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eba.c

/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Author: Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * The UBI Eraseblock Association (EBA) unit.
 *
 * This unit is responsible for I/O to/from logical eraseblock.
 *
 * Although in this implementation the EBA table is fully kept and managed in
 * RAM, which assumes poor scalability, it might be (partially) maintained on
 * flash in future implementations.
 *
 * The EBA unit implements per-logical eraseblock locking. Before accessing a
 * logical eraseblock it is locked for reading or writing. The per-logical
 * eraseblock locking is implemented by means of the lock tree. The lock tree
 * is an RB-tree which refers all the currently locked logical eraseblocks. The
 * lock tree elements are &struct ltree_entry objects. They are indexed by
 * (@vol_id, @lnum) pairs.
 *
 * EBA also maintains the global sequence counter which is incremented each
 * time a logical eraseblock is mapped to a physical eraseblock and it is
 * stored in the volume identifier header. This means that each VID header has
 * a unique sequence number. The sequence number is only increased an we assume
 * 64 bits is enough to never overflow.
 */

#include <linux/slab.h>
#include <linux/crc32.h>
#include <linux/err.h>
#include "ubi.h"

/* Number of physical eraseblocks reserved for atomic LEB change operation */
#define EBA_RESERVED_PEBS 1

/**
 * struct ltree_entry - an entry in the lock tree.
 * @rb: links RB-tree nodes
 * @vol_id: volume ID of the locked logical eraseblock
 * @lnum: locked logical eraseblock number
 * @users: how many tasks are using this logical eraseblock or wait for it
 * @mutex: read/write mutex to implement read/write access serialization to
 * the (@vol_id, @lnum) logical eraseblock
 *
 * When a logical eraseblock is being locked - corresponding &struct ltree_entry
 * object is inserted to the lock tree (@ubi->ltree).
 */
00064 struct ltree_entry {
      struct rb_node rb;
      int vol_id;
      int lnum;
      int users;
      struct rw_semaphore mutex;
};

/* Slab cache for lock-tree entries */
static struct kmem_cache *ltree_slab;

/**
 * next_sqnum - get next sequence number.
 * @ubi: UBI device description object
 *
 * This function returns next sequence number to use, which is just the current
 * global sequence counter value. It also increases the global sequence
 * counter.
 */
static unsigned long long next_sqnum(struct ubi_device *ubi)
{
      unsigned long long sqnum;

      spin_lock(&ubi->ltree_lock);
      sqnum = ubi->global_sqnum++;
      spin_unlock(&ubi->ltree_lock);

      return sqnum;
}

/**
 * ubi_get_compat - get compatibility flags of a volume.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 *
 * This function returns compatibility flags for an internal volume. User
 * volumes have no compatibility flags, so %0 is returned.
 */
static int ubi_get_compat(const struct ubi_device *ubi, int vol_id)
{
      if (vol_id == UBI_LAYOUT_VOL_ID)
            return UBI_LAYOUT_VOLUME_COMPAT;
      return 0;
}

/**
 * ltree_lookup - look up the lock tree.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 *
 * This function returns a pointer to the corresponding &struct ltree_entry
 * object if the logical eraseblock is locked and %NULL if it is not.
 * @ubi->ltree_lock has to be locked.
 */
static struct ltree_entry *ltree_lookup(struct ubi_device *ubi, int vol_id,
                              int lnum)
{
      struct rb_node *p;

      p = ubi->ltree.rb_node;
      while (p) {
            struct ltree_entry *le;

            le = rb_entry(p, struct ltree_entry, rb);

            if (vol_id < le->vol_id)
                  p = p->rb_left;
            else if (vol_id > le->vol_id)
                  p = p->rb_right;
            else {
                  if (lnum < le->lnum)
                        p = p->rb_left;
                  else if (lnum > le->lnum)
                        p = p->rb_right;
                  else
                        return le;
            }
      }

      return NULL;
}

/**
 * ltree_add_entry - add new entry to the lock tree.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 *
 * This function adds new entry for logical eraseblock (@vol_id, @lnum) to the
 * lock tree. If such entry is already there, its usage counter is increased.
 * Returns pointer to the lock tree entry or %-ENOMEM if memory allocation
 * failed.
 */
static struct ltree_entry *ltree_add_entry(struct ubi_device *ubi, int vol_id,
                                 int lnum)
{
      struct ltree_entry *le, *le1, *le_free;

      le = kmem_cache_alloc(ltree_slab, GFP_NOFS);
      if (!le)
            return ERR_PTR(-ENOMEM);

      le->vol_id = vol_id;
      le->lnum = lnum;

      spin_lock(&ubi->ltree_lock);
      le1 = ltree_lookup(ubi, vol_id, lnum);

      if (le1) {
            /*
             * This logical eraseblock is already locked. The newly
             * allocated lock entry is not needed.
             */
            le_free = le;
            le = le1;
      } else {
            struct rb_node **p, *parent = NULL;

