unix_io.c

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/* 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)