Re: [PATCH 2/3] mm: Allow large pages to be added to the page cache

[Matthew Wilcox <willy@infradead.org>]

On Thu, Sep 05, 2019 at 11:23:47AM -0700, Matthew Wilcox wrote:
> +		xas_for_each_conflict(&xas, old) {
> +			if (!xa_is_value(old))
> +				break;
> +			exceptional++;
> +			if (shadowp)
> +				*shadowp = old;
> +		}
> +		if (old) {
>  			xas_set_err(&xas, -EEXIST);
> -		xas_store(&xas, page);
> +			break;

Of course, one cannot see one's own bugs until one has posted them
publically.  This will exit the loop with the lock held.

> +		}
> +		xas_create_range(&xas);
>  		if (xas_error(&xas))
>  			goto unlock;
>  

The stanza should read:

                if (old) 
                        xas_set_err(&xas, -EEXIST);
                xas_create_range(&xas);
                if (xas_error(&xas))
                        goto unlock;

just like the corresponding stanza in mm/shmem.c.

(while the xa_state is in an error condition, the xas_create_range()
function will return without doing anything).