Message-Id: <1210070159-22794-24-git-send-email-Artem.Bityutskiy@nokia.com>
Date:	Tue,  6 May 2008 13:35:54 +0300
From:	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Adrian Hunter <ext-adrian.hunter@...ia.com>,
	Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Subject: [PATCH take 2 23/28] UBIFS: add budgeting

Because of compression and space wastage (due to paddings) it is not
always possible to know whether the cached data fits the flash space
or not. Sometimes this problem is called "ENOSPC" problem. UBIFS
implements the budgeting sub-system to solve the issue. All the FS
operations have to acquire the budget. The budgeting subsystem does
pessimistic space calculations (e.g., assumes the data is not
compressible) and forces write-back or garbage-collection if needed.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@...ia.com>
Signed-off-by: Adrian Hunter <ext-adrian.hunter@...ia.com>
---
 fs/ubifs/budget.c |  857 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 857 insertions(+), 0 deletions(-)

diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
new file mode 100644
index 0000000..90a9397
--- /dev/null
+++ b/fs/ubifs/budget.c
@@ -0,0 +1,857 @@
+/*
+ * 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 unit 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)
+{
+	struct writeback_control wbc = {
+		.sync_mode   = WB_SYNC_NONE,
+		.range_end   = LLONG_MAX,
+		.nr_to_write = nr_to_write,
+	};
+
+	writeback_inodes_sb(c->vfs_sb, &wbc);
+	dbg_budg("%ld pages were written back", nr_to_write - wbc.nr_to_write);
+	return nr_to_write - wbc.nr_to_write;
+}
+
+
+/**
+ * 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
+ *
+ * This function calculates and returns amount of FS space available for use.
+ */
+long long ubifs_calc_available(const struct ubifs_info *c)
+{
+	long long available, subtract_lebs;
+
+	/*
+	 * 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 = c->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 -= 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 > c->min_idx_lebs) {
+		subtract_lebs = c->lst.idx_lebs - c->min_idx_lebs;
+		available -= subtract_lebs * c->dark_wm;
+	}
+
+	return available;
+}
+
+/**
+ * rp_can_write - check whether the user is allowed to write.
+ * @c: UBIFS file-system description object
+ * @avail: available space on FS
+ *
+ * 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 write
+ * to the file-system - it returns %1 if there is plenty of space or the user
+ * is eligible to use the reserved pool and %0 otherwise.
+ */
+static int rp_can_write(struct ubifs_info *c, long long avail)
+{
+	if (avail > c->rp_size || 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).
+	 */
+	lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
+	       c->lst.taken_empty_lebs;
+	ubifs_assert(lebs + c->lst.idx_lebs >= c->min_idx_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);
+	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 (!rp_can_write(c, available - outstanding))
+		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 + 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;
+
+	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);
+
+	c->budg_idx_growth += idx_growth;
+	c->budg_data_growth += data_growth;
+	c->budg_dd_growth += dd_growth;
+
+	err = do_budget_space(c);
+	if (unlikely(err)) {
+		/* 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);
+
+		goto make_space;
+	}
+
+	req->idx_growth = idx_growth;
+	req->data_growth = data_growth;
+	req->dd_growth = dd_growth;
+	spin_unlock(&c->space_lock);
+
+	return 0;
+
+make_space:
+	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");
+	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)
+{
+	if (!req->data_growth && !req->dd_growth)
+		return;
+
+	if (req->idx_growth == -1)
+		req->idx_growth = calc_idx_growth(c, req);
+
+	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 not larger
+ * 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;
+	/* 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_budget_inode_op - budget an operation on inode.
+ * @c: UBIFS file-system description object
+ * @inode: VFS inode which will be made dirty by the operation
+ * @req: budget request of the operation
+ *
+ * This function is called to get budget for an operation which changes an
+ * inode. The inode may be in dirty or clean state. The former means there is
+ * no need to allocate the budget as it has already been allocated before. The
+ * latter means that the inode change budget has to be allocated.
+ *
+ * The caller has to pass the inode which is going to be changed. This function
+ * acquires budget the for as described in @req plus the budget for changing
+ * the inode dirty, if needed. Returns zero in case of success, %-ENOSPC if
+ * there is no more flash space, and other negative error codes in case of
+ * failure.
+ *
+ * Note, upon exit, this function leaves the inode locked, and the
+ * 'ubifs_release_ino_dirty()' or 'ubifs_release_ino_clean()' function has to
+ * be called to unlock it.
+ */
+int ubifs_budget_inode_op(struct ubifs_info *c, struct inode *inode,
+			      struct ubifs_budget_req *req)
+{
+	struct ubifs_inode *ui = ubifs_inode(inode);
+	int err, old = req->dirtied_ino;
+
+	ubifs_assert(req->dirtied_ino <= 3);
