Re: Creating large folios in iomap buffered write path

[Matthew Wilcox <willy@infradead.org>]

On Thu, May 18, 2023 at 10:46:43PM +0100, Matthew Wilcox wrote:
> -struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos)
> +struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)
>  {
>  	unsigned fgp = FGP_WRITEBEGIN | FGP_NOFS;
> +	struct folio *folio;
>  
>  	if (iter->flags & IOMAP_NOWAIT)
>  		fgp |= FGP_NOWAIT;
> +	fgp |= fgp_order(len);
>  
> -	return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
> +	folio = __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
>  			fgp, mapping_gfp_mask(iter->inode->i_mapping));
> +	if (!IS_ERR(folio) && folio_test_large(folio))
> +		printk("index:%lu len:%zu order:%u\n", (unsigned long)(pos / PAGE_SIZE), len, folio_order(folio));
> +	return folio;
>  }

Forgot to take the debugging out.  This should read:

-struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos)
+struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len)
 {
 	unsigned fgp = FGP_WRITEBEGIN | FGP_NOFS;
 	if (iter->flags & IOMAP_NOWAIT)
 		fgp |= FGP_NOWAIT;
+	fgp |= fgp_order(len);
 
 	return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
 			fgp, mapping_gfp_mask(iter->inode->i_mapping));
 }