io.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * This file is part of UBIFS.
   4 *
   5 * Copyright (C) 2006-2008 Nokia Corporation.
   6 * Copyright (C) 2006, 2007 University of Szeged, Hungary
   7 *
   8 * Authors: Artem Bityutskiy (Битюцкий Артём)
   9 *          Adrian Hunter
  10 *          Zoltan Sogor
  11 */
  12
  13/*
  14 * This file implements UBIFS I/O subsystem which provides various I/O-related
  15 * helper functions (reading/writing/checking/validating nodes) and implements
  16 * write-buffering support. Write buffers help to save space which otherwise
  17 * would have been wasted for padding to the nearest minimal I/O unit boundary.
  18 * Instead, data first goes to the write-buffer and is flushed when the
  19 * buffer is full or when it is not used for some time (by timer). This is
  20 * similar to the mechanism is used by JFFS2.
  21 *
  22 * UBIFS distinguishes between minimum write size (@c->min_io_size) and maximum
  23 * write size (@c->max_write_size). The latter is the maximum amount of bytes
  24 * the underlying flash is able to program at a time, and writing in
  25 * @c->max_write_size units should presumably be faster. Obviously,
  26 * @c->min_io_size <= @c->max_write_size. Write-buffers are of
  27 * @c->max_write_size bytes in size for maximum performance. However, when a
  28 * write-buffer is flushed, only the portion of it (aligned to @c->min_io_size
  29 * boundary) which contains data is written, not the whole write-buffer,
  30 * because this is more space-efficient.
  31 *
  32 * This optimization adds few complications to the code. Indeed, on the one
  33 * hand, we want to write in optimal @c->max_write_size bytes chunks, which
  34 * also means aligning writes at the @c->max_write_size bytes offsets. On the
  35 * other hand, we do not want to waste space when synchronizing the write
  36 * buffer, so during synchronization we writes in smaller chunks. And this makes
  37 * the next write offset to be not aligned to @c->max_write_size bytes. So the
  38 * have to make sure that the write-buffer offset (@wbuf->offs) becomes aligned
  39 * to @c->max_write_size bytes again. We do this by temporarily shrinking
  40 * write-buffer size (@wbuf->size).
  41 *
  42 * Write-buffers are defined by 'struct ubifs_wbuf' objects and protected by
  43 * mutexes defined inside these objects. Since sometimes upper-level code
  44 * has to lock the write-buffer (e.g. journal space reservation code), many
  45 * functions related to write-buffers have "nolock" suffix which means that the
  46 * caller has to lock the write-buffer before calling this function.
  47 *
  48 * UBIFS stores nodes at 64 bit-aligned addresses. If the node length is not
  49 * aligned, UBIFS starts the next node from the aligned address, and the padded
  50 * bytes may contain any rubbish. In other words, UBIFS does not put padding
  51 * bytes in those small gaps. Common headers of nodes store real node lengths,
  52 * not aligned lengths. Indexing nodes also store real lengths in branches.
  53 *
  54 * UBIFS uses padding when it pads to the next min. I/O unit. In this case it
  55 * uses padding nodes or padding bytes, if the padding node does not fit.
  56 *
  57 * All UBIFS nodes are protected by CRC checksums and UBIFS checks CRC when
  58 * they are read from the flash media.
  59 */
  60
  61#include <linux/crc32.h>
  62#include <linux/slab.h>
  63#include "ubifs.h"
  64
  65/**
  66 * ubifs_ro_mode - switch UBIFS to read read-only mode.
  67 * @c: UBIFS file-system description object
  68 * @err: error code which is the reason of switching to R/O mode
  69 */
  70void ubifs_ro_mode(struct ubifs_info *c, int err)
  71{
  72	if (!c->ro_error) {
  73		c->ro_error = 1;
  74		c->no_chk_data_crc = 0;
  75		c->vfs_sb->s_flags |= SB_RDONLY;
  76		ubifs_warn(c, "switched to read-only mode, error %d", err);
  77		dump_stack();
  78	}
  79}
  80
  81/*
  82 * Below are simple wrappers over UBI I/O functions which include some
  83 * additional checks and UBIFS debugging stuff. See corresponding UBI function
  84 * for more information.
  85 */
  86
  87int ubifs_leb_read(const struct ubifs_info *c, int lnum, void *buf, int offs,
  88		   int len, int even_ebadmsg)
  89{
  90	int err;
  91
  92	err = ubi_read(c->ubi, lnum, buf, offs, len);
  93	/*
  94	 * In case of %-EBADMSG print the error message only if the
  95	 * @even_ebadmsg is true.
