diff options
Diffstat (limited to 'fs/ubifs/budget.c')
| -rw-r--r-- | fs/ubifs/budget.c | 511 |
1 files changed, 255 insertions, 256 deletions
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c index d81fb9ed2b8..eb997e9c4ab 100644 --- a/fs/ubifs/budget.c +++ b/fs/ubifs/budget.c @@ -32,18 +32,15 @@ #include "ubifs.h" #include <linux/writeback.h> -#include <asm/div64.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 constants define maximum number of times UBIFS + * or committing. The below constant defines maximum number of times UBIFS * repeats the operations. */ -#define MAX_SHRINK_RETRIES 8 -#define MAX_GC_RETRIES 4 -#define MAX_CMT_RETRIES 2 -#define MAX_NOSPC_RETRIES 1 +#define MAX_MKSPC_RETRIES 3 /* * The below constant defines amount of dirty pages which should be written @@ -52,73 +49,24 @@ #define NR_TO_WRITE 16 /** - * struct retries_info - information about re-tries while making free space. - * @prev_liability: previous liability - * @shrink_cnt: how many times the liability was shrinked - * @shrink_retries: count of liability shrink re-tries (increased when - * liability does not shrink) - * @try_gc: GC should be tried first - * @gc_retries: how many times GC was run - * @cmt_retries: how many times commit has been done - * @nospc_retries: how many times GC returned %-ENOSPC - * - * Since we consider budgeting to be the fast-path, and this structure has to - * be allocated on stack and zeroed out, we make it smaller using bit-fields. - */ -struct retries_info { - long long prev_liability; - unsigned int shrink_cnt; - unsigned int shrink_retries:5; - unsigned int try_gc:1; - unsigned int gc_retries:4; - unsigned int cmt_retries:3; - unsigned int nospc_retries:1; -}; - -/** * 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. Returns the amount of pages which were - * written back. The returned value does not include dirty inodes which were - * synchronized. + * 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 int shrink_liability(struct ubifs_info *c, int nr_to_write) +static void shrink_liability(struct ubifs_info *c, int nr_to_write) { - int nr_written; - struct writeback_control wbc = { - .sync_mode = WB_SYNC_NONE, - .range_end = LLONG_MAX, - .nr_to_write = nr_to_write, - }; - - generic_sync_sb_inodes(c->vfs_sb, &wbc); - nr_written = nr_to_write - wbc.nr_to_write; - - if (!nr_written) { - /* - * Re-try again but wait on pages/inodes which are being - * written-back concurrently (e.g., by pdflush). - */ - memset(&wbc, 0, sizeof(struct writeback_control)); - wbc.sync_mode = WB_SYNC_ALL; - wbc.range_end = LLONG_MAX; - wbc.nr_to_write = nr_to_write; - generic_sync_sb_inodes(c->vfs_sb, &wbc); - nr_written = nr_to_write - wbc.nr_to_write; - } - - dbg_budg("%d pages were written back", nr_written); - return nr_written; + down_read(&c->vfs_sb->s_umount); + writeback_inodes_sb(c->vfs_sb, WB_REASON_FS_FREE_SPACE); + up_read(&c->vfs_sb->s_umount); } - /** * run_gc - run garbage collector. * @c: UBIFS file-system description object @@ -147,13 +95,29 @@ static int run_gc(struct ubifs_info *c) } /** + * 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 - * @ri: information about previous invocations of this function * * 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 then it is actually + * 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 @@ -165,129 +129,74 @@ static int run_gc(struct ubifs_info *c) * 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, struct retries_info *ri) +static int make_free_space(struct ubifs_info *c) { - int err; - - /* - * If we have some dirty pages and inodes (liability), try to write - * them back unless this was tried too many times without effect - * already. - */ - if (ri->shrink_retries < MAX_SHRINK_RETRIES && !ri->try_gc) { - long long liability; + int err, retries = 0; + long long liab1, liab2; - spin_lock(&c->space_lock); - liability = c->budg_idx_growth + c->budg_data_growth + - c->budg_dd_growth; - spin_unlock(&c->space_lock); - - if (ri->prev_liability >= liability) { - /* Liability does not shrink, next time try GC then */ - ri->shrink_retries += 1; - if (ri->gc_retries < MAX_GC_RETRIES) - ri->try_gc = 1; - dbg_budg("liability did not shrink: retries %d of %d", - ri->shrink_retries, MAX_SHRINK_RETRIES); - } - - dbg_budg("force write-back (count %d)", ri->shrink_cnt); - shrink_liability(c, NR_TO_WRITE + ri->shrink_cnt); + 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); - ri->prev_liability = liability; - ri->shrink_cnt += 1; - return -EAGAIN; - } + liab2 = get_liability(c); + if (liab2 < liab1) + return -EAGAIN; - /* - * Try to run garbage collector unless it was already tried too many - * times. - */ - if (ri->gc_retries < MAX_GC_RETRIES) { - ri->gc_retries += 1; - dbg_budg("run GC, retries %d of %d", - ri->gc_retries, MAX_GC_RETRIES); + dbg_budg("new liability %lld (not shrunk)", liab2); - ri->try_gc = 0; + /* Liability did not shrink again, try GC */ + dbg_budg("Run GC"); err = run_gc(c); if (!err) return -EAGAIN; - if (err == -EAGAIN) { - dbg_budg("GC asked to commit"); - err = ubifs_run_commit(c); - if (err) - return err; - return -EAGAIN; - } - - if (err != -ENOSPC) + if (err != -EAGAIN && err != -ENOSPC) + /* Some real error happened */ return err; - /* - * GC could not make any progress. If this is the first time, - * then it makes sense to try to commit, because it might make - * some dirty space. - */ - dbg_budg("GC returned -ENOSPC, retries %d", - ri->nospc_retries); - if (ri->nospc_retries >= MAX_NOSPC_RETRIES) - return err; - ri->nospc_retries += 1; - } - - /* Neither GC nor write-back helped, try to commit */ - if (ri->cmt_retries < MAX_CMT_RETRIES) { - ri->cmt_retries += 1; - dbg_budg("run commit, retries %d of %d", - ri->cmt_retries, MAX_CMT_RETRIES); + dbg_budg("Run commit (retries %d)", retries); err = ubifs_run_commit(c); if (err) return err; - return -EAGAIN; - } + } while (retries++ < MAX_MKSPC_RETRIES); + return -ENOSPC; } /** - * ubifs_calc_min_idx_lebs - calculate amount of eraseblocks for the index. + * 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 eraseblocks which should - * be kept for index usage. + * 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 ret; - uint64_t idx_size; - - idx_size = c->old_idx_sz + c->budg_idx_growth + c->budg_uncommitted_idx; - - /* And make sure we have twice the index size of space reserved */ - idx_size <<= 1; + 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. */ - if (do_div(idx_size, c->leb_size - c->max_idx_node_sz)) - ret = idx_size + 1; - else - ret = idx_size; + 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. */ - ret += 1; - /* - * At present the index needs at least 2 LEBs: one for the index head - * and one for in-the-gaps method (which currently does not cater for - * the index head and so excludes it from consideration). - */ - if (ret < 2) - ret = 2; - return ret; + idx_lebs += 1; + if (idx_lebs < MIN_INDEX_LEBS) + idx_lebs = MIN_INDEX_LEBS; + return idx_lebs; } /** @@ -302,18 +211,6 @@ long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs) int subtract_lebs; long long available; - /* - * Force the amount available to the total size reported if the used - * space is zero. - */ - if (c->lst.total_used <= UBIFS_INO_NODE_SZ && - c->budg_data_growth + c->budg_dd_growth == 0) { - /* Do the same calculation as for c->block_cnt */ - available = c->main_lebs - 2; - available *= c->leb_size - c->dark_wm; - return available; - } - available = c->main_bytes - c->lst.total_used; /* @@ -375,8 +272,8 @@ long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs) */ static int can_use_rp(struct ubifs_info *c) { - if (current->fsuid == c->rp_uid || capable(CAP_SYS_RESOURCE) || - (c->rp_gid != 0 && in_group_p(c->rp_gid))) + 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; } @@ -385,23 +282,23 @@ static int can_use_rp(struct ubifs_info *c) * 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 eraseblocks for index growth - * and data. + * This function makes sure UBIFS has enough free LEBs for index growth and + * data. * - * When budgeting index space, UBIFS reserves twice as more LEBs as the index + * 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 2, - * and makes sure this does not exceed the amount of free eraseblocks. + * 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->min_idx_lebs and @c->lst.idx_lebs variables: + * 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->min_idx_lebs is the the index presumably takes. IOW, the index may be - * consolidated to take up to @c->min_idx_lebs LEBs. + * 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. @@ -426,31 +323,32 @@ static int do_budget_space(struct