/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include <u.h>#include <libc.h>#include <fcall.h>#include <thread.h>#include <9p.h>#include "dat.h"#include "fns.h"  static Xfs	*xhead;static Xfile *freelist;static Lock	xlock, freelock; int	client; Xfs *getxfs(char *name){	int fd;	Dir *dir;	Xfs *xf, *fxf; 	if(name==0 || name[0]==0)		name = deffile;	if(name == 0){		errno = Enofilsys;		return 0;	}	fd = open(name, rdonly ? OREAD : ORDWR);	if(fd < 0){		errno = Enonexist;		return 0;	}	if((dir = dirfstat(fd)) == 0){		errno = Eio;		close(fd);		return 0;	}	lock(&xlock);	for(fxf=0, xf=xhead; xf; xf=xf->next){		if(xf->ref == 0){			if(fxf == 0)				fxf = xf;			continue;		}		if(xf->qid.path != dir->qid.path || xf->qid.vers != dir->qid.vers)			continue;		if(strcmp(xf->name, name) != 0 || xf->dev < 0)			continue;		chat("incref \"%s\", dev=%d...", xf->name, xf->dev);		++xf->ref;		unlock(&xlock);		close(fd);		free(dir);		return xf;	}	if(fxf==0){		fxf = malloc(sizeof(Xfs));		if(fxf==0){			unlock(&xlock);			close(fd);			free(dir);			errno = Enomem;			return 0;		}		fxf->next = xhead;		xhead = fxf;	}	chat("alloc \"%s\", dev=%d...", name, fd);	fxf->name = strdup(name);	fxf->ref = 1;	fxf->qid = dir->qid;	fxf->dev = fd;	fxf->fmt = 0;	fxf->ptr = 0;	free(dir);	if( ext2fs(fxf)<0 ){ 		xhead = fxf->next;		free(fxf);		unlock(&xlock);		return 0;	}	unlock(&xlock);	return fxf;} voidrefxfs(Xfs *xf, int delta){	lock(&xlock);	xf->ref += delta;	if(xf->ref == 0){		/*mchat("free \"%s\", dev=%d...", xf->name, xf->dev);		dumpbuf();*/		CleanSuper(xf);		syncbuf();		free(xf->name);		purgebuf(xf);		if(xf->dev >= 0){			close(xf->dev);			xf->dev = -1;		}	}	unlock(&xlock);} Xfile *xfile(Fid *fid, int flag){	Xfile *f; 	f = (Xfile*)fid->aux;	switch(flag){	default:		panic("xfile");	case Asis:		return (f && f->xf && f->xf->dev < 0) ? 0 : f;	case Clean:		if (f) chat("Clean and fid->aux already exists\n");		break;	case Clunk:		if(f){			clean(f);			lock(&freelock);			f->next = freelist;			freelist = f;			unlock(&freelock);			fid->aux = 0;		}		return 0;	}	if(f)		return clean(f);	lock(&freelock);	if(f = freelist){	/* assign = */		freelist = f->next;		unlock(&freelock);	} else {		unlock(&freelock);		f = malloc(sizeof(Xfile));	}	fid->aux = f;	f->fid = fid->fid;	f->client = client;	f->xf = 0;	f->ptr = 0;	f->root = 0;	return f;}Xfile *clean(Xfile *f){	if(f->xf && f->root){		refxfs(f->xf, -1);		f->xf = 0;	}	f->xf = 0;	f->root = 0;	f->dirindex = 0;	return f;}