e2fsprogs/old_e2fsprogs/ext2fs/unix_io.c - nest-cam/v179/busybox - Git at Google

 /* vi: set sw=4 ts=4: */
 /*
  * 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 Public
  * License.
  * %End-Header%
  */

 #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_STAT_H
 #include <sys/stat.h>
 #endif
 #if HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
 #include <sys/resource.h>

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

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

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

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

 #define 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	access_time;
 	ext2_loff_t offset;
 	struct unix_cache cache[CACHE_SIZE];
 };

 static errcode_t unix_open(const char *name, int flags, io_channel *channel);
 static errcode_t unix_close(io_channel channel);
 static errcode_t unix_set_blksize(io_channel channel, int blksize);
 static errcode_t unix_read_blk(io_channel channel, unsigned long block,
 			       int count, void *data);
 static errcode_t unix_write_blk(io_channel channel, unsigned long block,
 				int count, const void *data);
 static errcode_t unix_flush(io_channel channel);
 static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
 				int size, const void *data);
 static errcode_t unix_set_option(io_channel channel, const char *option,
 				 const char *arg);

 static void reuse_cache(io_channel channel, struct unix_private_data *data,
 		 struct unix_cache *cache, unsigned long block);

 /* __FreeBSD_kernel__ is defined by GNU/kFreeBSD - the FreeBSD kernel
  * does not know buffered block devices - everything is raw. */
 #if defined(__CYGWIN__) || defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 #define NEED_BOUNCE_BUFFER
 #else
 #undef NEED_BOUNCE_BUFFER
 #endif

 static struct struct_io_manager struct_unix_manager = {
 	EXT2_ET_MAGIC_IO_MANAGER,
 	"Unix I/O Manager",
 	unix_open,
 	unix_close,
 	unix_set_blksize,
 	unix_read_blk,
 	unix_write_blk,
 	unix_flush,
 #ifdef NEED_BOUNCE_BUFFER
 	0,
 #else
 	unix_write_byte,
 #endif
 	unix_set_option
 };

 io_manager unix_io_manager = &struct_unix_manager;

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

 	size = (count < 0) ? -count : count * channel->block_size;
 	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
 		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 		goto error_out;
 	}
 	actual = read(data->dev, buf, size);
 	if (actual != size) {
 		if (actual < 0)
 			actual = 0;
 		retval = EXT2_ET_SHORT_READ;
 		goto error_out;
 	}
 	return 0;

 error_out:
 	memset((char *) buf+actual, 0, size-actual);
 	if (channel->read_error)
 		retval = (channel->read_error)(channel, block, count, buf,
 					       size, actual, retval);
 	return retval;
 }
 #else /* NEED_BOUNCE_BUFFER */
 /*
  * Windows and FreeBSD block devices only allow sector alignment IO in offset and size
  */
 static errcode_t raw_read_blk(io_channel channel,
 			      struct unix_private_data *data,
 			      unsigned long block,
 			      int count, void *buf)
 {
 	errcode_t	retval;
 	size_t		size, alignsize, fragment;
 	ext2_loff_t	location;
 	int		total = 0, actual;
 #define BLOCKALIGN 512
 	char		sector[BLOCKALIGN];

 	size = (count < 0) ? -count : count * channel->block_size;
 	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 #ifdef DEBUG
 	printf("count=%d, size=%d, block=%d, blk_size=%d, location=%lx\n",
 			count, size, block, channel->block_size, location);
 #endif
 	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
 		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 		goto error_out;
 	}
 	fragment = size % BLOCKALIGN;
 	alignsize = size - fragment;
 	if (alignsize) {
 		actual = read(data->dev, buf, alignsize);
 		if (actual != alignsize)
 			goto short_read;
 	}
 	if (fragment) {
 		actual = read(data->dev, sector, BLOCKALIGN);
 		if (actual != BLOCKALIGN)
 			goto short_read;
 		memcpy(buf+alignsize, sector, fragment);
 	}
 	return 0;

 short_read:
 	if (actual>0)
 		total += actual;
 	retval = EXT2_ET_SHORT_READ;

 error_out:
 	memset((char *) buf+total, 0, size-actual);
 	if (channel->read_error)
 		retval = (channel->read_error)(channel, block, count, buf,
 					       size, actual, retval);
 	return retval;
 }
 #endif

