/*
   * This file is part of UBIFS.
   *
   * Copyright (C) 2006-2008 Nokia Corporation.
   * Copyright (C) 2006, 2007 University of Szeged, Hungary
   *
   * 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: Artem Bityutskiy (Битюцкий Артём)
   *          Adrian Hunter
   *          Zoltan Sogor
   */
  
  /*
   * This file implements UBIFS I/O subsystem which provides various I/O-related
   * helper functions (reading/writing/checking/validating nodes) and implements
   * write-buffering support. Write buffers help to save space which otherwise
   * would have been wasted for padding to the nearest minimal I/O unit boundary.
   * Instead, data first goes to the write-buffer and is flushed when the
   * buffer is full or when it is not used for some time (by timer). This is
   * similar to the mechanism is used by JFFS2.
   *
   * UBIFS distinguishes between minimum write size (@c->min_io_size) and maximum
   * write size (@c->max_write_size). The latter is the maximum amount of bytes
   * the underlying flash is able to program at a time, and writing in
   * @c->max_write_size units should presumably be faster. Obviously,
   * @c->min_io_size <= @c->max_write_size. Write-buffers are of
   * @c->max_write_size bytes in size for maximum performance. However, when a
   * write-buffer is flushed, only the portion of it (aligned to @c->min_io_size
   * boundary) which contains data is written, not the whole write-buffer,
   * because this is more space-efficient.
   *
   * This optimization adds few complications to the code. Indeed, on the one
   * hand, we want to write in optimal @c->max_write_size bytes chunks, which
   * also means aligning writes at the @c->max_write_size bytes offsets. On the
   * other hand, we do not want to waste space when synchronizing the write
   * buffer, so during synchronization we writes in smaller chunks. And this makes
   * the next write offset to be not aligned to @c->max_write_size bytes. So the
   * have to make sure that the write-buffer offset (@wbuf->offs) becomes aligned
   * to @c->max_write_size bytes again. We do this by temporarily shrinking
   * write-buffer size (@wbuf->size).
   *
   * Write-buffers are defined by 'struct ubifs_wbuf' objects and protected by
   * mutexes defined inside these objects. Since sometimes upper-level code
   * has to lock the write-buffer (e.g. journal space reservation code), many
   * functions related to write-buffers have "nolock" suffix which means that the
   * caller has to lock the write-buffer before calling this function.
   *
   * UBIFS stores nodes at 64 bit-aligned addresses. If the node length is not
   * aligned, UBIFS starts the next node from the aligned address, and the padded
   * bytes may contain any rubbish. In other words, UBIFS does not put padding
   * bytes in those small gaps. Common headers of nodes store real node lengths,
   * not aligned lengths. Indexing nodes also store real lengths in branches.
   *
   * UBIFS uses padding when it pads to the next min. I/O unit. In this case it
   * uses padding nodes or padding bytes, if the padding node does not fit.
   *
   * All UBIFS nodes are protected by CRC checksums and UBIFS checks CRC when
   * they are read from the flash media.
   */
  
  #include <linux/crc32.h>
  #include <linux/slab.h>
  #include "ubifs.h"
  
  /**
   * ubifs_ro_mode - switch UBIFS to read read-only mode.
   * @c: UBIFS file-system description object
   * @err: error code which is the reason of switching to R/O mode
   */
  void ubifs_ro_mode(struct ubifs_info *c, int err)
  {
  	if (!c->ro_error) {
  		c->ro_error = 1;
  		c->no_chk_data_crc = 0;
  		c->vfs_sb->s_flags |= MS_RDONLY;
  		ubifs_warn(c, "switched to read-only mode, error %d", err);
  		dump_stack();
  	}
  }
  
  /*
   * Below are simple wrappers over UBI I/O functions which include some
   * additional checks and UBIFS debugging stuff. See corresponding UBI function
   * for more information.
   */
  
  int ubifs_leb_read(const struct ubifs_info *c, int lnum, void *buf, int offs,
  		   int len, int even_ebadmsg)
  {
  	int err;
  
  	err = ubi_read(c->ubi, lnum, buf, offs, len);
  	/*
  	 * In case of %-EBADMSG print the error message only if the
  	 * @even_ebadmsg is true.
  	 */
  	if (err && (err != -EBADMSG || even_ebadmsg)) {
  		ubifs_err(c, "reading %d bytes from LEB %d:%d failed, error %d",
  			  len, lnum, offs, err);
  		dump_stack();
  	}
  	return err;
  }
  
  int ubifs_leb_write(struct ubifs_info *c, int lnum, const void *buf, int offs,
  		    int len)
  {
  	int err;
  
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (c->ro_error)
  		return -EROFS;
  	if (!dbg_is_tst_rcvry(c))
  		err = ubi_leb_write(c->ubi, lnum, buf, offs, len);
  	else
  		err = dbg_leb_write(c, lnum, buf, offs, len);
  	if (err) {
  		ubifs_err(c, "writing %d bytes to LEB %d:%d failed, error %d",
  			  len, lnum, offs, err);
  		ubifs_ro_mode(c, err);
  		dump_stack();
  	}
  	return err;
  }
  
  int ubifs_leb_change(struct ubifs_info *c, int lnum, const void *buf, int len)
  {
  	int err;
  
