Re: [PATCH] mm: remove WARN_ON_ONCE() in file_has_valid_mmap_hooks()

[Pedro Falcato <pfalcato@suse.de>]

On Wed, May 14, 2025 at 10:42:53AM +0200, Vlastimil Babka wrote:
> On 5/14/25 10:40, Lorenzo Stoakes wrote:
> > Having encountered a trinity report in linux-next (Linked in the 'Closes'
> > tag) it appears that there are legitimate situations where a file-backed
> > mapping can be acquired but no file->f_op->mmap or file->f_op->mmap_prepare
> > is set, at which point do_mmap() should simply error out with -ENODEV.
> > 
> > Since previously we did not warn in this scenario and it appears we rely
> > upon this, restore this situation, while retaining a WARN_ON_ONCE() for the
> > case where both are set, which is absolutely incorrect and must be
> > addressed and thus always requires a warning.
> > 
> > If further work is required to chase down precisely what is causing this,
> > then we can later restore this, but it makes no sense to hold up this
> > series to do so, as this is existing and apparently expected behaviour.
> > 
> > Reported-by: kernel test robot <oliver.sang@intel.com>
> > Closes: https://lore.kernel.org/oe-lkp/202505141434.96ce5e5d-lkp@intel.com
> > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> 
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Reviewed-by: Pedro Falcato <pfalcato@suse.de>

-- 
Pedro