Note, the multiplier 3 is because UBIFS reserves thrice as more space636 * 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(free, divisor);644}645 646/**647 * ubifs_get_free_space_nolock - return amount of free space.648 * @c: UBIFS file-system description object649 *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 of654 * 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 would656 * bread user expectations about what free space is. Users seem to accustomed657 * to assume that if the file-system reports N bytes of free space, they would658 * be able to fit a file of N bytes to the FS. This almost works for659 * 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 */662long 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, c->bi.min_idx_lebs);670 671 /*672 * When reporting free space to user-space, UBIFS guarantees that it is673 * possible to write a file of free space size. This means that for674 * empty LEBs we may use more precise calculations than675 * 'ubifs_calc_available()' is using. Namely, we know that in empty676 * 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 in680 * '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 else685 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, available - outstanding);693 else694 free = 0;695 return free;696}697 698/**699 * ubifs_get_free_space - return amount of free space.700 * @c: UBIFS file-system description object701 *702 * This function calculates and returns amount of free space to report to703 * user-space.704 */705long long ubifs_get_free_space(struct ubifs_info *c)706{707 long long free;708 709 spin_lock(&c->space_lock);710 free = ubifs_get_free_space_nolock(c);711 spin_unlock(&c->space_lock);712 713 return free;714}715