code: plan9front

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hjfs: defer parent directory permission check for wstat

check parent directory permission *after* we determined
that the new name does not exist in the parent, so that
when the new name is the same as old name then no write
permission is required in the parent directory.

--- a/sys/src/cmd/hjfs/fs2.c

+++ b/sys/src/cmd/hjfs/fs2.c

@@ -698,18 +698,17 @@

 		d = getdent(ch->loc->next, pb);

 		if(d == nil)

 			goto error;

-		if((ch->flags & CHFNOPERM) == 0)

-			if(!permcheck(ch->fs, d, ch->uid, OWRITE))

-				goto perm;

 		rc = findentry(ch->fs, ch->loc->next, pb, di->name, &f, ch->flags & CHFDUMP);

-		if(rc > 0){

-			if(f.blk == ch->loc->blk && f.deind == ch->loc->deind)

-				rc = 0;

-			else

-				werrstr(Eexists);

-		}

-		if(rc != 0)

+		if(rc < 0)

 			goto error;

+		else if(rc == 0){

+			if((ch->flags & CHFNOPERM) == 0)

+				if(!permcheck(ch->fs, d, ch->uid, OWRITE))

+					goto perm;

+		} else if(f.blk != ch->loc->blk || f.deind != ch->loc->deind){

+			werrstr(Eexists);

+			goto error;

+		}

 	}

 	b = getbuf(ch->fs->d, ch->loc->blk, TDENTRY, 0);

 	if(b == nil)