/src/e2fsprogs/lib/ext2fs/unix_io.c

Source
/*
 * unix_io.c --- This is the Unix (well, really POSIX) implementation
 *  of the I/O manager.
 *
 * Implements a one-block write-through cache.
 *
 * Includes support for Windows NT support under Cygwin.
 *
 * Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
 *  2002 by Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Library
 * General Public License, version 2.
 * %End-Header%
 */

#if !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(__OpenBSD__)
#define _XOPEN_SOURCE 600
#define _DARWIN_C_SOURCE
#ifndef _LARGEFILE_SOURCE
#define _LARGEFILE_SOURCE
#endif
#ifndef _LARGEFILE64_SOURCE
#define _LARGEFILE64_SOURCE
#endif
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#endif

#include "config.h"
#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_ERRNO_H
#include <errno.h>
#endif
#include <fcntl.h>
#include <time.h>
#ifdef __linux__
#include <sys/utsname.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif
#ifdef HAVE_SYS_MOUNT_H
#include <sys/mount.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
#if HAVE_LINUX_FALLOC_H
#include <linux/falloc.h>
#endif
#ifdef HAVE_PTHREAD
#include <pthread.h>
#endif
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif

#if defined(__linux__) && defined(_IO) && !defined(BLKROGET)
#define BLKROGET   _IO(0x12, 94) /* Get read-only status (0 = read_write).  */
#endif

#undef ALIGN_DEBUG

#include "ext2_fs.h"
#include "ext2fs.h"
#include "ext2fsP.h"

static inline int find_last_bit_set(int x)
{
  int r = 32;

  if (!x)
    return 0;
  if (!(x & 0xffff0000u)) {
    x = (x & 0xffffu) << 16;
    r -= 16;
  }
  if (!(x & 0xff000000u)) {
    x = (x & 0xffffffu) << 8;
    r -= 8;
  }
  if (!(x & 0xf0000000u)) {
    x = (x & 0xfffffffu) << 4;
    r -= 4;
  }
  if (!(x & 0xc0000000u)) {
    x = (x & 0x3fffffffu) << 2;
    r -= 2;
  }
  if (!(x & 0x80000000u)) {
    r -= 1;
  }
  return r;
}

/* Get high bit set out of 32-bit argument, -1 if none set */
static inline int highbit32(uint32_t v)
{
  return find_last_bit_set(v) - 1;
}

/*
 * For checking structure magic numbers...
 */

#define EXT2_CHECK_MAGIC(struct, code) \
    if ((struct)->magic != (code)) return (code)

struct unix_cache {
  char      *buf;
  unsigned long long  block;
  int     access_time;
  unsigned    dirty:1;
  unsigned    in_use:1;
  unsigned    write_err:1;
};

#define DEFAULT_CACHE_SIZE 8
#define WRITE_DIRECT_SIZE 4  /* Must be smaller than CACHE_SIZE */
#define READ_DIRECT_SIZE 4  /* Should be smaller than CACHE_SIZE */

struct unix_private_data {
  int magic;
  int dev;
  int flags;
  int align;
  int access_time;
  int unix_flock_flags;
  ext2_loff_t offset;
  struct unix_cache *cache;
  unsigned int cache_size;
  unsigned int cache_hash_shift;
  void  *bounce;
  struct struct_io_stats io_stats;
#ifdef HAVE_PTHREAD
  pthread_mutex_t cache_mutex;
  pthread_mutex_t bounce_mutex;
  pthread_mutex_t stats_mutex;
#endif
};

#define IS_ALIGNED(n, align) ((((uintptr_t) n) & \
             ((uintptr_t) ((align)-1))) == 0)

typedef enum lock_kind {
  CACHE_MTX, BOUNCE_MTX, STATS_MTX
} kind_t;

#ifdef HAVE_PTHREAD
static inline pthread_mutex_t *get_mutex(struct unix_private_data *data,
           kind_t kind)
{
  if (data->flags & IO_FLAG_THREADS) {
    switch (kind) {
    case CACHE_MTX:
      return &data->cache_mutex;
    case BOUNCE_MTX:
      return &data->bounce_mutex;
    case STATS_MTX:
      return &data->stats_mutex;
    }
  }
  return NULL;
}
#endif

static inline void mutex_lock(struct unix_private_data *data, kind_t kind)
{
#ifdef HAVE_PTHREAD
  pthread_mutex_t *mtx = get_mutex(data,kind);

  if (mtx)
    pthread_mutex_lock(mtx);
#endif
}

static inline void mutex_unlock(struct unix_private_data *data, kind_t kind)
{
#ifdef HAVE_PTHREAD
  pthread_mutex_t *mtx = get_mutex(data,kind);

  if (mtx)
    pthread_mutex_unlock(mtx);
#endif
}

static errcode_t unix_get_stats(io_channel channel, io_stats *stats)
{
  errcode_t retval = 0;

  struct unix_private_data *data;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (stats) {
    mutex_lock(data, STATS_MTX);
    *stats = &data->io_stats;
    mutex_unlock(data, STATS_MTX);
  }

  return retval;
}

/*
 * Here are the raw I/O functions
 */
static errcode_t raw_read_blk(io_channel channel,
            struct unix_private_data *data,
            unsigned long long block,
            int count, void *bufv)
{
  errcode_t retval;
  ssize_t   size;
  ext2_loff_t location;
  int   actual = 0;
  unsigned char *buf = bufv;
  ssize_t   really_read = 0;
  unsigned long long aligned_blk;
  int   align_size, offset;

  size = (count < 0) ? -count : (ext2_loff_t) count * channel->block_size;
  mutex_lock(data, STATS_MTX);
  data->io_stats.bytes_read += size;
  mutex_unlock(data, STATS_MTX);
  location = ((ext2_loff_t) block * channel->block_size) + data->offset;

  if (data->flags & IO_FLAG_FORCE_BOUNCE)
    goto bounce_read;

