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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * This file is part of UBIFS.
  *
  * Copyright (C) 2006-2008 Nokia Corporation.
  *
  * Authors: Adrian Hunter
  *          Artem Bityutskiy (Битюцкий Артём)
  */
 
 /*
  * This file implements the budgeting sub-system which is responsible for UBIFS
  * space management.
  *
  * Factors such as compression, wasted space at the ends of LEBs, space in other
  * journal heads, the effect of updates on the index, and so on, make it
  * impossible to accurately predict the amount of space needed. Consequently
  * approximations are used.
  */
 
 #include "ubifs.h"
 #include <linux/writeback.h>
 #include <linux/math64.h>
 
 /*
  * When pessimistic budget calculations say that there is no enough space,
  * UBIFS starts writing back dirty inodes and pages, doing garbage collection,
  * or committing. The below constant defines maximum number of times UBIFS
  * repeats the operations.
  */
 #define MAX_MKSPC_RETRIES 3
 
 /*
  * The below constant defines amount of dirty pages which should be written
  * back at when trying to shrink the liability.
  */
 #define NR_TO_WRITE 16
 
 /**
  * shrink_liability - write-back some dirty pages/inodes.
  * @c: UBIFS file-system description object
  * @nr_to_write: how many dirty pages to write-back
  *
  * This function shrinks UBIFS liability by means of writing back some amount
  * of dirty inodes and their pages.
  *
  * Note, this function synchronizes even VFS inodes which are locked
  * (@i_mutex) by the caller of the budgeting function, because write-back does
  * not touch @i_mutex.
  */
 static void shrink_liability(struct ubifs_info *c, int nr_to_write)
 {
     down_read(&c->vfs_sb->s_umount);
     writeback_inodes_sb_nr(c->vfs_sb, nr_to_write, WB_REASON_FS_FREE_SPACE);
     up_read(&c->vfs_sb->s_umount);
 }
 
 /**
  * run_gc - run garbage collector.
  * @c: UBIFS file-system description object
  *
  * This function runs garbage collector to make some more free space. Returns
  * zero if a free LEB has been produced, %-EAGAIN if commit is required, and a
  * negative error code in case of failure.
  */
 static int run_gc(struct ubifs_info *c)
 {
     int lnum;
 
     /* Make some free space by garbage-collecting dirty space */
     down_read(&c->commit_sem);
     lnum = ubifs_garbage_collect(c, 1);
     up_read(&c->commit_sem);
     if (lnum < 0)
         return lnum;
 
     /* GC freed one LEB, return it to lprops */
     dbg_budg("GC freed LEB %d", lnum);
     return ubifs_return_leb(c, lnum);
 }
 
 /**
  * get_liability - calculate current liability.
  * @c: UBIFS file-system description object
  *
  * This function calculates and returns current UBIFS liability, i.e. the
  * amount of bytes UBIFS has "promised" to write to the media.
  */
 static long long get_liability(struct ubifs_info *c)
 {
     long long liab;
 
     spin_lock(&c->space_lock);
     liab = c->bi.idx_growth + c->bi.data_growth + c->bi.dd_growth;
     spin_unlock(&c->space_lock);
     return liab;
 }
 
 /**
  * make_free_space - make more free space on the file-system.
  * @c: UBIFS file-system description object
  *
  * This function is called when an operation cannot be budgeted because there
  * is supposedly no free space. But in most cases there is some free space:
  *   o budgeting is pessimistic, so it always budgets more than it is actually
  *     needed, so shrinking the liability is one way to make free space - the
  *     cached data will take less space then it was budgeted for;
  *   o GC may turn some dark space into free space (budgeting treats dark space
  *     as not available);
  *   o commit may free some LEB, i.e., turn freeable LEBs into free LEBs.
  *
  * So this function tries to do the above. Returns %-EAGAIN if some free space
  * was presumably made and the caller has to re-try budgeting the operation.
  * Returns %-ENOSPC if it couldn't do more free space, and other negative error
  * codes on failures.
  */
 static int make_free_space(struct ubifs_info *c)
 {
     int err, retries = 0;
     long long liab1, liab2;
 
     do {
         liab1 = get_liability(c);
         /*
          * We probably have some dirty pages or inodes (liability), try
          * to write them back.
          */
         dbg_budg("liability %lld, run write-back", liab1);
         shrink_liability(c, NR_TO_WRITE);
 
         liab2 = get_liability(c);
         if (liab2 < liab1)
             return -EAGAIN;
 
         dbg_budg("new liability %lld (not shrunk)", liab2);
 
