linux-kernel - Re: [PATCH v5 1/4] kernfs: add a WARN_ON

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Message-ID: <2024081141-cattail-kick-3ff5@gregkh>
Date: Sun, 11 Aug 2024 10:31:57 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Martin Oliveira <martin.oliveira@...eticom.com>
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Artemy Kovalyov <artemyko@...dia.com>,
	Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
	Logan Gunthorpe <logang@...tatee.com>,
	Michael Guralnik <michaelgur@...dia.com>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
	Shiraz Saleem <shiraz.saleem@...el.com>, Tejun Heo <tj@...nel.org>,
	John Hubbard <jhubbard@...dia.com>,
	Dan Williams <dan.j.williams@...el.com>,
	David Sloan <david.sloan@...eticom.com>
Subject: Re: [PATCH v5 1/4] kernfs: add a WARN_ON_ONCE if ->close is set

On Fri, Aug 09, 2024 at 09:41:48AM -0600, Martin Oliveira wrote:
> On 2024-08-08 23:37, Greg Kroah-Hartman wrote:
> >> diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
> >> index 8502ef68459b..72cc51dcf870 100644
> >> --- a/fs/kernfs/file.c
> >> +++ b/fs/kernfs/file.c
> >> @@ -479,7 +479,7 @@ static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
> >>        * It is not possible to successfully wrap close.
> >>        * So error if someone is trying to use close.
> >>        */
> >> -     if (vma->vm_ops && vma->vm_ops->close)
> >> +     if (WARN_ON_ONCE(vma->vm_ops && vma->vm_ops->close))
> > 
> > So you just rebooted a machine that hits this, loosing data everywhere.
> > Not nice :(
> 
> Well, apologies for that, but there's no way to know what every single machine
> out there is doing...
> 
> However if this machine is using ->close when that's clearly marked as
> unsupported then shouldn't we fix that?

return an error properly?