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (c->ro_error)
  		return -EROFS;
  	if (!dbg_is_tst_rcvry(c))
  		err = ubi_leb_change(c->ubi, lnum, buf, len);
  	else
  		err = dbg_leb_change(c, lnum, buf, len);
  	if (err) {
  		ubifs_err(c, "changing %d bytes in LEB %d failed, error %d",
  			  len, lnum, err);
  		ubifs_ro_mode(c, err);
  		dump_stack();
  	}
  	return err;
  }
  
  int ubifs_leb_unmap(struct ubifs_info *c, int lnum)
  {
  	int err;
  
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (c->ro_error)
  		return -EROFS;
  	if (!dbg_is_tst_rcvry(c))
  		err = ubi_leb_unmap(c->ubi, lnum);
  	else
  		err = dbg_leb_unmap(c, lnum);
  	if (err) {
  		ubifs_err(c, "unmap LEB %d failed, error %d", lnum, err);
  		ubifs_ro_mode(c, err);
  		dump_stack();
  	}
  	return err;
  }
  
  int ubifs_leb_map(struct ubifs_info *c, int lnum)
  {
  	int err;
  
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (c->ro_error)
  		return -EROFS;
  	if (!dbg_is_tst_rcvry(c))
  		err = ubi_leb_map(c->ubi, lnum);
  	else
  		err = dbg_leb_map(c, lnum);
  	if (err) {
  		ubifs_err(c, "mapping LEB %d failed, error %d", lnum, err);
  		ubifs_ro_mode(c, err);
  		dump_stack();
  	}
  	return err;
  }
  
  int ubifs_is_mapped(const struct ubifs_info *c, int lnum)
  {
  	int err;
  
  	err = ubi_is_mapped(c->ubi, lnum);
  	if (err < 0) {
  		ubifs_err(c, "ubi_is_mapped failed for LEB %d, error %d",
  			  lnum, err);
  		dump_stack();
  	}
  	return err;
  }
  
  /**
   * ubifs_check_node - check node.
   * @c: UBIFS file-system description object
   * @buf: node to check
   * @lnum: logical eraseblock number
   * @offs: offset within the logical eraseblock
   * @quiet: print no messages
   * @must_chk_crc: indicates whether to always check the CRC
   *
   * This function checks node magic number and CRC checksum. This function also
   * validates node length to prevent UBIFS from becoming crazy when an attacker
   * feeds it a file-system image with incorrect nodes. For example, too large
   * node length in the common header could cause UBIFS to read memory outside of
   * allocated buffer when checking the CRC checksum.
   *
   * This function may skip data nodes CRC checking if @c->no_chk_data_crc is
   * true, which is controlled by corresponding UBIFS mount option. However, if
   * @must_chk_crc is true, then @c->no_chk_data_crc is ignored and CRC is
   * checked. Similarly, if @c->mounting or @c->remounting_rw is true (we are
   * mounting or re-mounting to R/W mode), @c->no_chk_data_crc is ignored and CRC
   * is checked. This is because during mounting or re-mounting from R/O mode to
   * R/W mode we may read journal nodes (when replying the journal or doing the
   * recovery) and the journal nodes may potentially be corrupted, so checking is
   * required.
   *
   * This function returns zero in case of success and %-EUCLEAN in case of bad
   * CRC or magic.
   */
  int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,
  		     int offs, int quiet, int must_chk_crc)
  {
  	int err = -EINVAL, type, node_len;
  	uint32_t crc, node_crc, magic;
  	const struct ubifs_ch *ch = buf;
  
  	ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
  	ubifs_assert(!(offs & 7) && offs < c->leb_size);
  
  	magic = le32_to_cpu(ch->magic);
  	if (magic != UBIFS_NODE_MAGIC) {
  		if (!quiet)
  			ubifs_err(c, "bad magic %#08x, expected %#08x",
  				  magic, UBIFS_NODE_MAGIC);
  		err = -EUCLEAN;
  		goto out;
  	}
  
  	type = ch->node_type;
  	if (type < 0 || type >= UBIFS_NODE_TYPES_CNT) {
  		if (!quiet)
  			ubifs_err(c, "bad node type %d", type);
  		goto out;
  	}
  
  	node_len = le32_to_cpu(ch->len);
  	if (node_len + offs > c->leb_size)
  		goto out_len;
  
  	if (c->ranges[type].max_len == 0) {
  		if (node_len != c->ranges[type].len)
  			goto out_len;
  	} else if (node_len < c->ranges[type].min_len ||
  		   node_len > c->ranges[type].max_len)
  		goto out_len;
  
  	if (!must_chk_crc && type == UBIFS_DATA_NODE && !c->mounting &&
  	    !c->remounting_rw && c->no_chk_data_crc)
  		return 0;
  
  	crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);
  	node_crc = le32_to_cpu(ch->crc);
  	if (crc != node_crc) {
  		if (!quiet)
  			ubifs_err(c, "bad CRC: calculated %#08x, read %#08x",
  				  crc, node_crc);
  		err = -EUCLEAN;
  		goto out;
  	}
  
  	return 0;
  
  out_len:
  	if (!quiet)
  		ubifs_err(c, "bad node length %d", node_len);
  out:
  	if (!quiet) {
  		ubifs_err(c, "bad node at LEB %d:%d", lnum, offs);
  		ubifs_dump_node(c, buf);
  		dump_stack();
  	}
  	return err;
  }
  