            /*
             * No lock entry, add the newly allocated one to the
             * @ubi->ltree RB-tree.
             */
            le_free = NULL;

            p = &ubi->ltree.rb_node;
            while (*p) {
                  parent = *p;
                  le1 = rb_entry(parent, struct ltree_entry, rb);

                  if (vol_id < le1->vol_id)
                        p = &(*p)->rb_left;
                  else if (vol_id > le1->vol_id)
                        p = &(*p)->rb_right;
                  else {
                        ubi_assert(lnum != le1->lnum);
                        if (lnum < le1->lnum)
                              p = &(*p)->rb_left;
                        else
                              p = &(*p)->rb_right;
                  }
            }

            rb_link_node(&le->rb, parent, p);
            rb_insert_color(&le->rb, &ubi->ltree);
      }
      le->users += 1;
      spin_unlock(&ubi->ltree_lock);

      if (le_free)
            kmem_cache_free(ltree_slab, le_free);

      return le;
}

/**
 * leb_read_lock - lock logical eraseblock for reading.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 *
 * This function locks a logical eraseblock for reading. Returns zero in case
 * of success and a negative error code in case of failure.
 */
static int leb_read_lock(struct ubi_device *ubi, int vol_id, int lnum)
{
      struct ltree_entry *le;

      le = ltree_add_entry(ubi, vol_id, lnum);
      if (IS_ERR(le))
            return PTR_ERR(le);
      down_read(&le->mutex);
      return 0;
}

/**
 * leb_read_unlock - unlock logical eraseblock.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 */
static void leb_read_unlock(struct ubi_device *ubi, int vol_id, int lnum)
{
      int free = 0;
      struct ltree_entry *le;

      spin_lock(&ubi->ltree_lock);
      le = ltree_lookup(ubi, vol_id, lnum);
      le->users -= 1;
      ubi_assert(le->users >= 0);
      if (le->users == 0) {
            rb_erase(&le->rb, &ubi->ltree);
            free = 1;
      }
      spin_unlock(&ubi->ltree_lock);

      up_read(&le->mutex);
      if (free)
            kmem_cache_free(ltree_slab, le);
}

/**
 * leb_write_lock - lock logical eraseblock for writing.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 *
 * This function locks a logical eraseblock for writing. Returns zero in case
 * of success and a negative error code in case of failure.
 */
static int leb_write_lock(struct ubi_device *ubi, int vol_id, int lnum)
{
      struct ltree_entry *le;

      le = ltree_add_entry(ubi, vol_id, lnum);
      if (IS_ERR(le))
            return PTR_ERR(le);
      down_write(&le->mutex);
      return 0;
}

/**
 * leb_write_unlock - unlock logical eraseblock.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 */
static void leb_write_unlock(struct ubi_device *ubi, int vol_id, int lnum)
{
      int free;
      struct ltree_entry *le;

      spin_lock(&ubi->ltree_lock);
      le = ltree_lookup(ubi, vol_id, lnum);
      le->users -= 1;
      ubi_assert(le->users >= 0);
      if (le->users == 0) {
            rb_erase(&le->rb, &ubi->ltree);
            free = 1;
      } else
            free = 0;
      spin_unlock(&ubi->ltree_lock);

      up_write(&le->mutex);
      if (free)
            kmem_cache_free(ltree_slab, le);
}

/**
 * ubi_eba_unmap_leb - un-map logical eraseblock.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 *
 * This function un-maps logical eraseblock @lnum and schedules corresponding
 * physical eraseblock for erasure. Returns zero in case of success and a
 * negative error code in case of failure.
 */
int ubi_eba_unmap_leb(struct ubi_device *ubi, int vol_id, int lnum)
{
      int idx = vol_id2idx(ubi, vol_id), err, pnum;
      struct ubi_volume *vol = ubi->volumes[idx];

      if (ubi->ro_mode)
            return -EROFS;

      err = leb_write_lock(ubi, vol_id, lnum);
      if (err)
            return err;

      pnum = vol->eba_tbl[lnum];
      if (pnum < 0)
            /* This logical eraseblock is already unmapped */
            goto out_unlock;

      dbg_eba("erase LEB %d:%d, PEB %d", vol_id, lnum, pnum);

      vol->eba_tbl[lnum] = UBI_LEB_UNMAPPED;
      err = ubi_wl_put_peb(ubi, pnum, 0);

