linux-kernel - Re: [PATCH v2] mm/hugetlb: Fix incorrect error return from hugetlb_reserve

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Message-ID: <20251024145119.2315897-1-joshua.hahnjy@gmail.com>
Date: Fri, 24 Oct 2025 07:51:19 -0700
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: Shameer Kolothum <skolothumtho@...dia.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	muchun.song@...ux.dev,
	osalvador@...e.de,
	vivek.kasireddy@...el.com,
	joshua.hahnjy@...il.com,
	jgg@...dia.com,
	nicolinc@...dia.com,
	nathanc@...dia.com,
	mochs@...dia.com
Subject: Re: [PATCH v2] mm/hugetlb: Fix incorrect error return from hugetlb_reserve_pages()

On Fri, 24 Oct 2025 10:42:40 +0100 Shameer Kolothum <skolothumtho@...dia.com> wrote:

> The function hugetlb_reserve_pages() returns the number of pages added
> to the reservation map on success and a negative error code on failure
> (e.g. -EINVAL, -ENOMEM). However, in some error paths, it may return -1
> directly.
> 
> For example, a failure at:
> 
>     if (hugetlb_acct_memory(h, gbl_reserve) < 0)
>         goto out_put_pages;
> 
> results in returning -1 (since add = -1), which may be misinterpreted
> in userspace as -EPERM.
> 
> Fix this by explicitly capturing and propagating the return values from
> helper functions, and using -EINVAL for all other failure cases.
> 
> Fixes: 986f5f2b4be3 ("mm/hugetlb: make hugetlb_reserve_pages() return nr of entries updated")
> Signed-off-by: Shameer Kolothum <skolothumtho@...dia.com>
> ---
>  Addressed commenst from v1. Thanks!
>  https://lore.kernel.org/linux-mm/20251022102956.245736-1-skolothumtho@nvidia.com/
> ---
>  mm/hugetlb.c | 25 ++++++++++++++++++-------
>  1 file changed, 18 insertions(+), 7 deletions(-)

Hello Shameer, LGTM, thank you for addressing the comments! Feel free to add:

Reviewed-by: Joshua Hahn <joshua.hahnjy@...il.com>

[...snip...]

> +		/* region_chg() above can return -ENOMEM */
> +		err = (chg == -ENOMEM) ? -ENOMEM : -EINVAL;

And this looks much more elegant than the version I wrote : -)