  /**
   * ubifs_pad - pad flash space.
   * @c: UBIFS file-system description object
   * @buf: buffer to put padding to
   * @pad: how many bytes to pad
   *
   * The flash media obliges us to write only in chunks of %c->min_io_size and
   * when we have to write less data we add padding node to the write-buffer and
   * pad it to the next minimal I/O unit's boundary. Padding nodes help when the
   * media is being scanned. If the amount of wasted space is not enough to fit a
   * padding node which takes %UBIFS_PAD_NODE_SZ bytes, we write padding bytes
   * pattern (%UBIFS_PADDING_BYTE).
   *
   * Padding nodes are also used to fill gaps when the "commit-in-gaps" method is
   * used.
   */
  void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
  {
  	uint32_t crc;
  
  	ubifs_assert(pad >= 0 && !(pad & 7));
  
  	if (pad >= UBIFS_PAD_NODE_SZ) {
  		struct ubifs_ch *ch = buf;
  		struct ubifs_pad_node *pad_node = buf;
  
  		ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
  		ch->node_type = UBIFS_PAD_NODE;
  		ch->group_type = UBIFS_NO_NODE_GROUP;
  		ch->padding[0] = ch->padding[1] = 0;
  		ch->sqnum = 0;
  		ch->len = cpu_to_le32(UBIFS_PAD_NODE_SZ);
  		pad -= UBIFS_PAD_NODE_SZ;
  		pad_node->pad_len = cpu_to_le32(pad);
  		crc = crc32(UBIFS_CRC32_INIT, buf + 8, UBIFS_PAD_NODE_SZ - 8);
  		ch->crc = cpu_to_le32(crc);
  		memset(buf + UBIFS_PAD_NODE_SZ, 0, pad);
  	} else if (pad > 0)
  		/* Too little space, padding node won't fit */
  		memset(buf, UBIFS_PADDING_BYTE, pad);
  }
  
  /**
   * next_sqnum - get next sequence number.
   * @c: UBIFS file-system description object
   */
  static unsigned long long next_sqnum(struct ubifs_info *c)
  {
  	unsigned long long sqnum;
  
  	spin_lock(&c->cnt_lock);
  	sqnum = ++c->max_sqnum;
  	spin_unlock(&c->cnt_lock);
  
  	if (unlikely(sqnum >= SQNUM_WARN_WATERMARK)) {
  		if (sqnum >= SQNUM_WATERMARK) {
  			ubifs_err(c, "sequence number overflow %llu, end of life",
  				  sqnum);
  			ubifs_ro_mode(c, -EINVAL);
  		}
  		ubifs_warn(c, "running out of sequence numbers, end of life soon");
  	}
  
  	return sqnum;
  }
  
  /**
   * ubifs_prepare_node - prepare node to be written to flash.
   * @c: UBIFS file-system description object
   * @node: the node to pad
   * @len: node length
   * @pad: if the buffer has to be padded
   *
   * This function prepares node at @node to be written to the media - it
   * calculates node CRC, fills the common header, and adds proper padding up to
   * the next minimum I/O unit if @pad is not zero.
   */
  void ubifs_prepare_node(struct ubifs_info *c, void *node, int len, int pad)
  {
  	uint32_t crc;
  	struct ubifs_ch *ch = node;
  	unsigned long long sqnum = next_sqnum(c);
  
  	ubifs_assert(len >= UBIFS_CH_SZ);
  
  	ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
  	ch->len = cpu_to_le32(len);
  	ch->group_type = UBIFS_NO_NODE_GROUP;
  	ch->sqnum = cpu_to_le64(sqnum);
  	ch->padding[0] = ch->padding[1] = 0;
  	crc = crc32(UBIFS_CRC32_INIT, node + 8, len - 8);
  	ch->crc = cpu_to_le32(crc);
  
  	if (pad) {
  		len = ALIGN(len, 8);
  		pad = ALIGN(len, c->min_io_size) - len;
  		ubifs_pad(c, node + len, pad);
  	}
  }
  
  /**
   * ubifs_prep_grp_node - prepare node of a group to be written to flash.
   * @c: UBIFS file-system description object
   * @node: the node to pad
   * @len: node length
   * @last: indicates the last node of the group
   *
   * This function prepares node at @node to be written to the media - it
   * calculates node CRC and fills the common header.
   */
  void ubifs_prep_grp_node(struct ubifs_info *c, void *node, int len, int last)
  {
  	uint32_t crc;
  	struct ubifs_ch *ch = node;
  	unsigned long long sqnum = next_sqnum(c);
  
  	ubifs_assert(len >= UBIFS_CH_SZ);
  
  	ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
  	ch->len = cpu_to_le32(len);
  	if (last)
  		ch->group_type = UBIFS_LAST_OF_NODE_GROUP;
  	else
  		ch->group_type = UBIFS_IN_NODE_GROUP;
  	ch->sqnum = cpu_to_le64(sqnum);
  	ch->padding[0] = ch->padding[1] = 0;
  	crc = crc32(UBIFS_CRC32_INIT, node + 8, len - 8);
  	ch->crc = cpu_to_le32(crc);
  }
  