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

 	if (count == 1)
 		size = channel->block_size;
 	else {
 		if (count < 0)
 			size = -count;
 		else
 			size = count * channel->block_size;
 	}

 	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
 		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 		goto error_out;
 	}

 	actual = write(data->dev, buf, size);
 	if (actual != size) {
 		retval = EXT2_ET_SHORT_WRITE;
 		goto error_out;
 	}
 	return 0;

 error_out:
 	if (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;
 	int			i;

 	data->access_time = 0;
 	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 		cache->block = 0;
 		cache->access_time = 0;
 		cache->dirty = 0;
 		cache->in_use = 0;
 		if ((retval = ext2fs_get_mem(channel->block_size,
 					     &cache->buf)))
 			return retval;
 	}
 	return 0;
 }

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

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

 #ifndef NO_IO_CACHE
 /*
  * 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 block,
 					    struct unix_cache **eldest)
 {
 	struct unix_cache	*cache, *unused_cache, *oldest_cache;
 	int			i;

 	unused_cache = oldest_cache = 0;
 	for (i=0, cache = data->cache; i < 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;
 			return cache;
 		}
 		if (!oldest_cache ||
 		    (cache->access_time < oldest_cache->access_time))
 			oldest_cache = cache;
 	}
 	if (eldest)
 		*eldest = (unused_cache) ? unused_cache : oldest_cache;
 	return 0;
 }

 /*
  * Reuse a particular cache entry for another block.
  */
 static void reuse_cache(io_channel channel, struct unix_private_data *data,
 		 struct unix_cache *cache, unsigned long block)
 {
 	if (cache->dirty && cache->in_use)
 		raw_write_blk(channel, data, cache->block, 1, cache->buf);

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

 /*
  * Flush all of the blocks in the cache
  */
 static errcode_t flush_cached_blocks(io_channel channel,
 				     struct unix_private_data *data,
 				     int invalidate)

 {
 	struct unix_cache	*cache;
 	errcode_t		retval, retval2;
 	int			i;

 	retval2 = 0;
 	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 		if (!cache->in_use)
 			continue;

 		if (invalidate)
 			cache->in_use = 0;

 		if (!cache->dirty)
 			continue;

 		retval = raw_write_blk(channel, data,
 				       cache->block, 1, cache->buf);
 		if (retval)
 			retval2 = retval;
 		else
 			cache->dirty = 0;
 	}
 	return retval2;
 }
 #endif /* NO_IO_CACHE */

 static errcode_t unix_open(const char *name, int flags, io_channel *channel)
 {
 	io_channel	io = NULL;
 	struct unix_private_data *data = NULL;
 	errcode_t	retval;
 	int		open_flags;
 	struct stat	st;
 #ifdef __linux__
 	struct		utsname ut;
 #endif

 	if (name == 0)
 		return EXT2_ET_BAD_DEVICE_NAME;
 	retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
 	if (retval)
 		return retval;
 	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 = unix_io_manager;
 	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;

 	memset(data, 0, sizeof(struct unix_private_data));
 	data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;

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

 	open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
 #ifdef CONFIG_LFS
 	data->dev = open64(io->name, open_flags);
 #else
 	data->dev = open(io->name, open_flags);
 #endif
 	if (data->dev < 0) {
 		retval = errno;
 		goto cleanup;
 	}

 #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')) &&
 	    (fstat(data->dev, &st) == 0) &&
 	    (S_ISBLK(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
 	*channel = io;
 	return 0;

 cleanup:
 	if (data) {
 		free_cache(data);
 		ext2fs_free_mem(&data);
 	}
 	ext2fs_free_mem(&io);
 	return retval;
 }

 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

 	if (close(data->dev) < 0)
 		retval = errno;
 	free_cache(data);

 	ext2fs_free_mem(&channel->private_data);
 	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;

