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/*
* 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 thrice the index size of space reserved */
idx_size = idx_size + (idx_size << 1);
/*
* We do not maintain 'old_
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