  /**
   * wbuf_timer_callback - write-buffer timer callback function.
   * @timer: timer data (write-buffer descriptor)
   *
   * This function is called when the write-buffer timer expires.
   */
  static enum hrtimer_restart wbuf_timer_callback_nolock(struct hrtimer *timer)
  {
  	struct ubifs_wbuf *wbuf = container_of(timer, struct ubifs_wbuf, timer);
  
  	dbg_io("jhead %s", dbg_jhead(wbuf->jhead));
  	wbuf->need_sync = 1;
  	wbuf->c->need_wbuf_sync = 1;
  	ubifs_wake_up_bgt(wbuf->c);
  	return HRTIMER_NORESTART;
  }
  
  /**
   * new_wbuf_timer - start new write-buffer timer.
   * @wbuf: write-buffer descriptor
   */
  static void new_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
  {
  	ubifs_assert(!hrtimer_active(&wbuf->timer));
  
  	if (wbuf->no_timer)
  		return;
  	dbg_io("set timer for jhead %s, %llu-%llu millisecs",
  	       dbg_jhead(wbuf->jhead),
  	       div_u64(ktime_to_ns(wbuf->softlimit), USEC_PER_SEC),
  	       div_u64(ktime_to_ns(wbuf->softlimit) + wbuf->delta,
  		       USEC_PER_SEC));
  	hrtimer_start_range_ns(&wbuf->timer, wbuf->softlimit, wbuf->delta,
  			       HRTIMER_MODE_REL);
  }
  
  /**
   * cancel_wbuf_timer - cancel write-buffer timer.
   * @wbuf: write-buffer descriptor
   */
  static void cancel_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
  {
  	if (wbuf->no_timer)
  		return;
  	wbuf->need_sync = 0;
  	hrtimer_cancel(&wbuf->timer);
  }
  
  /**
   * ubifs_wbuf_sync_nolock - synchronize write-buffer.
   * @wbuf: write-buffer to synchronize
   *
   * This function synchronizes write-buffer @buf and returns zero in case of
   * success or a negative error code in case of failure.
   *
   * Note, although write-buffers are of @c->max_write_size, this function does
   * not necessarily writes all @c->max_write_size bytes to the flash. Instead,
   * if the write-buffer is only partially filled with data, only the used part
   * of the write-buffer (aligned on @c->min_io_size boundary) is synchronized.
   * This way we waste less space.
   */
  int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf)
  {
  	struct ubifs_info *c = wbuf->c;
  	int err, dirt, sync_len;
  
  	cancel_wbuf_timer_nolock(wbuf);
  	if (!wbuf->used || wbuf->lnum == -1)
  		/* Write-buffer is empty or not seeked */
  		return 0;
  
  	dbg_io("LEB %d:%d, %d bytes, jhead %s",
  	       wbuf->lnum, wbuf->offs, wbuf->used, dbg_jhead(wbuf->jhead));
  	ubifs_assert(!(wbuf->avail & 7));
  	ubifs_assert(wbuf->offs + wbuf->size <= c->leb_size);
  	ubifs_assert(wbuf->size >= c->min_io_size);
  	ubifs_assert(wbuf->size <= c->max_write_size);
  	ubifs_assert(wbuf->size % c->min_io_size == 0);
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (c->leb_size - wbuf->offs >= c->max_write_size)
  		ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size));
  
  	if (c->ro_error)
  		return -EROFS;
  
  	/*
  	 * Do not write whole write buffer but write only the minimum necessary
  	 * amount of min. I/O units.
  	 */
  	sync_len = ALIGN(wbuf->used, c->min_io_size);
  	dirt = sync_len - wbuf->used;
  	if (dirt)
  		ubifs_pad(c, wbuf->buf + wbuf->used, dirt);
  	err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf, wbuf->offs, sync_len);
  	if (err)
  		return err;
  
  	spin_lock(&wbuf->lock);
  	wbuf->offs += sync_len;
  	/*
  	 * Now @wbuf->offs is not necessarily aligned to @c->max_write_size.
  	 * But our goal is to optimize writes and make sure we write in
  	 * @c->max_write_size chunks and to @c->max_write_size-aligned offset.
  	 * Thus, if @wbuf->offs is not aligned to @c->max_write_size now, make
  	 * sure that @wbuf->offs + @wbuf->size is aligned to
  	 * @c->max_write_size. This way we make sure that after next
  	 * write-buffer flush we are again at the optimal offset (aligned to
  	 * @c->max_write_size).
  	 */
  	if (c->leb_size - wbuf->offs < c->max_write_size)
  		wbuf->size = c->leb_size - wbuf->offs;
  	else if (wbuf->offs & (c->max_write_size - 1))
  		wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
  	else
  		wbuf->size = c->max_write_size;
  	wbuf->avail = wbuf->size;
  	wbuf->used = 0;
  	wbuf->next_ino = 0;
  	spin_unlock(&wbuf->lock);
  
  	if (wbuf->sync_callback)
  		err = wbuf->sync_callback(c, wbuf->lnum,
  					  c->leb_size - wbuf->offs, dirt);
  	return err;
  }
  