  96	 */
  97	if (err && (err != -EBADMSG || even_ebadmsg)) {
  98		ubifs_err(c, "reading %d bytes from LEB %d:%d failed, error %d",
  99			  len, lnum, offs, err);
 100		dump_stack();
 101	}
 102	return err;
 103}
 104
 105int ubifs_leb_write(struct ubifs_info *c, int lnum, const void *buf, int offs,
 106		    int len)
 107{
 108	int err;
 109
 110	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 111	if (c->ro_error)
 112		return -EROFS;
 113	if (!dbg_is_tst_rcvry(c))
 114		err = ubi_leb_write(c->ubi, lnum, buf, offs, len);
 115	else
 116		err = dbg_leb_write(c, lnum, buf, offs, len);
 117	if (err) {
 118		ubifs_err(c, "writing %d bytes to LEB %d:%d failed, error %d",
 119			  len, lnum, offs, err);
 120		ubifs_ro_mode(c, err);
 121		dump_stack();
 122	}
 123	return err;
 124}
 125
 126int ubifs_leb_change(struct ubifs_info *c, int lnum, const void *buf, int len)
 127{
 128	int err;
 129
 130	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 131	if (c->ro_error)
 132		return -EROFS;
 133	if (!dbg_is_tst_rcvry(c))
 134		err = ubi_leb_change(c->ubi, lnum, buf, len);
 135	else
 136		err = dbg_leb_change(c, lnum, buf, len);
 137	if (err) {
 138		ubifs_err(c, "changing %d bytes in LEB %d failed, error %d",
 139			  len, lnum, err);
 140		ubifs_ro_mode(c, err);
 141		dump_stack();
 142	}
 143	return err;
 144}
 145
 146int ubifs_leb_unmap(struct ubifs_info *c, int lnum)
 147{
 148	int err;
 149
 150	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 151	if (c->ro_error)
 152		return -EROFS;
 153	if (!dbg_is_tst_rcvry(c))
 154		err = ubi_leb_unmap(c->ubi, lnum);
 155	else
 156		err = dbg_leb_unmap(c, lnum);
 157	if (err) {
 158		ubifs_err(c, "unmap LEB %d failed, error %d", lnum, err);
 159		ubifs_ro_mode(c, err);
 160		dump_stack();
 161	}
 162	return err;
 163}
 164
 165int ubifs_leb_map(struct ubifs_info *c, int lnum)
 166{
 167	int err;
 168
 169	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 170	if (c->ro_error)
 171		return -EROFS;
 172	if (!dbg_is_tst_rcvry(c))
 173		err = ubi_leb_map(c->ubi, lnum);
 174	else
 175		err = dbg_leb_map(c, lnum);
 176	if (err) {
 177		ubifs_err(c, "mapping LEB %d failed, error %d", lnum, err);
 178		ubifs_ro_mode(c, err);
 179		dump_stack();
 180	}
 181	return err;
 182}
 183
 184int ubifs_is_mapped(const struct ubifs_info *c, int lnum)
 185{
 186	int err;
 187
 188	err = ubi_is_mapped(c->ubi, lnum);
 189	if (err < 0) {
 190		ubifs_err(c, "ubi_is_mapped failed for LEB %d, error %d",
 191			  lnum, err);
 192		dump_stack();
 193	}
 194	return err;
 195}
 196
 197static void record_magic_error(struct ubifs_stats_info *stats)
 198{
 199	if (stats)
 200		stats->magic_errors++;
 201}
 202
 203static void record_node_error(struct ubifs_stats_info *stats)
 204{
 205	if (stats)
 206		stats->node_errors++;
 207}
 208
 209static void record_crc_error(struct ubifs_stats_info *stats)
 210{
 211	if (stats)
 212		stats->crc_errors++;
 213}
 214
 215/**
 216 * ubifs_check_node - check node.
 217 * @c: UBIFS file-system description object
 218 * @buf: node to check
 219 * @len: node length
 220 * @lnum: logical eraseblock number
 221 * @offs: offset within the logical eraseblock
 222 * @quiet: print no messages
 223 * @must_chk_crc: indicates whether to always check the CRC
 224 *
 225 * This function checks node magic number and CRC checksum. This function also
 226 * validates node length to prevent UBIFS from becoming crazy when an attacker
 227 * feeds it a file-system image with incorrect nodes. For example, too large
 228 * node length in the common header could cause UBIFS to read memory outside of
 229 * allocated buffer when checking the CRC checksum.
 230 *
 231 * This function may skip data nodes CRC checking if @c->no_chk_data_crc is
 232 * true, which is controlled by corresponding UBIFS mount option. However, if
 233 * @must_chk_crc is true, then @c->no_chk_data_crc is ignored and CRC is
 234 * checked. Similarly, if @c->mounting or @c->remounting_rw is true (we are
 235 * mounting or re-mounting to R/W mode), @c->no_chk_data_crc is ignored and CRC
 236 * is checked. This is because during mounting or re-mounting from R/O mode to
 237 * R/W mode we may read journal nodes (when replying the journal or doing the
 238 * recovery) and the journal nodes may potentially be corrupted, so checking is
 239 * required.
 240 *
 241 * This function returns zero in case of success and %-EUCLEAN in case of bad
 242 * CRC or magic.
 243 */
 244int ubifs_check_node(const struct ubifs_info *c, const void *buf, int len,
 245		     int lnum, int offs, int quiet, int must_chk_crc)
 246{
 247	int err = -EINVAL, type, node_len;
 248	uint32_t crc, node_crc, magic;
 249	const struct ubifs_ch *ch = buf;
 250
 251	ubifs_assert(c, lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
 252	ubifs_assert(c, !(offs & 7) && offs < c->leb_size);
 253
 254	magic = le32_to_cpu(ch->magic);
 255	if (magic != UBIFS_NODE_MAGIC) {
 256		if (!quiet)
 257			ubifs_err(c, "bad magic %#08x, expected %#08x",
 258				  magic, UBIFS_NODE_MAGIC);
 259		record_magic_error(c->stats);
 260		err = -EUCLEAN;
 261		goto out;
 262	}
 263
 264	type = ch->node_type;
 265	if (type < 0 || type >= UBIFS_NODE_TYPES_CNT) {
 266		if (!quiet)
 267			ubifs_err(c, "bad node type %d", type);
 268		record_node_error(c->stats);
 269		goto out;
 270	}
 271
 272	node_len = le32_to_cpu(ch->len);
 273	if (node_len + offs > c->leb_size)
 274		goto out_len;
 275
 276	if (c->ranges[type].max_len == 0) {
 277		if (node_len != c->ranges[type].len)
 278			goto out_len;
 279	} else if (node_len < c->ranges[type].min_len ||
 280		   node_len > c->ranges[type].max_len)
 281		goto out_len;
 282
 283	if (!must_chk_crc && type == UBIFS_DATA_NODE && !c->mounting &&
 284	    !c->remounting_rw && c->no_chk_data_crc)
 285		return 0;
 286
 287	crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);
 288	node_crc = le32_to_cpu(ch->crc);
 289	if (crc != node_crc) {
 290		if (!quiet)
 291			ubifs_err(c, "bad CRC: calculated %#08x, read %#08x",
 292				  crc, node_crc);
 293		record_crc_error(c->stats);
 294		err = -EUCLEAN;
 295		goto out;
 296	}
 297
 298	return 0;
 299
 300out_len:
 301	if (!quiet)
 302		ubifs_err(c, "bad node length %d", node_len);
 303out:
 304	if (!quiet) {
 305		ubifs_err(c, "bad node at LEB %d:%d", lnum, offs);
 306		ubifs_dump_node(c, buf, len);
 307		dump_stack();
 308	}
 309	return err;
 310}
 311
 312/**
 313 * ubifs_pad - pad flash space.
 314 * @c: UBIFS file-system description object
 315 * @buf: buffer to put padding to
 316 * @pad: how many bytes to pad
 317 *
 318 * The flash media obliges us to write only in chunks of %c->min_io_size and
 319 * when we have to write less data we add padding node to the write-buffer and
 320 * pad it to the next minimal I/O unit's boundary. Padding nodes help when the
 321 * media is being scanned. If the amount of wasted space is not enough to fit a
 322 * padding node which takes %UBIFS_PAD_NODE_SZ bytes, we write padding bytes
 323 * pattern (%UBIFS_PADDING_BYTE).
