// 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; /* * Since different write types go to different heads, we should * reserve one leb for each head. */ subtract_lebs += c->jhead_cnt; /* 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; 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; }
