/*
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* This file is part of UBIFS.
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*
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* Copyright (C) 2006-2008 Nokia Corporation.
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*
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* SPDX-License-Identifier: GPL-2.0+
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*
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* Authors: Adrian Hunter
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* Artem Bityutskiy (Битюцкий Артём)
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*/
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/*
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* This file implements the budgeting sub-system which is responsible for UBIFS
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* space management.
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*
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* Factors such as compression, wasted space at the ends of LEBs, space in other
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* journal heads, the effect of updates on the index, and so on, make it
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* impossible to accurately predict the amount of space needed. Consequently
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* approximations are used.
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*/
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#include "ubifs.h"
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#ifndef __UBOOT__
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#include <linux/writeback.h>
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#else
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#include <linux/err.h>
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#endif
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#include <linux/math64.h>
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/*
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* When pessimistic budget calculations say that there is no enough space,
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* UBIFS starts writing back dirty inodes and pages, doing garbage collection,
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* or committing. The below constant defines maximum number of times UBIFS
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* repeats the operations.
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*/
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#define MAX_MKSPC_RETRIES 3
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|
/*
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* The below constant defines amount of dirty pages which should be written
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* back at when trying to shrink the liability.
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*/
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#define NR_TO_WRITE 16
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#ifndef __UBOOT__
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/**
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* shrink_liability - write-back some dirty pages/inodes.
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* @c: UBIFS file-system description object
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* @nr_to_write: how many dirty pages to write-back
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*
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* This function shrinks UBIFS liability by means of writing back some amount
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* of dirty inodes and their pages.
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*
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* Note, this function synchronizes even VFS inodes which are locked
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* (@i_mutex) by the caller of the budgeting function, because write-back does
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* not touch @i_mutex.
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*/
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static void shrink_liability(struct ubifs_info *c, int nr_to_write)
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{
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down_read(&c->vfs_sb->s_umount);
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writeback_inodes_sb(c->vfs_sb, WB_REASON_FS_FREE_SPACE);
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up_read(&c->vfs_sb->s_umount);
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}
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/**
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* run_gc - run garbage collector.
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* @c: UBIFS file-system description object
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*
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* This function runs garbage collector to make some more free space. Returns
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* zero if a free LEB has been produced, %-EAGAIN if commit is required, and a
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* negative error code in case of failure.
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*/
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static int run_gc(struct ubifs_info *c)
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{
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int err, lnum;
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/* Make some free space by garbage-collecting dirty space */
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down_read(&c->commit_sem);
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lnum = ubifs_garbage_collect(c, 1);
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up_read(&c->commit_sem);
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if (lnum < 0)
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return lnum;
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/* GC freed one LEB, return it to lprops */
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dbg_budg("GC freed LEB %d", lnum);
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err = ubifs_return_leb(c, lnum);
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if (err)
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return err;
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return 0;
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}
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/**
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* get_liability - calculate current liability.
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* @c: UBIFS file-system description object
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*
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* This function calculates and returns current UBIFS liability, i.e. the
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* amount of bytes UBIFS has "promised" to write to the media.
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*/
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static long long get_liability(struct ubifs_info *c)
|
{
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long long liab;
|
|
spin_lock(&c->space_lock);
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liab = c->bi.idx_growth + c->bi.data_growth + c->bi.dd_growth;
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spin_unlock(&c->space_lock);
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return liab;
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}
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/**
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* make_free_space - make more free space on the file-system.
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* @c: UBIFS file-system description object
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*
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* This function is called when an operation cannot be budgeted because there
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* is supposedly no free space. But in most cases there is some free space:
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* o budgeting is pessimistic, so it always budgets more than it is actually
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* needed, so shrinking the liability is one way to make free space - the
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* cached data will take less space then it was budgeted for;
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* o GC may turn some dark space into free space (budgeting treats dark space
|
* as not available);
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* o commit may free some LEB, i.e., turn freeable LEBs into free LEBs.
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*
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* So this function tries to do the above. Returns %-EAGAIN if some free space
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* was presumably made and the caller has to re-try budgeting the operation.
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* Returns %-ENOSPC if it couldn't do more free space, and other negative error
|
* codes on failures.
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*/
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static int make_free_space(struct ubifs_info *c)
|
{
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int err, retries = 0;
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long long liab1, liab2;
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|
do {
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liab1 = get_liability(c);
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/*
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* We probably have some dirty pages or inodes (liability), try
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* to write them back.
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*/
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dbg_budg("liability %lld, run write-back", liab1);
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shrink_liability(c, NR_TO_WRITE);
|
|
liab2 = get_liability(c);
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if (liab2 < liab1)
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return -EAGAIN;
|
|
dbg_budg("new liability %lld (not shrunk)", liab2);
|
|
/* Liability did not shrink again, try GC */
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dbg_budg("Run GC");
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err = run_gc(c);
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if (!err)
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return -EAGAIN;
|
|
if (err != -EAGAIN && err != -ENOSPC)
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/* Some real error happened */
|
return err;
|
|
dbg_budg("Run commit (retries %d)", retries);
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err = ubifs_run_commit(c);
|
if (err)
|
return err;
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} while (retries++ < MAX_MKSPC_RETRIES);
|
|
return -ENOSPC;
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}
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#endif
|
|
/**
|
* 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.
|
*/
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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);
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/*
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* The index head is not available for the in-the-gaps method, so add an
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* extra LEB to compensate.
|
*/
|
idx_lebs += 1;
|
if (idx_lebs < MIN_INDEX_LEBS)
|
idx_lebs = MIN_INDEX_LEBS;
|
return idx_lebs;
|
}
|
|
#ifndef __UBOOT__
|
/**
|
* ubifs_calc_available - calculate available FS space.