         /* Liability did not shrink again, try GC */
         dbg_budg("Run GC");
         err = run_gc(c);
         if (!err)
             return -EAGAIN;
 
         if (err != -EAGAIN && err != -ENOSPC)
             /* Some real error happened */
             return err;
 
         dbg_budg("Run commit (retries %d)", retries);
         err = ubifs_run_commit(c);
         if (err)
             return err;
     } while (retries++ < MAX_MKSPC_RETRIES);
 
     return -ENOSPC;
 }
 
 /**
  * ubifs_calc_min_idx_lebs - calculate amount of LEBs for the index.
  * @c: UBIFS file-system description object
  *
  * This function calculates and returns the number of LEBs which should be kept
  * for index usage.
  */
 int ubifs_calc_min_idx_lebs(struct ubifs_info *c)
 {
     int idx_lebs;
     long long idx_size;
 
     idx_size = c->bi.old_idx_sz + c->bi.idx_growth + c->bi.uncommitted_idx;
     /* And make sure we have thrice the index size of space reserved */
     idx_size += idx_size << 1;
     /*
      * We do not maintain 'old_idx_size' as 'old_idx_lebs'/'old_idx_bytes'
      * pair, nor similarly the two variables for the new index size, so we
      * have to do this costly 64-bit division on fast-path.
      */
     idx_lebs = div_u64(idx_size + c->idx_leb_size - 1, c->idx_leb_size);
     /*
      * The index head is not available for the in-the-gaps method, so add an
      * extra LEB to compensate.
      */
     idx_lebs += 1;
     if (idx_lebs < MIN_INDEX_LEBS)
         idx_lebs = MIN_INDEX_LEBS;
     return idx_lebs;
 }
 
 /**
  * ubifs_calc_available - calculate available FS space.
  * @c: UBIFS file-system description object
  * @min_idx_lebs: minimum number of LEBs reserved for the index
  *
  * This function calculates and returns amount of FS space available for use.
  */
 long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs)
 {
     int subtract_lebs;
     long long available;
 
     available = c->main_bytes - c->lst.total_used;
 
     /*
      * Now 'available' contains theoretically available flash space
      * assuming there is no index, so we have to subtract the space which
      * is reserved for the index.
      */
     subtract_lebs = min_idx_lebs;
 
     /* Take into account that GC reserves one LEB for its own needs */
     subtract_lebs += 1;
 
     /*
      * The GC journal head LEB is not really accessible. And since
      * different write types go to different heads, we may count only on
      * one head's space.
      */
     subtract_lebs += c->jhead_cnt - 1;
 
     /* We also reserve one LEB for deletions, which bypass budgeting */
     subtract_lebs += 1;
 
     available -= (long long)subtract_lebs * c->leb_size;
 
     /* Subtract the dead space which is not available for use */
     available -= c->lst.total_dead;
 
     /*
      * Subtract dark space, which might or might not be usable - it depends
      * on the data which we have on the media and which will be written. If
      * this is a lot of uncompressed or not-compressible data, the dark
      * space cannot be used.
      */
     available -= c->lst.total_dark;
 
     /*
      * However, there is more dark space. The index may be bigger than
      * @min_idx_lebs. Those extra LEBs are assumed to be available, but
      * their dark space is not included in total_dark, so it is subtracted
      * here.
      */
     if (c->lst.idx_lebs > min_idx_lebs) {
         subtract_lebs = c->lst.idx_lebs - min_idx_lebs;
         available -= subtract_lebs * c->dark_wm;
     }
 
     /* The calculations are rough and may end up with a negative number */
     return available > 0 ? available : 0;
 }
 
 /**
  * can_use_rp - check whether the user is allowed to use reserved pool.
  * @c: UBIFS file-system description object
  *
  * UBIFS has so-called "reserved pool" which is flash space reserved
  * for the superuser and for uses whose UID/GID is recorded in UBIFS superblock.
  * This function checks whether current user is allowed to use reserved pool.
  * Returns %1  current user is allowed to use reserved pool and %0 otherwise.
  */
 static int can_use_rp(struct ubifs_info *c)
 {
     if (uid_eq(current_fsuid(), c->rp_uid) || capable(CAP_SYS_RESOURCE) ||
         (!gid_eq(c->rp_gid, GLOBAL_ROOT_GID) && in_group_p(c->rp_gid)))
         return 1;
     return 0;
 }
 