ubifs_info *c) * @c->lst.empty_lebs + @c->freeable_cnt + @c->idx_gc_cnt - * @c->lst.taken_empty_lebs * - * @empty_lebs are available because they are empty. @freeable_cnt are - * available because they contain only free and dirty space and the - * index allocation always occurs after wbufs are synch'ed. - * @idx_gc_cnt are available because they are index LEBs that have been - * garbage collected (including trivial GC) and are awaiting the commit - * before they can be unmapped - note that the in-the-gaps method will - * grab these if it needs them. @taken_empty_lebs are empty_lebs that - * have already been allocated for some purpose (also includes those - * LEBs on the @idx_gc list). + * @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, @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()'. + * 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->min_idx_lebs, - rsvd_idx_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->budg_data_growth + c->budg_dd_growth; + outstanding = c->bi.data_growth + c->bi.dd_growth; if (unlikely(available < outstanding)) { dbg_budg("out of data space: available %lld, outstanding %lld", @@ -461,7 +359,7 @@ static int do_budget_space(struct ubifs_info *c) if (available - outstanding <= c->rp_size && !can_use_rp(c)) return -ENOSPC; - c->min_idx_lebs = min_idx_lebs; + c->bi.min_idx_lebs = min_idx_lebs; return 0; } @@ -494,11 +392,11 @@ static int calc_data_growth(const struct ubifs_info *c, { int data_growth; - data_growth = req->new_ino ? c->inode_budget : 0; + data_growth = req->new_ino ? c->bi.inode_budget : 0; if (req->new_page) - data_growth += c->page_budget; + data_growth += c->bi.page_budget; if (req->new_dent) - data_growth += c->dent_budget; + data_growth += c->bi.dent_budget; data_growth += req->new_ino_d; return data_growth; } @@ -514,12 +412,12 @@ static int calc_dd_growth(const struct ubifs_info *c, { int dd_growth; - dd_growth = req->dirtied_page ? c->page_budget : 0; + dd_growth = req->dirtied_page ? c->bi.page_budget : 0; if (req->dirtied_ino) - dd_growth += c->inode_budget << (req->dirtied_ino - 1); + dd_growth += c->bi.inode_budget << (req->dirtied_ino - 1); if (req->mod_dent) - dd_growth += c->dent_budget; + dd_growth += c->bi.dent_budget; dd_growth += req->dirtied_ino_d; return dd_growth; } @@ -539,35 +437,40 @@ static int calc_dd_growth(const struct ubifs_info *c, */ int ubifs_budget_space(struct ubifs_info *c, struct ubifs_budget_req *req) { - int uninitialized_var(cmt_retries), uninitialized_var(wb_retries); - int err, idx_growth, data_growth, dd_growth; - struct retries_info ri; - + int err, idx_growth, data_growth, dd_growth, retried = 0; + + ubifs_assert(req->new_page <= 1); + ubifs_assert(req->dirtied_page <= 1); + ubifs_assert(req->new_dent <= 1); + ubifs_assert(req->mod_dent <= 1); + ubifs_assert(req->new_ino <= 1); + ubifs_assert(req->new_ino_d <= UBIFS_MAX_INO_DATA); ubifs_assert(req->dirtied_ino <= 4); ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); + ubifs_assert(!(req->new_ino_d & 7)); + ubifs_assert(!(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); - memset(&ri, 0, sizeof(struct retries_info)); again: spin_lock(&c->space_lock); - ubifs_assert(c->budg_idx_growth >= 0); - ubifs_assert(c->budg_data_growth >= 0); - ubifs_assert(c->budg_dd_growth >= 0); + ubifs_assert(c->bi.idx_growth >= 0); + ubifs_assert(c->bi.data_growth >= 0); + ubifs_assert(c->bi.dd_growth >= 0); - if (unlikely(c->nospace) && (c->nospace_rp || !can_use_rp(c))) { + 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->budg_idx_growth += idx_growth; - c->budg_data_growth += data_growth; - c->budg_dd_growth += dd_growth; + 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)) { @@ -579,9 +482,9 @@ again: } /* Restore the old values */ - c->budg_idx_growth -= idx_growth; - c->budg_data_growth -= data_growth; - c->budg_dd_growth -= dd_growth; + 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) { @@ -589,16 +492,21 @@ again: return err; } - err = make_free_space(c, &ri); + err = make_free_space(c); + cond_resched(); if (err == -EAGAIN) { dbg_budg("try again"); - cond_resched(); 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->nospace = 1; + c->bi.nospace = 1; if (can_use_rp(c) || c->rp_size == 0) - c->nospace_rp = 1; + c->bi.nospace_rp = 1; smp_wmb(); } else ubifs_err("cannot budget space, error %d", err); @@ -613,13 +521,21 @@ again: * 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->budg_idx_growth to @c->budg_uncommitted_idx. The latter will be - * zeroed by the commit operation. + * 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(req->new_page <= 1); + ubifs_assert(req->dirtied_page <= 1); + ubifs_assert(req->new_dent <= 1); + ubifs_assert(req->mod_dent <= 1); + ubifs_assert(req->new_ino <= 1); + ubifs_assert(req->new_ino_d <= UBIFS_MAX_INO_DATA); ubifs_assert(req->dirtied_ino <= 4); ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); + ubifs_assert(!