out_unlock:
      leb_write_unlock(ubi, vol_id, lnum);
      return err;
}

/**
 * ubi_eba_read_leb - read data.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 * @buf: buffer to store the read data
 * @offset: offset from where to read
 * @len: how many bytes to read
 * @check: data CRC check flag
 *
 * If the logical eraseblock @lnum is unmapped, @buf is filled with 0xFF
 * bytes. The @check flag only makes sense for static volumes and forces
 * eraseblock data CRC checking.
 *
 * In case of success this function returns zero. In case of a static volume,
 * if data CRC mismatches - %-EBADMSG is returned. %-EBADMSG may also be
 * returned for any volume type if an ECC error was detected by the MTD device
 * driver. Other negative error cored may be returned in case of other errors.
 */
int ubi_eba_read_leb(struct ubi_device *ubi, int vol_id, int lnum, void *buf,
                 int offset, int len, int check)
{
      int err, pnum, scrub = 0, idx = vol_id2idx(ubi, vol_id);
      struct ubi_vid_hdr *vid_hdr;
      struct ubi_volume *vol = ubi->volumes[idx];
      uint32_t uninitialized_var(crc);

      err = leb_read_lock(ubi, vol_id, lnum);
      if (err)
            return err;

      pnum = vol->eba_tbl[lnum];
      if (pnum < 0) {
            /*
             * The logical eraseblock is not mapped, fill the whole buffer
             * with 0xFF bytes. The exception is static volumes for which
             * it is an error to read unmapped logical eraseblocks.
             */
            dbg_eba("read %d bytes from offset %d of LEB %d:%d (unmapped)",
                  len, offset, vol_id, lnum);
            leb_read_unlock(ubi, vol_id, lnum);
            ubi_assert(vol->vol_type != UBI_STATIC_VOLUME);
            memset(buf, 0xFF, len);
            return 0;
      }

      dbg_eba("read %d bytes from offset %d of LEB %d:%d, PEB %d",
            len, offset, vol_id, lnum, pnum);

      if (vol->vol_type == UBI_DYNAMIC_VOLUME)
            check = 0;

retry:
      if (check) {
            vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
            if (!vid_hdr) {
                  err = -ENOMEM;
                  goto out_unlock;
            }

            err = ubi_io_read_vid_hdr(ubi, pnum, vid_hdr, 1);
            if (err && err != UBI_IO_BITFLIPS) {
                  if (err > 0) {
                        /*
                         * The header is either absent or corrupted.
                         * The former case means there is a bug -
                         * switch to read-only mode just in case.
                         * The latter case means a real corruption - we
                         * may try to recover data. FIXME: but this is
                         * not implemented.
                         */
                        if (err == UBI_IO_BAD_VID_HDR) {
                              ubi_warn("bad VID header at PEB %d, LEB"
                                     "%d:%d", pnum, vol_id, lnum);
                              err = -EBADMSG;
                        } else
                              ubi_ro_mode(ubi);
                  }
                  goto out_free;
            } else if (err == UBI_IO_BITFLIPS)
                  scrub = 1;

            ubi_assert(lnum < be32_to_cpu(vid_hdr->used_ebs));
            ubi_assert(len == be32_to_cpu(vid_hdr->data_size));

            crc = be32_to_cpu(vid_hdr->data_crc);
            ubi_free_vid_hdr(ubi, vid_hdr);
      }

      err = ubi_io_read_data(ubi, buf, pnum, offset, len);
      if (err) {
            if (err == UBI_IO_BITFLIPS) {
                  scrub = 1;
                  err = 0;
            } else if (err == -EBADMSG) {
                  if (vol->vol_type == UBI_DYNAMIC_VOLUME)
                        goto out_unlock;
                  scrub = 1;
                  if (!check) {
                        ubi_msg("force data checking");
                        check = 1;
                        goto retry;
                  }
            } else
                  goto out_unlock;
      }

      if (check) {
            uint32_t crc1 = crc32(UBI_CRC32_INIT, buf, len);
            if (crc1 != crc) {
                  ubi_warn("CRC error: calculated %#08x, must be %#08x",
                         crc1, crc);
                  err = -EBADMSG;
                  goto out_unlock;
            }
      }

      if (scrub)
            err = ubi_wl_scrub_peb(ubi, pnum);

      leb_read_unlock(ubi, vol_id, lnum);
      return err;

out_free:
      ubi_free_vid_hdr(ubi, vid_hdr);
out_unlock:
      leb_read_unlock(ubi, vol_id, lnum);
      return err;
}

/**
 * recover_peb - recover from write failure.
 * @ubi: UBI device description object
 * @pnum: the physical eraseblock to recover
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 * @buf: data which was not written because of the write failure
 * @offset: offset of the failed write
 * @len: how many bytes should have been written
 *
 * This function is called in case of a write failure and moves all good data
 * from the potentially bad physical eraseblock to a good physical eraseblock.
 * This function also writes the data which was not written due to the failure.
 * Returns new physical eraseblock number in case of success, and a negative
 * error code in case of failure.
 */
static int recover_peb(struct ubi_device *ubi, int pnum, int vol_id, int lnum,
                   const void *buf, int offset, int len)
{
      int err, idx = vol_id2idx(ubi, vol_id), new_pnum, data_size, tries = 0;
      struct ubi_volume *vol = ubi->volumes[idx];
      struct ubi_vid_hdr *vid_hdr;

      vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
      if (!vid_hdr) {
            return -ENOMEM;
      }

      mutex_lock(&ubi->buf_mutex);

retry:
      new_pnum = ubi_wl_get_peb(ubi, UBI_UNKNOWN);
      if (new_pnum < 0) {
            mutex_unlock(&ubi->buf_mutex);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return new_pnum;
      }

      ubi_msg("recover PEB %d, move data to PEB %d", pnum, new_pnum);

      err = ubi_io_read_vid_hdr(ubi, pnum, vid_hdr, 1);
      if (err && err != UBI_IO_BITFLIPS) {
            if (err > 0)
                  err = -EIO;
            goto out_put;
      }

