[src/trunk]: src/lib/libpuffs Allow calling puffs_mount(3) before puffs_daemo...

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

details:   https://anonhg.NetBSD.org/src/rev/813962832bb1
branches:  trunk
changeset: 359756:813962832bb1
user:      pho <pho%NetBSD.org@localhost>
date:      Sat Jan 22 07:35:26 2022 +0000

description:
Allow calling puffs_mount(3) before puffs_daemon(3)

puffs_daemon(3) creates a pipe before forking, and the parent process
waits for the child to either complete puffs_mount(3) or fail. If a
user calls puffs_daemon(3) after puffs_mount(3), the function
deadlocks. While this error-reporting functionality is really a nice
thing to have, deadlocking is not great. If the filesystem has already
been mounted, puffs_mount(3) should just daemonize the process and
return.

This became an issue because fuse_daemonize(3) in FUSE API had no such
requirement and some FUSE filesystems in the wild suffered deadlocks.

diffstat:

 lib/libpuffs/Makefile     |   3 +--
 lib/libpuffs/puffs.3      |   8 +++++---
 lib/libpuffs/puffs.c      |  44 ++++++++++++++++++++++++++------------------
 lib/libpuffs/puffs_priv.h |   3 ++-
 4 files changed, 34 insertions(+), 24 deletions(-)

diffs (156 lines):

diff -r 9999ceb18b65 -r 813962832bb1 lib/libpuffs/Makefile
--- a/lib/libpuffs/Makefile     Fri Jan 21 21:40:31 2022 +0000
+++ b/lib/libpuffs/Makefile     Sat Jan 22 07:35:26 2022 +0000
@@ -1,4 +1,4 @@
-#      $NetBSD: Makefile,v 1.26 2016/01/23 21:22:46 christos Exp $
+#      $NetBSD: Makefile,v 1.27 2022/01/22 07:35:26 pho Exp $
 #
 
 .include <bsd.own.mk>
@@ -16,7 +16,6 @@
                puffs_framebuf.3 puffs_node.3 puffs_ops.3 puffs_path.3
 INCS=          puffs.h puffsdump.h
 INCSDIR=       /usr/include
-CPPFLAGS+=     -D_KERNTYPES
 LINTFLAGS+=-S -w
 
 .include <bsd.lib.mk>
diff -r 9999ceb18b65 -r 813962832bb1 lib/libpuffs/puffs.3
--- a/lib/libpuffs/puffs.3      Fri Jan 21 21:40:31 2022 +0000
+++ b/lib/libpuffs/puffs.3      Sat Jan 22 07:35:26 2022 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: puffs.3,v 1.66 2021/12/03 17:12:17 pho Exp $
+.\"    $NetBSD: puffs.3,v 1.67 2022/01/22 07:35:26 pho Exp $
 .\"
 .\" Copyright (c) 2006, 2007, 2008 Antti Kantee.  All rights reserved.
 .\"
@@ -455,11 +455,13 @@
 .It Fn puffs_daemon pu nochdir noclose
 Detach from the console like
 .Fn daemon 3 .
-This call synchronizes with
+If it is called before
+.Fn puffs_mount ,
+this call synchronizes with
 .Fn puffs_mount
 and the foreground process does not exit before the file system mount
 call has returned from the kernel.
-Since this routine internally calls fork, it has to be called
+Since this routine internally calls fork, it is highly recommended to call it
 .Em before
 .Fn puffs_mount .
 .It Fn puffs_mainloop pu flags
diff -r 9999ceb18b65 -r 813962832bb1 lib/libpuffs/puffs.c
--- a/lib/libpuffs/puffs.c      Fri Jan 21 21:40:31 2022 +0000
+++ b/lib/libpuffs/puffs.c      Sat Jan 22 07:35:26 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: puffs.c,v 1.127 2021/12/03 17:12:17 pho Exp $  */
+/*     $NetBSD: puffs.c,v 1.128 2022/01/22 07:35:26 pho Exp $  */
 
 /*
  * Copyright (c) 2005, 2006, 2007  Antti Kantee.  All Rights Reserved.
@@ -31,7 +31,7 @@
 
