shithub: unionfs

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Rewrite and simplify the whole lot

Directory reads are done using union binds which allows
removal of a bunch of code.
Fid state management is simplified. Instead of refcounting
clones etc. we just copy everything, which makes things
easier to reason about and removes the need to introduce
locking for FILE structs.
Various other minor improvements are included as well.

--- a/unionfs.c

+++ b/unionfs.c

@@ -5,316 +5,322 @@

 #include <9p.h>

 #include "unionfs.h"

+Srv thefs;

 Branch *branch;

 usize nbranch;

-F *root;

-Srv thefs;

+QLock mtptlock;

+Mtpt *mtpt;

-F*

-filenew(Dir *d)

+Mtpt*

+mtptgrab(void)

 {

-	F *f;

+	static int mtptnext = 0;

+	Mtpt *m;

-	f = emalloc(sizeof(*f));

-	f->ref = 1;

-	f->Dir = *d;

-	f->qid = qencode(d);

-	f->name = estrdup(d->name);

-	f->uid = estrdup(d->uid);

-	f->gid = estrdup(d->gid);

-	f->muid = estrdup(d->muid);

-	return f;

+	qlock(&mtptlock);

+	if(mtpt == nil){

+		mtpt = emalloc(sizeof(Mtpt));

+		mtpt->path = smprint("/mnt/mtpt%d", mtptnext++);

+	}

+	m = mtpt;

+	mtpt = m->next;

+	qunlock(&mtptlock);

+	unmount(nil, m->path);

+	return m;

 }

 void

-filefree(F *f)

+mtptfree(Mtpt *m)

 {

-	if(f == root)

-		return;

-	if(decref(f))

-		return;

-	free(f->name);

-	free(f->uid);

-	free(f->gid);

-	free(f->muid);

-	free(f->path);

-	free(f->fspath);

-	free(f);

+	qlock(&mtptlock);

+	m->next = mtpt;

+	mtpt = m;

+	qunlock(&mtptlock);

 }

-uint

-fthash(char *s)

+FILE*

+filenew(void)

 {

-	uint h;

-	for(h = 0; *s; s++)

-		h = *s + 31*h;

-	return h % Nftab;

-}

+	FILE *f;

-Ftab*

-ftnew(void)

-{

-	int i;

-	Ftab *ft, *p;

-	

-	ft = emalloc(Nftab*sizeof(Ftab));

-	for(i = 0; i < Nftab; i++){

-		p = &ft[i];

-		p->sz = Nftlist;

-		p->l = emalloc(p->sz*sizeof(*p->l));

-	}

-	return ft;

+	f = emalloc(sizeof(FILE));

+	f->fd = -1;

+	return f;

 }

 void

-ftfree(Ftab *ft)

+filefree(FILE *f)

 {

-	int i, j;

-	Ftab *p;

-	

-	for(i = 0; i < Nftab; i++){

-		p = &ft[i];

-		for(j = 0; j < p->n; j++)

-			filefree(p->l[j]);

-		free(p->l);

-	}

-	free(ft);

+	if(f == nil)

+		return;

+	if(f->name) free(f->name);

+	if(f->uid) free(f->uid);

+	if(f->gid) free(f->gid);

+	if(f->muid) free(f->muid);

+	if(f->path) free(f->path);

+	if(f->realpath) free(f->realpath);

+	if(f->fd != -1) close(f->fd);

+	if(f->dirs) free(f->dirs);

+	if(f->mtpt) mtptfree(f->mtpt);

+	free(f);

 }

 void

-ftadd(Ftab *ft, F *f)

+dircopy(Dir *a, Dir *b)

 {

-	Ftab *p;

-	

-	p = &ft[fthash(f->name)];

-	if(p->n == p->sz){

-		p->sz *= 2;

-		p->l = erealloc(p->l, p->sz*sizeof(*p->l));

-	}

-	p->l[p->n++] = f;

+	a->type = b->type;

+	a->dev = b->dev;

+	a->qid = b->qid;

+	a->mode = b->mode;

+	a->mtime = b->mtime;

+	a->atime = b->atime;