 324 *
 325 * Padding nodes are also used to fill gaps when the "commit-in-gaps" method is
 326 * used.
 327 */
 328void ubifs_pad(const struct ubifs_info *c, void *buf, int pad)
 329{
 330	ubifs_assert(c, pad >= 0);
 331
 332	if (pad >= UBIFS_PAD_NODE_SZ) {
 333		struct ubifs_ch *ch = buf;
 334		struct ubifs_pad_node *pad_node = buf;
 335
 336		ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
 337		ch->node_type = UBIFS_PAD_NODE;
 338		ch->group_type = UBIFS_NO_NODE_GROUP;
 339		ch->padding[0] = ch->padding[1] = 0;
 340		ch->sqnum = 0;
 341		ch->len = cpu_to_le32(UBIFS_PAD_NODE_SZ);
 342		pad -= UBIFS_PAD_NODE_SZ;
 343		pad_node->pad_len = cpu_to_le32(pad);
 344		ubifs_crc_node(buf, UBIFS_PAD_NODE_SZ);
 345		memset(buf + UBIFS_PAD_NODE_SZ, 0, pad);
 346	} else if (pad > 0)
 347		/* Too little space, padding node won't fit */
 348		memset(buf, UBIFS_PADDING_BYTE, pad);
 349}
 350
 351/**
 352 * next_sqnum - get next sequence number.
 353 * @c: UBIFS file-system description object
 354 */
 355static unsigned long long next_sqnum(struct ubifs_info *c)
 356{
 357	unsigned long long sqnum;
 358
 359	spin_lock(&c->cnt_lock);
 360	sqnum = ++c->max_sqnum;
 361	spin_unlock(&c->cnt_lock);
 362
 363	if (unlikely(sqnum >= SQNUM_WARN_WATERMARK)) {
 364		if (sqnum >= SQNUM_WATERMARK) {
 365			ubifs_err(c, "sequence number overflow %llu, end of life",
 366				  sqnum);
 367			ubifs_ro_mode(c, -EINVAL);
 368		}
 369		ubifs_warn(c, "running out of sequence numbers, end of life soon");
 370	}
 371
 372	return sqnum;
 373}
 374
 375void ubifs_init_node(struct ubifs_info *c, void *node, int len, int pad)
 376{
 377	struct ubifs_ch *ch = node;
 378	unsigned long long sqnum = next_sqnum(c);
 379
 380	ubifs_assert(c, len >= UBIFS_CH_SZ);
 381
 382	ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
 383	ch->len = cpu_to_le32(len);
 384	ch->group_type = UBIFS_NO_NODE_GROUP;
 385	ch->sqnum = cpu_to_le64(sqnum);
 386	ch->padding[0] = ch->padding[1] = 0;
 387
 388	if (pad) {
 389		len = ALIGN(len, 8);
 390		pad = ALIGN(len, c->min_io_size) - len;
 391		ubifs_pad(c, node + len, pad);
 392	}
 393}
 394
 395void ubifs_crc_node(void *node, int len)
 396{
 397	struct ubifs_ch *ch = node;
 398	uint32_t crc;
 399
 400	crc = crc32(UBIFS_CRC32_INIT, node + 8, len - 8);
 401	ch->crc = cpu_to_le32(crc);
 402}
 403
 404/**
 405 * ubifs_prepare_node_hmac - prepare node to be written to flash.
 406 * @c: UBIFS file-system description object
 407 * @node: the node to pad
 408 * @len: node length
 409 * @hmac_offs: offset of the HMAC in the node
 410 * @pad: if the buffer has to be padded
 411 *
 412 * This function prepares node at @node to be written to the media - it
 413 * calculates node CRC, fills the common header, and adds proper padding up to
 414 * the next minimum I/O unit if @pad is not zero. if @hmac_offs is positive then
 415 * a HMAC is inserted into the node at the given offset.
 416 *
 417 * This function returns 0 for success or a negative error code otherwise.
 418 */
 419int ubifs_prepare_node_hmac(struct ubifs_info *c, void *node, int len,
 420			    int hmac_offs, int pad)
 421{
 422	int err;
 423
 424	ubifs_init_node(c, node, len, pad);
 425
 426	if (hmac_offs > 0) {
 427		err = ubifs_node_insert_hmac(c, node, len, hmac_offs);
 428		if (err)
 429			return err;
 430	}
 431
 432	ubifs_crc_node(node, len);
 433
 434	return 0;
 435}
 436
 437/**
 438 * ubifs_prepare_node - prepare node to be written to flash.
 439 * @c: UBIFS file-system description object
 440 * @node: the node to pad
 441 * @len: node length
 442 * @pad: if the buffer has to be padded
 443 *
 444 * This function prepares node at @node to be written to the media - it
 445 * calculates node CRC, fills the common header, and adds proper padding up to
 446 * the next minimum I/O unit if @pad is not zero.
 447 */
 448void ubifs_prepare_node(struct ubifs_info *c, void *node, int len, int pad)
 449{
 450	/*
 451	 * Deliberately ignore return value since this function can only fail
 452	 * when a hmac offset is given.
 453	 */
 454	ubifs_prepare_node_hmac(c, node, len, 0, pad);
 455}
 456
 457/**
 458 * ubifs_prep_grp_node - prepare node of a group to be written to flash.
 459 * @c: UBIFS file-system description object
 460 * @node: the node to pad
 461 * @len: node length
 462 * @last: indicates the last node of the group
 463 *
 464 * This function prepares node at @node to be written to the media - it
 465 * calculates node CRC and fills the common header.
 466 */
 467void ubifs_prep_grp_node(struct ubifs_info *c, void *node, int len, int last)
 468{
 469	struct ubifs_ch *ch = node;
 470	unsigned long long sqnum = next_sqnum(c);
 471
 472	ubifs_assert(c, len >= UBIFS_CH_SZ);
 473
 474	ch->magic = cpu_to_le32(UBIFS_NODE_MAGIC);
 475	ch->len = cpu_to_le32(len);
 476	if (last)
 477		ch->group_type = UBIFS_LAST_OF_NODE_GROUP;
 478	else
 479		ch->group_type = UBIFS_IN_NODE_GROUP;
 480	ch->sqnum = cpu_to_le64(sqnum);
 481	ch->padding[0] = ch->padding[1] = 0;
 482	ubifs_crc_node(node, len);
 483}
 484
 485/**
 486 * wbuf_timer_callback_nolock - write-buffer timer callback function.