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

 		channel->block_size = blksize;
 		free_cache(data);
 		if ((retval = alloc_cache(channel, data)))
 			return retval;
 	}
 	return 0;
 }


 static errcode_t unix_read_blk(io_channel channel, unsigned long block,
 			       int count, void *buf)
 {
 	struct unix_private_data *data;
 	struct unix_cache *cache, *reuse[READ_DIRECT_SIZE];
 	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 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;
 	while (count > 0) {
 		/* If it's in the cache, use it! */
 		if ((cache = find_cached_block(data, block, &reuse[0]))) {
 #ifdef DEBUG
 			printf("Using cached block %d\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, &reuse[i]))
 				break;
 #ifdef DEBUG
 		printf("Reading %d blocks starting at %d\n", i, block);
 #endif
 		if ((retval = raw_read_blk(channel, data, block, i, cp)))
 			return retval;

 		/* Save the results in the cache */
 		for (j=0; j < i; j++) {
 			count--;
 			cache = reuse[j];
 			reuse_cache(channel, data, cache, block++);
 			memcpy(cache->buf, cp, channel->block_size);
 			cp += channel->block_size;
 		}
 	}
 	return 0;
 #endif /* NO_IO_CACHE */
 }

 static errcode_t unix_write_blk(io_channel channel, unsigned 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);
 #else
 	/*
 	 * 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, 1)))
 			return retval;
 		return raw_write_blk(channel, data, block, count, buf);
 	}

 	/*
 	 * 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);

 	cp = buf;
 	while (count > 0) {
 		cache = find_cached_block(data, block, &reuse);
 		if (!cache) {
 			cache = reuse;
 			reuse_cache(channel, data, cache, block);
 		}
 		memcpy(cache->buf, cp, channel->block_size);
 		cache->dirty = !writethrough;
 		count--;
 		block++;
 		cp += channel->block_size;
 	}
 	return retval;
 #endif /* NO_IO_CACHE */
 }

 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);

 #ifndef NO_IO_CACHE
 	/*
 	 * Flush out the cache completely
 	 */
 	if ((retval = flush_cached_blocks(channel, data, 1)))
 		return retval;
 #endif

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

 	actual = write(data->dev, buf, size);
 	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
 	fsync(data->dev);
 	return retval;
 }

 static errcode_t unix_set_option(io_channel channel, const char *option,
 				 const char *arg)
 {
 	struct unix_private_data *data;
 	unsigned long tmp;
 	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 = strtoul(arg, &end, 0);
 		if (*end)
 			return EXT2_ET_INVALID_ARGUMENT;
 		data->offset = tmp;
 		return 0;
 	}
 	return EXT2_ET_INVALID_ARGUMENT;
 }
	/* vi: set sw=4 ts=4: */
	/*
	* 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 Public
	* License.
	* %End-Header%
	*/

	#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_STAT_H
	#include <sys/stat.h>
	#endif
	#if HAVE_SYS_TYPES_H
	#include <sys/types.h>
	#endif
	#include <sys/resource.h>

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

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

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

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

	#define 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 access_time;
	ext2_loff_t offset;
	struct unix_cache cache[CACHE_SIZE];
	};

	static errcode_t unix_open(const char name, int flags, io_channel channel);
	static errcode_t unix_close(io_channel channel);
	static errcode_t unix_set_blksize(io_channel channel, int blksize);
	static errcode_t unix_read_blk(io_channel channel, unsigned long block,
	int count, void *data);
	static errcode_t unix_write_blk(io_channel channel, unsigned long block,
	int count, const void *data);
	static errcode_t unix_flush(io_channel channel);
	static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
	int size, const void *data);
	static errcode_t unix_set_option(io_channel channel, const char *option,
	const char *arg);

	static void reuse_cache(io_channel channel, struct unix_private_data *data,
	struct unix_cache *cache, unsigned long block);

	/* __FreeBSD_kernel__ is defined by GNU/kFreeBSD - the FreeBSD kernel
	* does not know buffered block devices - everything is raw. */
	#if defined(__CYGWIN__) \|\| defined(__FreeBSD__) \|\| defined(__FreeBSD_kernel__)
	#define NEED_BOUNCE_BUFFER
	#else
	#undef NEED_BOUNCE_BUFFER
	#endif

	static struct struct_io_manager struct_unix_manager = {
	EXT2_ET_MAGIC_IO_MANAGER,
	"Unix I/O Manager",
	unix_open,
	unix_close,
	unix_set_blksize,
	unix_read_blk,
	unix_write_blk,
	unix_flush,
	#ifdef NEED_BOUNCE_BUFFER
	0,
	#else
	unix_write_byte,
	#endif
	unix_set_option
	};

	io_manager unix_io_manager = &struct_unix_manager;

