From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oo1-xc36.google.com (mail-oo1-xc36.google.com [IPv6:2607:f8b0:4864:20::c36]) by sourceware.org (Postfix) with ESMTPS id 47B173858C2B; Thu, 24 Aug 2023 16:45:21 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 47B173858C2B Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-oo1-xc36.google.com with SMTP id 006d021491bc7-5733789a44cso59166eaf.2; Thu, 24 Aug 2023 09:45:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1692895520; x=1693500320; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=I6/LmBKza9vp0FlJk6xoCNqc8uovzavRefz/P3Onh74=; b=PDh1WPzuJJuGrmxmyL9BCEaMJ7aJuKfdDB79JT4M8Jc0I+nBY2fJCOq2qbnbJM7o3J atiHBnpYNdABUMc4yy4m+EnqZANy+LogsCaiOY39ylZn/KR2G+E5cJaBCpXber6Iw1v2 U4uNOOA/9UFsHwlNIOUf/ViF+rMZDJ9LNTdxFBWfuDLIWIbxitRRth3s58QtsulLUa2w u0qkqrKf6pCuFqTv2zWl8krdoweWg5kX0z2824c1rfXrUP+JMQA+GZSDPDKUewr+H9a1 mzARWIEx0Z2j+4KYvlkbRzmn+PfPCm/CQHsGsig+tKnyLuluxbKK5mKxXKzg8UP/XDTc RJQA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692895520; x=1693500320; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=I6/LmBKza9vp0FlJk6xoCNqc8uovzavRefz/P3Onh74=; b=Imn9LRkvYQke/pWlBs80GyaB0gXhWHBXZZRJ01UsZWeno8VzvVNU09/KTjbKUEkICS vkKk4ynmX677sG0MjXnp1MbmJGjXP1siedf0iK7mXqi9YlxVWZY3Ok4bSZUCLrZ8GVx7 5RhPMRxLVY8Jl21u+tsDmlGa1Rx9MoFOHS/T84N8B4LXJvDUdl9aGggHmyP8g95O3Ss3 yAiMFZHKmDpRjUngXq5yUDYP3dMEHb7nL+TJBTESYx77sdF2qUUk6mNxSXr+eYpXJoiE sQCwti8OIYc4vJbwtMExDVWCjgfpK1gBcj/ekbFhgTNrYEKKWpL0jTlg6oeO1vpwT4XY QHGA== X-Gm-Message-State: AOJu0Yx2vUmM2Juk7zUw33BNlyKKhvp8+yaMrmSPKOS6vz4fa5VPC83I 909opZ8IQl68UwmbWZZXXjo/OfGvyRQrYFyyR22h9xTdFIAoeg== X-Google-Smtp-Source: AGHT+IEH9ok3znTW9n+I9BCaXaw2a2SFcBd8FLZti5cyd2fUmpv2J/Yc9f5IMr0pGxXIVMLpEUu4c5UYDN+zDs8S7/o= X-Received: by 2002:a4a:251c:0:b0:56e:4dea:bc5b with SMTP id g28-20020a4a251c000000b0056e4deabc5bmr2681323ooa.8.1692895520378; Thu, 24 Aug 2023 09:45:20 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Martin Wege Date: Thu, 24 Aug 2023 18:45:09 +0200 Message-ID: Subject: Re: How to fix |mkfifo()| failure if |pathname| is on NFS ? / was: Re: [EXTERNAL] Re: mkfifo: cannot set permissions of 'x.fifo': Not a directory To: "cygwin@cygwin.com" , Corinna Vinschen Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=0.5 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Wed, Aug 23, 2023 at 1:06=E2=80=AFAM Roland Mainz via Cygwin wrote: > > On Tue, Aug 22, 2023 at 4:52=E2=80=AFPM Lavrentiev, Anton (NIH/NLM/NCBI) = [C] > via Cygwin wrote: > > > FIFOs which don't make *any* sense > > > ... FWIW, a remote NFS fileystem. > > > > I got an impression that the OP is trying to deploy something (maybe th= e entire Cygwin) onto an > > NFS share. So the named FIFO "file" is also created in there. > > I agree with that impression. This is basically what large sites > (universities etc) do with UNIX and Linux: The machines mount an > user's ${HOMR} directory via automounter over NFS, and users are > discouraged (e.g. grumpy admin visiting you in person, blocking all > escape routes... =3D:-) ) from using the machine's local filesystems (in > Cygwin's case that includes "C:"!). > > In that case people want to