 487 * @timer: timer data (write-buffer descriptor)
 488 *
 489 * This function is called when the write-buffer timer expires.
 490 */
 491static enum hrtimer_restart wbuf_timer_callback_nolock(struct hrtimer *timer)
 492{
 493	struct ubifs_wbuf *wbuf = container_of(timer, struct ubifs_wbuf, timer);
 494
 495	dbg_io("jhead %s", dbg_jhead(wbuf->jhead));
 496	wbuf->need_sync = 1;
 497	wbuf->c->need_wbuf_sync = 1;
 498	ubifs_wake_up_bgt(wbuf->c);
 499	return HRTIMER_NORESTART;
 500}
 501
 502/**
 503 * new_wbuf_timer_nolock - start new write-buffer timer.
 504 * @c: UBIFS file-system description object
 505 * @wbuf: write-buffer descriptor
 506 */
 507static void new_wbuf_timer_nolock(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
 508{
 509	ktime_t softlimit = ms_to_ktime(dirty_writeback_interval * 10);
 510	unsigned long long delta = dirty_writeback_interval;
 511
 512	/* centi to milli, milli to nano, then 10% */
 513	delta *= 10ULL * NSEC_PER_MSEC / 10ULL;
 514
 515	ubifs_assert(c, !hrtimer_active(&wbuf->timer));
 516	ubifs_assert(c, delta <= ULONG_MAX);
 517
 518	if (wbuf->no_timer)
 519		return;
 520	dbg_io("set timer for jhead %s, %llu-%llu millisecs",
 521	       dbg_jhead(wbuf->jhead),
 522	       div_u64(ktime_to_ns(softlimit), USEC_PER_SEC),
 523	       div_u64(ktime_to_ns(softlimit) + delta, USEC_PER_SEC));
 524	hrtimer_start_range_ns(&wbuf->timer, softlimit, delta,
 525			       HRTIMER_MODE_REL);
 526}
 527
 528/**
 529 * cancel_wbuf_timer_nolock - cancel write-buffer timer.
 530 * @wbuf: write-buffer descriptor
 531 */
 532static void cancel_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
 533{
 534	if (wbuf->no_timer)
 535		return;
 536	wbuf->need_sync = 0;
 537	hrtimer_cancel(&wbuf->timer);
 538}
 539
 540/**
 541 * ubifs_wbuf_sync_nolock - synchronize write-buffer.
 542 * @wbuf: write-buffer to synchronize
 543 *
 544 * This function synchronizes write-buffer @buf and returns zero in case of
 545 * success or a negative error code in case of failure.
 546 *
 547 * Note, although write-buffers are of @c->max_write_size, this function does
 548 * not necessarily writes all @c->max_write_size bytes to the flash. Instead,
 549 * if the write-buffer is only partially filled with data, only the used part
 550 * of the write-buffer (aligned on @c->min_io_size boundary) is synchronized.
 551 * This way we waste less space.
 552 */
 553int ubifs_wbuf_sync_nolock(struct ubifs_wbuf *wbuf)
 554{
 555	struct ubifs_info *c = wbuf->c;
 556	int err, dirt, sync_len;
 557
 558	cancel_wbuf_timer_nolock(wbuf);
 559	if (!wbuf->used || wbuf->lnum == -1)
 560		/* Write-buffer is empty or not seeked */
 561		return 0;
 562
 563	dbg_io("LEB %d:%d, %d bytes, jhead %s",
 564	       wbuf->lnum, wbuf->offs, wbuf->used, dbg_jhead(wbuf->jhead));
 565	ubifs_assert(c, !(wbuf->avail & 7));
 566	ubifs_assert(c, wbuf->offs + wbuf->size <= c->leb_size);
 567	ubifs_assert(c, wbuf->size >= c->min_io_size);
 568	ubifs_assert(c, wbuf->size <= c->max_write_size);
 569	ubifs_assert(c, wbuf->size % c->min_io_size == 0);
 570	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 571	if (c->leb_size - wbuf->offs >= c->max_write_size)
 572		ubifs_assert(c, !((wbuf->offs + wbuf->size) % c->max_write_size));
 573
 574	if (c->ro_error)
 575		return -EROFS;
 576
 577	/*
 578	 * Do not write whole write buffer but write only the minimum necessary
 579	 * amount of min. I/O units.
 580	 */
 581	sync_len = ALIGN(wbuf->used, c->min_io_size);
 582	dirt = sync_len - wbuf->used;
 583	if (dirt)
 584		ubifs_pad(c, wbuf->buf + wbuf->used, dirt);
 585	err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf, wbuf->offs, sync_len);
 586	if (err)
 587		return err;
 588
 589	spin_lock(&wbuf->lock);
 590	wbuf->offs += sync_len;
 591	/*
 592	 * Now @wbuf->offs is not necessarily aligned to @c->max_write_size.
 593	 * But our goal is to optimize writes and make sure we write in
 594	 * @c->max_write_size chunks and to @c->max_write_size-aligned offset.
 595	 * Thus, if @wbuf->offs is not aligned to @c->max_write_size now, make
 596	 * sure that @wbuf->offs + @wbuf->size is aligned to
 597	 * @c->max_write_size. This way we make sure that after next
 598	 * write-buffer flush we are again at the optimal offset (aligned to
 599	 * @c->max_write_size).
 600	 */
 601	if (c->leb_size - wbuf->offs < c->max_write_size)
 602		wbuf->size = c->leb_size - wbuf->offs;
 603	else if (wbuf->offs & (c->max_write_size - 1))
 604		wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
 605	else
 606		wbuf->size = c->max_write_size;
 607	wbuf->avail = wbuf->size;
 608	wbuf->used = 0;
 609	wbuf->next_ino = 0;
 610	spin_unlock(&wbuf->lock);
 611
 612	if (wbuf->sync_callback)
 613		err = wbuf->sync_callback(c, wbuf->lnum,
 614					  c->leb_size - wbuf->offs, dirt);
 615	return err;
 616}
 617
 618/**
 619 * ubifs_wbuf_seek_nolock - seek write-buffer.