+	a->name = estrdup(b->name);

+	a->uid = estrdup(b->uid);

+	a->gid = estrdup(b->gid);

+	a->muid = estrdup(b->muid);

 }

-int

-fthas(Ftab *ft, char *name)

+void

+fsattach(Req *r)

 {

-	int i;

-	Ftab *p;

+	FILE *f;

+	char *user;

-	p = &ft[fthash(name)];

-	for(i = 0; i < p->n; i++)

-		if(strcmp(p->l[i]->name, name) == 0)

-			return 1;

-	return 0;

-}

-

-F*

-ftidx(Ftab *ft, long i)

-{

-	long y;

-	Ftab *p;

+	f = filenew();

+	f->name = estrdup("/");

+	f->mode = 0777|DMDIR;

+	user = getuser();

+	f->uid = estrdup(user);

+	f->gid = estrdup(user);

+	f->muid = estrdup(user);

+	f->mtime = f->atime = time(0);

+	f->type = 0xFFFFFFFF;

+	f->dev = 0xFFFFFFFFFFFFFFFF;

+	f->qid = (Qid){0, 0, QTDIR};

+	f->qid = qencode(f);

+	f->path = estrdup(f->name);

+	f->realpath = estrdup(f->name);

-	for(y = 0; y < Nftab; y++){

-		p = &ft[y];

-		if(p->n == 0)

-			continue;

-		if(i >= p->n){

-			i -= p->n;

-			continue;

-		}

-		return p->l[i];

-	}

-	return nil;

+	r->fid->aux = f;

+	r->fid->qid = f->qid;

+	r->ofcall.qid = f->qid;

+	respond(r, nil);

 }

-Fstate*

-fstatenew(F *f)

+char*

+mkpath(char *a0, ...)

 {

-	Fstate *st;

-	

-	st = emalloc(sizeof(*st));

-	st->fd = -1;

-	st->file = (F*)copyref(f);

-	return st;

-}

+	va_list args;

+	int i;

+	char *a;

+	char *ap[] = {a0, "", ""};

-void

-fstatefree(Fstate *st)

-{

-	if(st->file)

-		filefree(st->file);

-	if(st->ftab)

-		ftfree(st->ftab);

-	close(st->fd);

-	free(st);

-}

+	va_start(args, a0);

+	for(i = 1; (a = va_arg(args, char*)) != nil && i < 3; i++)

+		ap[i] = a;

+	va_end(args);

+	if((a = smprint("%s/%s/%s", ap[0], ap[1], ap[2])) == nil)

+		sysfatal("smprint: %r");

-void

-initroot(void)

-{

-	char *user;

-	Dir d;

-	

-	nulldir(&d);

-	d.qid = (Qid){0, 0, QTDIR};

-	d.name = ".";

-	d.mode = 0777|DMDIR;

-	user = getuser();

-	d.uid = user;

-	d.gid = user;

-	d.muid = user;

-	d.mtime = time(0);

-	d.atime = time(0);

-	d.length = 0;

-	

-	root = filenew(&d);

-	root->fspath = estrdup(d.name);

-	root->path = estrdup(d.name);

+	return cleanname(a);

 }

-void

-fsattach(Req *r)

+char*

+clone(Fid *fid, Fid *newfid, void*)

 {

-	Fstate *st;

+	FILE *f;

+	FILE *parent = fid->aux;

-	st = fstatenew(root);

-	r->fid->aux = st;

-	r->fid->qid = root->qid;

-	r->ofcall.qid = root->qid;

-	respond(r, nil);

+	f = filenew();

+	dircopy(f, parent);

+	f->qid = parent->qid;

+	f->path = estrdup(parent->path);

+	f->realpath = estrdup(parent->realpath);

+	newfid->aux = f;

+	return nil;

 }

-F*

-filewalk(F *p, char *name)

+char*

+walkto(Fid *fid, char *name, void *aux)

 {

-	char *path, *np;

+	Req *r;

 	Dir *d;

-	F *f;

+	FILE *f;

+	char *path, *realpath;

+	int i, *nwalk;

