Re: [PATCH 22/25] fs/buffer: prevent WARN_ON in __alloc_pages_slowpath() when BS > PS

[Matthew Wilcox]

On Sat, Oct 25, 2025 at 11:22:18AM +0800, libaokun@xxxxxxxxxxxxxxx wrote:
> +	while (1) {
> +		folio = __filemap_get_folio(mapping, index, fgp_flags,
> +					    gfp & ~__GFP_NOFAIL);
> +		if (!IS_ERR(folio) || !(gfp & __GFP_NOFAIL))
> +			return folio;
> +
> +		if (PTR_ERR(folio) != -ENOMEM && PTR_ERR(folio) != -EAGAIN)
> +			return folio;
> +
> +		memalloc_retry_wait(gfp);
> +	}

No, absolutely not.  We're not having open-coded GFP_NOFAIL semantics.
The right way forward is for ext4 to use iomap, not for buffer heads
to support large block sizes.