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
      if (err)
            goto write_error;

      data_size = offset + len;
      memset(ubi->peb_buf1 + offset, 0xFF, len);

      /* Read everything before the area where the write failure happened */
      if (offset > 0) {
            err = ubi_io_read_data(ubi, ubi->peb_buf1, pnum, 0, offset);
            if (err && err != UBI_IO_BITFLIPS)
                  goto out_put;
      }

      memcpy(ubi->peb_buf1 + offset, buf, len);

      err = ubi_io_write_data(ubi, ubi->peb_buf1, new_pnum, 0, data_size);
      if (err)
            goto write_error;

      mutex_unlock(&ubi->buf_mutex);
      ubi_free_vid_hdr(ubi, vid_hdr);

      vol->eba_tbl[lnum] = new_pnum;
      ubi_wl_put_peb(ubi, pnum, 1);

      ubi_msg("data was successfully recovered");
      return 0;

out_put:
      mutex_unlock(&ubi->buf_mutex);
      ubi_wl_put_peb(ubi, new_pnum, 1);
      ubi_free_vid_hdr(ubi, vid_hdr);
      return err;

write_error:
      /*
       * Bad luck? This physical eraseblock is bad too? Crud. Let's try to
       * get another one.
       */
      ubi_warn("failed to write to PEB %d", new_pnum);
      ubi_wl_put_peb(ubi, new_pnum, 1);
      if (++tries > UBI_IO_RETRIES) {
            mutex_unlock(&ubi->buf_mutex);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }
      ubi_msg("try again");
      goto retry;
}

/**
 * ubi_eba_write_leb - write data to dynamic volume.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 * @buf: the data to write
 * @offset: offset within the logical eraseblock where to write
 * @len: how many bytes to write
 * @dtype: data type
 *
 * This function writes data to logical eraseblock @lnum of a dynamic volume
 * @vol_id. Returns zero in case of success and a negative error code in case
 * of failure. In case of error, it is possible that something was still
 * written to the flash media, but may be some garbage.
 */
int ubi_eba_write_leb(struct ubi_device *ubi, int vol_id, int lnum,
                  const void *buf, int offset, int len, int dtype)
{
      int idx = vol_id2idx(ubi, vol_id), err, pnum, tries = 0;
      struct ubi_volume *vol = ubi->volumes[idx];
      struct ubi_vid_hdr *vid_hdr;

      if (ubi->ro_mode)
            return -EROFS;

      err = leb_write_lock(ubi, vol_id, lnum);
      if (err)
            return err;

      pnum = vol->eba_tbl[lnum];
      if (pnum >= 0) {
            dbg_eba("write %d bytes at offset %d of LEB %d:%d, PEB %d",
                  len, offset, vol_id, lnum, pnum);

            err = ubi_io_write_data(ubi, buf, pnum, offset, len);
            if (err) {
                  ubi_warn("failed to write data to PEB %d", pnum);
                  if (err == -EIO && ubi->bad_allowed)
                        err = recover_peb(ubi, pnum, vol_id, lnum, buf, offset, len);
                  if (err)
                        ubi_ro_mode(ubi);
            }
            leb_write_unlock(ubi, vol_id, lnum);
            return err;
      }

      /*
       * The logical eraseblock is not mapped. We have to get a free physical
       * eraseblock and write the volume identifier header there first.
       */
      vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
      if (!vid_hdr) {
            leb_write_unlock(ubi, vol_id, lnum);
            return -ENOMEM;
      }

      vid_hdr->vol_type = UBI_VID_DYNAMIC;
      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      vid_hdr->vol_id = cpu_to_be32(vol_id);
      vid_hdr->lnum = cpu_to_be32(lnum);
      vid_hdr->compat = ubi_get_compat(ubi, vol_id);
      vid_hdr->data_pad = cpu_to_be32(vol->data_pad);

retry:
      pnum = ubi_wl_get_peb(ubi, dtype);
      if (pnum < 0) {
            ubi_free_vid_hdr(ubi, vid_hdr);
            leb_write_unlock(ubi, vol_id, lnum);
            return pnum;
      }

      dbg_eba("write VID hdr and %d bytes at offset %d of LEB %d:%d, PEB %d",
            len, offset, vol_id, lnum, pnum);