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

	size = (count < 0) ? -count : count * channel->block_size;
	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
	retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
	goto error_out;
	}
	actual = read(data->dev, buf, size);
	if (actual != size) {
	if (actual < 0)
	actual = 0;
	retval = EXT2_ET_SHORT_READ;
	goto error_out;
	}
	return 0;

	error_out:
	memset((char *) buf+actual, 0, size-actual);
	if (channel->read_error)
	retval = (channel->read_error)(channel, block, count, buf,
	size, actual, retval);
	return retval;
	}
	#else /* NEED_BOUNCE_BUFFER */
	/*
	* Windows and FreeBSD block devices only allow sector alignment IO in offset and size
	*/
	static errcode_t raw_read_blk(io_channel channel,
	struct unix_private_data *data,
	unsigned long block,
	int count, void *buf)
	{
	errcode_t retval;
	size_t size, alignsize, fragment;
	ext2_loff_t location;
	int total = 0, actual;
	#define BLOCKALIGN 512
	char sector[BLOCKALIGN];

	size = (count < 0) ? -count : count * channel->block_size;
	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
	#ifdef DEBUG
	printf("count=%d, size=%d, block=%d, blk_size=%d, location=%lx\n",
	count, size, block, channel->block_size, location);
	#endif
	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
	retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
	goto error_out;
	}
	fragment = size % BLOCKALIGN;
	alignsize = size - fragment;
	if (alignsize) {
	actual = read(data->dev, buf, alignsize);
	if (actual != alignsize)
	goto short_read;
	}
	if (fragment) {
	actual = read(data->dev, sector, BLOCKALIGN);
	if (actual != BLOCKALIGN)
	goto short_read;
	memcpy(buf+alignsize, sector, fragment);
	}
	return 0;

	short_read:
	if (actual>0)
	total += actual;
	retval = EXT2_ET_SHORT_READ;

	error_out:
	memset((char *) buf+total, 0, size-actual);
	if (channel->read_error)
	retval = (channel->read_error)(channel, block, count, buf,
	size, actual, retval);
	return retval;
	}
	#endif

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

	if (count == 1)
	size = channel->block_size;
	else {
	if (count < 0)
	size = -count;
	else
	size = count * channel->block_size;
	}

	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
	retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
	goto error_out;
	}

	actual = write(data->dev, buf, size);
	if (actual != size) {
	retval = EXT2_ET_SHORT_WRITE;
	goto error_out;
	}
	return 0;

	error_out:
	if (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;
	int i;

	data->access_time = 0;
	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
	cache->block = 0;
	cache->access_time = 0;
	cache->dirty = 0;
	cache->in_use = 0;
	if ((retval = ext2fs_get_mem(channel->block_size,
	&cache->buf)))
	return retval;
	}
	return 0;
	}

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

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

	#ifndef NO_IO_CACHE
	/*
	* 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 block,
	struct unix_cache **eldest)
	{
	struct unix_cache cache, unused_cache, *oldest_cache;
	int i;

	unused_cache = oldest_cache = 0;
	for (i=0, cache = data->cache; i < 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;
	return cache;
	}
	if (!oldest_cache \|\|
	(cache->access_time < oldest_cache->access_time))
	oldest_cache = cache;
	}
	if (eldest)
	*eldest = (unused_cache) ? unused_cache : oldest_cache;
	return 0;
	}

	/*
	* Reuse a particular cache entry for another block.
	*/
	static void reuse_cache(io_channel channel, struct unix_private_data *data,
	struct unix_cache *cache, unsigned long block)
	{
	if (cache->dirty && cache->in_use)
	raw_write_blk(channel, data, cache->block, 1, cache->buf);

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

	/*
	* Flush all of the blocks in the cache
	*/
	static errcode_t flush_cached_blocks(io_channel channel,
	struct unix_private_data *data,
	int invalidate)