#ifdef HAVE_PREAD64
  /* Try an aligned pread */
  if ((channel->align == 0) ||
      (IS_ALIGNED(buf, channel->align) &&
       IS_ALIGNED(location, channel->align) &&
       IS_ALIGNED(size, channel->align))) {
    actual = pread64(data->dev, buf, size, location);
    if (actual == size)
      return 0;
    actual = 0;
  }
#elif HAVE_PREAD
  /* Try an aligned pread */
  if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
      ((channel->align == 0) ||
       (IS_ALIGNED(buf, channel->align) &&
        IS_ALIGNED(location, channel->align) &&
        IS_ALIGNED(size, channel->align)))) {
    actual = pread(data->dev, buf, size, location);
    if (actual == size)
      return 0;
    actual = 0;
  }
#endif /* HAVE_PREAD */

  if ((channel->align == 0) ||
      (IS_ALIGNED(buf, channel->align) &&
       IS_ALIGNED(location, channel->align) &&
       IS_ALIGNED(size, channel->align))) {
    mutex_lock(data, BOUNCE_MTX);
    if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
      retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
      goto error_unlock;
    }
    actual = read(data->dev, buf, size);
    if (actual != size) {
    short_read:
      if (actual < 0) {
        retval = errno;
        actual = 0;
      } else
        retval = EXT2_ET_SHORT_READ;
      goto error_unlock;
    }
    goto success_unlock;
  }

#ifdef ALIGN_DEBUG
  printf("raw_read_blk: O_DIRECT fallback: %p %lu\n", buf,
         (unsigned long) size);
#endif

  /*
   * The buffer or size which we're trying to read isn't aligned
   * to the O_DIRECT rules, so we need to do this the hard way...
   */
bounce_read:
  if (channel->align == 0)
    channel->align = 1;
  if ((channel->block_size > channel->align) &&
      (channel->block_size % channel->align) == 0)
    align_size = channel->block_size;
  else
    align_size = channel->align;
  aligned_blk = location / align_size;
  offset = location % align_size;

  mutex_lock(data, BOUNCE_MTX);
  if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
    retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
    goto error_unlock;
  }
  while (size > 0) {
    actual = read(data->dev, data->bounce, align_size);
    if (actual != align_size) {
      actual = really_read;
      buf -= really_read;
      size += really_read;
      goto short_read;
    }
    if ((actual + offset) > align_size)
      actual = align_size - offset;
    if (actual > size)
      actual = size;
    memcpy(buf, (char *)data->bounce + offset, actual);

    really_read += actual;
    size -= actual;
    buf += actual;
    offset = 0;
    aligned_blk++;
  }
success_unlock:
  mutex_unlock(data, BOUNCE_MTX);
  return 0;

error_unlock:
  mutex_unlock(data, BOUNCE_MTX);
  if (actual >= 0 && actual < size)
    memset((char *) buf+actual, 0, size-actual);
  if (channel->read_error)
    retval = (channel->read_error)(channel, block, count, buf,
                 size, actual, retval);
  return retval;
}

#define RAW_WRITE_NO_HANDLER  (1U << 0)
#define RAW_WRITE_NOLOCK  (1U << 1)

static errcode_t raw_write_blk(io_channel channel,
             struct unix_private_data *data,
             unsigned long long block,
             int count, const void *bufv,
             int flags)
{
  ssize_t   size;
  ext2_loff_t location;
  int   actual = 0;
  errcode_t retval;
  const unsigned char *buf = bufv;
  unsigned long long aligned_blk;
  int   align_size, offset;

  if (count == 1)
    size = channel->block_size;
  else {
    if (count < 0)
      size = -count;
    else
      size = (ext2_loff_t) count * channel->block_size;
  }
  mutex_lock(data, STATS_MTX);
  data->io_stats.bytes_written += size;
  mutex_unlock(data, STATS_MTX);

  location = ((ext2_loff_t) block * channel->block_size) + data->offset;

  if (data->flags & IO_FLAG_FORCE_BOUNCE)
    goto bounce_write;

#ifdef HAVE_PWRITE64
  /* Try an aligned pwrite */
  if ((channel->align == 0) ||
      (IS_ALIGNED(buf, channel->align) &&
       IS_ALIGNED(location, channel->align) &&
       IS_ALIGNED(size, channel->align))) {
    actual = pwrite64(data->dev, buf, size, location);
    if (actual == size)
      return 0;
  }
#elif HAVE_PWRITE
  /* Try an aligned pwrite */
  if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
      ((channel->align == 0) ||
       (IS_ALIGNED(buf, channel->align) &&
        IS_ALIGNED(location, channel->align) &&
        IS_ALIGNED(size, channel->align)))) {
    actual = pwrite(data->dev, buf, size, location);
    if (actual == size)
      return 0;
  }
#endif /* HAVE_PWRITE */

  if ((channel->align == 0) ||
      (IS_ALIGNED(buf, channel->align) &&
       IS_ALIGNED(location, channel->align) &&
       IS_ALIGNED(size, channel->align))) {
    if (!(flags & RAW_WRITE_NOLOCK))
      mutex_lock(data, BOUNCE_MTX);
    if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
      retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
      goto error_unlock;
    }
    actual = write(data->dev, buf, size);
    if (!(flags & RAW_WRITE_NOLOCK))
      mutex_unlock(data, BOUNCE_MTX);
    if (actual < 0) {
      retval = errno;
      goto error_out;
    }
    if (actual != size) {
    short_write:
      retval = EXT2_ET_SHORT_WRITE;
      goto error_out;
    }
    return 0;
  }

#ifdef ALIGN_DEBUG
  printf("raw_write_blk: O_DIRECT fallback: %p %lu\n", buf,
         (unsigned long) size);
#endif
  /*
   * The buffer or size which we're trying to write isn't aligned
   * to the O_DIRECT rules, so we need to do this the hard way...
   */
bounce_write:
  if (channel->align == 0)
    channel->align = 1;
  if ((channel->block_size > channel->align) &&
      (channel->block_size % channel->align) == 0)
    align_size = channel->block_size;
  else
    align_size = channel->align;
  aligned_blk = location / align_size;
  offset = location % align_size;

  while (size > 0) {
    int actual_w;

