/* * Clumsy hack to be able to create mountable files in /srv that * correspond to certain directories, kind of like an in-kernel exportfs: * *	fd = open("#~/mntloop", ORDWR); *	fprint(fd, "/mnt/foo"); *	sfd = create("/srv/foo", ORDWR, 0666); *	fprint(sfd, "%d", fd); *	close(sfd); *	close(fd); * * is almost equivalent to * *	srvfs /mnt/foo foo * * but avoids the translation to 9P and back when you later * mount /srv/foo.  There are a few inaccuracies compared * to what srvfs does: * * 	binds and mounts inside the tree rooted at /mnt/foo *	in the original name space are not present when a *	different name space mounts /srv/foo. * *	if the exported tree is a kernel device, then the kernel *	device will use the name of the user who mounted /srv/foo *	(not the name of the user who exported it) for permissions checks. * * This is all so that we can provide a /srv/boot file even if the * root is from a kernel device.  It's not intended for general use. */ #include	"u.h"#include	"lib.h"#include	"mem.h"#include	"dat.h"#include	"fns.h"#include	"error.h" enum {	Qdir = 0,	Qmntloop = 1}; static Chan*mntloopattach(char *spec){	Chan *c;	c = devattach('~', spec);	mkqid(&c->qid, Qdir, 0, QTDIR);	return c;} static Dirtab dir[] = {	"#~",	{Qdir, 0, QTDIR},	0,	DMDIR|0555,	"mntloop",	{Qmntloop, 0, 0},	0,	0666,}; static intmntloopgen(Chan *c, char *name, Dirtab *tab, int ntab, int s, Dir *dp){	if(s == DEVDOTDOT){		devdir(c, c->qid, "#~", 0, eve, DMDIR|0555, dp);		return 1;	}		return devgen(c, name, dir, nelem(dir), s, dp);} static Walkqid*mntloopwalk(Chan *c, Chan *nc, char **name, int nname){	return devwalk(c, nc, name, nname, nil, 0, mntloopgen);} static intmntloopstat(Chan *c, uchar *dp, int n){	return devstat(c, dp, n, nil, 0, mntloopgen);} static Chan*mntloopopen(Chan *c, int omode){	return devopen(c, omode, nil, 0, mntloopgen);} static voidmntloopclose(Chan *c){	if(c->aux)		cclose(c->aux);} static longmntloopread(Chan *c, void *va, long n, vlong off){	error(Egreg);	return -1;} static longmntloopwrite(Chan *c, void *va, long n, vlong off){	char *p;	Chan *nc; 	if(c->aux || off != 0 || n >= BY2PG)		error(Ebadarg); 	p = smalloc(n+1);	memmove(p, va, n);	p[n] = 0;	if(waserror()){		free(p);		nexterror();	}	nc = namec(p, Atodir, 0, 0);	free(p);	poperror();	lock(&c->ref.lk);	if(c->aux){		unlock(&c->ref.lk);		cclose(nc);		error(Ebadarg);	}	c->aux = nc;	unlock(&c->ref.lk);	return n;} Dev mntloopdevtab = {	/* known to mntattach */	'~',	"mntloop",		devreset,	devinit,	devshutdown,	mntloopattach,	mntloopwalk,	mntloopstat,	mntloopopen,	devcreate,	mntloopclose,	mntloopread,	devbread,	mntloopwrite,	devbwrite,	devremove,	devwstat,};