-	np = mkpath(p->fspath, name, nil);

-	for(int i = 0; i < nbranch; i++){

-		path = mkpath(branch[i].root, np, nil);

-		if((d = dirstat(path)) == nil){

-			free(path);

+	r = aux;

+	f = fid->aux;

+	nwalk = r->aux;

+	path = mkpath(f->path, name, nil);

+	for(i = 0; i < nbranch; i++){

+		realpath = mkpath(branch[i].root, path, nil);

+		if((d = dirstat(realpath)) == nil)

 			continue;

+		if(*nwalk == r->ifcall.nwname){

+			filefree(f);

+			f = filenew();

+			dircopy(f, d);

+		}else{

+			free(f->path);

+			free(f->realpath);

 		}

-		f = filenew(d);

+		f->qid = qencode(d);

 		free(d);

-		f->fspath = np;

 		f->path = path;

-		filefree(p);

-		return f;

+		f->realpath = realpath;

+		fid->aux = f;

+		fid->qid = f->qid;

+		*nwalk = *nwalk + 1;

+		return nil;

 	}

-	free(np);

-	return nil;

+	return "not found";

 }

-char*

-walk1(Fid *fid, char *name, void *)

+void

+fswalk(Req *r)

 {

-	F *p, *f;

-	Fstate *st;

+	int nwalk;

-	st = fid->aux;

-	p = st->file;

-	if((f = filewalk(p, name)) == nil)

-		return "not found";

-	st->file = f;

-

-	fid->qid = f->qid;

-	return nil;

+	nwalk = 1;

+	r->aux = &nwalk;

+	walkandclone(r, walkto, clone, r);

 }

-char*

-clone(Fid *old, Fid *new, void*)

-{

-	Fstate *fs;

-

-	fs = old->aux;

-	new->aux = fstatenew(fs->file);

-	return nil;

-}

-

 void

 destroyfid(Fid *fid)

 {

 	if(fid->aux)

-		fstatefree(fid->aux);

+		filefree(fid->aux);

 	fid->aux = nil;

 }

 void

-fswalk(Req *r)

+fsopen(Req *r)

 {

+	Fcall *T, *R;

+	FILE *f;

+	usize i;

+	char *path;

+	Dir *d;

+	

+	T = &r->ifcall;

+	R = &r->ofcall;

+	f = r->fid->aux;

+

 	srvrelease(&thefs);

-	walkandclone(r, walk1, clone, nil);

+	if(f->mode & DMDIR){

+		f->mtpt = mtptgrab();

+		for(i = 0; i < nbranch; i++){

+			path = mkpath(branch[i].root, f->path, nil);

+			if((d = dirstat(path)) != nil){

+				if(d->mode & DMDIR)

+				if(bind(path, f->mtpt->path, MAFTER) == -1)

+					sysfatal("bind: %r");

+				free(d);

+			}

+			free(path);

+		}

+		if((f->fd = open(f->mtpt->path, T->mode)) < 0){

+			responderror(r);

+			goto done;

+		}

+	}else{

+		if((f->fd = open(f->realpath, T->mode)) < 0){

+			responderror(r);

+			goto done;

+		}

+	}

+	R->iounit = iounit(f->fd);

+	respond(r, nil);

+done:

 	srvacquire(&thefs);

 }

-Ftab*

-filereaddir(F *p)

+void

+fsremove(Req *r)

 {

-	int fd;

-	long n;

-	Dir *dir, *d;

-	char *path;

-	F *f;

-	Ftab *ft;

+	FILE *f;

+	

+	f = r->fid->aux;

+	srvrelease(&thefs);

+	if(remove(f->path) < 0){

+		responderror(r);

+		goto done;

+	}

+	respond(r, nil);

+done:

+	srvacquire(&thefs);

+}

-	ft = ftnew();

-	for(usize i = 0; i < nbranch; i++){

-		path = mkpath(branch[i].root, p->fspath, nil);

-		if((d = dirstat(path)) == nil){

-		err:

-			free(path);

-			continue;

+int

+dirgen(int i, Dir *d, void *aux)