  /**
   * ubifs_wbuf_seek_nolock - seek write-buffer.
   * @wbuf: write-buffer
   * @lnum: logical eraseblock number to seek to
   * @offs: logical eraseblock offset to seek to
   *
   * This function targets the write-buffer to logical eraseblock @lnum:@offs.
   * The write-buffer has to be empty. Returns zero in case of success and a
   * negative error code in case of failure.
   */
  int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs)
  {
  	const struct ubifs_info *c = wbuf->c;
  
  	dbg_io("LEB %d:%d, jhead %s", lnum, offs, dbg_jhead(wbuf->jhead));
  	ubifs_assert(lnum >= 0 && lnum < c->leb_cnt);
  	ubifs_assert(offs >= 0 && offs <= c->leb_size);
  	ubifs_assert(offs % c->min_io_size == 0 && !(offs & 7));
  	ubifs_assert(lnum != wbuf->lnum);
  	ubifs_assert(wbuf->used == 0);
  
  	spin_lock(&wbuf->lock);
  	wbuf->lnum = lnum;
  	wbuf->offs = offs;
  	if (c->leb_size - wbuf->offs < c->max_write_size)
  		wbuf->size = c->leb_size - wbuf->offs;
  	else if (wbuf->offs & (c->max_write_size - 1))
  		wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
  	else
  		wbuf->size = c->max_write_size;
  	wbuf->avail = wbuf->size;
  	wbuf->used = 0;
  	spin_unlock(&wbuf->lock);
  
  	return 0;
  }
  
  /**
   * ubifs_bg_wbufs_sync - synchronize write-buffers.
   * @c: UBIFS file-system description object
   *
   * This function is called by background thread to synchronize write-buffers.
   * Returns zero in case of success and a negative error code in case of
   * failure.
   */
  int ubifs_bg_wbufs_sync(struct ubifs_info *c)
  {
  	int err, i;
  
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	if (!c->need_wbuf_sync)
  		return 0;
  	c->need_wbuf_sync = 0;
  
  	if (c->ro_error) {
  		err = -EROFS;
  		goto out_timers;
  	}
  
  	dbg_io("synchronize");
  	for (i = 0; i < c->jhead_cnt; i++) {
  		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
  
  		cond_resched();
  
  		/*
  		 * If the mutex is locked then wbuf is being changed, so
  		 * synchronization is not necessary.
  		 */
  		if (mutex_is_locked(&wbuf->io_mutex))
  			continue;
  
  		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
  		if (!wbuf->need_sync) {
  			mutex_unlock(&wbuf->io_mutex);
  			continue;
  		}
  
  		err = ubifs_wbuf_sync_nolock(wbuf);
  		mutex_unlock(&wbuf->io_mutex);
  		if (err) {
  			ubifs_err(c, "cannot sync write-buffer, error %d", err);
  			ubifs_ro_mode(c, err);
  			goto out_timers;
  		}
  	}
  
  	return 0;
  
  out_timers:
  	/* Cancel all timers to prevent repeated errors */
  	for (i = 0; i < c->jhead_cnt; i++) {
  		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
  
  		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
  		cancel_wbuf_timer_nolock(wbuf);
  		mutex_unlock(&wbuf->io_mutex);
  	}
  	return err;
  }
  
  /**
   * ubifs_wbuf_write_nolock - write data to flash via write-buffer.
   * @wbuf: write-buffer
   * @buf: node to write
   * @len: node length
   *
   * This function writes data to flash via write-buffer @wbuf. This means that
   * the last piece of the node won't reach the flash media immediately if it
   * does not take whole max. write unit (@c->max_write_size). Instead, the node
   * will sit in RAM until the write-buffer is synchronized (e.g., by timer, or
   * because more data are appended to the write-buffer).
   *
   * This function returns zero in case of success and a negative error code in
   * case of failure. If the node cannot be written because there is no more
   * space in this logical eraseblock, %-ENOSPC is returned.
   */
  int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
  {
  	struct ubifs_info *c = wbuf->c;
  	int err, written, n, aligned_len = ALIGN(len, 8);
  
  	dbg_io("%d bytes (%s) to jhead %s wbuf at LEB %d:%d", len,
  	       dbg_ntype(((struct ubifs_ch *)buf)->node_type),
  	       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs + wbuf->used);
  	ubifs_assert(len > 0 && wbuf->lnum >= 0 && wbuf->lnum < c->leb_cnt);
  	ubifs_assert(wbuf->offs >= 0 && wbuf->offs % c->min_io_size == 0);
  	ubifs_assert(!(wbuf->offs & 7) && wbuf->offs <= c->leb_size);
  	ubifs_assert(wbuf->avail > 0 && wbuf->avail <= wbuf->size);
  	ubifs_assert(wbuf->size >= c->min_io_size);
  	ubifs_assert(wbuf->size <= c->max_write_size);
  	ubifs_assert(wbuf->size % c->min_io_size == 0);
  	ubifs_assert(mutex_is_locked(&wbuf->io_mutex));
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	ubifs_assert(!c->space_fixup);
  	if (c->leb_size - wbuf->offs >= c->max_write_size)
  		ubifs_assert(!((wbuf->offs + wbuf->size) % c->max_write_size));
  
  	if (c->leb_size - wbuf->offs - wbuf->used < aligned_len) {
  		err = -ENOSPC;
  		goto out;
  	}
  
  	cancel_wbuf_timer_nolock(wbuf);
  
  	if (c->ro_error)
  		return -EROFS;
  
