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

	pthread_mutexattr_destroy(&attr);

	return ts;
}

/* Free the contents of a transaction structure */
void jtrans_free(struct jtrans *ts)
{
	struct operation *tmpop;

	ts->fs = NULL;

	while (ts->op != NULL) {
		tmpop = ts->op->next;

		if (ts->op->buf && ts->op->direction == D_WRITE)
			free(ts->op->buf);
		if (ts->op->pdata)
			free(ts->op->pdata);
		free(ts->op);

		ts->op = tmpop;
	}
	pthread_mutex_destroy(&(ts->lock));

	free(ts);
}

/** Lock/unlock the ranges of the file covered by the transaction. mode must
 * be either F_LOCKW or F_UNLOCK. Returns 0 on success, -1 on error. */
static int lock_file_ranges(struct jtrans *ts, int mode)
{
	unsigned int nops;
	off_t lr, min_offset;
	struct operation *op, *start_op;

	if (ts->flags & J_NOLOCK)
		return 0;

	/* Lock/unlock always in the same order to avoid deadlocks. We will
	 * begin with the operation that has the smallest start offset, and go
	 * from there.
	 * Note that this is O(n^2), but n is usually (very) small, and we're
	 * about to do synchronous I/O, so it's not really worrying. It has a
	 * small optimization to help when the operations tend to be in the
	 * right order. */
	nops = 0;
	min_offset = 0;
	start_op = ts->op;
	while (nops < ts->numops_r + ts->numops_w) {
		for (op = start_op; op != NULL; op = op->next) {
			if (min_offset < op->offset)
				continue;
			min_offset = op->offset;
			start_op = op->next;

			if (mode == F_LOCKW) {
				lr = plockf(ts->fs->fd, F_LOCKW, op->offset, op->len);
				if (lr == -1)
					goto error;
				op->locked = 1;
			} else if (mode == F_UNLOCK && op->locked) {
				lr = plockf(ts->fs->fd, F_UNLOCK, op->offset,
						op->len);
				if (lr == -1)
					goto error;
				op->locked = 0;
			}
		}

		nops++;
	}

	return 0;

error:
	return -1;
}

/** Read the previous information from the disk into the given operation
 * structure. Returns 0 on success, -1 on error. */
static int operation_read_prev(struct jtrans *ts, struct operation *op)
{
	ssize_t rv;

	op->pdata = malloc(op->len);
	if (op->pdata == NULL)
		return -1;

	rv = spread(ts->fs->fd, op->pdata, op->len,
			op->offset);
	if (rv < 0) {
		free(op->pdata);
		op->pdata = NULL;
		return -1;
	}

	op->plen = op->len;
	if (rv < op->len) {
		/* we are extending the file! */
		/* ftruncate(ts->fs->fd, op->offset + op->len); */
		op->plen = rv;
	}

	return 0;
}

/** Common function to add an operation to a transaction */
static int jtrans_add_common(struct jtrans *ts, const void *buf, size_t count,
		off_t offset, enum op_direction direction)
{
	struct operation *op, *tmpop;

	op = tmpop = NULL;

	pthread_mutex_lock(&(ts->lock));

	/* Writes are not allowed in read-only mode, they fail early */
	if ((ts->flags & J_RDONLY) && direction == D_WRITE)
		goto error;

	if (count == 0)
		goto error;

	if ((long long) ts->len_w + count > MAX_TSIZE)
		goto error;

	op = malloc(sizeof(struct operation));
	if (op == NULL)
		goto error;

	if (direction == D_WRITE) {
		op->buf = malloc(count);
		if (op->buf == NULL)
			goto error;

		ts->numops_w++;
	} else {
		ts->numops_r++;
	}

	/* add op to the end of the linked list */
	op->next = NULL;
	if (ts->op == NULL) {
		ts->op = op;
		op->prev = NULL;
	} else {
		for (tmpop = ts->op; tmpop->next != NULL; tmpop = tmpop->next)
			;
		tmpop->next = op;
		op->prev = tmpop;
	}

	pthread_mutex_unlock(&(ts->lock));

	op->len = count;
	op->offset = offset;
	op->plen = 0;
	op->pdata = NULL;
	op->locked = 0;
	op->direction = direction;

	if (direction == D_WRITE) {
		memcpy(op->buf, buf, count);

		if (!(ts->flags & J_NOROLLBACK)) {
			/* jtrans_commit() will want to read the current data,
			 * so we tell the kernel about that */
			posix_fadvise(ts->fs->fd, offset, count,
					POSIX_FADV_WILLNEED);
		}
	} else {
		/* this casts the const away, which is ugly but let us have a
		 * common read/write path and avoid useless code repetition
		 * just to handle it */
		op->buf = (void *) buf;

