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Diffstat (limited to 'fs/ubifs/budget.c')
| -rw-r--r-- | fs/ubifs/budget.c | 731 |
1 files changed, 731 insertions, 0 deletions
diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c new file mode 100644 index 0000000..d81fb9e --- /dev/null +++ b/fs/ubifs/budget.c @@ -0,0 +1,731 @@ +/* + * This file is part of UBIFS. + * + * Copyright (C) 2006-2008 Nokia Corporation. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + * + * You should have received a copy of the GNU General Public License along with + * this program; if not, write to the Free Software Foundation, Inc., 51 + * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + * 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 <asm/div64.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 + * repeats the operations. + */ +#define MAX_SHRINK_RETRIES 8 +#define MAX_GC_RETRIES 4 +#define MAX_CMT_RETRIES 2 +#define MAX_NOSPC_RETRIES 1 + +/* + * 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 + +/** + * 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. + * + * 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) +{ + 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; +} + + +/** + * 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 err, 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); + err = ubifs_return_leb(c, lnum); + if (err) + return err; + return 0; +} + +/** + * 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 + * 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, struct retries_info *ri) +{ + 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; + + 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); + + ri->prev_liability = liability; + ri->shrink_cnt += 1; + 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); + + ri->try_gc = 0; + 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) + 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); + err = ubifs_run_commit(c); + if (err) + return err; + return -EAGAIN; + } + return -ENOSPC; +} + +/** + * ubifs_calc_min_idx_lebs - calculate amount of eraseblocks 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. + */ +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; + + /* + * 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; + /* + * 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; +} + +/** + * 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; + + /* + * 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; + + /* + * 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 (current->fsuid == c->rp_uid || capable(CAP_SYS_RESOURCE) || + (c->rp_gid != 0 && 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 eraseblocks for index growth + * and data. + * + * When budgeting index space, UBIFS reserves twice as more 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. + * + * Notes about @c->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. + * + * 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 + * + * @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). + * + * 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()'. + */ + 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); + return -ENOSPC; + } + + available = ubifs_calc_available(c, min_idx_lebs); + outstanding = c->budg_data_growth + c->budg_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->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->inode_budget : 0; + if (req->new_page) + data_growth += c->page_budget; + if (req->new_dent) + data_growth += c->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->page_budget : 0; + + if (req->dirtied_ino) + dd_growth += c->inode_budget << (req->dirtied_ino - 1); + if (req->mod_dent) + dd_growth += c->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 uninitialized_var(cmt_retries), uninitialized_var(wb_retries); + int err, idx_growth, data_growth, dd_growth; + struct retries_info ri; + + ubifs_assert(req->dirtied_ino <= 4); + ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); + + 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); + + if (unlikely(c->nospace) && (c->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; + + 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->budg_idx_growth -= idx_growth; + c->budg_data_growth -= data_growth; + c->budg_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, &ri); + if (err == -EAGAIN) { + dbg_budg("try again"); + cond_resched(); + goto again; + } else if (err == -ENOSPC) { + dbg_budg("FS is full, -ENOSPC"); + c->nospace = 1; + if (can_use_rp(c) || c->rp_size == 0) + c->nospace_rp = 1; + smp_wmb(); + } else + ubifs_err("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->budg_idx_growth to @c->budg_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->dirtied_ino <= 4); + ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4); + if (!req->recalculate) { + ubifs_assert(req->idx_growth >= 0); + ubifs_assert(req->data_growth >= 0); + ubifs_assert(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->nospace = c->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); + 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 then + * 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->budg_idx_growth -= c->max_idx_node_sz << UBIFS_BLOCKS_PER_PAGE_SHIFT; + /* Release the data growth reservation */ + c->budg_data_growth -= c->page_budget; + /* Increase the dirty data growth reservation instead */ + c->budg_dd_growth += c->page_budget; + /* And re-calculate the indexing space reservation */ + c->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. + */ +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}; + + ubifs_release_budget(c, &req); +} + +/** + * ubifs_budg_get_free_space - return amount of free space. + * @c: UBIFS file-system description object + * + * This function returns amount of free space on the file-system. + */ +long long ubifs_budg_get_free_space(struct ubifs_info *c) +{ + int min_idx_lebs, rsvd_idx_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); + + if (min_idx_lebs > c->lst.idx_lebs) + rsvd_idx_lebs = 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); + + if (available > outstanding) + free = ubifs_reported_space(c, available - outstanding); + else + free = 0; + return free; +} |
