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

[Matthew Wilcox]

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?