UBIFS: add new flash file system

/*

 * 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)