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libjio/libjio/trans.c  view on Meta::CPAN

	if (fs == NULL)
		return NULL;

	fs->fd = -1;
	fs->jfd = -1;
	fs->jdir = NULL;
	fs->jdirfd = -1;
	fs->jmap = MAP_FAILED;
	fs->as_cfg = NULL;

	/* we provide either read-only or read-write access, because when we
	 * commit a transaction we read the current contents before applying,
	 * and write access is needed for locking with fcntl; the test is done
	 * this way because O_RDONLY is usually 0, so "if (flags & O_RDONLY)"
	 * will fail. */
	if ((flags & O_WRONLY) || (flags & O_RDWR)) {
		flags = flags & ~O_WRONLY;
		flags = flags & ~O_RDONLY;
		flags = flags | O_RDWR;
	} else {
		jflags = jflags | J_RDONLY;
	}

	fs->name = strdup(name);
	fs->flags = jflags;
	fs->open_flags = flags;
	fs->ltrans = NULL;
	fs->ltrans_len = 0;

	/* Note on fs->lock usage: this lock is used only to protect the file
	 * pointer. This means that it must only be held while performing
	 * operations that depend or alter the file pointer (jread, jreadv,
	 * jwrite, jwritev), but the others (jpread, jpwrite) are left
	 * unprotected because they can be performed in parallel as long as
	 * they don't affect the same portion of the file (this is protected
	 * by lockf). The lock doesn't slow things down tho: any threaded app
	 * MUST implement this kind of locking anyways if it wants to prevent
	 * data corruption, we only make it easier for them by taking care of
	 * it here. If performance is essential, the jpread/jpwrite functions
	 * should be used, just as real life.
	 * About fs->ltlock, it's used to protect the lingering transactions
	 * list, fs->ltrans. */
	pthread_mutexattr_init(&attr);
	pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_NORMAL);
	pthread_mutex_init( &(fs->lock), &attr);
	pthread_mutex_init( &(fs->ltlock), &attr);
	pthread_mutexattr_destroy(&attr);

	fs->fd = open(name, flags, mode);
	if (fs->fd < 0)
		goto error_exit;

	/* nothing else to do for read-only access */
	if (jflags & J_RDONLY) {
		return fs;
	}

	if (!get_jdir(name, jdir))
		goto error_exit;
	rv = mkdir(jdir, 0750);
	rv = lstat(jdir, &sinfo);
	if (rv < 0 || !S_ISDIR(sinfo.st_mode))
		goto error_exit;

	fs->jdir = (char *) malloc(strlen(jdir) + 1);
	if (fs->jdir == NULL)
		goto error_exit;
	strcpy(fs->jdir, jdir);

	/* open the directory, we will use it to flush transaction files'
	 * metadata in jtrans_commit() */
	fs->jdirfd = open(jdir, O_RDONLY);
	if (fs->jdirfd < 0)
		goto error_exit;

	snprintf(jlockfile, PATH_MAX, "%s/lock", jdir);
	jfd = open(jlockfile, O_RDWR | O_CREAT, 0600);
	if (jfd < 0)
		goto error_exit;

	fs->jfd = jfd;

	/* initialize the lock file by writing the first tid to it, but only
	 * if its empty, otherwise there is a race if two processes call
	 * jopen() simultaneously and both initialize the file */
	plockf(jfd, F_LOCKW, 0, 0);
	lstat(jlockfile, &sinfo);
	if (sinfo.st_size != sizeof(unsigned int)) {
		t = 0;
		rv = spwrite(jfd, &t, sizeof(t), 0);
		if (rv != sizeof(t)) {
			goto error_exit;
		}
	}
	plockf(jfd, F_UNLOCK, 0, 0);

	fs->jmap = (unsigned int *) mmap(NULL, sizeof(unsigned int),
			PROT_READ | PROT_WRITE, MAP_SHARED, jfd, 0);
	if (fs->jmap == MAP_FAILED)
		goto error_exit;

	return fs;

error_exit:
	/* if there was an error, clean up as much as possible so we don't
	 * leak anything, and return failure; jclose just does this cleaning
	 * for us */
	jclose(fs);
	return NULL;
}

/* Sync a file */
int jsync(struct jfs *fs)
{
	int rv;
	struct jlinger *ltmp;

	if (fs->fd < 0)
		return -1;

	rv = fdatasync(fs->fd);
	if (rv != 0)
		return rv;

	/* note the jops will be in order, so if we crash or fail in the
	 * middle of this, there will be no problem applying the remaining
	 * transactions */
	pthread_mutex_lock(&(fs->ltlock));
	while (fs->ltrans != NULL) {
		fiu_exit_on("jio/jsync/pre_unlink");
		if (journal_free(fs->ltrans->jop, 1) != 0) {
			pthread_mutex_unlock(&(fs->ltlock));
			return -1;
		}

		ltmp = fs->ltrans->next;
		free(fs->ltrans);
		fs->ltrans = ltmp;
	}

	fs->ltrans_len = 0;
	pthread_mutex_unlock(&(fs->ltlock));
	return 0;
}

/* Change the location of the journal directory */
int jmove_journal(struct jfs *fs, const char *newpath)