 620 * @wbuf: write-buffer
 621 * @lnum: logical eraseblock number to seek to
 622 * @offs: logical eraseblock offset to seek to
 623 *
 624 * This function targets the write-buffer to logical eraseblock @lnum:@offs.
 625 * The write-buffer has to be empty. Returns zero in case of success and a
 626 * negative error code in case of failure.
 627 */
 628int ubifs_wbuf_seek_nolock(struct ubifs_wbuf *wbuf, int lnum, int offs)
 629{
 630	const struct ubifs_info *c = wbuf->c;
 631
 632	dbg_io("LEB %d:%d, jhead %s", lnum, offs, dbg_jhead(wbuf->jhead));
 633	ubifs_assert(c, lnum >= 0 && lnum < c->leb_cnt);
 634	ubifs_assert(c, offs >= 0 && offs <= c->leb_size);
 635	ubifs_assert(c, offs % c->min_io_size == 0 && !(offs & 7));
 636	ubifs_assert(c, lnum != wbuf->lnum);
 637	ubifs_assert(c, wbuf->used == 0);
 638
 639	spin_lock(&wbuf->lock);
 640	wbuf->lnum = lnum;
 641	wbuf->offs = offs;
 642	if (c->leb_size - wbuf->offs < c->max_write_size)
 643		wbuf->size = c->leb_size - wbuf->offs;
 644	else if (wbuf->offs & (c->max_write_size - 1))
 645		wbuf->size = ALIGN(wbuf->offs, c->max_write_size) - wbuf->offs;
 646	else
 647		wbuf->size = c->max_write_size;
 648	wbuf->avail = wbuf->size;
 649	wbuf->used = 0;
 650	spin_unlock(&wbuf->lock);
 651
 652	return 0;
 653}
 654
 655/**
 656 * ubifs_bg_wbufs_sync - synchronize write-buffers.
 657 * @c: UBIFS file-system description object
 658 *
 659 * This function is called by background thread to synchronize write-buffers.
 660 * Returns zero in case of success and a negative error code in case of
 661 * failure.
 662 */
 663int ubifs_bg_wbufs_sync(struct ubifs_info *c)
 664{
 665	int err, i;
 666
 667	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 668	if (!c->need_wbuf_sync)
 669		return 0;
 670	c->need_wbuf_sync = 0;
 671
 672	if (c->ro_error) {
 673		err = -EROFS;
 674		goto out_timers;
 675	}
 676
 677	dbg_io("synchronize");
 678	for (i = 0; i < c->jhead_cnt; i++) {
 679		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
 680
 681		cond_resched();
 682
 683		/*
 684		 * If the mutex is locked then wbuf is being changed, so
 685		 * synchronization is not necessary.
 686		 */
 687		if (mutex_is_locked(&wbuf->io_mutex))
 688			continue;
 689
 690		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 691		if (!wbuf->need_sync) {
 692			mutex_unlock(&wbuf->io_mutex);
 693			continue;
 694		}
 695
 696		err = ubifs_wbuf_sync_nolock(wbuf);
 697		mutex_unlock(&wbuf->io_mutex);
 698		if (err) {
 699			ubifs_err(c, "cannot sync write-buffer, error %d", err);
 700			ubifs_ro_mode(c, err);
 701			goto out_timers;
 702		}
 703	}
 704
 705	return 0;
 706
 707out_timers:
 708	/* Cancel all timers to prevent repeated errors */
 709	for (i = 0; i < c->jhead_cnt; i++) {
 710		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
 711
 712		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 713		cancel_wbuf_timer_nolock(wbuf);
 714		mutex_unlock(&wbuf->io_mutex);
 715	}
 716	return err;
 717}
 718
 719/**
 720 * ubifs_wbuf_write_nolock - write data to flash via write-buffer.
 721 * @wbuf: write-buffer
 722 * @buf: node to write
 723 * @len: node length
 724 *
 725 * This function writes data to flash via write-buffer @wbuf. This means that
 726 * the last piece of the node won't reach the flash media immediately if it
 727 * does not take whole max. write unit (@c->max_write_size). Instead, the node
 728 * will sit in RAM until the write-buffer is synchronized (e.g., by timer, or
 729 * because more data are appended to the write-buffer).
 730 *
 731 * This function returns zero in case of success and a negative error code in
 732 * case of failure. If the node cannot be written because there is no more
 733 * space in this logical eraseblock, %-ENOSPC is returned.
 734 */
 735int ubifs_wbuf_write_nolock(struct ubifs_wbuf *wbuf, void *buf, int len)
 736{
 737	struct ubifs_info *c = wbuf->c;
 738	int err, n, written = 0, aligned_len = ALIGN(len, 8);
 739
 740	dbg_io("%d bytes (%s) to jhead %s wbuf at LEB %d:%d", len,
 741	       dbg_ntype(((struct ubifs_ch *)buf)->node_type),
 742	       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs + wbuf->used);
 743	ubifs_assert(c, len > 0 && wbuf->lnum >= 0 && wbuf->lnum < c->leb_cnt);
 744	ubifs_assert(c, wbuf->offs >= 0 && wbuf->offs % c->min_io_size == 0);
 745	ubifs_assert(c, !(wbuf->offs & 7) && wbuf->offs <= c->leb_size);
 746	ubifs_assert(c, wbuf->avail > 0 && wbuf->avail <= wbuf->size);
 747	ubifs_assert(c, wbuf->size >= c->min_io_size);
 748	ubifs_assert(c, wbuf->size <= c->max_write_size);
 749	ubifs_assert(c, wbuf->size % c->min_io_size == 0);
 750	ubifs_assert(c, mutex_is_locked(&wbuf->io_mutex));
 751	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 752	ubifs_assert(c, !c->space_fixup);
 753	if (c->leb_size - wbuf->offs >= c->max_write_size)
 754		ubifs_assert(c, !((wbuf->offs + wbuf->size) % c->max_write_size));
 755
 756	if (c->leb_size - wbuf->offs - wbuf->used < aligned_len) {
 757		err = -ENOSPC;
 758		goto out;
 759	}
 760
 761	cancel_wbuf_timer_nolock(wbuf);
 762
 763	if (c->ro_error)
 764		return -EROFS;
 765
 766	if (aligned_len <= wbuf->avail) {
 767		/*
 768		 * The node is not very large and fits entirely within
 769		 * write-buffer.