    if (!(flags & RAW_WRITE_NOLOCK))
      mutex_lock(data, BOUNCE_MTX);
    if (size < align_size || offset) {
      if (ext2fs_llseek(data->dev, aligned_blk * align_size,
            SEEK_SET) < 0) {
        retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
        goto error_unlock;
      }
      actual = read(data->dev, data->bounce,
              align_size);
      if (actual != align_size) {
        if (actual < 0) {
          retval = errno;
          goto error_unlock;
        }
        memset((char *) data->bounce + actual, 0,
               align_size - actual);
      }
    }
    actual = size;
    if ((actual + offset) > align_size)
      actual = align_size - offset;
    if (actual > size)
      actual = size;
    memcpy(((char *)data->bounce) + offset, buf, actual);
    if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
      retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
      goto error_unlock;
    }
    actual_w = write(data->dev, data->bounce, align_size);
    if (!(flags & RAW_WRITE_NOLOCK))
      mutex_unlock(data, BOUNCE_MTX);
    if (actual_w < 0) {
      retval = errno;
      goto error_out;
    }
    if (actual_w != align_size)
      goto short_write;
    size -= actual;
    buf += actual;
    location += actual;
    aligned_blk++;
    offset = 0;
  }
  return 0;

error_unlock:
  if (!(flags & RAW_WRITE_NOLOCK))
    mutex_unlock(data, BOUNCE_MTX);
error_out:
  if (((flags & RAW_WRITE_NO_HANDLER) == 0) && channel->write_error)
    retval = (channel->write_error)(channel, block, count, buf,
            size, actual, retval);
  return retval;
}


/*
 * Here we implement the cache functions
 */

/* Allocate the cache buffers */
static errcode_t alloc_cache(io_channel channel,
           struct unix_private_data *data)
{
  errcode_t   retval;
  struct unix_cache *cache;
  unsigned int    i;

  data->access_time = 0;
  for (i=0, cache = data->cache; i < data->cache_size; i++, cache++) {
    cache->block = 0;
    cache->access_time = 0;
    cache->dirty = 0;
    cache->in_use = 0;
    if (cache->buf)
      ext2fs_free_mem(&cache->buf);
    retval = io_channel_alloc_buf(channel, 0, &cache->buf);
    if (retval)
      return retval;
  }
  if (channel->align || data->flags & IO_FLAG_FORCE_BOUNCE) {
    if (data->bounce)
      ext2fs_free_mem(&data->bounce);
    retval = io_channel_alloc_buf(channel, 0, &data->bounce);
  }
  return retval;
}

/* Free the cache buffers */
static void free_cache(struct unix_private_data *data)
{
  struct unix_cache *cache;
  unsigned int    i;

  data->access_time = 0;
  for (i=0, cache = data->cache; i < data->cache_size; i++, cache++) {
    cache->block = 0;
    cache->access_time = 0;
    cache->dirty = 0;
    cache->in_use = 0;
    if (cache->buf)
      ext2fs_free_mem(&cache->buf);
  }
  if (data->bounce)
    ext2fs_free_mem(&data->bounce);
}

#ifndef NO_IO_CACHE

/*  2^63 + 2^61 - 2^57 + 2^54 - 2^51 - 2^18 + 1 */
#define GOLDEN_RATIO_PRIME  0x9e37fffffffc0001UL
#ifndef CACHE_LINE_SIZE
/* if the system didn't tell us, guess something reasonable */
#define CACHE_LINE_SIZE   64
#endif

/* buffer cache hashing function, crudely stolen from xfsprogs */
static unsigned int
cache_hash(struct unix_private_data *data, blk64_t blkno)
{
  uint64_t  hashval = blkno;
  uint64_t  tmp;

  /* the default cache size is small, just do a linear scan */
  if (data->cache_size <= DEFAULT_CACHE_SIZE)
    return 0;

  tmp = hashval ^ (GOLDEN_RATIO_PRIME + hashval) / CACHE_LINE_SIZE;
  tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> data->cache_hash_shift);
  return tmp % data->cache_size;
}

/*
 * Try to find a block in the cache.  If the block is not found, and
 * eldest is a non-zero pointer, then fill in eldest with the cache
 * entry to that should be reused.
 */
static struct unix_cache *find_cached_block(struct unix_private_data *data,
              unsigned long long block,
              struct unix_cache **eldest)
{
  struct unix_cache *cache, *unused_cache, *oldest_cache;
  unsigned int    hash = cache_hash(data, block);
  unsigned int    i;

  unused_cache = oldest_cache = 0;
  /* walk [hash..] cache elements */
  for (i = hash, cache = data->cache + hash;
       i < data->cache_size;
       i++, cache++) {
    if (!cache->in_use) {
      if (!unused_cache)
        unused_cache = cache;
      continue;
    }
    if (cache->block == block) {
      cache->access_time = ++data->access_time;
      data->io_stats.cache_hits++;
      return cache;
    }
    if (!oldest_cache ||
        (cache->access_time < oldest_cache->access_time))
      oldest_cache = cache;
  }
  /* walk [..hash] since we didnt find a good slot yet */
  for (i = 0, cache = data->cache; i < hash; i++, cache++) {
    if (!cache->in_use) {
      if (!unused_cache)
        unused_cache = cache;
      continue;
    }
    if (cache->block == block) {
      cache->access_time = ++data->access_time;
      data->io_stats.cache_hits++;
      return cache;
    }
    if (!oldest_cache ||
        (cache->access_time < oldest_cache->access_time))
      oldest_cache = cache;
  }
  if (eldest)
    *eldest = (unused_cache) ? unused_cache : oldest_cache;
  data->io_stats.cache_misses++;
  return 0;
}

/*
 * Reuse a particular cache entry for another block.
 */
static errcode_t reuse_cache(io_channel channel,
    struct unix_private_data *data, struct unix_cache *cache,
    unsigned long long block)
{
  if (cache->dirty && cache->in_use) {
    errcode_t retval;

    retval = raw_write_blk(channel, data, cache->block, 1,
               cache->buf, RAW_WRITE_NO_HANDLER);
    if (retval) {
      cache->write_err = 1;
      return retval;
    }
  }

  cache->in_use = 1;
  cache->dirty = 0;
  cache->write_err = 0;
  cache->block = block;
  cache->access_time = ++data->access_time;
  return 0;
}