(req->new_ino_d & 7)); + ubifs_assert(!(req->dirtied_ino_d & 7)); if (!req->recalculate) { ubifs_assert(req->idx_growth >= 0); ubifs_assert(req->data_growth >= 0); @@ -635,19 +551,23 @@ void ubifs_release_budget(struct ubifs_info *c, struct ubifs_budget_req *req) if (!req->data_growth && !req->dd_growth) return; - c->nospace = c->nospace_rp = 0; + c->bi.nospace = c->bi.nospace_rp = 0; smp_wmb(); spin_lock(&c->space_lock); - c->budg_idx_growth -= req->idx_growth; - c->budg_uncommitted_idx += req->idx_growth; - c->budg_data_growth -= req->data_growth; - c->budg_dd_growth -= req->dd_growth; - c->min_idx_lebs = ubifs_calc_min_idx_lebs(c); - - ubifs_assert(c->budg_idx_growth >= 0); - ubifs_assert(c->budg_data_growth >= 0); - ubifs_assert(c->min_idx_lebs < c->main_lebs); + 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->bi.idx_growth >= 0); + ubifs_assert(c->bi.data_growth >= 0); + ubifs_assert(c->bi.dd_growth >= 0); + ubifs_assert(c->bi.min_idx_lebs < c->main_lebs); + ubifs_assert(!(c->bi.idx_growth & 7)); + ubifs_assert(!(c->bi.data_growth & 7)); + ubifs_assert(!(c->bi.dd_growth & 7)); spin_unlock(&c->space_lock); } @@ -656,7 +576,7 @@ void ubifs_release_budget(struct ubifs_info *c, struct ubifs_budget_req *req) * @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 then + * 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. */ @@ -664,13 +584,13 @@ void ubifs_convert_page_budget(struct ubifs_info *c) { spin_lock(&c->space_lock); /* Release the index growth reservation */ - c->budg_idx_growth -= c->max_idx_node_sz << UBIFS_BLOCKS_PER_PAGE_SHIFT; + c->bi.idx_growth -= c->max_idx_node_sz << UBIFS_BLOCKS_PER_PAGE_SHIFT; /* Release the data growth reservation */ - c->budg_data_growth -= c->page_budget; + c->bi.data_growth -= c->bi.page_budget; /* Increase the dirty data growth reservation instead */ - c->budg_dd_growth += c->page_budget; + c->bi.dd_growth += c->bi.page_budget; /* And re-calculate the indexing space reservation */ - c->min_idx_lebs = ubifs_calc_min_idx_lebs(c); + c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c); spin_unlock(&c->space_lock); } @@ -681,47 +601,108 @@ void ubifs_convert_page_budget(struct ubifs_info *c) * * 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. + * 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 = {.dd_growth = c->inode_budget, - .dirtied_ino_d = ui->data_len}; + 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_budg_get_free_space - return amount of free space. + * 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 returns amount of free space on the file-system. + * 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_budg_get_free_space(struct ubifs_info *c) +long long ubifs_get_free_space_nolock(struct ubifs_info *c) { - int min_idx_lebs, rsvd_idx_lebs; + int rsvd_idx_lebs, lebs; long long available, outstanding, free; - /* Do exactly the same calculations as in 'do_budget_space()' */ - spin_lock(&c->space_lock); - min_idx_lebs = ubifs_calc_min_idx_lebs(c); + ubifs_assert(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); - if (min_idx_lebs > c->lst.idx_lebs) - rsvd_idx_lebs = min_idx_lebs - c->lst.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; - - if (rsvd_idx_lebs > c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt - - c->lst.taken_empty_lebs) { - spin_unlock(&c->space_lock); - return 0; - } - - available = ubifs_calc_available(c, min_idx_lebs); - outstanding = c->budg_data_growth + c->budg_dd_growth; - c->min_idx_lebs = min_idx_lebs; - spin_unlock(&c->space_lock); + 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); @@ -729,3 +710,21 @@ long long ubifs_budg_get_free_space(struct ubifs_info *c) 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; +} |