io.c

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/*
 * 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"

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("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("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("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("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("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("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("ubi_is_mapped failed for LEB %d, error %d",
              lnum, err);
        dump_stack();
    }
    return err;
}

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("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("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("bad CRC: calculated %#08x, read %#08x",
                  crc, node_crc);
        err = -EUCLEAN;
        goto out;
    }

    return 0;

out_len:
    if (!quiet)
        ubifs_err("bad node length %d", node_len);
out:
    if (!quiet) {
        ubifs_err("bad node at LEB %d:%d", lnum, offs);
        ubifs_dump_node(c, buf);
        dump_stack();
    }
    return err;
}

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);
}

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("sequence number overflow %llu, end of life",
                  sqnum);
            ubifs_ro_mode(c, -EINVAL);
        }
        ubifs_warn("running out of sequence numbers, end of life soon");
    }

    return sqnum;
}

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);
    }
}

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);
}

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;
}

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);
}

static void cancel_wbuf_timer_nolock(struct ubifs_wbuf *wbuf)
{
    if (wbuf->no_timer)
        return;
    wbuf->need_sync = 0;
    hrtimer_cancel(&wbuf->timer);
}

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;
}

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;
}

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("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;
}

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("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;
}

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;
}

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("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("expected node type %d", type);
        return err;
    }

    rlen = le32_to_cpu(ch->len);
    if (rlen != len) {
        ubifs_err("bad node length %d, expected %d", rlen, len);
        goto out;
    }

    return 0;

out:
    ubifs_err("bad node at LEB %d:%d", lnum, offs);
    ubifs_dump_node(c, buf);
    dump_stack();
    return -EINVAL;
}

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_err("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("expected node type %d", type);
        return err;
    }

    l = le32_to_cpu(ch->len);
    if (l != len) {
        ubifs_err("bad node length %d, expected %d", l, len);
        goto out;
    }

    return 0;

out:
    ubifs_err("bad node at LEB %d:%d, LEB mapping status %d", lnum, offs,
          ubi_is_mapped(c->ubi, lnum));
    ubifs_dump_node(c, buf);
    dump_stack();
    return -EINVAL;
}

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;
}

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);
}

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;
}

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;
}