  	if (aligned_len <= wbuf->avail) {
  		/*
  		 * The node is not very large and fits entirely within
  		 * write-buffer.
  		 */
  		memcpy(wbuf->buf + wbuf->used, buf, len);
  
  		if (aligned_len == wbuf->avail) {
  			dbg_io("flush jhead %s wbuf to LEB %d:%d",
  			       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
  			err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf,
  					      wbuf->offs, wbuf->size);
  			if (err)
  				goto out;
  
  			spin_lock(&wbuf->lock);
  			wbuf->offs += wbuf->size;
  			if (c->leb_size - wbuf->offs >= c->max_write_size)
  				wbuf->size = c->max_write_size;
  			else
  				wbuf->size = c->leb_size - wbuf->offs;
  			wbuf->avail = wbuf->size;
  			wbuf->used = 0;
  			wbuf->next_ino = 0;
  			spin_unlock(&wbuf->lock);
  		} else {
  			spin_lock(&wbuf->lock);
  			wbuf->avail -= aligned_len;
  			wbuf->used += aligned_len;
  			spin_unlock(&wbuf->lock);
  		}
  
  		goto exit;
  	}
  
  	written = 0;
  
  	if (wbuf->used) {
  		/*
  		 * The node is large enough and does not fit entirely within
  		 * current available space. We have to fill and flush
  		 * write-buffer and switch to the next max. write unit.
  		 */
  		dbg_io("flush jhead %s wbuf to LEB %d:%d",
  		       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
  		memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail);
  		err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf, wbuf->offs,
  				      wbuf->size);
  		if (err)
  			goto out;
  
  		wbuf->offs += wbuf->size;
  		len -= wbuf->avail;
  		aligned_len -= wbuf->avail;
  		written += wbuf->avail;
  	} else if (wbuf->offs & (c->max_write_size - 1)) {
  		/*
  		 * The write-buffer offset is not aligned to
  		 * @c->max_write_size and @wbuf->size is less than
  		 * @c->max_write_size. Write @wbuf->size bytes to make sure the
  		 * following writes are done in optimal @c->max_write_size
  		 * chunks.
  		 */
  		dbg_io("write %d bytes to LEB %d:%d",
  		       wbuf->size, wbuf->lnum, wbuf->offs);
  		err = ubifs_leb_write(c, wbuf->lnum, buf, wbuf->offs,
  				      wbuf->size);
  		if (err)
  			goto out;
  
  		wbuf->offs += wbuf->size;
  		len -= wbuf->size;
  		aligned_len -= wbuf->size;
  		written += wbuf->size;
  	}
  
  	/*
  	 * The remaining data may take more whole max. write units, so write the
  	 * remains multiple to max. write unit size directly to the flash media.
  	 * We align node length to 8-byte boundary because we anyway flash wbuf
  	 * if the remaining space is less than 8 bytes.
  	 */
  	n = aligned_len >> c->max_write_shift;
  	if (n) {
  		n <<= c->max_write_shift;
  		dbg_io("write %d bytes to LEB %d:%d", n, wbuf->lnum,
  		       wbuf->offs);
  		err = ubifs_leb_write(c, wbuf->lnum, buf + written,
  				      wbuf->offs, n);
  		if (err)
  			goto out;
  		wbuf->offs += n;
  		aligned_len -= n;
  		len -= n;
  		written += n;
  	}
  
  	spin_lock(&wbuf->lock);
  	if (aligned_len)
  		/*
  		 * And now we have what's left and what does not take whole
  		 * max. write unit, so write it to the write-buffer and we are
  		 * done.
  		 */
  		memcpy(wbuf->buf, buf + written, len);
  
  	if (c->leb_size - wbuf->offs >= c->max_write_size)
  		wbuf->size = c->max_write_size;
  	else
  		wbuf->size = c->leb_size - wbuf->offs;
  	wbuf->avail = wbuf->size - aligned_len;
  	wbuf->used = aligned_len;
  	wbuf->next_ino = 0;
  	spin_unlock(&wbuf->lock);
  
  exit:
  	if (wbuf->sync_callback) {
  		int free = c->leb_size - wbuf->offs - wbuf->used;
  
  		err = wbuf->sync_callback(c, wbuf->lnum, free, 0);
  		if (err)
  			goto out;
  	}
  
  	if (wbuf->used)
  		new_wbuf_timer_nolock(wbuf);
  
  	return 0;
  
  out:
  	ubifs_err(c, "cannot write %d bytes to LEB %d:%d, error %d",
  		  len, wbuf->lnum, wbuf->offs, err);
  	ubifs_dump_node(c, buf);
  	dump_stack();
  	ubifs_dump_leb(c, wbuf->lnum);
  	return err;
  }
  
