[src/trunk]: src/lib/librefuse Change the way how puffs_fuse_node_create() be...

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

details:   https://anonhg.NetBSD.org/src/rev/59db1c716860
branches:  trunk
changeset: 819096:59db1c716860
user:      pho <pho%NetBSD.org@localhost>
date:      Thu Nov 17 14:20:25 2016 +0000

description:
Change the way how puffs_fuse_node_create() behaves.

In puffs "create" and "open" are two separate operations with
atomicity achieved by locking the parent vnode. In fuse, on the other
hand, "create" is actually a create-and-open-atomically and the open
flags (O_RDWR, O_APPEND, ...) are passed via fi.flags. So the only way
to emulate the fuse semantics is to open the file with dummy flags and
then immediately close it.

You might think that we could simply use fuse->op.mknod all the time
but no, that's not possible because most file systems nowadays expect
op.mknod to be called only for non-regular files and many don't even
support it.

diffstat:

 lib/librefuse/refuse.c |  29 +++++++++++++++++++++--------
 1 files changed, 21 insertions(+), 8 deletions(-)

diffs (59 lines):

diff -r 3f739b7b044d -r 59db1c716860 lib/librefuse/refuse.c
--- a/lib/librefuse/refuse.c    Thu Nov 17 09:29:01 2016 +0000
+++ b/lib/librefuse/refuse.c    Thu Nov 17 14:20:25 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: refuse.c,v 1.96 2012/12/30 10:04:22 tron Exp $ */
+/*     $NetBSD: refuse.c,v 1.97 2016/11/17 14:20:25 pho Exp $  */
 
 /*
  * Copyright © 2007 Alistair Crooks.  All rights reserved.
@@ -31,7 +31,7 @@
 
 #include <sys/cdefs.h>
 #if !defined(lint)
-__RCSID("$NetBSD: refuse.c,v 1.96 2012/12/30 10:04:22 tron Exp $");
+__RCSID("$NetBSD: refuse.c,v 1.97 2016/11/17 14:20:25 pho Exp $");
 #endif /* !lint */
 
 #include <sys/types.h>
@@ -765,8 +765,22 @@
 
        set_fuse_context_uid_gid(pcn->pcn_cred);
 
+       memset(&fi, 0, sizeof(fi));
        created = 0;
        if (fuse->op.create) {
+               /* In puffs "create" and "open" are two separate operations
+                * with atomicity achieved by locking the parent vnode. In
+                * fuse, on the other hand, "create" is actually a
+                * create-and-open-atomically and the open flags (O_RDWR,
+                * O_APPEND, ...) are passed via fi.flags. So the only way to
+                * emulate the fuse semantics is to open the file with dummy
+                * flags and then immediately close it.
+                *
+                * You might think that we could simply use fuse->op.mknod all
+                * the time but no, that's not possible because most file
+                * systems nowadays expect op.mknod to be called only for
+                * non-regular files and many don't even support it. */
+               fi.flags = O_WRONLY | O_CREAT | O_EXCL;
                ret = fuse->op.create(path, mode | S_IFREG, &fi);
                if (ret == 0)
                        created = 1;
@@ -782,12 +796,11 @@
                ret = fuse_newnode(pu, path, va, &fi, pni, &pn);
 
                /* sweet..  create also open the file */
-               if (created) {
-                       struct refusenode *rn;
-
-                       rn = pn->pn_data;
-                       rn->flags |= RN_OPEN;
-                       rn->opencount++;
+               if (created && fuse->op.release) {
+                       struct refusenode *rn = pn->pn_data;
+                       /* The return value of op.release is expected to be
+                        * discarded. */
+                       (void)fuse->op.release(path, &rn->file_info);
                }
        }