linux-kernel - Re: Question about vmalloc(GFP

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Message-ID: <ZzxMW-AzPY7C27_L@tiehlicka>
Date: Tue, 19 Nov 2024 09:29:15 +0100
From: Michal Hocko <mhocko@...e.com>
To: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
Cc: Linux Memory Management List <linux-mm@...ck.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Question about vmalloc(GFP_NOFS)

On Tue 19-11-24 15:24:03, Pavel Tikhomirov wrote:
[...]
> In commit 451769ebb7e79 ("mm/vmalloc: alloc GFP_NO{FS,IO} for vmalloc") we
> add implicit memalloc_noXX_save/memalloc_noXX_restore at this code path:
> 
>   +->kvmalloc
>     +-> ...
>       +-> __kvmalloc_node_noprof
>         +-> __vmalloc_node_range_noprof
>           +-> __vmalloc_area_node
> 
> So kvmalloc should be safe now with GFP_NOIO.

Correct.

> Should we correct the documentation?

Yes, please. I think it would be useful to explicitly name the above
commit because pre 5.17 kernels or those who haven't backported it are
still in same position and that could get dangerous if they try to
backport [k]vmalloc GFP_NOFS patches. Thanks!

-- 
Michal Hocko
SUSE Labs