linux-kernel - Re: [PATCH v2 2/2] mm: kvmalloc: align kvrealloc() with krealloc()

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Message-ID: <Zp_8Eo4AuoZOfuZ8@tiehlicka>
Date: Tue, 23 Jul 2024 20:53:06 +0200
From: Michal Hocko <mhocko@...e.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
	iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
	roman.gushchin@...ux.dev, 42.hyeyoo@...il.com, urezki@...il.com,
	hch@...radead.org, kees@...nel.org, ojeda@...nel.org,
	wedsonaf@...il.com, mpe@...erman.id.au, chandan.babu@...cle.com,
	christian.koenig@....com, maz@...nel.org, oliver.upton@...ux.dev,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mm: kvmalloc: align kvrealloc() with krealloc()

On Tue 23-07-24 15:33:32, Danilo Krummrich wrote:
> On Tue, Jul 23, 2024 at 02:12:23PM +0200, Michal Hocko wrote:
> > On Tue 23-07-24 13:55:48, Danilo Krummrich wrote:
[...]
> > void *kvrealloc_noprof(const void *p, size_t size, gfp_t flags)
> > {
> >         void *newp;
> > 
> >         if (!size && p) {
> >                 kvfree(p);
> >                 return NULL;
> >         }
> > 
> >         if (!is_vmalloc_addr(p))
> >                 newp = krealloc_noprof(p, size, kmalloc_gfp_adjust(flags, size));
> > 
> >         if (newp)
> >                 return newp;
> > 
> >         return vrealloc_noprof(p, size, flags);
> > }
> > EXPORT_SYMBOL(kvrealloc_noprof);
> 
> This looks weird. The fact that you're passing p to vrealloc_noprof() if
> krealloc_noprof() fails, implies that vrealloc_noprof() must be able to deal
> with pointers to kmalloc'd memory.

You are right I have oversimplified this. I was hoping to follow
kvmalloc model with a clear fallback and that should be possible but it
would require more changes. Scratch that.
-- 
Michal Hocko
SUSE Labs