#define FLUSH_INVALIDATE  0x01
#define FLUSH_NOLOCK    0x02

/*
 * Flush all of the blocks in the cache
 */
static errcode_t flush_cached_blocks(io_channel channel,
             struct unix_private_data *data,
             int flags)
{
  struct unix_cache *cache;
  errcode_t   retval, retval2 = 0;
  unsigned int    i;
  int     errors_found = 0;

  if ((flags & FLUSH_NOLOCK) == 0)
    mutex_lock(data, CACHE_MTX);
  for (i=0, cache = data->cache; i < data->cache_size; i++, cache++) {
    if (!cache->in_use)
      continue;
    if (cache->dirty) {
      int raw_flags = RAW_WRITE_NO_HANDLER;

      if (flags & FLUSH_NOLOCK)
        raw_flags |= RAW_WRITE_NOLOCK;

      retval = raw_write_blk(channel, data,
                 cache->block, 1, cache->buf,
                 raw_flags);
      if (retval) {
        cache->write_err = 1;
        errors_found = 1;
        retval2 = retval;
      } else {
        cache->dirty = 0;
        cache->write_err = 0;
        if (flags & FLUSH_INVALIDATE)
          cache->in_use = 0;
      }
    } else if (flags & FLUSH_INVALIDATE) {
      cache->in_use = 0;
    }
  }
  if ((flags & FLUSH_NOLOCK) == 0)
    mutex_unlock(data, CACHE_MTX);
retry:
  while (errors_found) {
    if ((flags & FLUSH_NOLOCK) == 0)
      mutex_lock(data, CACHE_MTX);
    errors_found = 0;
    for (i=0, cache = data->cache; i < data->cache_size; i++, cache++) {
      if (!cache->in_use || !cache->write_err)
        continue;
      errors_found = 1;
      if (cache->write_err && channel->write_error) {
        char *err_buf = NULL;
        unsigned long long err_block = cache->block;

        cache->dirty = 0;
        cache->in_use = 0;
        cache->write_err = 0;
        if (io_channel_alloc_buf(channel, 0,
               &err_buf))
          err_buf = NULL;
        else
          memcpy(err_buf, cache->buf,
                 channel->block_size);
        mutex_unlock(data, CACHE_MTX);
        (channel->write_error)(channel, err_block,
          1, err_buf, channel->block_size, -1,
          retval2);
        if (err_buf)
          ext2fs_free_mem(&err_buf);
        mutex_lock(data, CACHE_MTX);
        goto retry;
      } else
        cache->write_err = 0;
    }
    if ((flags & FLUSH_NOLOCK) == 0)
      mutex_unlock(data, CACHE_MTX);
  }
  return retval2;
}

/* Shrink the cache buffers */
static errcode_t shrink_cache(io_channel channel,
            struct unix_private_data *data,
            unsigned int new_size)
{
  struct unix_cache *cache, *new_cache;
  unsigned int    i;
  errcode_t   retval;

  mutex_lock(data, CACHE_MTX);

  retval = flush_cached_blocks(channel, data,
      FLUSH_INVALIDATE | FLUSH_NOLOCK);
  if (retval)
    goto unlock;

  for (i = new_size, cache = data->cache + new_size;
       i < data->cache_size;
       i++, cache++) {
    cache->block = 0;
    cache->access_time = 0;
    cache->dirty = 0;
    cache->in_use = 0;
    if (cache->buf)
      ext2fs_free_mem(&cache->buf);
  }

  new_cache = realloc(data->cache, new_size * sizeof(struct unix_cache));
  if (!new_cache) {
    retval = EXT2_ET_NO_MEMORY;
    goto unlock;
  }

  data->cache = new_cache;
  data->cache_size = new_size;
  data->cache_hash_shift = highbit32(data->cache_size);

unlock:
  mutex_unlock(data, CACHE_MTX);
  return retval;
}

/* Grow the cache buffers */
static errcode_t grow_cache(io_channel channel,
          struct unix_private_data *data,
          unsigned int new_size)
{
  struct unix_cache *cache, *new_cache;
  unsigned int    i;
  errcode_t   retval;

  mutex_lock(data, CACHE_MTX);

  retval = flush_cached_blocks(channel, data,
      FLUSH_INVALIDATE | FLUSH_NOLOCK);
  if (retval)
    goto unlock;

  new_cache = realloc(data->cache, new_size * sizeof(struct unix_cache));
  if (!new_cache) {
    retval = EXT2_ET_NO_MEMORY;
    goto unlock;
  }
  data->cache = new_cache;

  for (i = data->cache_size, cache = new_cache + data->cache_size;
       i < new_size;
       i++, cache++) {
    cache->block = 0;
    cache->access_time = 0;
    cache->dirty = 0;
    cache->in_use = 0;
    retval = io_channel_alloc_buf(channel, 0, &cache->buf);
    if (retval) {
      while (i > data->cache_size) {
        cache--; i--;
        if (cache->buf)
          ext2fs_free_mem(&cache->buf);
      }
      goto unlock;
    }
  }

  data->cache_size = new_size;
  data->cache_hash_shift = highbit32(data->cache_size);

unlock:
  mutex_unlock(data, CACHE_MTX);
  return retval;
}
#endif /* NO_IO_CACHE */

#ifdef __linux__
#ifndef BLKDISCARDZEROES
#define BLKDISCARDZEROES _IO(0x12,124)
#endif
#endif

int ext2fs_open_file(const char *pathname, int flags, mode_t mode)
{
  if (mode)
#if defined(HAVE_OPEN64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
    return open64(pathname, flags, mode);
  else
    return open64(pathname, flags);
#else
    return open(pathname, flags, mode);
  else
    return open(pathname, flags);
#endif
}

int ext2fs_stat(const char *path, ext2fs_struct_stat *buf)
{
#if defined(HAVE_FSTAT64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
  return stat64(path, buf);
#else
  return stat(path, buf);
#endif
}

int ext2fs_fstat(int fd, ext2fs_struct_stat *buf)
{
#if defined(HAVE_FSTAT64) && !defined(__OSX_AVAILABLE_BUT_DEPRECATED)
  return fstat64(fd, buf);
#else
  return fstat(fd, buf);
#endif
}