      err = ubi_io_write_vid_hdr(ubi, pnum, vid_hdr);
      if (err) {
            ubi_warn("failed to write VID header to LEB %d:%d, PEB %d",
                   vol_id, lnum, pnum);
            goto write_error;
      }

      err = ubi_io_write_data(ubi, buf, pnum, offset, len);
      if (err) {
            ubi_warn("failed to write %d bytes at offset %d of LEB %d:%d, "
                   "PEB %d", len, offset, vol_id, lnum, pnum);
            goto write_error;
      }

      vol->eba_tbl[lnum] = pnum;

      leb_write_unlock(ubi, vol_id, lnum);
      ubi_free_vid_hdr(ubi, vid_hdr);
      return 0;

write_error:
      if (err != -EIO || !ubi->bad_allowed) {
            ubi_ro_mode(ubi);
            leb_write_unlock(ubi, vol_id, lnum);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }

      /*
       * Fortunately, this is the first write operation to this physical
       * eraseblock, so just put it and request a new one. We assume that if
       * this physical eraseblock went bad, the erase code will handle that.
       */
      err = ubi_wl_put_peb(ubi, pnum, 1);
      if (err || ++tries > UBI_IO_RETRIES) {
            ubi_ro_mode(ubi);
            leb_write_unlock(ubi, vol_id, lnum);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      ubi_msg("try another PEB");
      goto retry;
}

/**
 * ubi_eba_write_leb_st - write data to static volume.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 * @buf: data to write
 * @len: how many bytes to write
 * @dtype: data type
 * @used_ebs: how many logical eraseblocks will this volume contain
 *
 * This function writes data to logical eraseblock @lnum of static volume
 * @vol_id. The @used_ebs argument should contain total number of logical
 * eraseblock in this static volume.
 *
 * When writing to the last logical eraseblock, the @len argument doesn't have
 * to be aligned to the minimal I/O unit size. Instead, it has to be equivalent
 * to the real data size, although the @buf buffer has to contain the
 * alignment. In all other cases, @len has to be aligned.
 *
 * It is prohibited to write more then once to logical eraseblocks of static
 * volumes. This function returns zero in case of success and a negative error
 * code in case of failure.
 */
int ubi_eba_write_leb_st(struct ubi_device *ubi, int vol_id, int lnum,
                   const void *buf, int len, int dtype, int used_ebs)
{
      int err, pnum, tries = 0, data_size = len;
      int idx = vol_id2idx(ubi, vol_id);
      struct ubi_volume *vol = ubi->volumes[idx];
      struct ubi_vid_hdr *vid_hdr;
      uint32_t crc;

      if (ubi->ro_mode)
            return -EROFS;

      if (lnum == used_ebs - 1)
            /* If this is the last LEB @len may be unaligned */
            len = ALIGN(data_size, ubi->min_io_size);
      else
            ubi_assert(len % ubi->min_io_size == 0);

      vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
      if (!vid_hdr)
            return -ENOMEM;

      err = leb_write_lock(ubi, vol_id, lnum);
      if (err) {
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      vid_hdr->vol_id = cpu_to_be32(vol_id);
      vid_hdr->lnum = cpu_to_be32(lnum);
      vid_hdr->compat = ubi_get_compat(ubi, vol_id);
      vid_hdr->data_pad = cpu_to_be32(vol->data_pad);

      crc = crc32(UBI_CRC32_INIT, buf, data_size);
      vid_hdr->vol_type = UBI_VID_STATIC;
      vid_hdr->data_size = cpu_to_be32(data_size);
      vid_hdr->used_ebs = cpu_to_be32(used_ebs);
      vid_hdr->data_crc = cpu_to_be32(crc);

retry:
      pnum = ubi_wl_get_peb(ubi, dtype);
      if (pnum < 0) {
            ubi_free_vid_hdr(ubi, vid_hdr);
            leb_write_unlock(ubi, vol_id, lnum);
            return pnum;
      }

      dbg_eba("write VID hdr and %d bytes at LEB %d:%d, PEB %d, used_ebs %d",
            len, vol_id, lnum, pnum, used_ebs);

      err = ubi_io_write_vid_hdr(ubi, pnum, vid_hdr);
      if (err) {
            ubi_warn("failed to write VID header to LEB %d:%d, PEB %d",
                   vol_id, lnum, pnum);
            goto write_error;
      }

      err = ubi_io_write_data(ubi, buf, pnum, 0, len);
      if (err) {
            ubi_warn("failed to write %d bytes of data to PEB %d",
                   len, pnum);
            goto write_error;
      }

      ubi_assert(vol->eba_tbl[lnum] < 0);
      vol->eba_tbl[lnum] = pnum;

      leb_write_unlock(ubi, vol_id, lnum);
      ubi_free_vid_hdr(ubi, vid_hdr);
      return 0;

write_error:
      if (err != -EIO || !ubi->bad_allowed) {
            /*
             * This flash device does not admit of bad eraseblocks or
             * something nasty and unexpected happened. Switch to read-only
             * mode just in case.
             */
            ubi_ro_mode(ubi);
            leb_write_unlock(ubi, vol_id, lnum);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }

      err = ubi_wl_put_peb(ubi, pnum, 1);
      if (err || ++tries > UBI_IO_RETRIES) {
            ubi_ro_mode(ubi);
            leb_write_unlock(ubi, vol_id, lnum);
            ubi_free_vid_hdr(ubi, vid_hdr);
            return err;
      }