 770		 */
 771		memcpy(wbuf->buf + wbuf->used, buf, len);
 772		if (aligned_len > len) {
 773			ubifs_assert(c, aligned_len - len < 8);
 774			ubifs_pad(c, wbuf->buf + wbuf->used + len, aligned_len - len);
 775		}
 776
 777		if (aligned_len == wbuf->avail) {
 778			dbg_io("flush jhead %s wbuf to LEB %d:%d",
 779			       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
 780			err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf,
 781					      wbuf->offs, wbuf->size);
 782			if (err)
 783				goto out;
 784
 785			spin_lock(&wbuf->lock);
 786			wbuf->offs += wbuf->size;
 787			if (c->leb_size - wbuf->offs >= c->max_write_size)
 788				wbuf->size = c->max_write_size;
 789			else
 790				wbuf->size = c->leb_size - wbuf->offs;
 791			wbuf->avail = wbuf->size;
 792			wbuf->used = 0;
 793			wbuf->next_ino = 0;
 794			spin_unlock(&wbuf->lock);
 795		} else {
 796			spin_lock(&wbuf->lock);
 797			wbuf->avail -= aligned_len;
 798			wbuf->used += aligned_len;
 799			spin_unlock(&wbuf->lock);
 800		}
 801
 802		goto exit;
 803	}
 804
 805	if (wbuf->used) {
 806		/*
 807		 * The node is large enough and does not fit entirely within
 808		 * current available space. We have to fill and flush
 809		 * write-buffer and switch to the next max. write unit.
 810		 */
 811		dbg_io("flush jhead %s wbuf to LEB %d:%d",
 812		       dbg_jhead(wbuf->jhead), wbuf->lnum, wbuf->offs);
 813		memcpy(wbuf->buf + wbuf->used, buf, wbuf->avail);
 814		err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf, wbuf->offs,
 815				      wbuf->size);
 816		if (err)
 817			goto out;
 818
 819		wbuf->offs += wbuf->size;
 820		len -= wbuf->avail;
 821		aligned_len -= wbuf->avail;
 822		written += wbuf->avail;
 823	} else if (wbuf->offs & (c->max_write_size - 1)) {
 824		/*
 825		 * The write-buffer offset is not aligned to
 826		 * @c->max_write_size and @wbuf->size is less than
 827		 * @c->max_write_size. Write @wbuf->size bytes to make sure the
 828		 * following writes are done in optimal @c->max_write_size
 829		 * chunks.
 830		 */
 831		dbg_io("write %d bytes to LEB %d:%d",
 832		       wbuf->size, wbuf->lnum, wbuf->offs);
 833		err = ubifs_leb_write(c, wbuf->lnum, buf, wbuf->offs,
 834				      wbuf->size);
 835		if (err)
 836			goto out;
 837
 838		wbuf->offs += wbuf->size;
 839		len -= wbuf->size;
 840		aligned_len -= wbuf->size;
 841		written += wbuf->size;
 842	}
 843
 844	/*
 845	 * The remaining data may take more whole max. write units, so write the
 846	 * remains multiple to max. write unit size directly to the flash media.
 847	 * We align node length to 8-byte boundary because we anyway flash wbuf
 848	 * if the remaining space is less than 8 bytes.
 849	 */
 850	n = aligned_len >> c->max_write_shift;
 851	if (n) {
 852		int m = n - 1;
 853
 854		dbg_io("write %d bytes to LEB %d:%d", n, wbuf->lnum,
 855		       wbuf->offs);
 856
 857		if (m) {
 858			/* '(n-1)<<c->max_write_shift < len' is always true. */
 859			m <<= c->max_write_shift;
 860			err = ubifs_leb_write(c, wbuf->lnum, buf + written,
 861					      wbuf->offs, m);
 862			if (err)
 863				goto out;
 864			wbuf->offs += m;
 865			aligned_len -= m;
 866			len -= m;
 867			written += m;
 868		}
 869
 870		/*
 871		 * The non-written len of buf may be less than 'n' because
 872		 * parameter 'len' is not 8 bytes aligned, so here we read
 873		 * min(len, n) bytes from buf.
 874		 */
 875		n = 1 << c->max_write_shift;
 876		memcpy(wbuf->buf, buf + written, min(len, n));
 877		if (n > len) {
 878			ubifs_assert(c, n - len < 8);
 879			ubifs_pad(c, wbuf->buf + len, n - len);
 880		}
 881
 882		err = ubifs_leb_write(c, wbuf->lnum, wbuf->buf, wbuf->offs, n);
 883		if (err)
 884			goto out;
 885		wbuf->offs += n;
 886		aligned_len -= n;
 887		len -= min(len, n);
 888		written += n;
 889	}
 890
 891	spin_lock(&wbuf->lock);
 892	if (aligned_len) {
 893		/*
 894		 * And now we have what's left and what does not take whole
 895		 * max. write unit, so write it to the write-buffer and we are
 896		 * done.
 897		 */
 898		memcpy(wbuf->buf, buf + written, len);
 899		if (aligned_len > len) {
 900			ubifs_assert(c, aligned_len - len < 8);
 901			ubifs_pad(c, wbuf->buf + len, aligned_len - len);
 902		}
 903	}
 904
 905	if (c->leb_size - wbuf->offs >= c->max_write_size)
 906		wbuf->size = c->max_write_size;
 907	else
 908		wbuf->size = c->leb_size - wbuf->offs;
 909	wbuf->avail = wbuf->size - aligned_len;
 910	wbuf->used = aligned_len;
 911	wbuf->next_ino = 0;
 912	spin_unlock(&wbuf->lock);
 913
 914exit:
 915	if (wbuf->sync_callback) {
 916		int free = c->leb_size - wbuf->offs - wbuf->used;
 917
 918		err = wbuf->sync_callback(c, wbuf->lnum, free, 0);
 919		if (err)
 920			goto out;
 921	}
 922
 923	if (wbuf->used)
 924		new_wbuf_timer_nolock(c, wbuf);
 925
 926	return 0;
 927
 928out:
 929	ubifs_err(c, "cannot write %d bytes to LEB %d:%d, error %d",
 930		  len, wbuf->lnum, wbuf->offs, err);
 931	ubifs_dump_node(c, buf, written + len);
 932	dump_stack();
 933	ubifs_dump_leb(c, wbuf->lnum);
 934	return err;
 935}
 936
 937/**
 938 * ubifs_write_node_hmac - write node to the media.
