linux-kernel - Re: [RFC PATCH v2 1/4] mm/vmalloc: warn on invalid vmalloc gfp flags

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Message-ID: <CA+KHdyWxjqAxVEBjOun9VxoeErWEyba3OvcJveLqnRuBLk2RLA@mail.gmail.com>
Date: Wed, 5 Nov 2025 14:16:24 +0100
From: Uladzislau Rezki <urezki@...il.com>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Andrew Morton <akpm@...ux-foundation.org>, Christoph Hellwig <hch@...radead.org>
Subject: Re: [RFC PATCH v2 1/4] mm/vmalloc: warn on invalid vmalloc gfp flags

> On Mon, Nov 03, 2025 at 11:04:26AM -0800, Vishal Moola (Oracle) wrote:
> > Vmalloc explicitly supports a list of flags, but we never enforce them.
> > vmalloc has been trying to handle unsupported flags by clearing and
> > setting flags wherever necessary. This is messy and makes the code
> > harder to understand, when we could simply check for a supported input
> > immediately instead.
> >
> > Define a helper mask and function telling callers they have passed in
> > invalid flags, and clear those unsupported vmalloc flags.
> >
> > Suggested-by: Christoph Hellwig <hch@...radead.org>
> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> > ---
> >  mm/vmalloc.c | 24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 0832f944544c..290016c7fb58 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -3911,6 +3911,26 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> >       return NULL;
> >  }
> >
> > +/*
> > + * See __vmalloc_node_range() for a clear list of supported vmalloc flags.
> > + * This gfp lists all flags currently passed through vmalloc. Currently,
> > + * __GFP_ZERO is used by BFP and __GFP_NORETRY is used by percpu.
> > + */
> > +#define GFP_VMALLOC_SUPPORTED (GFP_KERNEL | GFP_ATOMIC | GFP_NOWAIT |\
> > +                             __GFP_NOFAIL |  __GFP_ZERO | __GFP_NORETRY)
> > +
Also we do support %GFP_NOFS and %GFP_NOIO flags.

-- 
Uladzislau Rezki