Re: [PATCH] cifs: Fix support for creating SFU fifo

["Pali Rohár" <pali@kernel.org>]

I have verified WSL and it does not use "LnxFIFO". This looks like AI hallucination too.
WSL stores fifos as reparse point of IO_REPARSE_TAG_LX_FIFO type.

On Wednesday 08 July 2026 08:55:02 Steve French wrote:
> AI search says that "LnxFIFO" is used by WSL?  Have you verified this recently.
> 
> On Tue, Jul 7, 2026 at 4:13 AM Pali Rohár <pali@kernel.org> wrote:
> >
> > SFU fifos are natively supported (created and recognized) at least by:
> > - Microsoft POSIX subsystem
> > - OpenNT/Interix subsystem
> > - Microsoft SFU (Windows Services for UNIX)
> > - Microsoft SUA (Subsystem for UNIX-based Applications)
> > - Windows NFS server (up to the Windows Server 2008 R2)
> >
> > Windows NFS server since Windows Server 2012 uses new reparse point format
> > for storing new fifos, but still can recognize this old format (also in the
> > latest Windows Server 2022 version).
> >
> > SFU-style fifo is empty regular file which has system attribute set.
> >
> > These SFU-style fifos are already recognized by Linux SMB client.
> >
> > But Linux SMB client is currently creating new SFU fifos in different
> > format which is not compatible with all those SFU-style consumers. Fix this
> > by creating new fifos in correct SFU format which would be recognized by
> > all those applications and also by existing Linux SMB clients.
> >
> > This change affects only creating new fifos when mount option -o sfu is used.
> >
> > Signed-off-by: Pali Rohár <pali@kernel.org>
> > ---
> >  fs/smb/client/smb2ops.c | 6 ++----
> >  1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
> > index e59fda1b2230..1261b928edee 100644
> > --- a/fs/smb/client/smb2ops.c
> > +++ b/fs/smb/client/smb2ops.c
> > @@ -5293,10 +5293,8 @@ int __cifs_sfu_make_node(unsigned int xid, struct inode *inode,
> >                 type[0] = '\0';
> >                 break;
> >         case S_IFIFO:
> > -               type_len = 8;
> > -               strscpy(type, "LnxFIFO");
> > -               data = (u8 *)&pdev;
> > -               data_len = sizeof(pdev);
> > +               /* SFU fifo is system file which is empty */
> > +               type_len = 0;
> >                 break;
> >         default:
> >                 rc = -EPERM;
> > --
> > 2.20.1
> >
> >
> 
> 
> -- 
> Thanks,
> 
> Steve