+{

+	FILE *f = aux;

+	

+	if(i == 0){

+		if(f->dirs){

+			free(f->dirs);

+			f->dirs = nil;

+			f->ndirs = 0;

 		}

-		free(d);

-		if((fd = open(path, OREAD)) < 0)

-			goto err;

-		free(path);

-		while((n = dirread(fd, &dir)) > 0){

-			for(usize j = 0; j < n; j++){

-				if(i > 0 && fthas(ft, dir[j].name))

-					continue;

-				f = filenew(&dir[j]);

-				ftadd(ft, f);

-			}

-			free(dir);

-		}

-		if(n < 0)

-			fprint(2, "dirread: %r\n");

-		close(fd);

+		f->ndirs = dirreadall(f->fd, &f->dirs);

+		if(f->ndirs == -1)

+			sysfatal("dirreadall: %r");

 	}

-	return ft;

+	if(f->ndirs == i)

+		return -1;

+	dircopy(d, &f->dirs[i]);

+	d->qid = qencode(d);

+	return 0;

 }

 void

-fsopen(Req *r)

+fsread(Req *r)

 {

+	long n;

 	Fcall *T, *R;

-	Fstate *st;

-	F *f;

+	FILE *f;

 	T = &r->ifcall;

 	R = &r->ofcall;

-	st = r->fid->aux;

-	f = st->file;

+	f = r->fid->aux;

 	srvrelease(&thefs);

-	if(f->mode&DMDIR)

-		st->ftab = filereaddir(f);

-	else{

-		if((st->fd = open(f->path, T->mode)) < 0){

+	if(f->mode&DMDIR){

+		dirread9p(r, dirgen, f);

+	}else{

+		if((n = pread(f->fd, R->data, T->count, T->offset)) < 0){

 			responderror(r);

-			srvacquire(&thefs);

-			return;

+			goto done;

 		}

-		R->iounit = iounit(st->fd);

+		r->ofcall.count = n;

 	}

 	respond(r, nil);

+done:

 	srvacquire(&thefs);

 }

+void

+fswrite(Req *r)

+{

+	Fcall *T, *R;

+	FILE *f;

+	

+	T = &r->ifcall;

+	R = &r->ofcall;

+	f = r->fid->aux;

+	

+	srvrelease(&thefs);

+	if((R->count = pwrite(f->fd, T->data, T->count, T->offset)) != T->count){

+		responderror(r);

+		goto done;

+	}

+	respond(r, nil);

+done:

+	srvacquire(&thefs);

+}

+

 int

 mkdirp(char *path)

 {

@@ -351,155 +357,61 @@

 void

 fscreate(Req *r)

 {

-	char *path, *npath;

+	char *path, *realpath;

 	usize i;

 	Dir *d;

 	Fcall *T, *R;

-	Fstate *st;

-	F *f, *nf;

+	FILE *parent, *f;

+	int fd;

 	T = &r->ifcall;

 	R = &r->ofcall;

-	st = r->fid->aux;

-	f = st->file;

+	parent = r->fid->aux;

 	srvrelease(&thefs);

 	for(i = 0; i < nbranch; i++)

 		if(branch[i].create == 1)

 			break;

-	path = mkpath(branch[i].root, f->fspath, nil);

+	path = mkpath(branch[i].root, parent->path, nil);

 	if(mkdirp(path) < 0){

 		responderror(r);

-		srvacquire(&thefs);

-		return;

+		goto done;

 	}

-	npath = mkpath(path, T->name, nil);

+	realpath = mkpath(path, T->name, nil);

 	free(path);

-	st = emalloc(sizeof(*st));

-	if((st->fd = create(npath, T->mode, T->perm)) < 0){

+	if((fd = create(realpath, T->mode, T->perm)) < 0){

+		free(realpath);

 		responderror(r);

-		srvacquire(&thefs);

-		return;

+		goto done;

 	}

-	if((d = dirfstat(st->fd)) == nil){

-		fstatefree(st);

+	if((d = dirfstat(fd)) == nil){

+		free(realpath);

 		responderror(r);

-		srvacquire(&thefs);

