Re: [PATCH v2] mm: Fix error handling in __filemap_get_folio() with FGP_NOWAIT

[Christoph Hellwig]

On Mon, Feb 24, 2025 at 05:13:28AM -0300, Raphael S. Carvalho wrote:
> +		if (err) {
> +			/* Prevents -ENOMEM from escaping to user space with FGP_NOWAIT */
> +			if ((fgp_flags & FGP_NOWAIT) && err == -ENOMEM)
> +				err = -EAGAIN;
>  			return ERR_PTR(err);

I don't think the comment is all that useful.  It's also overly long.

I'd suggest this instead:

			/*
			 * When NOWAIT I/O fails to allocate folios this could
			 * be due to a nonblocking memory allocation and not
			 * because the system actually is out of memory.
			 * Return -EAGAIN so that there caller retries in a
			 * blocking fashion instead of propagating -ENOMEM
			 * to the application.
			 */