path: root/src/lib-fs/fs-metawrap.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "str.h"
#include "strescape.h"
#include "istream.h"
#include "istream-private.h"
#include "istream-concat.h"
#include "istream-metawrap.h"
#include "ostream.h"
#include "ostream-metawrap.h"
#include "iostream-temp.h"
#include "fs-api-private.h"

struct metawrap_fs {
	struct fs fs;
	bool wrap_metadata;
};

struct metawrap_fs_file {
	struct fs_file file;
	struct metawrap_fs *fs;
	struct fs_file *super_read;
	enum fs_open_mode open_mode;
	struct istream *input;
	bool metadata_read;

	struct ostream *super_output;
	struct ostream *temp_output;
	string_t *metadata_header;
	uoff_t metadata_write_size;
	bool metadata_changed_since_write;
};

#define METAWRAP_FS(ptr)	container_of((ptr), struct metawrap_fs, fs)
#define METAWRAP_FILE(ptr)	container_of((ptr), struct metawrap_fs_file, file)

static struct fs *fs_metawrap_alloc(void)
{
	struct metawrap_fs *fs;

	fs = i_new(struct metawrap_fs, 1);
	fs->fs = fs_class_metawrap;
	return &fs->fs;
}

static int
fs_metawrap_init(struct fs *_fs, const char *args,
		 const struct fs_settings *set, const char **error_r)
{
	struct metawrap_fs *fs = METAWRAP_FS(_fs);
	const char *parent_name, *parent_args;

	if (*args == '\0') {
		*error_r = "Parent filesystem not given as parameter";
		return -1;
	}

	parent_args = strchr(args, ':');
	if (parent_args == NULL) {
		parent_name = args;
		parent_args = "";
	} else {
		parent_name = t_strdup_until(args, parent_args);
		parent_args++;
	}
	if (fs_init(parent_name, parent_args, set, &_fs->parent, error_r) < 0)
		return -1;
	if ((fs_get_properties(_fs->parent) & FS_PROPERTY_METADATA) == 0)
		fs->wrap_metadata = TRUE;
	return 0;
}

static void fs_metawrap_free(struct fs *_fs)
{
	struct metawrap_fs *fs = METAWRAP_FS(_fs);

	i_free(fs);
}

static enum fs_properties fs_metawrap_get_properties(struct fs *_fs)
{
	const struct metawrap_fs *fs = METAWRAP_FS(_fs);
	enum fs_properties props;

	props = fs_get_properties(_fs->parent);
	if (fs->wrap_metadata) {
		/* we don't have a quick stat() to see the file's size,
		   because of the metadata header */
		props &= ENUM_NEGATE(FS_PROPERTY_STAT);
		/* Copying can copy the whole metadata. */
		props |= FS_PROPERTY_COPY_METADATA;
	}
	return props;
}

static struct fs_file *fs_metawrap_file_alloc(void)
{
	struct metawrap_fs_file *file = i_new(struct metawrap_fs_file, 1);
	return &file->file;
}

static void
fs_metawrap_file_init(struct fs_file *_file, const char *path,
		      enum fs_open_mode mode, enum fs_open_flags flags)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);
	struct metawrap_fs *fs = METAWRAP_FS(_file->fs);

	file->file.path = i_strdup(path);
	file->fs = fs;
	file->open_mode = mode;

	/* avoid unnecessarily creating two seekable streams */
	flags &= ENUM_NEGATE(FS_OPEN_FLAG_SEEKABLE);

	file->file.parent = fs_file_init_parent(_file, path, mode, flags);
	if (file->fs->wrap_metadata && mode == FS_OPEN_MODE_READONLY &&
	    (flags & FS_OPEN_FLAG_ASYNC) == 0) {
		/* use async stream for parent, so fs_read_stream() won't create
		   another seekable stream needlessly */
		file->super_read = fs_file_init_parent(_file, path,
			mode, flags | FS_OPEN_FLAG_ASYNC |
			FS_OPEN_FLAG_ASYNC_NOQUEUE);
	} else {
		file->super_read = file->file.parent;
	}
	fs_metadata_init(&file->file);
}

