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upas/common: deliver mail to mdir as .tmp file and rename after it has been fully written

theres a race condition when mail delivery to mdir is slow,
then upas/fs sees partial mail file and caches the truncated
file size.

to avoid this, delivery will create the new mail file with
the .tmp extension (which is ignored by upas/fs) and after
everything has been written, rename it to the final name.

--- a/sys/src/cmd/upas/common/common.h

+++ b/sys/src/cmd/upas/common/common.h

@@ -41,7 +41,7 @@

 /* folder.c */

 Biobuf	*openfolder(char*, long);

 int	closefolder(Biobuf*);

-int	appendfolder(Biobuf*, char*, long*, int);

+int	appendfolder(Biobuf*, char*, int);

 int	fappendfolder(char*, long, char *, int);

 int	fappendfile(char*, char*, int);

 char*	foldername(char*, char*, char*);

--- a/sys/src/cmd/upas/common/folder.c

+++ b/sys/src/cmd/upas/common/folder.c

@@ -12,6 +12,7 @@

 	int	type;

 	Biobuf	*out;

 	Mlock	*l;

+	long	t;

 };

 static Folder ftab[5];

@@ -44,12 +45,12 @@

 	r = 0;

 	if(f->l)

 		sysunlock(f->l);

-	if(f->out)

+	if(f->out){

 		r |= Bterm(f->out);

-	if(f->ofd > 0){

-		close(f->ofd);

 		free(f->out);

 	}

+	if(f->ofd >= 0)

+		close(f->ofd);

 	memset(f, 0, sizeof *f);

 	return r;

 }

@@ -59,7 +60,7 @@

 {

 	Folder *f;

-	f = getfolder(0);

+	f = getfolder(nil);

 	f->l = syslock(s);		/* traditional botch: ignore failure */

 	if((f->ofd = open(s, OWRITE)) == -1)

 	if((f->ofd = create(s, OWRITE|OEXCL, DMAPPEND|0600)) == -1){

@@ -79,13 +80,13 @@

 static Biobuf*

 mdiropen(char *s, long t)

 {

-	char buf[64];

-	long i;

+	char buf[Pathlen];

 	Folder *f;

+	int i;

-	f = getfolder(0);

+	f = getfolder(nil);

 	for(i = 0; i < 100; i++){

-		snprint(buf, sizeof buf, "%s/%lud.%.2ld", s, t, i);

+		snprint(buf, sizeof buf, "%s/%lud.%.2d.tmp", s, t, i);

 		if((f->ofd = create(buf, OWRITE|OEXCL, DMAPPEND|0660)) != -1)

 			goto found;

 	}

@@ -96,6 +97,7 @@

 	f->out = malloc(sizeof *f->out);

 	Binit(f->out, f->ofd, OWRITE);

 	f->type = Mdir;

+	f->t = t;

 	return f->out;

 }

@@ -122,32 +124,31 @@

 }

 int

-renamefolder(Biobuf *b, long t)

+closefolder(Biobuf *b)

 {

 	char buf[32];

-	int i;

-	Dir d;

 	Folder *f;

+	Dir d;

+	int i;

+	if(b == nil)

+		return 0;

 	f = getfolder(b);

 	if(f->type != Mdir)

-		return 0;

-	for(i = 0; i < 100; i++){

-		nulldir(&d);

-		snprint(buf, sizeof buf, "%lud.%.2d", t, i);

-		d.name = buf;

-		if(dirfwstat(Bfildes(b), &d) > 0)

-			return 0;

+		return putfolder(f);

+	if(Bflush(b) == 0){

+		for(i = 0; i < 100; i++){

+			nulldir(&d);

+			snprint(buf, sizeof buf, "%lud.%.2d", f->t, i);

+			d.name = buf;

+			if(dirfwstat(f->ofd, &d) > 0)

+				return putfolder(f);

+		}

 	}

+	putfolder(f);

 	return -1;

 }

-int

-closefolder(Biobuf *b)

-{

-	return putfolder(getfolder(b));

-}

-

 /*

  * escape "From " at the beginning of a line;

  * translate \r\n to \n for imap

@@ -181,7 +182,7 @@

 }

 int

-appendfolder(Biobuf *b, char *addr, long *t, int fd)

+appendfolder(Biobuf *b, char *addr, int fd)

 {

 	char *s;

 	int r;

@@ -194,9 +195,9 @@

 	Binit(&bin, fd, OREAD);

 	s = Brdstr(&bin, '\n', 0);

 	if(!s || strncmp(s, "From ", 5))

-		Bprint(f->out, "From %s %.28s\n", addr, ctime(*t));

+		Bprint(f->out, "From %s %.28s\n", addr, ctime(f->t));

 	else if(fromtotm(s, &tm) >= 0)

-		*t = tm2sec(&tm);

+		f->t = tm2sec(&tm);

 	if(s)

 		Bwrite(f->out, s, strlen(s));

 	free(s);

@@ -207,16 +208,13 @@

 int

 fappendfolder(char *addr, long t, char *s, int fd)

 {

-	long t0, r;

 	Biobuf *b;

+	int r;

 	b = openfolder(s, t);

 	if(b == nil)

 		return -1;

-	t0 = t;

-	r = appendfolder(b, addr, &t, fd);

-	if(t != t0)

-		renamefolder(b, t);

+	r = appendfolder(b, addr, fd);

 	r |= closefolder(b);

 	return r;

 }