use |mkfifo()|/|mkfifoat()| and/or > /usr/bin/mkfifo in their home directory, and don't expect that it does > not work. > > But that is what happens on Cygwin 3.4.8 right now, if someone tries > to do a |mkfifo()| on a NFS home directory (tested with MS NFSv3 and > CITI NFSv4 clients): > |mkfifo()| succeeds, but the resulting inode is *NOT* a FIFO as requested > > Example (/cygdrive/h/ is my home directory shared from my Linux machine): > ---- snip ---- > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ uname -a > CYGWIN_NT-10.0-19045 winkrakra1 3.4.8-1.x86_64 2023-08-17 17:02 UTC > x86_64 Cygwin > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ mount > C:/cygwin64/bin on /usr/bin type ntfs (binary,auto) > C:/cygwin64/lib on /usr/lib type ntfs (binary,auto) > C:/cygwin64 on / type ntfs (binary,auto) > C: on /cygdrive/c type ntfs (binary,posix=3D0,user,noumount,auto) > H: on /cygdrive/h type nfs (binary,posix=3D0,user,noumount,auto) > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ls -l > total 1 > -rw-rw-rw- 1 Unix_User+0 Unix_Group+0 330 Aug 22 23:58 cygwin_mkfifo_on_n= fs.c > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ cat -n cygwin_mkfifo_on_nfs.c > 1 #include > 2 #include > 3 #include > 4 #include > 5 #include > 6 #include > 7 > 8 int main(int ac, char *av[]) > 9 { > 10 (void)puts("# start"); > 11 > 12 if > (mkfifo("/cygdrive/h/work/cygwin_mkfifo_on_nfs/myfifo.fifo", 0) !=3D 0) > 13 perror("mkfifo failed"); > 14 (void)puts("# done."); > 15 return EXIT_SUCCESS; > 16 } > 17 > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ gcc -g cygwin_mkfifo_on_nfs.c > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ./a > # start > # done. > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ls -l > total 68 > -rwxr-xr-x 1 Unix_User+0 Unix_Group+0 66951 Aug 23 00:12 a.exe > -rw-rw-rw- 1 Unix_User+0 Unix_Group+0 330 Aug 22 23:58 cygwin_mkfifo_on= _nfs.c > lrwxrwxrwx 1 Unix_User+0 Unix_Group+0 11 Aug 23 00:12 myfifo.fifo > -> ':\0:c4:1000' > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ cat -bash: myfifo.fifo: No such file or directory > ---- snip ---- > > Note that Cygwin does not interpret the file |myfifo.fifo| as FIFO, > instead it comes back as a symlink "myfifo.fifo -> ':\0:c4:1000'". > > AFAIK there are (at least) these two options to fix the problems: > 1. Check whether the filesystem for the fifos path is NFS > (cgywin.dll's |fs.fs_is_nfs()|), and if it is a symlink check if it > starts with ':\0:c4:' (assuming "c4" is the prefix for inodes created > with |mkfifo()|). If this condition is |true|, then cygwin |stat()|, > |open()| etc. should treat this inode as FIFO. > 2. Check whether the filesystem for the fifos path is NFS > (cgywin.dll's |fs.fs_is_nfs()|), and then just refuse |mkfifo()| with > |ENOSYS| (not implemented) > > Better algorithm for [1] might be to check whether the inode is a > symlink, and then do a |fs.fs_is_nfs()| on the symlinks |pathname|, > assuming this is more performant. We would like to see option 1 implemented, maybe as an option in the CYGWIN environment variable (CYGWIN=3Dnfs_emulate_dev_special_files_as_symlink ?) Thanks, Martin