 /**
  * do_budget_space - reserve flash space for index and data growth.
  * @c: UBIFS file-system description object
  *
  * This function makes sure UBIFS has enough free LEBs for index growth and
  * data.
  *
  * When budgeting index space, UBIFS reserves thrice as many LEBs as the index
  * would take if it was consolidated and written to the flash. This guarantees
  * that the "in-the-gaps" commit method always succeeds and UBIFS will always
  * be able to commit dirty index. So this function basically adds amount of
  * budgeted index space to the size of the current index, multiplies this by 3,
  * and makes sure this does not exceed the amount of free LEBs.
  *
  * Notes about @c->bi.min_idx_lebs and @c->lst.idx_lebs variables:
  * o @c->lst.idx_lebs is the number of LEBs the index currently uses. It might
  *    be large, because UBIFS does not do any index consolidation as long as
  *    there is free space. IOW, the index may take a lot of LEBs, but the LEBs
  *    will contain a lot of dirt.
  * o @c->bi.min_idx_lebs is the number of LEBS the index presumably takes. IOW,
  *    the index may be consolidated to take up to @c->bi.min_idx_lebs LEBs.
  *
  * This function returns zero in case of success, and %-ENOSPC in case of
  * failure.
  */
 static int do_budget_space(struct ubifs_info *c)
 {
     long long outstanding, available;
     int lebs, rsvd_idx_lebs, min_idx_lebs;
 
     /* First budget index space */
     min_idx_lebs = ubifs_calc_min_idx_lebs(c);
 
     /* Now 'min_idx_lebs' contains number of LEBs to reserve */
     if (min_idx_lebs > c->lst.idx_lebs)
         rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs;
     else
         rsvd_idx_lebs = 0;
 
     /*
      * The number of LEBs that are available to be used by the index is:
      *
      *    @c->lst.empty_lebs + @c->freeable_cnt + @c->idx_gc_cnt -
      *    @c->lst.taken_empty_lebs
      *
      * @c->lst.empty_lebs are available because they are empty.
      * @c->freeable_cnt are available because they contain only free and
      * dirty space, @c->idx_gc_cnt are available because they are index
      * LEBs that have been garbage collected and are awaiting the commit
      * before they can be used. And the in-the-gaps method will grab these
      * if it needs them. @c->lst.taken_empty_lebs are empty LEBs that have
      * already been allocated for some purpose.
      *
      * Note, @c->idx_gc_cnt is included to both @c->lst.empty_lebs (because
      * these LEBs are empty) and to @c->lst.taken_empty_lebs (because they
      * are taken until after the commit).
      *
      * Note, @c->lst.taken_empty_lebs may temporarily be higher by one
      * because of the way we serialize LEB allocations and budgeting. See a
      * comment in 'ubifs_find_free_space()'.
      */
     lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
            c->lst.taken_empty_lebs;
     if (unlikely(rsvd_idx_lebs > lebs)) {
         dbg_budg("out of indexing space: min_idx_lebs %d (old %d), rsvd_idx_lebs %d",
              min_idx_lebs, c->bi.min_idx_lebs, rsvd_idx_lebs);
         return -ENOSPC;
     }
 
     available = ubifs_calc_available(c, min_idx_lebs);
     outstanding = c->bi.data_growth + c->bi.dd_growth;
 
     if (unlikely(available < outstanding)) {
         dbg_budg("out of data space: available %lld, outstanding %lld",
              available, outstanding);
         return -ENOSPC;
     }
 
     if (available - outstanding <= c->rp_size && !can_use_rp(c))
         return -ENOSPC;
 
     c->bi.min_idx_lebs = min_idx_lebs;
     return 0;
 }
 
 /**
  * calc_idx_growth - calculate approximate index growth from budgeting request.
  * @c: UBIFS file-system description object
  * @req: budgeting request
  *
  * For now we assume each new node adds one znode. But this is rather poor
  * approximation, though.
  */
 static int calc_idx_growth(const struct ubifs_info *c,
                const struct ubifs_budget_req *req)
 {
     int znodes;
 
     znodes = req->new_ino + (req->new_page << UBIFS_BLOCKS_PER_PAGE_SHIFT) +
          req->new_dent;
     return znodes * c->max_idx_node_sz;
 }
 