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* @c: UBIFS file-system description object
|
* @min_idx_lebs: minimum number of LEBs reserved for the index
|
*
|
* This function calculates and returns amount of FS space available for use.
|
*/
|
long long ubifs_calc_available(const struct ubifs_info *c, int min_idx_lebs)
|
{
|
int subtract_lebs;
|
long long available;
|
|
available = c->main_bytes - c->lst.total_used;
|
|
/*
|
* Now 'available' contains theoretically available flash space
|
* assuming there is no index, so we have to subtract the space which
|
* is reserved for the index.
|
*/
|
subtract_lebs = min_idx_lebs;
|
|
/* Take into account that GC reserves one LEB for its own needs */
|
subtract_lebs += 1;
|
|
/*
|
* The GC journal head LEB is not really accessible. And since
|
* different write types go to different heads, we may count only on
|
* one head's space.
|
*/
|
subtract_lebs += c->jhead_cnt - 1;
|
|
/* We also reserve one LEB for deletions, which bypass budgeting */
|
subtract_lebs += 1;
|
|
available -= (long long)subtract_lebs * c->leb_size;
|
|
/* Subtract the dead space which is not available for use */
|
available -= c->lst.total_dead;
|
|
/*
|
* Subtract dark space, which might or might not be usable - it depends
|
* on the data which we have on the media and which will be written. If
|
* this is a lot of uncompressed or not-compressible data, the dark
|
* space cannot be used.
|
*/
|
available -= c->lst.total_dark;
|
|
/*
|
* However, there is more dark space. The index may be bigger than
|
* @min_idx_lebs. Those extra LEBs are assumed to be available, but
|
* their dark space is not included in total_dark, so it is subtracted
|
* here.
|
*/
|
if (c->lst.idx_lebs > min_idx_lebs) {
|
subtract_lebs = c->lst.idx_lebs - min_idx_lebs;
|
available -= subtract_lebs * c->dark_wm;
|
}
|
|
/* The calculations are rough and may end up with a negative number */
|
return available > 0 ? available : 0;
|
}
|
|
/**
|
* can_use_rp - check whether the user is allowed to use reserved pool.
|
* @c: UBIFS file-system description object
|
*
|
* UBIFS has so-called "reserved pool" which is flash space reserved
|
* for the superuser and for uses whose UID/GID is recorded in UBIFS superblock.
|
* This function checks whether current user is allowed to use reserved pool.
|
* Returns %1 current user is allowed to use reserved pool and %0 otherwise.
|
*/
|
static int can_use_rp(struct ubifs_info *c)
|
{
|
if (uid_eq(current_fsuid(), c->rp_uid) || capable(CAP_SYS_RESOURCE) ||
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(!gid_eq(c->rp_gid, GLOBAL_ROOT_GID) && in_group_p(c->rp_gid)))
|
return 1;
|
return 0;
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}
|
|
/**
|
* 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
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* data.
|
*
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* 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
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* budgeted index space to the size of the current index, multiplies this by 3,
|
* and makes sure this does not exceed the amount of free LEBs.
|
*
|
* Notes about @c->bi.min_idx_lebs and @c->lst.idx_lebs variables:
|
* o @c->lst.idx_lebs is the number of LEBs the index currently uses. It might
|
* be large, because UBIFS does not do any index consolidation as long as
|
* there is free space. IOW, the index may take a lot of LEBs, but the LEBs
|
* will contain a lot of dirt.
|
* o @c->bi.min_idx_lebs is the number of LEBS the index presumably takes. IOW,
|
* the index may be consolidated to take up to @c->bi.min_idx_lebs LEBs.
|
*
|
* This function returns zero in case of success, and %-ENOSPC in case of
|
* failure.
|
*/
|
static int do_budget_space(struct ubifs_info *c)
|
{
|
long long outstanding, available;
|
int lebs, rsvd_idx_lebs, min_idx_lebs;
|
|
/* First budget index space */
|
min_idx_lebs = ubifs_calc_min_idx_lebs(c);
|
|
/* Now 'min_idx_lebs' contains number of LEBs to reserve */
|
if (min_idx_lebs > c->lst.idx_lebs)
|
rsvd_idx_lebs = min_idx_lebs - c->lst.idx_lebs;
|
else
|
rsvd_idx_lebs = 0;
|
|
/*
|
* The number of LEBs that are available to be used by the index is:
|
*
|
* @c->lst.empty_lebs + @c->freeable_cnt + @c->idx_gc_cnt -
|
* @c->lst.taken_empty_lebs
|
*
|
* @c->lst.empty_lebs are available because they are empty.
