Re: [PATCH 7/7] mm, swap: simplify folio swap allocation

[Matthew Wilcox]

On Sat, Feb 15, 2025 at 01:57:09AM +0800, Kairui Song wrote:
> @@ -1648,20 +1639,20 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
>  	if (list_empty(&info->swaplist))
>  		list_add(&info->swaplist, &shmem_swaplist);
>  
> -	if (add_to_swap_cache(folio, swap,
> -			__GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN,
> -			NULL) == 0) {
> +	if (folio_alloc_swap(folio, __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN)) {

add_to_swap_cache() returns 0 on success or -errno.

folio_alloc_swap returns true on success.

That would seem to indicate you should change the polarity of this test?

Or should folio_alloc_swap() return an errno?  Is there value in
distinguishing why we couldn't alloc swap (ENOMEM vs ENOSPC, perhaps?)