Re: [PATCH] mm/madvise: set ra_pages as device max request size during ADV_POPULATE_READ

[Ming Lei]

On Fri, Feb 02, 2024 at 04:15:39AM +0000, Matthew Wilcox wrote:
> On Fri, Feb 02, 2024 at 10:20:29AM +0800, Ming Lei wrote:
> > +static struct file *madvise_override_ra_win(struct file *f,
> > +		unsigned long start, unsigned long end,
> > +		unsigned int *old_ra_pages)
> > +{
> > +	unsigned int io_pages;
> > +
> > +	if (!f || !f->f_mapping || !f->f_mapping->host)
> > +		return NULL;
> 
> How can ->f_mapping be NULL?  How can f_mapping->host be NULL?

You are right, the two checks can be removed because both two won't
be NULL for opened file, and .f_ra is initialized with
f->f_mapping->host->i_mapping directly too. I will drop the checks
in next version.

BTW, looks the same check in madvise_remove() can removed too.

Thanks,
Ming