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      ubi_msg("try another PEB");
      goto retry;
}

/*
 * ubi_eba_atomic_leb_change - change logical eraseblock atomically.
 * @ubi: UBI device description object
 * @vol_id: volume ID
 * @lnum: logical eraseblock number
 * @buf: data to write
 * @len: how many bytes to write
 * @dtype: data type
 *
 * This function changes the contents of a logical eraseblock atomically. @buf
 * has to contain new logical eraseblock data, and @len - the length of the
 * data, which has to be aligned. This function guarantees that in case of an
 * unclean reboot the old contents is preserved. Returns zero in case of
 * success and a negative error code in case of failure.
 *
 * UBI reserves one LEB for the "atomic LEB change" operation, so only one
 * LEB change may be done at a time. This is ensured by @ubi->alc_mutex.
 */
int ubi_eba_atomic_leb_change(struct ubi_device *ubi, int vol_id, int lnum,
                        const void *buf, int len, int dtype)
{
      int err, pnum, tries = 0, idx = vol_id2idx(ubi, vol_id);
      struct ubi_volume *vol = ubi->volumes[idx];
      struct ubi_vid_hdr *vid_hdr;
      uint32_t crc;

      if (ubi->ro_mode)
            return -EROFS;

      vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
      if (!vid_hdr)
            return -ENOMEM;

      mutex_lock(&ubi->alc_mutex);
      err = leb_write_lock(ubi, vol_id, lnum);
      if (err)
            goto out_mutex;

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      vid_hdr->vol_id = cpu_to_be32(vol_id);
      vid_hdr->lnum = cpu_to_be32(lnum);
      vid_hdr->compat = ubi_get_compat(ubi, vol_id);
      vid_hdr->data_pad = cpu_to_be32(vol->data_pad);

      crc = crc32(UBI_CRC32_INIT, buf, len);
      vid_hdr->vol_type = UBI_VID_DYNAMIC;
      vid_hdr->data_size = cpu_to_be32(len);
      vid_hdr->copy_flag = 1;
      vid_hdr->data_crc = cpu_to_be32(crc);

retry:
      pnum = ubi_wl_get_peb(ubi, dtype);
      if (pnum < 0) {
            err = pnum;
            goto out_leb_unlock;
      }

      dbg_eba("change LEB %d:%d, PEB %d, write VID hdr to PEB %d",
            vol_id, lnum, vol->eba_tbl[lnum], pnum);

      err = ubi_io_write_vid_hdr(ubi, pnum, vid_hdr);
      if (err) {
            ubi_warn("failed to write VID header to LEB %d:%d, PEB %d",
                   vol_id, lnum, pnum);
            goto write_error;
      }

      err = ubi_io_write_data(ubi, buf, pnum, 0, len);
      if (err) {
            ubi_warn("failed to write %d bytes of data to PEB %d",
                   len, pnum);
            goto write_error;
      }

      if (vol->eba_tbl[lnum] >= 0) {
            err = ubi_wl_put_peb(ubi, vol->eba_tbl[lnum], 1);
            if (err)
                  goto out_leb_unlock;
      }

      vol->eba_tbl[lnum] = pnum;

out_leb_unlock:
      leb_write_unlock(ubi, vol_id, lnum);
out_mutex:
      mutex_unlock(&ubi->alc_mutex);
      ubi_free_vid_hdr(ubi, vid_hdr);
      return err;

write_error:
      if (err != -EIO || !ubi->bad_allowed) {
            /*
             * This flash device does not admit of bad eraseblocks or
             * something nasty and unexpected happened. Switch to read-only
             * mode just in case.
             */
            ubi_ro_mode(ubi);
            goto out_leb_unlock;
      }

      err = ubi_wl_put_peb(ubi, pnum, 1);
      if (err || ++tries > UBI_IO_RETRIES) {
            ubi_ro_mode(ubi);
            goto out_leb_unlock;
      }

      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));
      ubi_msg("try another PEB");
      goto retry;
}

