unix_io.c

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			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;
}