1990/1104/port/chan.c (diff list | history)

port/chan.c on 1990/0227
1990/0227		#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "errno.h" struct{ Lock; Chan *free; }chanalloc; int incref(Ref *r) {
1990/1104		int x;
1990/0227		lock(r);
1990/1104		x = ++r->ref;
1990/0227		unlock(r);
1990/1104		return x;
1990/0227		} int decref(Ref *r) {
1990/1104		int x;
1990/0227		lock(r);
1990/1104		x = --r->ref;
1990/0227		unlock(r);
1990/1104		return x;
1990/0227		} void chaninit(void) { int i; Chan *c; chanalloc.free = ialloc(conf.nchan*sizeof(Chan), 0); c = chanalloc.free; for(i=0; i<conf.nchan-1; i++,c++){ c->fid = i; c->next = c+1; } c->next = 0; } void chandevreset(void) { int i; for(i=0; i<strlen(devchar); i++) (*devtab[i].reset)(); } void chandevinit(void) { int i; for(i=0; i<strlen(devchar); i++) (*devtab[i].init)(); } Chan* newchan(void) { Chan *c; loop: lock(&chanalloc); if(c = chanalloc.free){ /* assign = */ chanalloc.free = c->next;
1990/0707		c->type = 0; /* if closed before changed, this calls rooterror, a nop */
1990/0227		c->flag = 0; c->ref = 1; unlock(&chanalloc); c->offset = 0; c->mnt = 0; c->stream = 0;
1990/0303		c->mchan = 0; c->mqid = 0;
1990/0227		return c; } unlock(&chanalloc); print("no chans\n"); if(u == 0) panic("newchan"); u->p->state = Wakeme; alarm(1000, wakeme, u->p); sched(); goto loop; } void close(Chan *c) {
1990/0907		if(c->flag & CFREE) panic("close");
1990/0227		if(decref(c) == 0){ if(!waserror()){ (*devtab[c->type].close)(c); poperror(); }
1990/0907		c->flag = CFREE;
1990/0227		lock(&chanalloc); c->next = chanalloc.free; chanalloc.free = c; unlock(&chanalloc); } } int eqchan(Chan *a, Chan *b, long qmask) { if((a->qid^b->qid) & qmask) return 0; if(a->type != b->type) return 0; if(a->dev != b->dev) return 0; return 1; } /* * omnt is locked. return with nmnt locked. */ Mount* mountsplit(Mount *omnt) { Mount *nmnt; nmnt = newmount(); lock(nmnt); nmnt->term = omnt->term; nmnt->mountid = omnt->mountid; nmnt->next = omnt->next; if(nmnt->next)
1990/0603		incref(nmnt->next);
1990/0227		nmnt->c = omnt->c; incref(nmnt->c); omnt->ref--; unlock(omnt); return nmnt; } int mount(Chan *new, Chan *old, int flag) { int i; Mtab *mt, *mz; Mount *mnt, *omnt, *nmnt, *pmnt; Pgrp *pg;
1990/0321		int islast;
1990/0227		if(CHDIR & (old->qid^new->qid)) error(0, Emount); if((old->qid&CHDIR)==0 && (flag&MORDER)!=MREPL) error(0, Emount); mz = 0;
1990/0321		islast = 0; mnt = 0;
1990/0227		pg = u->p->pgrp; lock(pg); if(waserror()){
1990/0321		if(mnt){ mnt->c = 0; /* caller will close new */ closemount(mnt); }
1990/0227		unlock(pg); nexterror(); } /* * Is old already in mount table? */ mt = pg->mtab; for(i=0; i<pg->nmtab; i++,mt++){ if(mt->c==0 && mz==0) mz = mt;
1990/0321		else if(eqchan(mt->c, old, CHDIR|QPATH)){ mz = 0;
1990/0227		goto Found;
1990/0321		}
1990/0227		} if(mz == 0){ if(i == conf.nmtab) error(0, Enomount); mz = &pg->mtab[i];
1990/0321		islast++;
1990/0227		} mz->mnt = 0; mt = mz; Found: new->flag = CMOUNT; if(flag & MCREATE) new->flag |= CCREATE; mnt = newmount(); mnt->c = new; switch(flag & MORDER){ /* * These two always go at head of list */ case MBEFORE: if(mt->mnt == 0) error(0, Enotunion); /* fall through */ case MREPL:
1990/0603		mnt->next = mt->mnt;
1990/0227		mt->mnt = mnt; if((flag&MORDER) == MBEFORE) mnt->term = 0;
1990/0603		else mnt->term = 1;
