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

Christoph Hellwig
2025-02-24T14:17:49Z

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.
*/