text: /*
   * 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%
   */
  
  #define _LARGEFILE_SOURCE
  #define _LARGEFILE64_SOURCE
  
  #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
  #if HAVE_SYS_RESOURCE_H
  #include <sys/resource.h>
  #endif
  
  #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;
  		if (cache->buf)
  			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;
  	if (flags & IO_FLAG_EXCLUSIVE)
  		open_flags |= O_EXCL;
  #ifdef HAVE_OPEN64
  	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);
  	}
  	if (io)
  		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);
  	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;
  
  	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;
  }
  