xfs: allow parent directory scans to be interrupted with fatal signals

struct xchk_parent_ctx {

	struct dir_context	dc;

	struct xfs_scrub	*sc;

	xfs_ino_t		ino;

	xfs_nlink_t		nlink;

	bool			cancelled;

};

/* Look for a single entry in a directory pointing to an inode. */

	unsigned		type)

{

	struct xchk_parent_ctx	*spc;

	int			error = 0;

	spc = container_of(dc, struct xchk_parent_ctx, dc);

	if (spc->ino == ino)

		spc->nlink++;

	return 0;

	/*

	 * If we're facing a fatal signal, bail out.  Store the cancellation

	 * status separately because the VFS readdir code squashes error codes

	 * into short directory reads.

	 */

	if (xchk_should_terminate(spc->sc, &error))

		spc->cancelled = true;

	return error;

}

/* Count the number of dentries in the parent dir that point to this inode. */

{

	struct xchk_parent_ctx	spc = {

		.dc.actor	= xchk_parent_actor,

		.dc.pos = 0,

		.ino		= sc->ip->i_ino,

		.nlink = 0,

		.sc		= sc,

	};

	size_t			bufsize;

	loff_t			oldpos;

		error = xfs_readdir(sc->tp, parent, &spc.dc, bufsize);

		if (error)

			goto out;

		if (spc.cancelled) {

			error = -EAGAIN;

			goto out;

		}

		if (oldpos == spc.dc.pos)

			break;

		oldpos = spc.dc.pos;