		/* if there are no overlapping writes, jtrans_commit() will
		 * want to read the data from the disk; and if there are we
		 * will already have submitted a request and one more won't
		 * hurt */
		posix_fadvise(ts->fs->fd, offset, count, POSIX_FADV_WILLNEED);
	}

	return 0;

error:
	pthread_mutex_unlock(&(ts->lock));

	if (op && direction == D_WRITE)
		free(op->buf);
	free(op);

	return -1;
}

int jtrans_add_r(struct jtrans *ts, void *buf, size_t count, off_t offset)
{
	return jtrans_add_common(ts, buf, count, offset, D_READ);
}

int jtrans_add_w(struct jtrans *ts, const void *buf, size_t count,
		off_t offset)
{
	return jtrans_add_common(ts, buf, count, offset, D_WRITE);
}


/* Commit a transaction */
ssize_t jtrans_commit(struct jtrans *ts)
{
	ssize_t r, retval = -1;
	struct operation *op;
	struct jlinger *linger;
	jop_t *jop = NULL;
	size_t written = 0;

	pthread_mutex_lock(&(ts->lock));

	/* clear the flags */

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

	return retval;
}

/* Rollback a transaction */
ssize_t jtrans_rollback(struct jtrans *ts)
{
	ssize_t rv;
	struct jtrans *newts;
	struct operation *op, *curop, *lop;

	newts = jtrans_new(ts->fs, 0);
	if (newts == NULL)
		return -1;

	newts->flags = ts->flags;
	newts->numops_r = 0;
	newts->numops_w = 0;
	newts->len_w = 0;

	if (ts->op == NULL || ts->flags & J_NOROLLBACK) {
		rv = -1;
		goto exit;
	}

	/* find the last operation */
	for (op = ts->op; op->next != NULL; op = op->next)
		;

	/* and traverse the list backwards, skipping read operations */
	for ( ; op != NULL; op = op->prev) {
		if (op->direction == D_READ)
			continue;

		/* if we extended the data in the previous transaction, we
		 * should truncate it back */
		/* DANGEROUS: this is one of the main reasons why rollbacking
		 * is dangerous and should only be done with extreme caution:
		 * if for some reason, after the previous transacton, we have
		 * extended the file further, this will cut it back to what it
		 * was; read the docs for more detail */
		if (op->plen < op->len) {
			rv = ftruncate(ts->fs->fd, op->offset + op->plen);
			if (rv != 0)
				goto exit;
		}

		/* manually add the operation to the new transaction */
		curop = malloc(sizeof(struct operation));
		if (curop == NULL) {
			rv = -1;
			goto exit;
		}

		curop->offset = op->offset;
		curop->len = op->plen;
		curop->buf = op->pdata;
		curop->plen = op->plen;
		curop->pdata = op->pdata;
		curop->direction = op->direction;
		curop->locked = 0;

		newts->numops_w++;
		newts->len_w += curop->len;

		/* add the new transaction to the list */
		if (newts->op == NULL) {
			newts->op = curop;
			curop->prev = NULL;
			curop->next = NULL;
		} else {
			for (lop = newts->op; lop->next != NULL; lop = lop->next)
				;
			lop->next = curop;
			curop->prev = lop;
			curop->next = NULL;
		}
	}

	rv = jtrans_commit(newts);

exit:
	/* free the transaction */
	for (curop = newts->op; curop != NULL; curop = curop->next) {
		curop->buf = NULL;
		curop->pdata = NULL;
	}
	jtrans_free(newts);

	return rv;
}


/*
 * Basic operations
 */

/* Open a file */
struct jfs *jopen(const char *name, int flags, int mode, unsigned int jflags)
{
	int jfd, rv;
	unsigned int t;
	char jdir[PATH_MAX], jlockfile[PATH_MAX];
	struct stat sinfo;
	pthread_mutexattr_t attr;
	struct jfs *fs;

	fs = malloc(sizeof(struct jfs));
	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