static void fs_metawrap_file_deinit(struct fs_file *_file)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	if (file->super_read != _file->parent)
		fs_file_deinit(&file->super_read);
	str_free(&file->metadata_header);
	fs_file_free(_file);
	i_free(file->file.path);
	i_free(file);
}

static void fs_metawrap_file_close(struct fs_file *_file)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	i_stream_unref(&file->input);
	fs_file_close(file->super_read);
	fs_file_close(_file->parent);
}

static void
fs_metawrap_set_metadata(struct fs_file *_file, const char *key,
			 const char *value)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	if (!file->fs->wrap_metadata ||
	    strcmp(key, FS_METADATA_WRITE_FNAME) == 0)
		fs_set_metadata(_file->parent, key, value);
	else {
		fs_default_set_metadata(_file, key, value);
		file->metadata_changed_since_write = TRUE;
	}
}

static int
fs_metawrap_get_metadata(struct fs_file *_file,
			 enum fs_get_metadata_flags flags,
			 const ARRAY_TYPE(fs_metadata) **metadata_r)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);
	ssize_t ret;
	char c;

	if (!file->fs->wrap_metadata)
		return fs_get_metadata_full(_file->parent, flags, metadata_r);

	if (file->metadata_read) {
		/* we have the metadata */
	} else if ((flags & FS_GET_METADATA_FLAG_LOADED_ONLY) != 0) {
		/* use the existing metadata only */
	} else if (file->input == NULL) {
		if (fs_read(_file, &c, 1) < 0)
			return -1;
	} else {
		/* use the existing istream to read it */
		while ((ret = i_stream_read(file->input)) == 0) {
			if (file->metadata_read)
				break;

			i_assert(!file->input->blocking);
			fs_wait_async(_file->fs);
		}
		if (ret == -1 && file->input->stream_errno != 0) {
			fs_set_error(_file->event, file->input->stream_errno,
				     "read(%s) failed: %s",
				     i_stream_get_name(file->input),
				     i_stream_get_error(file->input));
			return -1;
		}
		i_assert(file->metadata_read);
	}
	*metadata_r = &_file->metadata;
	return 0;
}

static bool fs_metawrap_prefetch(struct fs_file *_file, uoff_t length)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	if (!file->fs->wrap_metadata)
		return fs_prefetch(_file->parent, length);
	else
		return fs_prefetch(file->super_read, length);
}

static ssize_t fs_metawrap_read(struct fs_file *_file, void *buf, size_t size)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	if (!file->fs->wrap_metadata)
		return fs_read(_file->parent, buf, size);
	return fs_read_via_stream(_file, buf, size);
}

static void
fs_metawrap_callback(const char *key, const char *value, void *context)
{
	struct metawrap_fs_file *file = context;

	if (key == NULL) {
		file->metadata_read = TRUE;
		return;
	}

	T_BEGIN {
		key = str_tabunescape(t_strdup_noconst(key));
		value = str_tabunescape(t_strdup_noconst(value));
		fs_default_set_metadata(&file->file, key, value);
	} T_END;
}

static struct istream *
fs_metawrap_read_stream(struct fs_file *_file, size_t max_buffer_size)
{
	struct metawrap_fs_file *file = (struct metawrap_fs_file *)_file;
	struct istream *input;

	if (!file->fs->wrap_metadata)
		return fs_read_stream(_file->parent, max_buffer_size);

	if (file->input != NULL) {
		i_stream_ref(file->input);
		i_stream_seek(file->input, 0);
		return file->input;
	}

	input = fs_read_stream(file->super_read, max_buffer_size);
	file->input = i_stream_create_metawrap(input, fs_metawrap_callback, file);
	i_stream_unref(&input);
	i_stream_ref(file->input);
	return file->input;
}

static int fs_metawrap_write(struct fs_file *_file, const void *data, size_t size)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);

	if (!file->fs->wrap_metadata)
		return fs_write(_file->parent, data, size);
	return fs_write_via_stream(_file, data, size);
}

static void
fs_metawrap_append_metadata(struct metawrap_fs_file *file, string_t *str)
{
	const struct fs_metadata *metadata;

