[src/trunk]: src/usr.sbin/puffs/mount_9p getdfwithoffset - do not issue dummy...

[uwe <uwe%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/eb5a9c12b096
branches:  trunk
changeset: 933537:eb5a9c12b096
user:      uwe <uwe%NetBSD.org@localhost>
date:      Tue May 26 19:38:14 2020 +0000

description:
getdfwithoffset - do not issue dummy read to seek to offset zero on a
newly opened fid as it's already there.  This is redundant and also
seems to confuse inferno when issued against the root directory.  Now
you can ls the mount point of

    styxlisten -A 'tcp!*!styx' export /

While here fix the seek logic to actually repeatedly seek forward
instead of always doing it from zero.

diffstat:

 usr.sbin/puffs/mount_9p/subr.c |  71 +++++++++++++++++++++--------------------
 1 files changed, 36 insertions(+), 35 deletions(-)

diffs (117 lines):

diff -r 2b313feedac0 -r eb5a9c12b096 usr.sbin/puffs/mount_9p/subr.c
--- a/usr.sbin/puffs/mount_9p/subr.c    Tue May 26 19:29:59 2020 +0000
+++ b/usr.sbin/puffs/mount_9p/subr.c    Tue May 26 19:38:14 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr.c,v 1.7 2019/06/07 05:34:34 ozaki-r Exp $ */
+/*     $NetBSD: subr.c,v 1.8 2020/05/26 19:38:14 uwe Exp $     */
 
 /*
  * Copyright (c) 2007  Antti Kantee.  All Rights Reserved.
@@ -27,7 +27,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: subr.c,v 1.7 2019/06/07 05:34:34 ozaki-r Exp $");
+__RCSID("$NetBSD: subr.c,v 1.8 2020/05/26 19:38:14 uwe Exp $");
 #endif /* !lint */
 
 #include <sys/types.h>
@@ -104,11 +104,7 @@
 {
        struct puffs_cc *pcc = puffs_cc_getcc(pu);
        struct puffs9p *p9p = puffs_getspecific(pu);
-       struct puffs_framebuf *pb;
        struct dirfid *dfp = NULL;
-       p9ptag_t tag = NEXTTAG(p9p);
-       off_t curoff, advance;
-       uint32_t count;
        int rv;
 
        LIST_FOREACH(dfp, &p9n->dir_openlist, entries) {
@@ -120,52 +116,57 @@
        }
 
        /* didn't get off easy?  damn, do manual labour */
-       pb = p9pbuf_makeout();
        dfp = ecalloc(1, sizeof(struct dirfid));
        dfp->fid = NEXTFID(p9p);
        rv = proto_cc_open(pu, p9n->fid_base, dfp->fid, P9PROTO_OMODE_READ);
        if (rv)
                goto out;
 
-       for (curoff = 0;;) {
-               advance = wantoff - curoff;
+       off_t curoff = 0;
+       if (wantoff != 0) {
+               struct puffs_framebuf *pb = p9pbuf_makeout();
+               for (;;) {
+                       off_t advance = wantoff - curoff;
 
-               tag = NEXTTAG(p9p);
-               p9pbuf_put_1(pb, P9PROTO_T_READ);  
-               p9pbuf_put_2(pb, tag);
-               p9pbuf_put_4(pb, dfp->fid);       
-               p9pbuf_put_8(pb, 0);
-               p9pbuf_put_4(pb, advance);       
-               GETRESPONSE(pb);
+                       p9ptag_t tag = NEXTTAG(p9p);
+                       p9pbuf_put_1(pb, P9PROTO_T_READ);
+                       p9pbuf_put_2(pb, tag);
+                       p9pbuf_put_4(pb, dfp->fid);
+                       p9pbuf_put_8(pb, curoff);
+                       p9pbuf_put_4(pb, advance);
+                       GETRESPONSE(pb);
 
-               if (p9pbuf_get_type(pb) != P9PROTO_R_READ) {
-                       rv = proto_handle_rerror(pu, pb);
-                       goto out;
-               }
+                       if (p9pbuf_get_type(pb) != P9PROTO_R_READ) {
+                               rv = proto_handle_rerror(pu, pb);
+                               puffs_framebuf_destroy(pb);
+                               goto out;
+                       }
 
-               /*
-                * Check how many bytes we got.  If we got the amount we
-                * wanted, we are at the correct position.  If we got
-                * zero bytes, either the directory doesn't "support" the
-                * seek offset we want (someone has probably inserted an
-                * entry meantime) or we at the end of directory.  Either
-                * way, let the upper layer deal with it.
-                */
-               p9pbuf_get_4(pb, &count);
-               curoff += count;
-               if (count == advance || count == 0)
-                       break;
+                       /*
+                        * Check how many bytes we got.  If we got the
+                        * amount we wanted, we are at the correct position.
+                        * If we got zero bytes, either the directory
+                        * doesn't "support" the seek offset we want
+                        * (someone has probably inserted an entry
+                        * meantime) or we at the end of directory.
+                        * Either way, let the upper layer deal with it.
+                        */
+                       uint32_t count;
+                       p9pbuf_get_4(pb, &count);
+                       curoff += count;
+                       if (count == advance || count == 0)
+                               break;
 
-               p9pbuf_recycleout(pb);
+                       p9pbuf_recycleout(pb);
+               }
+               puffs_framebuf_destroy(pb);
        }
-       puffs_framebuf_destroy(pb);
 
        dfp->seekoff = curoff;
        *rfid = dfp;
        return 0;
 
  out:
-       puffs_framebuf_destroy(pb);
        free(dfp);
        return rv;
 }