/**
 * ltree_entry_ctor - lock tree entries slab cache constructor.
 * @obj: the lock-tree entry to construct
 * @cache: the lock tree entry slab cache
 * @flags: constructor flags
 */
static void ltree_entry_ctor(struct kmem_cache *cache, void *obj)
{
      struct ltree_entry *le = obj;

      le->users = 0;
      init_rwsem(&le->mutex);
}

/**
 * ubi_eba_copy_leb - copy logical eraseblock.
 * @ubi: UBI device description object
 * @from: physical eraseblock number from where to copy
 * @to: physical eraseblock number where to copy
 * @vid_hdr: VID header of the @from physical eraseblock
 *
 * This function copies logical eraseblock from physical eraseblock @from to
 * physical eraseblock @to. The @vid_hdr buffer may be changed by this
 * function. Returns zero in case of success, %UBI_IO_BITFLIPS if the operation
 * was canceled because bit-flips were detected at the target PEB, and a
 * negative error code in case of failure.
 */
int ubi_eba_copy_leb(struct ubi_device *ubi, int from, int to,
                 struct ubi_vid_hdr *vid_hdr)
{
      int err, vol_id, lnum, data_size, aldata_size, pnum, idx;
      struct ubi_volume *vol;
      uint32_t crc;

      vol_id = be32_to_cpu(vid_hdr->vol_id);
      lnum = be32_to_cpu(vid_hdr->lnum);

      dbg_eba("copy LEB %d:%d, PEB %d to PEB %d", vol_id, lnum, from, to);

      if (vid_hdr->vol_type == UBI_VID_STATIC) {
            data_size = be32_to_cpu(vid_hdr->data_size);
            aldata_size = ALIGN(data_size, ubi->min_io_size);
      } else
            data_size = aldata_size =
                      ubi->leb_size - be32_to_cpu(vid_hdr->data_pad);

      /*
       * We do not want anybody to write to this logical eraseblock while we
       * are moving it, so we lock it.
       */
      err = leb_write_lock(ubi, vol_id, lnum);
      if (err)
            return err;

      mutex_lock(&ubi->buf_mutex);

      /*
       * But the logical eraseblock might have been put by this time.
       * Cancel if it is true.
       */
      idx = vol_id2idx(ubi, vol_id);

      /*
       * We may race with volume deletion/re-size, so we have to hold
       * @ubi->volumes_lock.
       */
      spin_lock(&ubi->volumes_lock);
      vol = ubi->volumes[idx];
      if (!vol) {
            dbg_eba("volume %d was removed meanwhile", vol_id);
            spin_unlock(&ubi->volumes_lock);
            goto out_unlock;
      }

      pnum = vol->eba_tbl[lnum];
      if (pnum != from) {
            dbg_eba("LEB %d:%d is no longer mapped to PEB %d, mapped to "
                  "PEB %d, cancel", vol_id, lnum, from, pnum);
            spin_unlock(&ubi->volumes_lock);
            goto out_unlock;
      }
      spin_unlock(&ubi->volumes_lock);

      /* OK, now the LEB is locked and we can safely start moving it */

      dbg_eba("read %d bytes of data", aldata_size);
      err = ubi_io_read_data(ubi, ubi->peb_buf1, from, 0, aldata_size);
      if (err && err != UBI_IO_BITFLIPS) {
            ubi_warn("error %d while reading data from PEB %d",
                   err, from);
            goto out_unlock;
      }

      /*
       * Now we have got to calculate how much data we have to to copy. In
       * case of a static volume it is fairly easy - the VID header contains
       * the data size. In case of a dynamic volume it is more difficult - we
       * have to read the contents, cut 0xFF bytes from the end and copy only
       * the first part. We must do this to avoid writing 0xFF bytes as it
       * may have some side-effects. And not only this. It is important not
       * to include those 0xFFs to CRC because later the they may be filled
       * by data.
       */
      if (vid_hdr->vol_type == UBI_VID_DYNAMIC)
            aldata_size = data_size =
                  ubi_calc_data_len(ubi, ubi->peb_buf1, data_size);

      cond_resched();
      crc = crc32(UBI_CRC32_INIT, ubi->peb_buf1, data_size);
      cond_resched();

      /*
       * It may turn out to me that the whole @from physical eraseblock
       * contains only 0xFF bytes. Then we have to only write the VID header
       * and do not write any data. This also means we should not set
       * @vid_hdr->copy_flag, @vid_hdr->data_size, and @vid_hdr->data_crc.
       */
      if (data_size > 0) {
            vid_hdr->copy_flag = 1;
            vid_hdr->data_size = cpu_to_be32(data_size);
            vid_hdr->data_crc = cpu_to_be32(crc);
      }
      vid_hdr->sqnum = cpu_to_be64(next_sqnum(ubi));

      err = ubi_io_write_vid_hdr(ubi, to, vid_hdr);
      if (err)
            goto out_unlock;

      cond_resched();

      /* Read the VID header back and check if it was written correctly */
      err = ubi_io_read_vid_hdr(ubi, to, vid_hdr, 1);
      if (err) {
            if (err != UBI_IO_BITFLIPS)
                  ubi_warn("cannot read VID header back from PEB %d", to);
            goto out_unlock;
      }

      if (data_size > 0) {
            err = ubi_io_write_data(ubi, ubi->peb_buf1, to, 0, aldata_size);
            if (err)
                  goto out_unlock;

            cond_resched();