#ifdef HAVE_SYS_FILE_H
static errcode_t unix_funlock(io_channel channel)
{
  struct unix_private_data *data;
  int ret;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (data->unix_flock_flags) {
    ret = flock(data->dev, LOCK_UN);
    if (ret)
      return errno;

    data->unix_flock_flags = 0;
  }

  return 0;
}

static errcode_t unix_flock(io_channel channel, unsigned int flock_flags)
{
  struct unix_private_data *data;
  int unix_flock_flags = 0;
  errcode_t ret;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  ret = unix_funlock(channel);
  if (ret)
    return ret;

  if (flock_flags & IO_CHANNEL_FLOCK_EXCLUSIVE)
    unix_flock_flags |= LOCK_EX;

  if (flock_flags & IO_CHANNEL_FLOCK_SHARED)
    unix_flock_flags |= LOCK_SH;

  if (flock_flags & IO_CHANNEL_FLOCK_TRYLOCK)
    unix_flock_flags |= LOCK_NB;

  if (!unix_flock_flags)
    return 0;

  ret = flock(data->dev, unix_flock_flags);
  if (ret < 0)
    return errno;

  data->unix_flock_flags = unix_flock_flags & ~LOCK_NB;
  return 0;
}
#else
#define unix_flock    NULL

static errcode_t unix_funlock(io_channel channel)
{
  return 0;
}
#endif /* HAVE_SYS_FILE_H */

static errcode_t unix_open_channel(const char *name, int fd,
           int flags, io_channel *channel,
           io_manager io_mgr)
{
  io_channel  io = NULL;
  struct unix_private_data *data = NULL;
  errcode_t retval;
  ext2fs_struct_stat st;
#ifdef __linux__
  struct    utsname ut;
#endif

  if (ext2fs_safe_getenv("UNIX_IO_FORCE_BOUNCE"))
    flags |= IO_FLAG_FORCE_BOUNCE;

#ifdef __linux__
  /*
   * We need to make sure any previous errors in the block
   * device are thrown away, sigh.
   */
  (void) fsync(fd);
#endif

  retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
  if (retval)
    goto cleanup;
  memset(io, 0, sizeof(struct struct_io_channel));
  io->magic = EXT2_ET_MAGIC_IO_CHANNEL;
  retval = ext2fs_get_mem(sizeof(struct unix_private_data), &data);
  if (retval)
    goto cleanup;

  io->manager = io_mgr;
  retval = ext2fs_get_mem(strlen(name)+1, &io->name);
  if (retval)
    goto cleanup;

  strcpy(io->name, name);
  io->private_data = data;
  io->block_size = 1024;
  io->read_error = 0;
  io->write_error = 0;
  io->refcount = 1;
  io->flags = 0;

  if (ext2fs_safe_getenv("UNIX_IO_NOZEROOUT"))
    io->flags |= CHANNEL_FLAGS_NOZEROOUT;

  memset(data, 0, sizeof(struct unix_private_data));
  data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;
  data->io_stats.num_fields = 4;
  data->flags = flags;
  data->dev = fd;

  data->cache_size = DEFAULT_CACHE_SIZE;
  data->cache_hash_shift = highbit32(data->cache_size);
  data->cache = calloc(DEFAULT_CACHE_SIZE, sizeof(struct unix_cache));
  if (!data->cache) {
    retval = EXT2_ET_NO_MEMORY;
    goto cleanup;
  }

#if defined(O_DIRECT)
  if (flags & IO_FLAG_DIRECT_IO)
    io->align = ext2fs_get_dio_alignment(data->dev);
#elif defined(F_NOCACHE)
  if (flags & IO_FLAG_DIRECT_IO)
    io->align = 4096;
#endif

  /*
   * If the device is really a block device, then set the
   * appropriate flag, otherwise we can set DISCARD_ZEROES flag
   * because we are going to use punch hole instead of discard
   * and if it succeed, subsequent read from sparse area returns
   * zero.
   */
  if (ext2fs_fstat(data->dev, &st) == 0) {
    if (ext2fsP_is_disk_device(st.st_mode)) {
#ifdef BLKDISCARDZEROES
      int zeroes = 0;

      if (ioctl(data->dev, BLKDISCARDZEROES, &zeroes) == 0 &&
          zeroes)
        io->flags |= CHANNEL_FLAGS_DISCARD_ZEROES;
#endif
      io->flags |= CHANNEL_FLAGS_BLOCK_DEVICE;
    } else {
      io->flags |= CHANNEL_FLAGS_DISCARD_ZEROES;
    }
  }

#if defined(__CYGWIN__)
  /*
   * Some operating systems require that the buffers be aligned,
   * regardless of O_DIRECT
   */
  if (!io->align)
    io->align = 512;
#endif

#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
  if (io->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
    int dio_align = ext2fs_get_dio_alignment(fd);

    if (io->align < dio_align)
      io->align = dio_align;
  }
#endif

  if ((retval = alloc_cache(io, data)))
    goto cleanup;

#ifdef BLKROGET
  if (flags & IO_FLAG_RW) {
    int error;
    int readonly = 0;

    /* Is the block device actually writable? */
    error = ioctl(data->dev, BLKROGET, &readonly);
    if (!error && readonly) {
      retval = EPERM;
      goto cleanup;
    }
  }
#endif

#ifdef __linux__
#undef RLIM_INFINITY
#if (defined(__alpha__) || ((defined(__sparc__) || defined(__mips__)) && (SIZEOF_LONG == 4)))
#define RLIM_INFINITY ((unsigned long)(~0UL>>1))
#else
#define RLIM_INFINITY  (~0UL)
#endif
  /*
   * Work around a bug in 2.4.10-2.4.18 kernels where writes to
   * block devices are wrongly getting hit by the filesize
   * limit.  This workaround isn't perfect, since it won't work
   * if glibc wasn't built against 2.2 header files.  (Sigh.)
   *
   */
  if ((flags & IO_FLAG_RW) &&
      (uname(&ut) == 0) &&
      ((ut.release[0] == '2') && (ut.release[1] == '.') &&
       (ut.release[2] == '4') && (ut.release[3] == '.') &&
       (ut.release[4] == '1') && (ut.release[5] >= '0') &&
       (ut.release[5] < '8')) &&
      (ext2fs_fstat(data->dev, &st) == 0) &&
      (ext2fsP_is_disk_device(st.st_mode))) {
    struct rlimit rlim;