 #include <sys/cdefs.h>
 #if !defined(lint)
-__RCSID("$NetBSD: puffs.c,v 1.127 2021/12/03 17:12:17 pho Exp $");
+__RCSID("$NetBSD: puffs.c,v 1.128 2022/01/22 07:35:26 pho Exp $");
 #endif /* !lint */
 
 #include <sys/param.h>
@@ -440,9 +440,12 @@
 {
        long int n;
        int parent, value, fd;
+       bool is_beforemount;
 
-       if (pipe(pu->pu_dpipe) == -1)
-               return -1;
+       is_beforemount = (puffs_getstate(pu) < PUFFS_STATE_RUNNING);
+       if (is_beforemount)
+               if (pipe(pu->pu_dpipe) == -1)
+                       return -1;
 
        switch (fork()) {
        case -1:
@@ -454,18 +457,21 @@
                parent = 1;
                break;
        }
-       pu->pu_state |= PU_PUFFSDAEMON;
+       if (is_beforemount)
+               PU_SETSFLAG(pu, PU_PUFFSDAEMON);
 
        if (parent) {
-               close(pu->pu_dpipe[1]);
-               n = read(pu->pu_dpipe[0], &value, sizeof(int));
-               if (n == -1)
-                       err(1, "puffs_daemon");
-               if (n != sizeof(value))
-                       errx(1, "puffs_daemon got %ld bytes", n);
-               if (value) {
-                       errno = value;
-                       err(1, "puffs_daemon");
+               if (is_beforemount) {
+                       close(pu->pu_dpipe[1]);
+                       n = read(pu->pu_dpipe[0], &value, sizeof(int));
+                       if (n == -1)
+                               err(1, "puffs_daemon");
+                       if (n != sizeof(value))
+                               errx(1, "puffs_daemon got %ld bytes", n);
+                       if (value) {
+                               errno = value;
+                               err(1, "puffs_daemon");
+                       }
                }
                exit(0);
        } else {
@@ -489,8 +495,10 @@
        }
 
  fail:
-       n = write(pu->pu_dpipe[1], &errno, sizeof(int));
-       assert(n == 4);
+       if (is_beforemount) {
+               n = write(pu->pu_dpipe[1], &errno, sizeof(int));
+               assert(n == 4);
+       }
        return -1;
 }
 
@@ -614,7 +622,7 @@
        free(pu->pu_kargp);
        pu->pu_kargp = NULL;
 
-       if (pu->pu_state & PU_PUFFSDAEMON)
+       if (PU_GETSFLAG(pu, PU_PUFFSDAEMON))
                shutdaemon(pu, sverrno);
 
        errno = sverrno;
@@ -706,8 +714,8 @@
 void
 puffs_cancel(struct puffs_usermount *pu, int error)
 {
-
        assert(puffs_getstate(pu) < PUFFS_STATE_RUNNING);
+       assert(PU_GETSFLAG(pu, PU_PUFFSDAEMON));
        shutdaemon(pu, error);
        free(pu);
 }
diff -r 9999ceb18b65 -r 813962832bb1 lib/libpuffs/puffs_priv.h
--- a/lib/libpuffs/puffs_priv.h Fri Jan 21 21:40:31 2022 +0000
+++ b/lib/libpuffs/puffs_priv.h Sat Jan 22 07:35:26 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: puffs_priv.h,v 1.45 2012/04/18 00:57:22 manu Exp $     */
+/*     $NetBSD: puffs_priv.h,v 1.46 2022/01/22 07:35:26 pho Exp $      */
 
 /*
  * Copyright (c) 2006, 2007, 2008 Antti Kantee.  All Rights Reserved.
@@ -113,6 +113,7 @@
 #define PU_DONEXIT     0x2000
 #define PU_SETSTATE(pu, s) (pu->pu_state = (s) | (pu->pu_state & ~PU_STATEMASK))
 #define PU_SETSFLAG(pu, s) (pu->pu_state |= (s))
+#define PU_GETSFLAG(pu, s) (pu->pu_state & (s))
 #define PU_CLRSFLAG(pu, s) \
     (pu->pu_state = ((pu->pu_state & ~(s)) | (pu->pu_state & PU_STATEMASK)))
        int                     pu_dpipe[2];