1990/0227		break; /* * This one never goes at head of list */ case MAFTER: if(mt->mnt == 0) error(0, Enotunion); omnt = mt->mnt; pmnt = 0; while(!omnt->term){ lock(omnt); if(omnt->ref > 1){ omnt = mountsplit(omnt); if(pmnt) pmnt->next = omnt; else mt->mnt = omnt; } unlock(omnt); nmnt = omnt->next; if(nmnt == 0) panic("MAFTER term"); pmnt = omnt; omnt = nmnt; } mnt->next = omnt->next; omnt->next = mnt; mnt->term = 1; omnt->term = 0; break; } incref(new);
1990/0321		if(mz){ mz->c = old;
1990/0227		incref(old);
1990/0321		} if(islast) pg->nmtab++;
1990/0227		unlock(pg); poperror(); return mnt->mountid; } Chan* clone(Chan *c, Chan *nc) { return (*devtab[c->type].clone)(c, nc); } Chan* domount(Chan *c) { int i; ulong mntid; Mtab *mt; Mount *mnt; Pgrp *pg; Chan *nc, *mc; pg = u->p->pgrp; /* * Is c in in mount table? */ mt = pg->mtab; for(i=0; i<pg->nmtab; i++,mt++) if(mt->c && eqchan(mt->c, c, CHDIR|QPATH)) goto Found; /* * No; c is unaffected */ return c; /* * Yes; move c through table */ Found: lock(pg); if(!eqchan(mt->c, c, CHDIR|QPATH)){ /* table changed underfoot */
1990/0321		pprint("domount: changed underfoot?\n");
1990/0227		unlock(pg); return c; } mnt = mt->mnt; mntid = mnt->mountid; mc = mnt->c; incref(mc); unlock(pg); if(waserror()){ close(mc); nexterror(); } nc = clone(mc, 0); close(mc); poperror(); close(c); nc->mnt = mnt; nc->mountid = mntid; return nc; } Chan* walk(Chan *ac, char *name, int domnt) { Mount *mnt; int first = 1; Chan *c = ac; Chan *nc, *mc; Pgrp *pg = u->p->pgrp; /* * name may be empty if the file name is "/", "#c" etc. */ Again: if(name[0] && (*devtab[c->type].walk)(c, name)==0){ if(!(c->flag&CMOUNT)) goto Notfound; mnt = c->mnt; if(mnt == 0) panic("walk"); lock(pg); if(mnt->term){ unlock(pg); goto Notfound; } if(c->mountid != mnt->mountid){
1990/0820		pprint("walk: changed underfoot? '%s'\n", name);
1990/0227		unlock(pg); goto Notfound; } mnt = mnt->next; mc = mnt->c; incref(mc); unlock(pg); if(waserror()){ close(mc); nexterror(); } if(mnt == 0) panic("walk 1"); nc = clone(mc, 0); close(mc); poperror(); if(!first) close(c); nc->mnt = mnt;
1990/0321		nc->mountid = mnt->mountid;
1990/0227		c = nc; first = 0; goto Again; } if(name[0]) /* walk succeeded */ c->flag &= ~CMOUNT;
1990/0914		if(domnt){ if(waserror()){ if(!first) close(c); return 0; } c = domount(c); poperror(); }
1990/0227		if(!first) close(ac);
1990/0914
1990/0227		return c; Notfound: if(!first) close(c); return 0; } /* * c is a mounted non-creatable directory. find a creatable one. */ Chan* createdir(Chan *c) { Mount *mnt; Pgrp *pg = u->p->pgrp; Chan *mc, *nc; lock(pg); if(waserror()){ unlock(pg); nexterror(); } mnt = c->mnt; if(c->mountid != mnt->mountid){
1990/0321		pprint("createdir: changed underfoot?\n");
1990/0227		error(0, Enocreate); } do{ if(mnt->term) error(0, Enocreate); mnt = mnt->next; }while(!(mnt->c->flag&CCREATE)); mc = mnt->c; incref(mc); unlock(pg); if(waserror()){ close(mc); nexterror(); } nc = clone(mc, 0); poperror(); close(c); close(mc); nc->mnt = mnt; return nc; }
1990/0914		void saveregisters(void) { }
1990/0227		/* * Turn a name into a channel. * &name[0] is known to be a valid address. It may be a kernel address. */ Chan* namec(char *name, int amode, int omode, ulong perm) { Chan *c, *nc; int t;
1990/0820		int mntok, isdot;
1990/0821		char *p; char *elem;
1990/0227		if(name[0] == 0) error(0, Enonexist);
1990/0821		/* * Make sure all of name is o.k. first byte is validated * externally so if it's a kernel address we know it's o.k. */ if(!((ulong)name & KZERO)){ p = name; t = BY2PG-((ulong)p&(BY2PG-1)); while(vmemchr(p, 0, t) == 0){ p += t; t = BY2PG; } } elem = u->elem;
1990/0227		mntok = 1;
1990/0820		isdot = 0;