    rlim.rlim_cur = rlim.rlim_max = (unsigned long) RLIM_INFINITY;
    setrlimit(RLIMIT_FSIZE, &rlim);
    getrlimit(RLIMIT_FSIZE, &rlim);
    if (((unsigned long) rlim.rlim_cur) <
        ((unsigned long) rlim.rlim_max)) {
      rlim.rlim_cur = rlim.rlim_max;
      setrlimit(RLIMIT_FSIZE, &rlim);
    }
  }
#endif
#ifdef HAVE_PTHREAD
  if (flags & IO_FLAG_THREADS) {
    io->flags |= CHANNEL_FLAGS_THREADS;
    retval = pthread_mutex_init(&data->cache_mutex, NULL);
    if (retval)
      goto cleanup;
    retval = pthread_mutex_init(&data->bounce_mutex, NULL);
    if (retval) {
      pthread_mutex_destroy(&data->cache_mutex);
      goto cleanup;
    }
    retval = pthread_mutex_init(&data->stats_mutex, NULL);
    if (retval) {
      pthread_mutex_destroy(&data->cache_mutex);
      pthread_mutex_destroy(&data->bounce_mutex);
      goto cleanup;
    }
  }
#endif
  *channel = io;
  return 0;

cleanup:
  if (data) {
    unix_funlock(io);
    if (io->manager != unixfd_io_manager && data->dev >= 0)
      close(data->dev);
    if (data->cache) {
      free_cache(data);
      free(data->cache);
    }
    ext2fs_free_mem(&data);
  }
  if (io) {
    if (io->name) {
      ext2fs_free_mem(&io->name);
    }
    ext2fs_free_mem(&io);
  }
  return retval;
}

static errcode_t unixfd_open(const char *str_fd, int flags,
           io_channel *channel)
{
  int fd;
  int fd_flags;

  fd = atoi(str_fd);
#if defined(HAVE_FCNTL)
  fd_flags = fcntl(fd, F_GETFL);
  if (fd_flags == -1)
    return EBADF;

  /* O_EXCL is cleared by Linux at open and not returned by F_GETFL */
  flags &= IO_FLAG_EXCLUSIVE;
  if (fd_flags & O_RDWR)
    flags |= IO_FLAG_RW;
#if defined(O_DIRECT)
  if (fd_flags & O_DIRECT)
    flags |= IO_FLAG_DIRECT_IO;
#endif
#endif  /* HAVE_FCNTL */

  return unix_open_channel(str_fd, fd, flags, channel, unixfd_io_manager);
}

static errcode_t unix_open(const char *name, int flags,
         io_channel *channel)
{
  int fd = -1;
  int open_flags;

  if (name == 0)
    return EXT2_ET_BAD_DEVICE_NAME;

  open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
  if (flags & IO_FLAG_EXCLUSIVE)
    open_flags |= O_EXCL;
#if defined(O_DIRECT)
  if (flags & IO_FLAG_DIRECT_IO)
    open_flags |= O_DIRECT;
#endif
  fd = ext2fs_open_file(name, open_flags, 0);
  if (fd < 0)
    return errno;
#if defined(F_NOCACHE) && !defined(IO_DIRECT)
  if (flags & IO_FLAG_DIRECT_IO) {
    if (fcntl(fd, F_NOCACHE, 1) < 0)
      return errno;
  }
#endif
  return unix_open_channel(name, fd, flags, channel, unix_io_manager);
}

static errcode_t unix_close(io_channel channel)
{
  struct unix_private_data *data;
  errcode_t retval = 0;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (--channel->refcount > 0)
    return 0;

#ifndef NO_IO_CACHE
  retval = flush_cached_blocks(channel, data, 0);
#endif

  unix_funlock(channel);

  if (channel->manager != unixfd_io_manager && close(data->dev) < 0)
    retval = errno;
  free_cache(data);
  free(data->cache);
#ifdef HAVE_PTHREAD
  if (data->flags & IO_FLAG_THREADS) {
    pthread_mutex_destroy(&data->cache_mutex);
    pthread_mutex_destroy(&data->bounce_mutex);
    pthread_mutex_destroy(&data->stats_mutex);
  }
#endif

  ext2fs_free_mem(&channel->private_data);
  if (channel->name)
    ext2fs_free_mem(&channel->name);
  ext2fs_free_mem(&channel);
  return retval;
}

static errcode_t unix_set_blksize(io_channel channel, int blksize)
{
  struct unix_private_data *data;
  errcode_t   retval = 0;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (channel->block_size != blksize) {
    mutex_lock(data, CACHE_MTX);
    mutex_lock(data, BOUNCE_MTX);
#ifndef NO_IO_CACHE
    if ((retval = flush_cached_blocks(channel, data, FLUSH_NOLOCK))){
      mutex_unlock(data, BOUNCE_MTX);
      mutex_unlock(data, CACHE_MTX);
      return retval;
    }
#endif

    channel->block_size = blksize;
    free_cache(data);
    retval = alloc_cache(channel, data);
    mutex_unlock(data, BOUNCE_MTX);
    mutex_unlock(data, CACHE_MTX);
  }
  return retval;
}

static errcode_t unix_read_blk64(io_channel channel, unsigned long long block,
             int count, void *buf)
{
  struct unix_private_data *data;
  struct unix_cache *cache;
  errcode_t retval;
  char    *cp;
  int   i, j;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifdef NO_IO_CACHE
  return raw_read_blk(channel, data, block, count, buf);
#else
  if (data->flags & IO_FLAG_NOCACHE)
    return raw_read_blk(channel, data, block, count, buf);
  /*
   * If we're doing an odd-sized read or a very large read,
   * flush out the cache and then do a direct read.
   */
  if (count < 0 || count > WRITE_DIRECT_SIZE) {
    if ((retval = flush_cached_blocks(channel, data, 0)))
      return retval;
    return raw_read_blk(channel, data, block, count, buf);
  }

  cp = buf;
  mutex_lock(data, CACHE_MTX);
  while (count > 0) {
    /* If it's in the cache, use it! */
    if ((cache = find_cached_block(data, block, NULL))) {
#ifdef DEBUG
      printf("Using cached block %lu\n", block);
#endif
      memcpy(cp, cache->buf, channel->block_size);
      count--;
      block++;
      cp += channel->block_size;
      continue;
    }

    /*
     * Find the number of uncached blocks so we can do a
     * single read request
     */
    for (i=1; i < count; i++)
      if (find_cached_block(data, block+i, NULL))
        break;
#ifdef DEBUG
    printf("Reading %d blocks starting at %lu\n", i, block);
#endif
    mutex_unlock(data, CACHE_MTX);
    if ((retval = raw_read_blk(channel, data, block, i, cp)))
      return retval;
    mutex_lock(data, CACHE_MTX);