  /**
   * ubifs_write_node - write node to the media.
   * @c: UBIFS file-system description object
   * @buf: the node to write
   * @len: node length
   * @lnum: logical eraseblock number
   * @offs: offset within the logical eraseblock
   *
   * This function automatically fills node magic number, assigns sequence
   * number, and calculates node CRC checksum. The length of the @buf buffer has
   * to be aligned to the minimal I/O unit size. This function automatically
   * appends padding node and padding bytes if needed. Returns zero in case of
   * success and a negative error code in case of failure.
   */
  int ubifs_write_node(struct ubifs_info *c, void *buf, int len, int lnum,
  		     int offs)
  {
  	int err, buf_len = ALIGN(len, c->min_io_size);
  
  	dbg_io("LEB %d:%d, %s, length %d (aligned %d)",
  	       lnum, offs, dbg_ntype(((struct ubifs_ch *)buf)->node_type), len,
  	       buf_len);
  	ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
  	ubifs_assert(offs % c->min_io_size == 0 && offs < c->leb_size);
  	ubifs_assert(!c->ro_media && !c->ro_mount);
  	ubifs_assert(!c->space_fixup);
  
  	if (c->ro_error)
  		return -EROFS;
  
  	ubifs_prepare_node(c, buf, len, 1);
  	err = ubifs_leb_write(c, lnum, buf, offs, buf_len);
  	if (err)
  		ubifs_dump_node(c, buf);
  
  	return err;
  }
  
  /**
   * ubifs_read_node_wbuf - read node from the media or write-buffer.
   * @wbuf: wbuf to check for un-written data
   * @buf: buffer to read to
   * @type: node type
   * @len: node length
   * @lnum: logical eraseblock number
   * @offs: offset within the logical eraseblock
   *
   * This function reads a node of known type and length, checks it and stores
   * in @buf. If the node partially or fully sits in the write-buffer, this
   * function takes data from the buffer, otherwise it reads the flash media.
   * Returns zero in case of success, %-EUCLEAN if CRC mismatched and a negative
   * error code in case of failure.
   */
  int ubifs_read_node_wbuf(struct ubifs_wbuf *wbuf, void *buf, int type, int len,
  			 int lnum, int offs)
  {
  	const struct ubifs_info *c = wbuf->c;
  	int err, rlen, overlap;
  	struct ubifs_ch *ch = buf;
  
  	dbg_io("LEB %d:%d, %s, length %d, jhead %s", lnum, offs,
  	       dbg_ntype(type), len, dbg_jhead(wbuf->jhead));
  	ubifs_assert(wbuf && lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
  	ubifs_assert(!(offs & 7) && offs < c->leb_size);
  	ubifs_assert(type >= 0 && type < UBIFS_NODE_TYPES_CNT);
  
  	spin_lock(&wbuf->lock);
  	overlap = (lnum == wbuf->lnum && offs + len > wbuf->offs);
  	if (!overlap) {
  		/* We may safely unlock the write-buffer and read the data */
  		spin_unlock(&wbuf->lock);
  		return ubifs_read_node(c, buf, type, len, lnum, offs);
  	}
  
  	/* Don't read under wbuf */
  	rlen = wbuf->offs - offs;
  	if (rlen < 0)
  		rlen = 0;
  
  	/* Copy the rest from the write-buffer */
  	memcpy(buf + rlen, wbuf->buf + offs + rlen - wbuf->offs, len - rlen);
  	spin_unlock(&wbuf->lock);
  
  	if (rlen > 0) {
  		/* Read everything that goes before write-buffer */
  		err = ubifs_leb_read(c, lnum, buf, offs, rlen, 0);
  		if (err && err != -EBADMSG)
  			return err;
  	}
  
  	if (type != ch->node_type) {
  		ubifs_err(c, "bad node type (%d but expected %d)",
  			  ch->node_type, type);
  		goto out;
  	}
  
  	err = ubifs_check_node(c, buf, lnum, offs, 0, 0);
  	if (err) {
  		ubifs_err(c, "expected node type %d", type);
  		return err;
  	}
  
  	rlen = le32_to_cpu(ch->len);
  	if (rlen != len) {
  		ubifs_err(c, "bad node length %d, expected %d", rlen, len);
  		goto out;
  	}
  
  	return 0;
  
  out:
  	ubifs_err(c, "bad node at LEB %d:%d", lnum, offs);
  	ubifs_dump_node(c, buf);
  	dump_stack();
  	return -EINVAL;
  }
  
  /**
   * ubifs_read_node - read node.
   * @c: UBIFS file-system description object
   * @buf: buffer to read to
   * @type: node type
   * @len: node length (not aligned)
   * @lnum: logical eraseblock number
   * @offs: offset within the logical eraseblock
   *
   * This function reads a node of known type and and length, checks it and
   * stores in @buf. Returns zero in case of success, %-EUCLEAN if CRC mismatched
   * and a negative error code in case of failure.
   */
  int ubifs_read_node(const struct ubifs_info *c, void *buf, int type, int len,
  		    int lnum, int offs)
  {
  	int err, l;
  	struct ubifs_ch *ch = buf;
  
  	dbg_io("LEB %d:%d, %s, length %d", lnum, offs, dbg_ntype(type), len);
  	ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
  	ubifs_assert(len >= UBIFS_CH_SZ && offs + len <= c->leb_size);
  	ubifs_assert(!(offs & 7) && offs < c->leb_size);
  	ubifs_assert(type >= 0 && type < UBIFS_NODE_TYPES_CNT);
  
  	err = ubifs_leb_read(c, lnum, buf, offs, len, 0);
  	if (err && err != -EBADMSG)
  		return err;
  
  	if (type != ch->node_type) {
  		ubifs_errc(c, "bad node type (%d but expected %d)",
  			   ch->node_type, type);
  		goto out;
  	}
  
  	err = ubifs_check_node(c, buf, lnum, offs, 0, 0);
  	if (err) {
  		ubifs_errc(c, "expected node type %d", type);
  		return err;
  	}
  
  	l = le32_to_cpu(ch->len);
  	if (l != len) {
  		ubifs_errc(c, "bad node length %d, expected %d", l, len);
  		goto out;
  	}
  
  	return 0;
  
  out:
  	ubifs_errc(c, "bad node at LEB %d:%d, LEB mapping status %d", lnum,
  		   offs, ubi_is_mapped(c->ubi, lnum));
  	if (!c->probing) {
  		ubifs_dump_node(c, buf);
  		dump_stack();
  	}
  	return -EINVAL;
  }
  