|
* @c->freeable_cnt are available because they contain only free and
|
* dirty space, @c->idx_gc_cnt are available because they are index
|
* LEBs that have been garbage collected and are awaiting the commit
|
* before they can be used. And the in-the-gaps method will grab these
|
* if it needs them. @c->lst.taken_empty_lebs are empty LEBs that have
|
* already been allocated for some purpose.
|
*
|
* Note, @c->idx_gc_cnt is included to both @c->lst.empty_lebs (because
|
* these LEBs are empty) and to @c->lst.taken_empty_lebs (because they
|
* are taken until after the commit).
|
*
|
* Note, @c->lst.taken_empty_lebs may temporarily be higher by one
|
* because of the way we serialize LEB allocations and budgeting. See a
|
* comment in 'ubifs_find_free_space()'.
|
*/
|
lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
|
c->lst.taken_empty_lebs;
|
if (unlikely(rsvd_idx_lebs > lebs)) {
|
dbg_budg("out of indexing space: min_idx_lebs %d (old %d), rsvd_idx_lebs %d",
|
min_idx_lebs, c->bi.min_idx_lebs, rsvd_idx_lebs);
|
return -ENOSPC;
|
}
|
|
available = ubifs_calc_available(c, min_idx_lebs);
|
outstanding = c->bi.data_growth + c->bi.dd_growth;
|
|
if (unlikely(available < outstanding)) {
|
dbg_budg("out of data space: available %lld, outstanding %lld",
|
available, outstanding);
|
return -ENOSPC;
|
}
|
|
if (available - outstanding <= c->rp_size && !can_use_rp(c))
|
return -ENOSPC;
|
|
c->bi.min_idx_lebs = min_idx_lebs;
|
return 0;
|
}
|
|
/**
|
* calc_idx_growth - calculate approximate index growth from budgeting request.
|
* @c: UBIFS file-system description object
|
* @req: budgeting request
|
*
|
* For now we assume each new node adds one znode. But this is rather poor
|
* approximation, though.
|
*/
|
static int calc_idx_growth(const struct ubifs_info *c,
|
const struct ubifs_budget_req *req)
|
{
|
int znodes;
|
|
znodes = req->new_ino + (req->new_page << UBIFS_BLOCKS_PER_PAGE_SHIFT) +
|
req->new_dent;
|
return znodes * c->max_idx_node_sz;
|
}
|
|
/**
|
* calc_data_growth - calculate approximate amount of new data from budgeting
|
* request.
|
* @c: UBIFS file-system description object
|
* @req: budgeting request
|
*/
|
static int calc_data_growth(const struct ubifs_info *c,
|
const struct ubifs_budget_req *req)
|
{
|
int data_growth;
|
|
data_growth = req->new_ino ? c->bi.inode_budget : 0;
|
if (req->new_page)
|
data_growth += c->bi.page_budget;
|
if (req->new_dent)
|
data_growth += c->bi.dent_budget;
|
data_growth += req->new_ino_d;
|
return data_growth;
|
}
|
|
/**
|
* calc_dd_growth - calculate approximate amount of data which makes other data
|
* dirty from budgeting request.
|
* @c: UBIFS file-system description object
|
* @req: budgeting request
|
*/
|
static int calc_dd_growth(const struct ubifs_info *c,
|
const struct ubifs_budget_req *req)
|
{
|
int dd_growth;
|
|
dd_growth = req->dirtied_page ? c->bi.page_budget : 0;
|
|
if (req->dirtied_ino)
|
dd_growth += c->bi.inode_budget << (req->dirtied_ino - 1);
|
if (req->mod_dent)
|
dd_growth += c->bi.dent_budget;
|
dd_growth += req->dirtied_ino_d;
|
return dd_growth;
|
}
|
|
/**
|
* ubifs_budget_space - ensure there is enough space to complete an operation.
|
* @c: UBIFS file-system description object
|
* @req: budget request
|
*
|
* This function allocates budget for an operation. It uses pessimistic
|
* approximation of how much flash space the operation needs. The goal of this
|
* function is to make sure UBIFS always has flash space to flush all dirty
|
* pages, dirty inodes, and dirty znodes (liability). This function may force
|
* commit, garbage-collection or write-back. Returns zero in case of success,
|
* %-ENOSPC if there is no free space and other negative error codes in case of
|
* failures.
|
*/
|
int ubifs_budget_space(struct ubifs_info *c, struct ubifs_budget_req *req)
|
{
|
int err, idx_growth, data_growth, dd_growth, retried = 0;
|
|
ubifs_assert(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);
|
|
again:
|
spin_lock(&c->space_lock);
|
ubifs_assert(c->bi.idx_growth >= 0);
|
ubifs_assert(c->bi.data_growth >= 0);
|
ubifs_assert(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(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);
|
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->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->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);
|
}
|
|
/**
|
* 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);
|
}
|
#endif
|
|
/**
|
* 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);
|
}
|
|
#ifndef __UBOOT__
|
/**
|
* 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->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;
|
}
|
#endif
|