	array_foreach(&file->file.metadata, metadata) {
		if (str_begins(metadata->key, FS_METADATA_INTERNAL_PREFIX))
			continue;

		str_append_tabescaped(str, metadata->key);
		str_append_c(str, ':');
		str_append_tabescaped(str, metadata->value);
		str_append_c(str, '\n');
	}
	str_append_c(str, '\n');
}

static void
fs_metawrap_write_metadata_to(struct metawrap_fs_file *file,
			      struct ostream *output)
{
	string_t *str = t_str_new(256);
	ssize_t ret;

	fs_metawrap_append_metadata(file, str);
	file->metadata_write_size = str_len(str);

	ret = o_stream_send(output, str_data(str), str_len(str));
	if (ret < 0)
		o_stream_close(output);
	else
		i_assert((size_t)ret == str_len(str));
	file->metadata_changed_since_write = FALSE;
}

static void fs_metawrap_write_metadata(void *context)
{
	struct metawrap_fs_file *file = context;

	fs_metawrap_write_metadata_to(file, file->file.output);
}

static void fs_metawrap_write_stream(struct fs_file *_file)
{
	struct metawrap_fs_file *file = (struct metawrap_fs_file *)_file;

	i_assert(_file->output == NULL);

	if (!file->fs->wrap_metadata) {
		file->super_output = fs_write_stream(_file->parent);
		_file->output = file->super_output;
	} else {
		file->temp_output =
			iostream_temp_create_named(_file->fs->temp_path_prefix,
						   IOSTREAM_TEMP_FLAG_TRY_FD_DUP,
						   fs_file_path(_file));
		_file->output = o_stream_create_metawrap(file->temp_output,
			fs_metawrap_write_metadata, file);
	}
}

static struct istream *
fs_metawrap_create_updated_istream(struct metawrap_fs_file *file,
				   struct istream *input)
{
	struct istream *input2, *inputs[3];

	if (file->metadata_header != NULL)
		str_truncate(file->metadata_header, 0);
	else
		file->metadata_header = str_new(default_pool, 1024);
	fs_metawrap_append_metadata(file, file->metadata_header);
	inputs[0] = i_stream_create_from_data(str_data(file->metadata_header),
					       str_len(file->metadata_header));

	i_stream_seek(input, file->metadata_write_size);
	inputs[1] = i_stream_create_limit(input, UOFF_T_MAX);
	inputs[2] = NULL;
	input2 = i_stream_create_concat(inputs);
	i_stream_unref(&inputs[0]);
	i_stream_unref(&inputs[1]);

	file->metadata_write_size = str_len(file->metadata_header);
	return input2;
}

static int fs_metawrap_write_stream_finish(struct fs_file *_file, bool success)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);
	struct istream *input;
	int ret;

	if (_file->output != NULL) {
		if (_file->output == file->super_output)
			_file->output = NULL;
		else
			o_stream_unref(&_file->output);
	}
	if (!success) {
		if (file->super_output != NULL) {
			/* no metawrap */
			i_assert(file->temp_output == NULL);
			fs_write_stream_abort_parent(_file, &file->super_output);
		} else {
			i_assert(file->temp_output != NULL);
			o_stream_destroy(&file->temp_output);
		}
		return -1;
	}

	if (file->super_output != NULL) {
		/* no metawrap */
		i_assert(file->temp_output == NULL);
		return fs_write_stream_finish(_file->parent, &file->super_output);
	}
	if (file->temp_output == NULL) {
		/* finishing up */
		i_assert(file->super_output == NULL);
		return fs_write_stream_finish_async(_file->parent);
	}
	/* finish writing the temporary file */
	if (file->temp_output->offset == 0) {
		/* empty file - temp_output is already finished,
		   so we can't write to it. To make sure metadata is still
		   appended/written to file use metadata_changed_since_write */
		file->metadata_changed_since_write = TRUE;
	}
	input = iostream_temp_finish(&file->temp_output, IO_BLOCK_SIZE);
	if (file->metadata_changed_since_write) {
		/* we'll need to recreate the metadata. do this by creating a
		   new istream combining the new metadata header and the
		   old body. */
		struct istream *input2 = input;