  /**
   * ubifs_wbuf_init - initialize write-buffer.
   * @c: UBIFS file-system description object
   * @wbuf: write-buffer to initialize
   *
   * This function initializes write-buffer. Returns zero in case of success
   * %-ENOMEM in case of failure.
   */
  int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
  {
  	size_t size;
  
  	wbuf->buf = kmalloc(c->max_write_size, GFP_KERNEL);
  	if (!wbuf->buf)
  		return -ENOMEM;
  
  	size = (c->max_write_size / UBIFS_CH_SZ + 1) * sizeof(ino_t);
  	wbuf->inodes = kmalloc(size, GFP_KERNEL);
  	if (!wbuf->inodes) {
  		kfree(wbuf->buf);
  		wbuf->buf = NULL;
  		return -ENOMEM;
  	}
  
  	wbuf->used = 0;
  	wbuf->lnum = wbuf->offs = -1;
  	/*
  	 * If the LEB starts at the max. write size aligned address, then
  	 * write-buffer size has to be set to @c->max_write_size. Otherwise,
  	 * set it to something smaller so that it ends at the closest max.
  	 * write size boundary.
  	 */
  	size = c->max_write_size - (c->leb_start % c->max_write_size);
  	wbuf->avail = wbuf->size = size;
  	wbuf->sync_callback = NULL;
  	mutex_init(&wbuf->io_mutex);
  	spin_lock_init(&wbuf->lock);
  	wbuf->c = c;
  	wbuf->next_ino = 0;
  
  	hrtimer_init(&wbuf->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  	wbuf->timer.function = wbuf_timer_callback_nolock;
  	wbuf->softlimit = ktime_set(WBUF_TIMEOUT_SOFTLIMIT, 0);
  	wbuf->delta = WBUF_TIMEOUT_HARDLIMIT - WBUF_TIMEOUT_SOFTLIMIT;
  	wbuf->delta *= 1000000000ULL;
  	ubifs_assert(wbuf->delta <= ULONG_MAX);
  	return 0;
  }
  
  /**
   * ubifs_wbuf_add_ino_nolock - add an inode number into the wbuf inode array.
   * @wbuf: the write-buffer where to add
   * @inum: the inode number
   *
   * This function adds an inode number to the inode array of the write-buffer.
   */
  void ubifs_wbuf_add_ino_nolock(struct ubifs_wbuf *wbuf, ino_t inum)
  {
  	if (!wbuf->buf)
  		/* NOR flash or something similar */
  		return;
  
  	spin_lock(&wbuf->lock);
  	if (wbuf->used)
  		wbuf->inodes[wbuf->next_ino++] = inum;
  	spin_unlock(&wbuf->lock);
  }
  
  /**
   * wbuf_has_ino - returns if the wbuf contains data from the inode.
   * @wbuf: the write-buffer
   * @inum: the inode number
   *
   * This function returns with %1 if the write-buffer contains some data from the
   * given inode otherwise it returns with %0.
   */
  static int wbuf_has_ino(struct ubifs_wbuf *wbuf, ino_t inum)
  {
  	int i, ret = 0;
  
  	spin_lock(&wbuf->lock);
  	for (i = 0; i < wbuf->next_ino; i++)
  		if (inum == wbuf->inodes[i]) {
  			ret = 1;
  			break;
  		}
  	spin_unlock(&wbuf->lock);
  
  	return ret;
  }
  
  /**
   * ubifs_sync_wbufs_by_inode - synchronize write-buffers for an inode.
   * @c: UBIFS file-system description object
   * @inode: inode to synchronize
   *
   * This function synchronizes write-buffers which contain nodes belonging to
   * @inode. Returns zero in case of success and a negative error code in case of
   * failure.
   */
  int ubifs_sync_wbufs_by_inode(struct ubifs_info *c, struct inode *inode)
  {
  	int i, err = 0;
  
  	for (i = 0; i < c->jhead_cnt; i++) {
  		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
  
  		if (i == GCHD)
  			/*
  			 * GC head is special, do not look at it. Even if the
  			 * head contains something related to this inode, it is
  			 * a _copy_ of corresponding on-flash node which sits
  			 * somewhere else.
  			 */
  			continue;
  
  		if (!wbuf_has_ino(wbuf, inode->i_ino))
  			continue;
  
  		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
  		if (wbuf_has_ino(wbuf, inode->i_ino))
  			err = ubifs_wbuf_sync_nolock(wbuf);
  		mutex_unlock(&wbuf->io_mutex);
  
  		if (err) {
  			ubifs_ro_mode(c, err);
  			return err;
  		}
  	}
  	return 0;
  }