 /**
  * calc_data_growth - calculate approximate amount of new data from budgeting
  * request.
  * @c: UBIFS file-system description object
  * @req: budgeting request
  */
 static int calc_data_growth(const struct ubifs_info *c,
                 const struct ubifs_budget_req *req)
 {
     int data_growth;
 
     data_growth = req->new_ino  ? c->bi.inode_budget : 0;
     if (req->new_page)
         data_growth += c->bi.page_budget;
     if (req->new_dent)
         data_growth += c->bi.dent_budget;
     data_growth += req->new_ino_d;
     return data_growth;
 }
 
 /**
  * calc_dd_growth - calculate approximate amount of data which makes other data
  * dirty from budgeting request.
  * @c: UBIFS file-system description object
  * @req: budgeting request
  */
 static int calc_dd_growth(const struct ubifs_info *c,
               const struct ubifs_budget_req *req)
 {
     int dd_growth;
 
     dd_growth = req->dirtied_page ? c->bi.page_budget : 0;
 
     if (req->dirtied_ino)
         dd_growth += c->bi.inode_budget << (req->dirtied_ino - 1);
     if (req->mod_dent)
         dd_growth += c->bi.dent_budget;
     dd_growth += req->dirtied_ino_d;
     return dd_growth;
 }
 
 /**
  * ubifs_budget_space - ensure there is enough space to complete an operation.
  * @c: UBIFS file-system description object
  * @req: budget request
  *
  * This function allocates budget for an operation. It uses pessimistic
  * approximation of how much flash space the operation needs. The goal of this
  * function is to make sure UBIFS always has flash space to flush all dirty
  * pages, dirty inodes, and dirty znodes (liability). This function may force
  * commit, garbage-collection or write-back. Returns zero in case of success,
  * %-ENOSPC if there is no free space and other negative error codes in case of
  * failures.
  */
 int ubifs_budget_space(struct ubifs_info *c, struct ubifs_budget_req *req)
 {
     int err, idx_growth, data_growth, dd_growth, retried = 0;
 
     ubifs_assert(c, req->new_page <= 1);
     ubifs_assert(c, req->dirtied_page <= 1);
     ubifs_assert(c, req->new_dent <= 1);
     ubifs_assert(c, req->mod_dent <= 1);
     ubifs_assert(c, req->new_ino <= 1);
     ubifs_assert(c, req->new_ino_d <= UBIFS_MAX_INO_DATA);
     ubifs_assert(c, req->dirtied_ino <= 4);
     ubifs_assert(c, req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
     ubifs_assert(c, !(req->new_ino_d & 7));
     ubifs_assert(c, !(req->dirtied_ino_d & 7));
 
     data_growth = calc_data_growth(c, req);
     dd_growth = calc_dd_growth(c, req);
     if (!data_growth && !dd_growth)
         return 0;
     idx_growth = calc_idx_growth(c, req);
 
 again:
     spin_lock(&c->space_lock);
     ubifs_assert(c, c->bi.idx_growth >= 0);
     ubifs_assert(c, c->bi.data_growth >= 0);
     ubifs_assert(c, c->bi.dd_growth >= 0);
 
     if (unlikely(c->bi.nospace) && (c->bi.nospace_rp || !can_use_rp(c))) {
         dbg_budg("no space");
         spin_unlock(&c->space_lock);
         return -ENOSPC;
     }
 
     c->bi.idx_growth += idx_growth;
     c->bi.data_growth += data_growth;
     c->bi.dd_growth += dd_growth;
 
     err = do_budget_space(c);
     if (likely(!err)) {
         req->idx_growth = idx_growth;
         req->data_growth = data_growth;
         req->dd_growth = dd_growth;
         spin_unlock(&c->space_lock);
         return 0;
     }
 
     /* Restore the old values */
     c->bi.idx_growth -= idx_growth;
     c->bi.data_growth -= data_growth;
     c->bi.dd_growth -= dd_growth;
     spin_unlock(&c->space_lock);
 
     if (req->fast) {
         dbg_budg("no space for fast budgeting");
         return err;
     }
 
     err = make_free_space(c);
     cond_resched();
     if (err == -EAGAIN) {
         dbg_budg("try again");
         goto again;
     } else if (err == -ENOSPC) {
         if (!retried) {
             retried = 1;
             dbg_budg("-ENOSPC, but anyway try once again");
             goto again;
         }
         dbg_budg("FS is full, -ENOSPC");
         c->bi.nospace = 1;
         if (can_use_rp(c) || c->rp_size == 0)
             c->bi.nospace_rp = 1;
         smp_wmb();
     } else
         ubifs_err(c, "cannot budget space, error %d", err);
     return err;
 }
 