 939 * @c: UBIFS file-system description object
 940 * @buf: the node to write
 941 * @len: node length
 942 * @lnum: logical eraseblock number
 943 * @offs: offset within the logical eraseblock
 944 * @hmac_offs: offset of the HMAC within the node
 945 *
 946 * This function automatically fills node magic number, assigns sequence
 947 * number, and calculates node CRC checksum. The length of the @buf buffer has
 948 * to be aligned to the minimal I/O unit size. This function automatically
 949 * appends padding node and padding bytes if needed. Returns zero in case of
 950 * success and a negative error code in case of failure.
 951 */
 952int ubifs_write_node_hmac(struct ubifs_info *c, void *buf, int len, int lnum,
 953			  int offs, int hmac_offs)
 954{
 955	int err, buf_len = ALIGN(len, c->min_io_size);
 956
 957	dbg_io("LEB %d:%d, %s, length %d (aligned %d)",
 958	       lnum, offs, dbg_ntype(((struct ubifs_ch *)buf)->node_type), len,
 959	       buf_len);
 960	ubifs_assert(c, lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
 961	ubifs_assert(c, offs % c->min_io_size == 0 && offs < c->leb_size);
 962	ubifs_assert(c, !c->ro_media && !c->ro_mount);
 963	ubifs_assert(c, !c->space_fixup);
 964
 965	if (c->ro_error)
 966		return -EROFS;
 967
 968	err = ubifs_prepare_node_hmac(c, buf, len, hmac_offs, 1);
 969	if (err)
 970		return err;
 971
 972	err = ubifs_leb_write(c, lnum, buf, offs, buf_len);
 973	if (err)
 974		ubifs_dump_node(c, buf, len);
 975
 976	return err;
 977}
 978
 979/**
 980 * ubifs_write_node - write node to the media.
 981 * @c: UBIFS file-system description object
 982 * @buf: the node to write
 983 * @len: node length
 984 * @lnum: logical eraseblock number
 985 * @offs: offset within the logical eraseblock
 986 *
 987 * This function automatically fills node magic number, assigns sequence
 988 * number, and calculates node CRC checksum. The length of the @buf buffer has
 989 * to be aligned to the minimal I/O unit size. This function automatically
 990 * appends padding node and padding bytes if needed. Returns zero in case of
 991 * success and a negative error code in case of failure.
 992 */
 993int ubifs_write_node(struct ubifs_info *c, void *buf, int len, int lnum,
 994		     int offs)
 995{
 996	return ubifs_write_node_hmac(c, buf, len, lnum, offs, -1);
 997}
 998
 999/**
1000 * ubifs_read_node_wbuf - read node from the media or write-buffer.
1001 * @wbuf: wbuf to check for un-written data
1002 * @buf: buffer to read to
1003 * @type: node type
1004 * @len: node length
1005 * @lnum: logical eraseblock number
1006 * @offs: offset within the logical eraseblock
1007 *
1008 * This function reads a node of known type and length, checks it and stores
1009 * in @buf. If the node partially or fully sits in the write-buffer, this
1010 * function takes data from the buffer, otherwise it reads the flash media.
1011 * Returns zero in case of success, %-EUCLEAN if CRC mismatched and a negative
1012 * error code in case of failure.
1013 */
1014int ubifs_read_node_wbuf(struct ubifs_wbuf *wbuf, void *buf, int type, int len,
1015			 int lnum, int offs)
1016{
1017	const struct ubifs_info *c = wbuf->c;
1018	int err, rlen, overlap;
1019	struct ubifs_ch *ch = buf;
1020
1021	dbg_io("LEB %d:%d, %s, length %d, jhead %s", lnum, offs,
1022	       dbg_ntype(type), len, dbg_jhead(wbuf->jhead));
1023	ubifs_assert(c, wbuf && lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
1024	ubifs_assert(c, !(offs & 7) && offs < c->leb_size);
1025	ubifs_assert(c, type >= 0 && type < UBIFS_NODE_TYPES_CNT);
1026
1027	spin_lock(&wbuf->lock);
1028	overlap = (lnum == wbuf->lnum && offs + len > wbuf->offs);
1029	if (!overlap) {
1030		/* We may safely unlock the write-buffer and read the data */
1031		spin_unlock(&wbuf->lock);
1032		return ubifs_read_node(c, buf, type, len, lnum, offs);
1033	}
1034
1035	/* Don't read under wbuf */
1036	rlen = wbuf->offs - offs;
1037	if (rlen < 0)
1038		rlen = 0;
1039
1040	/* Copy the rest from the write-buffer */
1041	memcpy(buf + rlen, wbuf->buf + offs + rlen - wbuf->offs, len - rlen);
1042	spin_unlock(&wbuf->lock);
1043
1044	if (rlen > 0) {
1045		/* Read everything that goes before write-buffer */
1046		err = ubifs_leb_read(c, lnum, buf, offs, rlen, 0);
1047		if (err && err != -EBADMSG)
1048			return err;
1049	}
1050
1051	if (type != ch->node_type) {
1052		ubifs_err(c, "bad node type (%d but expected %d)",
1053			  ch->node_type, type);
1054		goto out;
1055	}
1056
1057	err = ubifs_check_node(c, buf, len, lnum, offs, 0, 0);
1058	if (err) {
1059		ubifs_err(c, "expected node type %d", type);
1060		return err;
1061	}
1062
1063	rlen = le32_to_cpu(ch->len);
1064	if (rlen != len) {
1065		ubifs_err(c, "bad node length %d, expected %d", rlen, len);
1066		goto out;
1067	}
1068
1069	return 0;
1070
1071out:
1072	ubifs_err(c, "bad node at LEB %d:%d", lnum, offs);
1073	ubifs_dump_node(c, buf, len);
1074	dump_stack();
1075	return -EINVAL;
1076}
1077
1078/**
1079 * ubifs_read_node - read node.
1080 * @c: UBIFS file-system description object
1081 * @buf: buffer to read to
1082 * @type: node type
1083 * @len: node length (not aligned)
1084 * @lnum: logical eraseblock number
1085 * @offs: offset within the logical eraseblock
1086 *
1087 * This function reads a node of known type and length, checks it and
1088 * stores in @buf. Returns zero in case of success, %-EUCLEAN if CRC mismatched
1089 * and a negative error code in case of failure.