    /* Save the results in the cache */
    for (j=0; j < i; j++) {
      if (!find_cached_block(data, block, &cache)) {
        retval = reuse_cache(channel, data,
                 cache, block);
        if (retval)
          goto call_write_handler;
        memcpy(cache->buf, cp, channel->block_size);
      }
      count--;
      block++;
      cp += channel->block_size;
    }
  }
  mutex_unlock(data, CACHE_MTX);
  return 0;

call_write_handler:
  if (cache->write_err && channel->write_error) {
    char *err_buf = NULL;
    unsigned long long err_block = cache->block;

    cache->dirty = 0;
    cache->in_use = 0;
    cache->write_err = 0;
    if (io_channel_alloc_buf(channel, 0, &err_buf))
      err_buf = NULL;
    else
      memcpy(err_buf, cache->buf, channel->block_size);
    mutex_unlock(data, CACHE_MTX);
    (channel->write_error)(channel, err_block, 1, err_buf,
               channel->block_size, -1,
               retval);
    if (err_buf)
      ext2fs_free_mem(&err_buf);
  } else
    mutex_unlock(data, CACHE_MTX);
  return retval;
#endif /* NO_IO_CACHE */
}

static errcode_t unix_read_blk(io_channel channel, unsigned long block,
             int count, void *buf)
{
  return unix_read_blk64(channel, block, count, buf);
}

static errcode_t unix_write_blk64(io_channel channel, unsigned long long block,
        int count, const void *buf)
{
  struct unix_private_data *data;
  struct unix_cache *cache, *reuse;
  errcode_t retval = 0;
  const char  *cp;
  int   writethrough;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifdef NO_IO_CACHE
  return raw_write_blk(channel, data, block, count, buf, 0);
#else
  if (data->flags & IO_FLAG_NOCACHE)
    return raw_write_blk(channel, data, block, count, buf, 0);
  /*
   * If we're doing an odd-sized write or a very large write,
   * flush out the cache completely and then do a direct write.
   */
  if (count < 0 || count > WRITE_DIRECT_SIZE) {
    if ((retval = flush_cached_blocks(channel, data,
              FLUSH_INVALIDATE)))
      return retval;
    return raw_write_blk(channel, data, block, count, buf, 0);
  }

  /*
   * For a moderate-sized multi-block write, first force a write
   * if we're in write-through cache mode, and then fill the
   * cache with the blocks.
   */
  writethrough = channel->flags & CHANNEL_FLAGS_WRITETHROUGH;
  if (writethrough)
    retval = raw_write_blk(channel, data, block, count, buf, 0);

  cp = buf;
  mutex_lock(data, CACHE_MTX);
  while (count > 0) {
    cache = find_cached_block(data, block, &reuse);
    if (!cache) {
      errcode_t err;

      cache = reuse;
      err = reuse_cache(channel, data, cache, block);
      if (err)
        goto call_write_handler;
    }
    if (cache->buf != cp)
      memcpy(cache->buf, cp, channel->block_size);
    cache->dirty = !writethrough;
    count--;
    block++;
    cp += channel->block_size;
  }
  mutex_unlock(data, CACHE_MTX);
  return retval;

call_write_handler:
  if (cache->write_err && channel->write_error) {
    char *err_buf = NULL;
    unsigned long long err_block = cache->block;

    cache->dirty = 0;
    cache->in_use = 0;
    cache->write_err = 0;
    if (io_channel_alloc_buf(channel, 0, &err_buf))
      err_buf = NULL;
    else
      memcpy(err_buf, cache->buf, channel->block_size);
    mutex_unlock(data, CACHE_MTX);
    (channel->write_error)(channel, err_block, 1, err_buf,
               channel->block_size, -1,
               retval);
    if (err_buf)
      ext2fs_free_mem(&err_buf);
  } else
    mutex_unlock(data, CACHE_MTX);
  return retval;
#endif /* NO_IO_CACHE */
}

static errcode_t unix_cache_readahead(io_channel channel,
              unsigned long long block,
              unsigned long long count)
{
#ifdef POSIX_FADV_WILLNEED
  struct unix_private_data *data;

  data = (struct unix_private_data *)channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
  return posix_fadvise(data->dev,
           (ext2_loff_t)block * channel->block_size + data->offset,
           (ext2_loff_t)count * channel->block_size,
           POSIX_FADV_WILLNEED);
#else
  return EXT2_ET_OP_NOT_SUPPORTED;
#endif
}

static errcode_t unix_write_blk(io_channel channel, unsigned long block,
        int count, const void *buf)
{
  return unix_write_blk64(channel, block, count, buf);
}

static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
         int size, const void *buf)
{
  struct unix_private_data *data;
  errcode_t retval = 0;
  ssize_t   actual;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (channel->align != 0) {
#ifdef ALIGN_DEBUG
    printf("unix_write_byte: O_DIRECT fallback\n");
#endif
    return EXT2_ET_UNIMPLEMENTED;
  }

#ifndef NO_IO_CACHE
  /*
   * Flush out the cache completely
   */
  if ((retval = flush_cached_blocks(channel, data, FLUSH_INVALIDATE)))
    return retval;
#endif

  if (lseek(data->dev, offset + data->offset, SEEK_SET) < 0)
    return errno;

  actual = write(data->dev, buf, size);
  if (actual < 0)
    return errno;
  if (actual != size)
    return EXT2_ET_SHORT_WRITE;

  return 0;
}

/*
 * Flush data buffers to disk.
 */
static errcode_t unix_flush(io_channel channel)
{
  struct unix_private_data *data;
  errcode_t retval = 0;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