 /**
  * ubifs_release_budget - release budgeted free space.
  * @c: UBIFS file-system description object
  * @req: budget request
  *
  * This function releases the space budgeted by 'ubifs_budget_space()'. Note,
  * since the index changes (which were budgeted for in @req->idx_growth) will
  * only be written to the media on commit, this function moves the index budget
  * from @c->bi.idx_growth to @c->bi.uncommitted_idx. The latter will be zeroed
  * by the commit operation.
  */
 void ubifs_release_budget(struct ubifs_info *c, struct ubifs_budget_req *req)
 {
     ubifs_assert(c, req->new_page <= 1);
     ubifs_assert(c, req->dirtied_page <= 1);
     ubifs_assert(c, req->new_dent <= 1);
     ubifs_assert(c, req->mod_dent <= 1);
     ubifs_assert(c, req->new_ino <= 1);
     ubifs_assert(c, req->new_ino_d <= UBIFS_MAX_INO_DATA);
     ubifs_assert(c, req->dirtied_ino <= 4);
     ubifs_assert(c, req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
     ubifs_assert(c, !(req->new_ino_d & 7));
     ubifs_assert(c, !(req->dirtied_ino_d & 7));
     if (!req->recalculate) {
         ubifs_assert(c, req->idx_growth >= 0);
         ubifs_assert(c, req->data_growth >= 0);
         ubifs_assert(c, req->dd_growth >= 0);
     }
 
     if (req->recalculate) {
         req->data_growth = calc_data_growth(c, req);
         req->dd_growth = calc_dd_growth(c, req);
         req->idx_growth = calc_idx_growth(c, req);
     }
 
     if (!req->data_growth && !req->dd_growth)
         return;
 
     c->bi.nospace = c->bi.nospace_rp = 0;
     smp_wmb();
 
     spin_lock(&c->space_lock);
     c->bi.idx_growth -= req->idx_growth;
     c->bi.uncommitted_idx += req->idx_growth;
     c->bi.data_growth -= req->data_growth;
     c->bi.dd_growth -= req->dd_growth;
     c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c);
 
     ubifs_assert(c, c->bi.idx_growth >= 0);
     ubifs_assert(c, c->bi.data_growth >= 0);
     ubifs_assert(c, c->bi.dd_growth >= 0);
     ubifs_assert(c, c->bi.min_idx_lebs < c->main_lebs);
     ubifs_assert(c, !(c->bi.idx_growth & 7));
     ubifs_assert(c, !(c->bi.data_growth & 7));
     ubifs_assert(c, !(c->bi.dd_growth & 7));
     spin_unlock(&c->space_lock);
 }
 
 /**
  * ubifs_convert_page_budget - convert budget of a new page.
  * @c: UBIFS file-system description object
  *
  * This function converts budget which was allocated for a new page of data to
  * the budget of changing an existing page of data. The latter is smaller than
  * the former, so this function only does simple re-calculation and does not
  * involve any write-back.
  */
 void ubifs_convert_page_budget(struct ubifs_info *c)
 {
     spin_lock(&c->space_lock);
     /* Release the index growth reservation */
     c->bi.idx_growth -= c->max_idx_node_sz << UBIFS_BLOCKS_PER_PAGE_SHIFT;
     /* Release the data growth reservation */
     c->bi.data_growth -= c->bi.page_budget;
     /* Increase the dirty data growth reservation instead */
     c->bi.dd_growth += c->bi.page_budget;
     /* And re-calculate the indexing space reservation */
     c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c);
     spin_unlock(&c->space_lock);
 }
 
 /**
  * ubifs_release_dirty_inode_budget - release dirty inode budget.
  * @c: UBIFS file-system description object
  * @ui: UBIFS inode to release the budget for
  *
  * This function releases budget corresponding to a dirty inode. It is usually
  * called when after the inode has been written to the media and marked as
  * clean. It also causes the "no space" flags to be cleared.
  */
 void ubifs_release_dirty_inode_budget(struct ubifs_info *c,
                       struct ubifs_inode *ui)
 {
     struct ubifs_budget_req req;
 
     memset(&req, 0, sizeof(struct ubifs_budget_req));
     /* The "no space" flags will be cleared because dd_growth is > 0 */
     req.dd_growth = c->bi.inode_budget + ALIGN(ui->data_len, 8);
     ubifs_release_budget(c, &req);
 }
 