            /*
             * We've written the data and are going to read it back to make
             * sure it was written correctly.
             */

            err = ubi_io_read_data(ubi, ubi->peb_buf2, to, 0, aldata_size);
            if (err) {
                  if (err != UBI_IO_BITFLIPS)
                        ubi_warn("cannot read data back from PEB %d",
                               to);
                  goto out_unlock;
            }

            cond_resched();

            if (memcmp(ubi->peb_buf1, ubi->peb_buf2, aldata_size)) {
                  ubi_warn("read data back from PEB %d - it is different",
                         to);
                  goto out_unlock;
            }
      }

      ubi_assert(vol->eba_tbl[lnum] == from);
      vol->eba_tbl[lnum] = to;

out_unlock:
      mutex_unlock(&ubi->buf_mutex);
      leb_write_unlock(ubi, vol_id, lnum);
      return err;
}

/**
 * ubi_eba_init_scan - initialize the EBA unit using scanning information.
 * @ubi: UBI device description object
 * @si: scanning information
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
int ubi_eba_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
{
      int i, j, err, num_volumes;
      struct ubi_scan_volume *sv;
      struct ubi_volume *vol;
      struct ubi_scan_leb *seb;
      struct rb_node *rb;

      dbg_eba("initialize EBA unit");

      spin_lock_init(&ubi->ltree_lock);
      mutex_init(&ubi->alc_mutex);
      ubi->ltree = RB_ROOT;

      if (ubi_devices_cnt == 0) {
            ltree_slab = kmem_cache_create("ubi_ltree_slab",
                                     sizeof(struct ltree_entry), 0,
                                     0, &ltree_entry_ctor);
            if (!ltree_slab)
                  return -ENOMEM;
      }

      ubi->global_sqnum = si->max_sqnum + 1;
      num_volumes = ubi->vtbl_slots + UBI_INT_VOL_COUNT;

      for (i = 0; i < num_volumes; i++) {
            vol = ubi->volumes[i];
            if (!vol)
                  continue;

            cond_resched();

            vol->eba_tbl = kmalloc(vol->reserved_pebs * sizeof(int),
                               GFP_KERNEL);
            if (!vol->eba_tbl) {
                  err = -ENOMEM;
                  goto out_free;
            }

            for (j = 0; j < vol->reserved_pebs; j++)
                  vol->eba_tbl[j] = UBI_LEB_UNMAPPED;

            sv = ubi_scan_find_sv(si, idx2vol_id(ubi, i));
            if (!sv)
                  continue;

            ubi_rb_for_each_entry(rb, seb, &sv->root, u.rb) {
                  if (seb->lnum >= vol->reserved_pebs)
                        /*
                         * This may happen in case of an unclean reboot
                         * during re-size.
                         */
                        ubi_scan_move_to_list(sv, seb, &si->erase);
                  vol->eba_tbl[seb->lnum] = seb->pnum;
            }
      }

      if (ubi->bad_allowed) {
            ubi_calculate_reserved(ubi);

            if (ubi->avail_pebs < ubi->beb_rsvd_level) {
                  /* No enough free physical eraseblocks */
                  ubi->beb_rsvd_pebs = ubi->avail_pebs;
                  ubi_warn("cannot reserve enough PEBs for bad PEB "
                         "handling, reserved %d, need %d",
                         ubi->beb_rsvd_pebs, ubi->beb_rsvd_level);
            } else
                  ubi->beb_rsvd_pebs = ubi->beb_rsvd_level;

            ubi->avail_pebs -= ubi->beb_rsvd_pebs;
            ubi->rsvd_pebs  += ubi->beb_rsvd_pebs;
      }

      if (ubi->avail_pebs < EBA_RESERVED_PEBS) {
            ubi_err("no enough physical eraseblocks (%d, need %d)",
                  ubi->avail_pebs, EBA_RESERVED_PEBS);
            err = -ENOSPC;
            goto out_free;
      }
      ubi->avail_pebs -= EBA_RESERVED_PEBS;
      ubi->rsvd_pebs += EBA_RESERVED_PEBS;

      dbg_eba("EBA unit is initialized");
      return 0;

out_free:
      for (i = 0; i < num_volumes; i++) {
            if (!ubi->volumes[i])
                  continue;
            kfree(ubi->volumes[i]->eba_tbl);
      }
      if (ubi_devices_cnt == 0)
            kmem_cache_destroy(ltree_slab);
      return err;
}

/**
 * ubi_eba_close - close EBA unit.
 * @ubi: UBI device description object
 */
void ubi_eba_close(const struct ubi_device *ubi)
{
      int i, num_volumes = ubi->vtbl_slots + UBI_INT_VOL_COUNT;

      dbg_eba("close EBA unit");

      for (i = 0; i < num_volumes; i++) {
            if (!ubi->volumes[i])
                  continue;
            kfree(ubi->volumes[i]->eba_tbl);
      }
      if (ubi_devices_cnt == 1)
            kmem_cache_destroy(ltree_slab);
}

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