+	ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 3);
+
+again:
+	/*
+	 * If the inode is clean, it will be dirtied by this operation and we
+	 * have to budget for this.
+	 */
+	req->dirtied_ino += !ui->dirty;
+	if (req->dirtied_ino > old)
+		req->dirtied_ino_d += ui->data_len;
+
+	/*
+	 * Note, if the budget request does not actually request anything
+	 * (i.e., @req contains only zeroes), 'ubifs_budget_space()' will
+	 * return almost straight away.
+	 */
+	err = ubifs_budget_space(c, req);
+	if (unlikely(err))
+		return err;
+
+	mutex_lock(&ui->budg_mutex);
+
+	if (req->dirtied_ino != old + !ui->dirty) {
+		/* The inode has probably been written back meanwhile */
+		ubifs_release_budget(c, req);
+		mutex_unlock(&ui->budg_mutex);
+		req->dirtied_ino = old;
+		req->dirtied_ino_d -= ui->data_len;
+		goto again;
+	}
+
+	UBIFS_DBG(ui->budgeted = 1);
+	return 0;
+}
+
+/**
+ * ubifs_release_ino_dirty - release budget of a "dirtying" operation.
+ * @c: UBIFS file-system description object
+ * @inode: VFS inode the operation worked on
+ * @req: budget to release
+ *
+ * This function has to be called at the end of VFS operations which acquired
+ * budget via 'ubifs_budget_inode_op()'. It assumes that the inode has been
+ * marked as dirty and will be synchronized later by write-back, so it does not
+ * release the budget of the inode.
+ *
+ * Note, this function also avoids releasing page budgets which are released
+ * separately.
+ */
+void ubifs_release_ino_dirty(struct ubifs_info *c, struct inode *inode,
+				struct ubifs_budget_req *req)
+{
+	ubifs_assert(req->dirtied_ino <= 4);
+	ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
+	ubifs_assert(req->idx_growth >= 0);
+	ubifs_assert(req->data_growth >= 0);
+	ubifs_assert(req->dd_growth >= 0);
+
+	if (req->dirtied_ino) {
+		req->dd_growth -= c->inode_budget;
+		req->dd_growth -= req->dirtied_ino_d;
+	}
+
+	if (req->dirtied_page) {
+		req->dd_growth -= c->page_budget;
+		ubifs_assert(req->new_page == 0);
+	} else if (req->new_page) {
+		req->idx_growth -= c->max_idx_node_sz;
+		req->data_growth -= c->page_budget;
+		ubifs_assert(req->dirtied_page == 0);
+	}
+
+	ubifs_assert(req->dd_growth >= 0);
+	ubifs_release_budget(c, req);
+	mutex_unlock(&ubifs_inode(inode)->budg_mutex);
+}
+
+/**
+ * ubifs_cancel_ino_op - cancel budget of an operation on inode.
+ * @c: UBIFS file-system description object
+ * @inode: VFS inode the operation worked on
+ * @req: budget to release
+ *
+ * This function has to be called if the operation failed and whole budget has
+ * to be released, including the budget for inode which would had been
+ * dirtied. It is important not to mark the inode dirty before calling this
+ * function.
+ */
+void ubifs_cancel_ino_op(struct ubifs_info *c, struct inode *inode,
+			 struct ubifs_budget_req *req)
+{
+	ubifs_assert(req->dirtied_ino <= 4);
+	ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
+	ubifs_assert(req->idx_growth >= 0);
+	ubifs_assert(req->data_growth >= 0);
+	ubifs_assert(req->dd_growth >= 0);
+
+	ubifs_release_budget(c, req);
+	mutex_unlock(&ubifs_inode(inode)->budg_mutex);
+}
+
+/**
+ * ubifs_release_ino_clean - release budget of a "cleaning" operation.
+ * @c: UBIFS file-system description object
+ * @inode: VFS inode the operation worked on
+ * @req: budget to release
+ *
+ * This function has to be called at the end of VFS operations which acquired
+ * budget via 'ubifs_budget_inode_op()'. It assumed the operation synchronized
+ * the inode, so it marks the inode clean, unlocks it and releases whole budget.
+ *
+ * Note, this function also avoids releasing page budgets which are released
+ * separately.
+ */
+void ubifs_release_ino_clean(struct ubifs_info *c, struct inode *inode,
+			     struct ubifs_budget_req *req)
+{
+	struct ubifs_inode *ui = ubifs_inode(inode);
+
+	ubifs_assert(req->dirtied_ino <= 4);
+	ubifs_assert(req->dirtied_ino_d <= UBIFS_MAX_INO_DATA * 4);
+	ubifs_assert(req->idx_growth >= 0);
+	ubifs_assert(req->data_growth >= 0);
+	ubifs_assert(req->dd_growth >= 0);
+	ubifs_assert(!req->dirtied_page);
+	ubifs_assert(!req->new_page);
+	UBIFS_DBG(ui->budgeted = 0);
+
+	ubifs_release_budget(c, req);
+	if (ui->dirty) {
+		ui->dirty = 0;
+		/*
+		 * Note, VFS still treats the inode as dirty and
+		 * 'ubifs_write_inode()' will be called, but it'll do nothing
+		 * because @ui->dirty is %0.
+		 */
+		atomic_long_dec(&c->dirty_ino_cnt);
+	}
+	mutex_unlock(&ubifs_inode(inode)->budg_mutex);
+}
+
+/**
+ * ubifs_release_new_page_budget - release budget of a new page.
+ * @c: UBIFS file-system description object
+ *
+ * This is a helper function which releases budget corresponding to the budget
+ * of one new page of data.
+ */
+void ubifs_release_new_page_budget(struct ubifs_info *c)
+{
+	struct ubifs_budget_req req = { .new_page = 1,
+					.idx_growth = -1,
+					.data_growth = c->page_budget};
+
+	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;
+	}
+
+	c->min_idx_lebs = min_idx_lebs;
+	available = ubifs_calc_available(c);
+	outstanding = c->budg_data_growth + c->budg_dd_growth;
+	spin_unlock(&c->space_lock);
+
+	if (available > outstanding)
+		free = ubifs_reported_space(c, available - outstanding);
+	else
+		free = 0;
+
+	return free;
+}
-- 
1.5.4.1

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