 /**
  * ubifs_reported_space - calculate reported free space.
  * @c: the UBIFS file-system description object
  * @free: amount of free space
  *
  * This function calculates amount of free space which will be reported to
  * user-space. User-space application tend to expect that if the file-system
  * (e.g., via the 'statfs()' call) reports that it has N bytes available, they
  * are able to write a file of size N. UBIFS attaches node headers to each data
  * node and it has to write indexing nodes as well. This introduces additional
  * overhead, and UBIFS has to report slightly less free space to meet the above
  * expectations.
  *
  * This function assumes free space is made up of uncompressed data nodes and
  * full index nodes (one per data node, tripled because we always allow enough
  * space to write the index thrice).
  *
  * Note, the calculation is pessimistic, which means that most of the time
  * UBIFS reports less space than it actually has.
  */
 long long ubifs_reported_space(const struct ubifs_info *c, long long free)
 {
     int divisor, factor, f;
 
     /*
      * Reported space size is @free * X, where X is UBIFS block size
      * divided by UBIFS block size + all overhead one data block
      * introduces. The overhead is the node header + indexing overhead.
      *
      * Indexing overhead calculations are based on the following formula:
      * I = N/(f - 1) + 1, where I - number of indexing nodes, N - number
      * of data nodes, f - fanout. Because effective UBIFS fanout is twice
      * as less than maximum fanout, we assume that each data node
      * introduces 3 * @c->max_idx_node_sz / (@c->fanout/2 - 1) bytes.
      * Note, the multiplier 3 is because UBIFS reserves thrice as more space
      * for the index.
      */
     f = c->fanout > 3 ? c->fanout >> 1 : 2;
     factor = UBIFS_BLOCK_SIZE;
     divisor = UBIFS_MAX_DATA_NODE_SZ;
     divisor += (c->max_idx_node_sz * 3) / (f - 1);
     free *= factor;
     return div_u64(free, divisor);
 }
 
 /**
  * ubifs_get_free_space_nolock - return amount of free space.
  * @c: UBIFS file-system description object
  *
  * This function calculates amount of free space to report to user-space.
  *
  * Because UBIFS may introduce substantial overhead (the index, node headers,
  * alignment, wastage at the end of LEBs, etc), it cannot report real amount of
  * free flash space it has (well, because not all dirty space is reclaimable,
  * UBIFS does not actually know the real amount). If UBIFS did so, it would
  * bread user expectations about what free space is. Users seem to accustomed
  * to assume that if the file-system reports N bytes of free space, they would
  * be able to fit a file of N bytes to the FS. This almost works for
  * traditional file-systems, because they have way less overhead than UBIFS.
  * So, to keep users happy, UBIFS tries to take the overhead into account.
  */
 long long ubifs_get_free_space_nolock(struct ubifs_info *c)
 {
     int rsvd_idx_lebs, lebs;
     long long available, outstanding, free;
 
     ubifs_assert(c, c->bi.min_idx_lebs == ubifs_calc_min_idx_lebs(c));
     outstanding = c->bi.data_growth + c->bi.dd_growth;
     available = ubifs_calc_available(c, c->bi.min_idx_lebs);
 
     /*
      * When reporting free space to user-space, UBIFS guarantees that it is
      * possible to write a file of free space size. This means that for
      * empty LEBs we may use more precise calculations than
      * 'ubifs_calc_available()' is using. Namely, we know that in empty
      * LEBs we would waste only @c->leb_overhead bytes, not @c->dark_wm.
      * Thus, amend the available space.
      *
      * Note, the calculations below are similar to what we have in
      * 'do_budget_space()', so refer there for comments.
      */
     if (c->bi.min_idx_lebs > c->lst.idx_lebs)
         rsvd_idx_lebs = c->bi.min_idx_lebs - c->lst.idx_lebs;
     else
         rsvd_idx_lebs = 0;
     lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
            c->lst.taken_empty_lebs;
     lebs -= rsvd_idx_lebs;
     available += lebs * (c->dark_wm - c->leb_overhead);
 
     if (available > outstanding)
         free = ubifs_reported_space(c, available - outstanding);
     else
         free = 0;
     return free;
 }
 
 /**
  * ubifs_get_free_space - return amount of free space.
  * @c: UBIFS file-system description object
  *
  * This function calculates and returns amount of free space to report to
  * user-space.
  */
 long long ubifs_get_free_space(struct ubifs_info *c)
 {
     long long free;
 
     spin_lock(&c->space_lock);
     free = ubifs_get_free_space_nolock(c);
     spin_unlock(&c->space_lock);
 
     return free;
 }

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