-		return;

+		goto done;

 	}

-	nf = filenew(d);

+	f = filenew();

+	dircopy(f, d);

+	f->fd = fd;

+	f->qid = qencode(d);

+	f->path = mkpath(parent->path, T->name, nil);

+	f->realpath = realpath;

 	free(d);

-	nf->path = npath;

-	nf->fspath = estrdup(f->fspath);

-	st->file = nf;

+	filefree(parent);

-	r->fid->aux = st;

-	r->fid->qid = nf->qid;

-	R->qid = nf->qid;

+	r->fid->aux = f;

+	R->qid = f->qid;

 	respond(r, nil);

+done:

 	srvacquire(&thefs);

 }

-void

-fsremove(Req *r)

-{

-	Fstate *st;

-	F *f;

-	

-	st = r->fid->aux;

-	f = st->file;

-	srvrelease(&thefs);

-	if(remove(f->path) < 0){

-		responderror(r);

-		srvacquire(&thefs);

-		return;

-	}

-	respond(r, nil);

-	srvacquire(&thefs);

-}

 void

-dirfill(Dir *dir, F *f)

-{

-	*dir = f->Dir;

-	dir->qid = f->qid;

-	dir->name = estrdup(f->name);

-	dir->uid = estrdup(f->uid);

-	dir->gid = estrdup(f->gid);

-	dir->muid = estrdup(f->muid);

-}

-

-int

-dirgen(int i, Dir *dir, void *aux)

-{

-	Fstate *fs;

-	F *f;

-	

-	fs = aux;

-	f = ftidx(fs->ftab, i);

-	if(f == nil)

-		return -1;

-	dirfill(dir, f);

-	return 0;

-}

-

-void

-fsread(Req *r)

-{

-	long n;

-	Fcall *T, *R;

-	F *f;

-	Fstate *st;

-	

-	T = &r->ifcall;

-	R = &r->ofcall;

-	st = r->fid->aux;

-	f = st->file;

-

-	srvrelease(&thefs);

-	if(f->mode&DMDIR){

-		dirread9p(r, dirgen, st);

-		respond(r, nil);

-		srvacquire(&thefs);

-		return;

-	}

-	if((n = pread(st->fd, R->data, T->count, T->offset)) < 0){

-		responderror(r);

-		srvacquire(&thefs);

-		return;

-	}

-	r->ofcall.count = n;

-	respond(r, nil);

-	srvacquire(&thefs);

-}

-

-void

-fswrite(Req *r)

-{

-	Fcall *T, *R;

-	Fstate *fs;

-	

-	T = &r->ifcall;

-	R = &r->ofcall;

-	fs = r->fid->aux;

-	

-	srvrelease(&thefs);

-	if((R->count = pwrite(fs->fd, T->data, T->count, T->offset)) != T->count){

-		responderror(r);

-		srvacquire(&thefs);

-		return;

-	}

-	respond(r, nil);

-	srvacquire(&thefs);

-}

-

-void

 fsstat(Req *r)

 {

-	Fstate *st;

+	FILE *f = r->fid->aux;

-	st = r->fid->aux;

-	dirfill(&r->d, st->file);

+	dircopy(&r->d, f);

 	respond(r, nil);

 }

@@ -506,19 +418,15 @@

 void

 fswstat(Req *r)

 {

-	Fstate *st;

-	F *f;

+	FILE *f = r->fid->aux;

-	st = r->fid->aux;

-	f = st->file;

-	

 	srvrelease(&thefs);

-	if(dirwstat(f->path, &r->d) < 0){

+	if(dirwstat(f->realpath, &r->d) < 0){

 		responderror(r);

-		srvacquire(&thefs);

-		return;

+		goto done;

 	}

 	respond(r, nil);

+done:

 	srvacquire(&thefs);

 }

@@ -539,13 +447,13 @@

 main(int argc, char *argv[])

 {

 	int c, i, mflag, stdio;

-	char *mtpt, *srvname, *path, *p;

+	char *mountat, *srvname, *path, *p;

 	Dir *d;

