linux-kernel - Re: [PATCH 06/18] fscrypt: Include <linux/prandom.h> instead of <linux/random.h>

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Message-ID: <CAFULd4YrEHpmdDUvp7syG6rBV5LO=C8rutORS-PJoUqEYU8-Mg@mail.gmail.com>
Date: Fri, 6 Sep 2024 10:09:50 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-kernel@...r.kernel.org, "Theodore Y. Ts'o" <tytso@....edu>, 
	Jaegeuk Kim <jaegeuk@...nel.org>, linux-fscrypt@...r.kernel.org
Subject: Re: [PATCH 06/18] fscrypt: Include <linux/prandom.h> instead of <linux/random.h>

On Fri, Sep 6, 2024 at 1:02 AM Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Thu, Sep 05, 2024 at 02:17:14PM +0200, Uros Bizjak wrote:
> > Usage of pseudo-random functions requires inclusion of
> > <linux/prandom.h> header instead of <linux/random.h>.
> >
> > Signed-off-by: Uros Bizjak <ubizjak@...il.com>
> > Cc: Eric Biggers <ebiggers@...nel.org>
> > Cc: "Theodore Y. Ts'o" <tytso@....edu>
> > Cc: Jaegeuk Kim <jaegeuk@...nel.org>
> > Cc. linux-fscrypt@...r.kernel.org
> > ---
> >  fs/crypto/keyring.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
> > index 6681a71625f0..e2c10b3b960b 100644
> > --- a/fs/crypto/keyring.c
> > +++ b/fs/crypto/keyring.c
> > @@ -21,7 +21,7 @@
> >  #include <asm/unaligned.h>
> >  #include <crypto/skcipher.h>
> >  #include <linux/key-type.h>
> > -#include <linux/random.h>
> > +#include <linux/prandom.h>
> >  #include <linux/seq_file.h>
> >
>
> 1. linux-fscrypt wasn't actually Cc'ed on this patch, due to the typo of
>    "Cc." instead of "Cc:".

Uh, thanks for noticing.

> 2. Currently <linux/random.h> includes <linux/prandom.h>, so the issue described
>    in the commit message does not exist.  I assume this in changing in a later
>    patch that was not sent to me.  The commit message should be rephrased to
>    clarify that this change is needed because of header refactoring, as
>    otherwise it sounds like a bug fix.

Yes, the goal of the patch series is to allow inclusion of
<linux/percpu.h> in linux/prandom.h. The major roadblock to achieve
this is the inclusion of <linux/prandom.h> in linux/random.h, since
this creates circular dependency which doesn't allow the inclusion of
<linux/percpu.h>. Please note that this legacy include is removed in
patch 17. I will mention this in the 0000 commit.

I will also mention header refactoring in individual commits.

OTOH, I think that while particular maintainers are CC'd only on their
individual patches, it is better to send the whole series to all
mentioned mailing lists. Will do that in v2.

> 3. The proposed change does not make sense, because fs/crypto/keyring.c does not
>    use any "pseudo-random functions".  It does use get_random_once(), which is
>    defined in <linux/once.h>.  Currently <linux/random.h> includes
>    <linux/prandom.h> which includes <linux/once.h>.  If the inclusion of
>    prandom.h by random.h is going away, then perhaps random.h should include
>    once.h directly so that get_random_once() continues to work?  If not, then
>    this file should include once.h.  Either way it should not include prandom.h.

Due to the tricky nature of the whole series I tried to make
individual patches as mechanical as possible, IOW, change the
inclusion of <linux/random.h> to <linux/prandom.h>.

Looking at fs/crypto/keyring.c, it should still include
<linux/random.h> but should also include <linux/once.h>. The latter
was just accidentally included via <linux/random.h>/<linux/prandom.h>
path which is going away.

Will fix in v2.

Thanks,
Uros.