		input = fs_metawrap_create_updated_istream(file, input);
		i_stream_unref(&input2);
	}
	file->super_output = fs_write_stream(_file->parent);
	o_stream_nsend_istream(file->super_output, input);
	/* because of the "end of metadata" LF, there's always at least
	   1 byte */
	i_assert(file->super_output->offset > 0 ||
		 file->super_output->stream_errno != 0);
	ret = fs_write_stream_finish(_file->parent, &file->super_output);
	i_stream_unref(&input);
	return ret;
}

static int fs_metawrap_stat(struct fs_file *_file, struct stat *st_r)
{
	struct metawrap_fs_file *file = METAWRAP_FILE(_file);
	struct istream *input;
	uoff_t input_size;
	ssize_t ret;

	if (!file->fs->wrap_metadata)
		return fs_stat(_file->parent, st_r);

	if (file->metadata_write_size != 0) {
		/* fs_stat() after a write. we can do this quickly. */
		if (fs_stat(_file->parent, st_r) < 0)
			return -1;
		if ((uoff_t)st_r->st_size < file->metadata_write_size) {
			fs_set_error(_file->event, EIO,
				"Just-written %s shrank unexpectedly "
				"(%"PRIuUOFF_T" < %"PRIuUOFF_T")",
				fs_file_path(_file), st_r->st_size,
				file->metadata_write_size);
			return -1;
		}
		st_r->st_size -= file->metadata_write_size;
		return 0;
	}

	if (file->input == NULL)
		input = fs_read_stream(_file, IO_BLOCK_SIZE);
	else {
		input = file->input;
		i_stream_ref(input);
	}
	if ((ret = i_stream_get_size(input, TRUE, &input_size)) < 0) {
		fs_set_error(_file->event, input->stream_errno,
			     "i_stream_get_size(%s) failed: %s",
			     fs_file_path(_file), i_stream_get_error(input));
		i_stream_unref(&input);
		return -1;
	}
	i_stream_unref(&input);
	if (ret == 0) {
		/* we shouldn't get here */
		fs_set_error(_file->event, EIO, "i_stream_get_size(%s) returned size as unknown",
			     fs_file_path(_file));
		return -1;
	}

	if (fs_stat(_file->parent, st_r) < 0) {
		i_assert(errno != EAGAIN); /* read should have caught this */
		return -1;
	}
	st_r->st_size = input_size;
	return 0;
}

static int fs_metawrap_copy(struct fs_file *_src, struct fs_file *_dest)
{
	struct metawrap_fs_file *dest = METAWRAP_FILE(_dest);

	if (!dest->fs->wrap_metadata || !_dest->metadata_changed)
		return fs_wrapper_copy(_src, _dest);
	else
		return fs_default_copy(_src, _dest);
}

const struct fs fs_class_metawrap = {
	.name = "metawrap",
	.v = {
		fs_metawrap_alloc,
		fs_metawrap_init,
		NULL,
		fs_metawrap_free,
		fs_metawrap_get_properties,
		fs_metawrap_file_alloc,
		fs_metawrap_file_init,
		fs_metawrap_file_deinit,
		fs_metawrap_file_close,
		fs_wrapper_file_get_path,
		fs_wrapper_set_async_callback,
		fs_wrapper_wait_async,
		fs_metawrap_set_metadata,
		fs_metawrap_get_metadata,
		fs_metawrap_prefetch,
		fs_metawrap_read,
		fs_metawrap_read_stream,
		fs_metawrap_write,
		fs_metawrap_write_stream,
		fs_metawrap_write_stream_finish,
		fs_wrapper_lock,
		fs_wrapper_unlock,
		fs_wrapper_exists,
		fs_metawrap_stat,
		fs_metawrap_copy,
		fs_wrapper_rename,
		fs_wrapper_delete,
		fs_wrapper_iter_alloc,
		fs_wrapper_iter_init,
		fs_wrapper_iter_next,
		fs_wrapper_iter_deinit,
		NULL,
		fs_wrapper_get_nlinks,
	}
};