 	Branch *b;

 	c = 0;

 	mflag = MREPL|MCREATE;

-	mtpt = nil;

+	mountat = nil;

 	srvname = nil;

 	stdio = 0;

 	ARGBEGIN{

@@ -565,7 +473,7 @@

 		chatty9p++;

 		break;

 	case 'm':

-		mtpt = EARGF(usage());

+		mountat = EARGF(usage());

 		break;

 	case 's':

 		srvname = EARGF(usage());

@@ -578,8 +486,8 @@

 	}ARGEND;

 	if(argc < 1)

 		usage();

-	if((mtpt || srvname) == 0)

-		mtpt = "/mnt/union";

+	if((mountat || srvname) == 0)

+		mountat = "/mnt/union";

 	nbranch = argc;

 	branch = b = emalloc(nbranch * sizeof(Branch));

 	for(i = 0; i < argc; i++){

@@ -596,7 +504,7 @@

 			continue;

 		}

 		free(d);

-		if(mtpt && strcmp(path, mtpt) == 0){

+		if(mountat && strcmp(path, mountat) == 0){

 			p = pivot(path);

 			free(path);

 			path = p;

@@ -620,9 +528,8 @@

 	thefs.stat = fsstat;

 	thefs.wstat = fswstat;

 	thefs.destroyfid = destroyfid;

-	initroot();

 	if(stdio == 0){

-		postmountsrv(&thefs, srvname, mtpt, mflag);

+		postmountsrv(&thefs, srvname, mountat, mflag);

 		exits(nil);

 	}

 	thefs.infd = 0;

--- a/unionfs.h

+++ b/unionfs.h

@@ -1,12 +1,6 @@

-enum {

-	Nftab = 32,

-	Nftlist = 32,

-};

-

 typedef struct Branch Branch;

-typedef struct F F;

-typedef struct Ftab Ftab;

-typedef struct Fstate Fstate;

+typedef struct FILE FILE;

+typedef struct Mtpt Mtpt;

 struct Branch {

 	char *root;

@@ -13,28 +7,24 @@

 	int create;

 };

-struct F {

-	Ref;

+struct FILE {

 	Dir;

-	char *path;   /* real path */

-	char *fspath; /* internal path */

-};

+	char *realpath;

+	char *path;

-struct Ftab {

-	long n, sz;

-	F **l;

+	int fd;

+	Mtpt *mtpt;

+	Dir *dirs;

+	long ndirs;

 };

-struct Fstate {

-	int fd;

-	F *file;

-	Ftab *ftab;

+struct Mtpt {

+	char *path;

+	Mtpt *next;

 };

 void usage(void);

 Qid qencode(Dir*);

 char *mkpath(char*, ...);

-Ref *copyref(Ref*);

 void *emalloc(ulong);

-void *erealloc(void*, ulong);

 char *estrdup(char*);

--- a/util.c

+++ b/util.c

@@ -10,35 +10,6 @@

 	exits("usage");

 }

-char*

-mkpath(char *a0, ...)

-{

-	va_list args;

-	int i;

-	char *a;

-	char *ap[] = {a0, "", ""};

-

-	va_start(args, a0);

-	for(i = 1; (a = va_arg(args, char*)) != nil && i < 3; i++)

-		ap[i] = a;

-	va_end(args);

-	if((a = smprint("%s/%s/%s", ap[0], ap[1], ap[2])) == nil)

-		sysfatal("smprint: %r");

-

-	return cleanname(a);

-}

-

-Ref*

-copyref(Ref *r)

-{

-	incref(r);

-	return r;

-}

-

-/*

- * Error-checked library functions

- */

-

 void*

 emalloc(ulong sz)

 {

@@ -48,15 +19,6 @@

 		sysfatal("emalloc: %r");

 	memset(v, 0, sz);

 	setmalloctag(v, getcallerpc(&sz));

-	return v;

-}

-

-void*

-erealloc(void *v, ulong sz)

-{

-	if((v = realloc(v, sz)) == nil && sz != 0)

-		sysfatal("realloc: %r");

-	setrealloctag(v, getcallerpc(&v));

 	return v;

 }