// 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;
}
Codebase Browser
linux