	{
	struct unix_cache *cache;
	errcode_t retval, retval2;
	int i;

	retval2 = 0;
	for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
	if (!cache->in_use)
	continue;

	if (invalidate)
	cache->in_use = 0;

	if (!cache->dirty)
	continue;

	retval = raw_write_blk(channel, data,
	cache->block, 1, cache->buf);
	if (retval)
	retval2 = retval;
	else
	cache->dirty = 0;
	}
	return retval2;
	}
	#endif /* NO_IO_CACHE */

	static errcode_t unix_open(const char name, int flags, io_channel channel)
	{
	io_channel io = NULL;
	struct unix_private_data *data = NULL;
	errcode_t retval;
	int open_flags;
	struct stat st;
	#ifdef __linux__
	struct utsname ut;
	#endif

	if (name == 0)
	return EXT2_ET_BAD_DEVICE_NAME;
	retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
	if (retval)
	return retval;
	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 = unix_io_manager;
	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;

	memset(data, 0, sizeof(struct unix_private_data));
	data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;

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

	open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
	#ifdef CONFIG_LFS
	data->dev = open64(io->name, open_flags);
	#else
	data->dev = open(io->name, open_flags);
	#endif
	if (data->dev < 0) {
	retval = errno;
	goto cleanup;
	}

	#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')) &&
	(fstat(data->dev, &st) == 0) &&
	(S_ISBLK(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
	*channel = io;
	return 0;

	cleanup:
	if (data) {
	free_cache(data);
	ext2fs_free_mem(&data);
	}
	ext2fs_free_mem(&io);
	return retval;
	}

	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

	if (close(data->dev) < 0)
	retval = errno;
	free_cache(data);

	ext2fs_free_mem(&channel->private_data);
	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;

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

	channel->block_size = blksize;
	free_cache(data);
	if ((retval = alloc_cache(channel, data)))
	return retval;
	}
	return 0;
	}


	static errcode_t unix_read_blk(io_channel channel, unsigned long block,
	int count, void *buf)
	{
	struct unix_private_data *data;
	struct unix_cache cache, reuse[READ_DIRECT_SIZE];
	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 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;
	while (count > 0) {
	/* If it's in the cache, use it! */
	if ((cache = find_cached_block(data, block, &reuse[0]))) {
	#ifdef DEBUG
	printf("Using cached block %d\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, &reuse[i]))
	break;
	#ifdef DEBUG
	printf("Reading %d blocks starting at %d\n", i, block);
	#endif
	if ((retval = raw_read_blk(channel, data, block, i, cp)))
	return retval;

	/* Save the results in the cache */
	for (j=0; j < i; j++) {
	count--;
	cache = reuse[j];
	reuse_cache(channel, data, cache, block++);
	memcpy(cache->buf, cp, channel->block_size);
	cp += channel->block_size;
	}
	}
	return 0;
	#endif /* NO_IO_CACHE */
	}

	static errcode_t unix_write_blk(io_channel channel, unsigned 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);
	#else
	/*
	* 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, 1)))
	return retval;
	return raw_write_blk(channel, data, block, count, buf);
	}

	/*
	* 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);

	cp = buf;
	while (count > 0) {
	cache = find_cached_block(data, block, &reuse);
	if (!cache) {
	cache = reuse;
	reuse_cache(channel, data, cache, block);
	}
	memcpy(cache->buf, cp, channel->block_size);
	cache->dirty = !writethrough;
	count--;
	block++;
	cp += channel->block_size;
	}
	return retval;
	#endif /* NO_IO_CACHE */
	}

	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);

	#ifndef NO_IO_CACHE
	/*
	* Flush out the cache completely
	*/
	if ((retval = flush_cached_blocks(channel, data, 1)))
	return retval;
	#endif

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

	actual = write(data->dev, buf, size);
	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
	fsync(data->dev);
	return retval;
	}

	static errcode_t unix_set_option(io_channel channel, const char *option,
	const char *arg)
	{
	struct unix_private_data *data;
	unsigned long tmp;
	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 = strtoul(arg, &end, 0);
	if (*end)
	return EXT2_ET_INVALID_ARGUMENT;
	data->offset = tmp;
	return 0;
	}
	return EXT2_ET_INVALID_ARGUMENT;
	}