1090 */
1091int ubifs_read_node(const struct ubifs_info *c, void *buf, int type, int len,
1092		    int lnum, int offs)
1093{
1094	int err, l;
1095	struct ubifs_ch *ch = buf;
1096
1097	dbg_io("LEB %d:%d, %s, length %d", lnum, offs, dbg_ntype(type), len);
1098	ubifs_assert(c, lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
1099	ubifs_assert(c, len >= UBIFS_CH_SZ && offs + len <= c->leb_size);
1100	ubifs_assert(c, !(offs & 7) && offs < c->leb_size);
1101	ubifs_assert(c, type >= 0 && type < UBIFS_NODE_TYPES_CNT);
1102
1103	err = ubifs_leb_read(c, lnum, buf, offs, len, 0);
1104	if (err && err != -EBADMSG)
1105		return err;
1106
1107	if (type != ch->node_type) {
1108		ubifs_errc(c, "bad node type (%d but expected %d)",
1109			   ch->node_type, type);
1110		goto out;
1111	}
1112
1113	err = ubifs_check_node(c, buf, len, lnum, offs, 0, 0);
1114	if (err) {
1115		ubifs_errc(c, "expected node type %d", type);
1116		return err;
1117	}
1118
1119	l = le32_to_cpu(ch->len);
1120	if (l != len) {
1121		ubifs_errc(c, "bad node length %d, expected %d", l, len);
1122		goto out;
1123	}
1124
1125	return 0;
1126
1127out:
1128	ubifs_errc(c, "bad node at LEB %d:%d, LEB mapping status %d", lnum,
1129		   offs, ubi_is_mapped(c->ubi, lnum));
1130	if (!c->probing) {
1131		ubifs_dump_node(c, buf, len);
1132		dump_stack();
1133	}
1134	return -EINVAL;
1135}
1136
1137/**
1138 * ubifs_wbuf_init - initialize write-buffer.
1139 * @c: UBIFS file-system description object
1140 * @wbuf: write-buffer to initialize
1141 *
1142 * This function initializes write-buffer. Returns zero in case of success
1143 * %-ENOMEM in case of failure.
1144 */
1145int ubifs_wbuf_init(struct ubifs_info *c, struct ubifs_wbuf *wbuf)
1146{
1147	size_t size;
1148
1149	wbuf->buf = kmalloc(c->max_write_size, GFP_KERNEL);
1150	if (!wbuf->buf)
1151		return -ENOMEM;
1152
1153	size = (c->max_write_size / UBIFS_CH_SZ + 1) * sizeof(ino_t);
1154	wbuf->inodes = kmalloc(size, GFP_KERNEL);
1155	if (!wbuf->inodes) {
1156		kfree(wbuf->buf);
1157		wbuf->buf = NULL;
1158		return -ENOMEM;
1159	}
1160
1161	wbuf->used = 0;
1162	wbuf->lnum = wbuf->offs = -1;
1163	/*
1164	 * If the LEB starts at the max. write size aligned address, then
1165	 * write-buffer size has to be set to @c->max_write_size. Otherwise,
1166	 * set it to something smaller so that it ends at the closest max.
1167	 * write size boundary.
1168	 */
1169	size = c->max_write_size - (c->leb_start % c->max_write_size);
1170	wbuf->avail = wbuf->size = size;
1171	wbuf->sync_callback = NULL;
1172	mutex_init(&wbuf->io_mutex);
1173	spin_lock_init(&wbuf->lock);
1174	wbuf->c = c;
1175	wbuf->next_ino = 0;
1176
1177	hrtimer_setup(&wbuf->timer, wbuf_timer_callback_nolock, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1178	return 0;
1179}
1180
1181/**
1182 * ubifs_wbuf_add_ino_nolock - add an inode number into the wbuf inode array.
1183 * @wbuf: the write-buffer where to add
1184 * @inum: the inode number
1185 *
1186 * This function adds an inode number to the inode array of the write-buffer.
1187 */
1188void ubifs_wbuf_add_ino_nolock(struct ubifs_wbuf *wbuf, ino_t inum)
1189{
1190	if (!wbuf->buf)
1191		/* NOR flash or something similar */
1192		return;
1193
1194	spin_lock(&wbuf->lock);
1195	if (wbuf->used)
1196		wbuf->inodes[wbuf->next_ino++] = inum;
1197	spin_unlock(&wbuf->lock);
1198}
1199
1200/**
1201 * wbuf_has_ino - returns if the wbuf contains data from the inode.
1202 * @wbuf: the write-buffer
1203 * @inum: the inode number
1204 *
1205 * This function returns with %1 if the write-buffer contains some data from the
1206 * given inode otherwise it returns with %0.
1207 */
1208static int wbuf_has_ino(struct ubifs_wbuf *wbuf, ino_t inum)
1209{
1210	int i, ret = 0;
1211
1212	spin_lock(&wbuf->lock);
1213	for (i = 0; i < wbuf->next_ino; i++)
1214		if (inum == wbuf->inodes[i]) {
1215			ret = 1;
1216			break;
1217		}
1218	spin_unlock(&wbuf->lock);
1219
1220	return ret;
1221}
1222
1223/**
1224 * ubifs_sync_wbufs_by_inode - synchronize write-buffers for an inode.
1225 * @c: UBIFS file-system description object
1226 * @inode: inode to synchronize
1227 *
1228 * This function synchronizes write-buffers which contain nodes belonging to
1229 * @inode. Returns zero in case of success and a negative error code in case of
1230 * failure.
1231 */
1232int ubifs_sync_wbufs_by_inode(struct ubifs_info *c, struct inode *inode)
1233{
1234	int i, err = 0;
1235
1236	for (i = 0; i < c->jhead_cnt; i++) {
1237		struct ubifs_wbuf *wbuf = &c->jheads[i].wbuf;
1238
1239		if (i == GCHD)
1240			/*
1241			 * GC head is special, do not look at it. Even if the
1242			 * head contains something related to this inode, it is
1243			 * a _copy_ of corresponding on-flash node which sits
1244			 * somewhere else.
1245			 */
1246			continue;
1247
1248		if (!wbuf_has_ino(wbuf, inode->i_ino))
1249			continue;
1250
1251		mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
1252		if (wbuf_has_ino(wbuf, inode->i_ino))
1253			err = ubifs_wbuf_sync_nolock(wbuf);
1254		mutex_unlock(&wbuf->io_mutex);
1255
1256		if (err) {
1257			ubifs_ro_mode(c, err);
1258			return err;
1259		}
1260	}
1261	return 0;
1262}