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

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Message-ID: <a9468d88-c2e9-431c-a2bc-847ce9743729@eideticom.com>
Date: Fri, 9 Aug 2024 09:41:48 -0600
From: Martin Oliveira <martin.oliveira@...eticom.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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 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?