1990/0227		if(name[0] == '/'){ c = clone(u->slash, 0); /* * Skip leading slashes. */ name = skipslash(name); }else if(name[0] == '#'){ mntok = 0;
1990/1009		if(name[1]=='M')
1990/0227		error(0, Enonexist); t = devno(name[1], 1); if(t == -1) error(0, Ebadsharp); name += 2; if(*name == '/'){ name = skipslash(name); elem[0]=0; }else name = nextelem(name, elem); c = (*devtab[t].attach)(elem);
1990/0820		}else{
1990/0227		c = clone(u->dot, 0);
1990/0820		name = skipslash(name); /* eat leading ./ */ if(*name == 0) isdot = 1; }
1990/0227		if(waserror()){ close(c); nexterror(); } name = nextelem(name, elem);
1990/0820		if(mntok && !isdot) if(!(amode==Amount && elem[0]==0)) /* don't domount on slash */
1990/0227		c = domount(c); /* see case Atodir below */ /* * How to treat the last element of the name depends on the operation. * Therefore do all but the last element by the easy algorithm. */ while(*name){ if((nc=walk(c, elem, mntok)) == 0) error(0, Enonexist); c = nc; name = nextelem(name, elem); }
1990/0820
1990/0227		/* * Last element; act according to type of access. */ switch(amode){ case Aaccess:
1990/0820		if(isdot) c = domount(c); else{ if((nc=walk(c, elem, mntok)) == 0) error(0, Enonexist); c = nc; }
1990/0227		break; case Atodir: /* * Directories (e.g. for cd) are left before the mount point, * so one may mount on / or . and see the effect. */ if((nc=walk(c, elem, 0)) == 0) error(0, Enonexist); c = nc; if(!(c->qid & CHDIR)) error(0, Enotdir); break; case Aopen:
1990/0820		if(isdot) c = domount(c); else{ if((nc=walk(c, elem, mntok)) == 0) error(0, Enonexist); c = nc; }
1990/0227		Open:
1990/0914		saveregisters(); /* else error() in open has wrong value of c saved */
1990/0227		c = (*devtab[c->type].open)(c, omode);
1990/08141		if(omode & OCEXEC) c->flag |= CCEXEC;
1990/0227		break; case Amount: /* * When mounting on an already mounted upon directory, one wants * the second mount to be attached to the original directory, not * the replacement. */ if((nc=walk(c, elem, 0)) == 0) error(0, Enonexist); c = nc; break; case Acreate:
1990/0820		if(isdot) error(0, Eisdir);
1990/0227		if((nc=walk(c, elem, 1)) != 0){ c = nc; omode |= OTRUNC; goto Open; } if((c->flag&(CMOUNT|CCREATE)) == CMOUNT) c = createdir(c); (*devtab[c->type].create)(c, elem, omode, perm);
1990/08141		if(omode & OCEXEC) c->flag |= CCEXEC;
1990/0227		break; default: panic("unknown namec access %d\n", amode); } poperror(); return c; } /* * name[0] is addressable. */ char* skipslash(char *name) {
1990/0820		Again:
1990/0821		while(*name == '/')
1990/0227		name++;
1990/0821		if(*name=='.' && (name[1]==0 || name[1]=='/')){ name++; goto Again;
1990/0820		}
1990/0227		return name; } char isfrog[]={ /*NUL*/ 1, 1, 1, 1, 1, 1, 1, 1, /*BKS*/ 1, 1, 1, 1, 1, 1, 1, 1, /*DLE*/ 1, 1, 1, 1, 1, 1, 1, 1, /*CAN*/ 1, 1, 1, 1, 1, 1, 1, 1, [' '] 1, ['/'] 1, [0x7f] 1, }; /* * name[0] should not be a slash. * Advance name to next element in path, copying current element into elem. * Return pointer to next element, skipping slashes. */ char* nextelem(char *name, char *elem) { int i, user, c; char *end, *e; if(*name == '/') error(0, Efilename);
1990/0821		end = memchr(name, 0, NAMELEN);
1990/0227		if(end == 0){
1990/0821		end = memchr(name, '/', NAMELEN);
1990/0227		if(end == 0) error(0, Efilename); }else{ e = memchr(name, '/', end-name); if(e) end = e; } while(name < end){ c = *name++; if((c&0x80) || isfrog[c]) error(0, Ebadchar); *elem++ = c; } *elem = 0; return skipslash(name); } void isdir(Chan *c) { if(c->qid & CHDIR) return; error(0, Enotdir); }