#ifndef NO_IO_CACHE
  retval = flush_cached_blocks(channel, data, 0);
#endif
#ifdef HAVE_FSYNC
  if (!retval && fsync(data->dev) != 0)
    return errno;
#endif
  return retval;
}

static errcode_t unix_set_option(io_channel channel, const char *option,
         const char *arg)
{
  struct unix_private_data *data;
  unsigned long long tmp;
  errcode_t retval;
  char *end;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (!strcmp(option, "offset")) {
    if (!arg)
      return EXT2_ET_INVALID_ARGUMENT;

    tmp = strtoull(arg, &end, 0);
    if (*end)
      return EXT2_ET_INVALID_ARGUMENT;
    data->offset = tmp;
    if (data->offset < 0)
      return EXT2_ET_INVALID_ARGUMENT;
    return 0;
  }
  if (!strcmp(option, "cache")) {
    if (!arg)
      return EXT2_ET_INVALID_ARGUMENT;
    if (!strcmp(arg, "on")) {
      data->flags &= ~IO_FLAG_NOCACHE;
      return 0;
    }
    if (!strcmp(arg, "off")) {
      retval = flush_cached_blocks(channel, data, 0);
      data->flags |= IO_FLAG_NOCACHE;
      return retval;
    }
    return EXT2_ET_INVALID_ARGUMENT;
  }
#ifndef NO_IO_CACHE
  if (!strcmp(option, "cache_blocks")) {
    unsigned long long  size;

    if (!arg)
      return EXT2_ET_INVALID_ARGUMENT;

    errno = 0;
    size = strtoll(arg, NULL, 0);
    if (errno || size == 0 || size > INT32_MAX)
      return EXT2_ET_INVALID_ARGUMENT;

    if (data->cache_size == size)
      return 0;
    if (data->cache_size > size)
      return shrink_cache(channel, data, size);
    return grow_cache(channel, data, size);
  }
#endif
  return EXT2_ET_INVALID_ARGUMENT;
}

#if defined(__linux__) && !defined(BLKDISCARD)
#define BLKDISCARD    _IO(0x12,119)
#endif

static errcode_t unix_discard(io_channel channel, unsigned long long block,
            unsigned long long count)
{
  struct unix_private_data *data;
  int   ret = EOPNOTSUPP;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (channel->flags & CHANNEL_FLAGS_NODISCARD)
    goto unimplemented;

  if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
#ifdef BLKDISCARD
    __u64 range[2];

    range[0] = (__u64)(block) * channel->block_size + data->offset;
    range[1] = (__u64)(count) * channel->block_size;

    ret = ioctl(data->dev, BLKDISCARD, &range);
#else
    goto unimplemented;
#endif
  } else {
#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE)
    /*
     * If we are not on block device, try to use punch hole
     * to reclaim free space.
     */
    ret = fallocate(data->dev,
        FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
        (off_t)(block) * channel->block_size + data->offset,
        (off_t)(count) * channel->block_size);
#else
    goto unimplemented;
#endif
  }
  if (ret < 0) {
    if (errno == EOPNOTSUPP) {
      channel->flags |= CHANNEL_FLAGS_NODISCARD;
      goto unimplemented;
    }
    return errno;
  }
  return 0;
unimplemented:
  return EXT2_ET_UNIMPLEMENTED;
}

/*
 * If we know about ZERO_RANGE, try that before we try PUNCH_HOLE because
 * ZERO_RANGE doesn't unmap preallocated blocks.  We prefer fallocate because
 * it always invalidates page cache, and libext2fs requires that reads after
 * ZERO_RANGE return zeroes.
 */
static int __unix_zeroout(int fd, off_t offset, off_t len)
{
  int ret = -1;

#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_ZERO_RANGE)
  ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, offset, len);
  if (ret == 0)
    return 0;
#endif
#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE)
  ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
      offset,  len);
  if (ret == 0)
    return 0;
#endif
  errno = EOPNOTSUPP;
  return ret;
}

/* parameters might not be used if OS doesn't support zeroout */
#if __GNUC_PREREQ (4, 6)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
#endif
static errcode_t unix_zeroout(io_channel channel, unsigned long long block,
            unsigned long long count)
{
  struct unix_private_data *data;
  int   ret;

  EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
  data = (struct unix_private_data *) channel->private_data;
  EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);

  if (!(channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE)) {
    /* Regular file, try to use truncate/punch/zero. */
    struct stat statbuf;

    if (count == 0)
      return 0;
    /*
     * If we're trying to zero a range past the end of the file,
     * extend the file size, then truncate everything.
     */
    ret = fstat(data->dev, &statbuf);
    if (ret)
      goto err;
    if ((unsigned long long) statbuf.st_size <
      (block + count) * channel->block_size + data->offset) {
      ret = ftruncate(data->dev,
          (block + count) * channel->block_size + data->offset);
      if (ret)
        goto err;
    }
  }

  if (channel->flags & CHANNEL_FLAGS_NOZEROOUT)
    goto unimplemented;

  ret = __unix_zeroout(data->dev,
      (off_t)(block) * channel->block_size + data->offset,
      (off_t)(count) * channel->block_size);
err:
  if (ret < 0) {
    if (errno == EOPNOTSUPP) {
      channel->flags |= CHANNEL_FLAGS_NOZEROOUT;
      goto unimplemented;
    }
    return errno;
  }
  return 0;
unimplemented:
  return EXT2_ET_UNIMPLEMENTED;
}
#if __GNUC_PREREQ (4, 6)
#pragma GCC diagnostic pop
#endif

static struct struct_io_manager struct_unix_manager = {
  .magic    = EXT2_ET_MAGIC_IO_MANAGER,
  .name   = "Unix I/O Manager",
  .open   = unix_open,
  .close    = unix_close,
  .set_blksize  = unix_set_blksize,
  .read_blk = unix_read_blk,
  .write_blk  = unix_write_blk,
  .flush    = unix_flush,
  .write_byte = unix_write_byte,
  .set_option = unix_set_option,
  .get_stats  = unix_get_stats,
  .read_blk64 = unix_read_blk64,
  .write_blk64  = unix_write_blk64,
  .discard  = unix_discard,
  .cache_readahead  = unix_cache_readahead,
  .zeroout  = unix_zeroout,
  .flock    = unix_flock,
};

io_manager unix_io_manager = &struct_unix_manager;

static struct struct_io_manager struct_unixfd_manager = {
  .magic    = EXT2_ET_MAGIC_IO_MANAGER,
  .name   = "Unix fd I/O Manager",
  .open   = unixfd_open,
  .close    = unix_close,
  .set_blksize  = unix_set_blksize,
  .read_blk = unix_read_blk,
  .write_blk  = unix_write_blk,
  .flush    = unix_flush,
  .write_byte = unix_write_byte,
  .set_option = unix_set_option,
  .get_stats  = unix_get_stats,
  .read_blk64 = unix_read_blk64,
  .write_blk64  = unix_write_blk64,
  .discard  = unix_discard,
  .cache_readahead  = unix_cache_readahead,
  .zeroout  = unix_zeroout,
  .flock    = unix_flock,
};

io_manager unixfd_io_manager = &struct_unixfd_manager;

Coverage Report

Created: 2026-10-17 07:17