Re: [PATCH] pstore/zone: Emit registration message as a single pr_info()

[Kartik Rajput]

Hi Kees,

Thanks for reviewing the patch!

On 24/04/26 21:03, Kees Cook wrote:
> External email: Use caution opening links or attachments
>
>
> On April 24, 2026 2:58:20 AM PDT, Kartik Rajput <kkartik@xxxxxxxxxx> wrote:
> > register_pstore_zone() prints its "registered ... as backend for ..."
> > summary as a pr_info() followed by several pr_cont() calls.
> >
> > pr_cont() is not atomic and has no log level of its own. It appends
> > to whichever line was most recently opened by a printk(). If a
> > pr_err() or pr_warn() from another CPU or an interrupt handler
> > preempts the pr_info() / pr_cont() sequence, it closes the
> > continuation between the fragments. This can cause parts of the
> > pstore registration message to appear at the wrong log level and be
> > interleaved with other messages.
> >
> > Furthermore, this causes the detection of new warning and error
> > messages in the kernel log to be unreliable.
> >
> > Format the registration line in a small local buffer using
> > scnprintf() and emit it with a single pr_info() call, making the
> > line atomic with respect to concurrent printk() callers.  No
> > functional change to registration.
> >
> > Signed-off-by: Kartik Rajput <kkartik@xxxxxxxxxx>
> > ---
> > fs/pstore/zone.c | 20 ++++++++++----------
> > 1 file changed, 10 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
> > index a3b003f9a3a0..fbe0a252dd2a 100644
> > --- a/fs/pstore/zone.c
> > +++ b/fs/pstore/zone.c
> > @@ -1301,6 +1301,8 @@ int register_pstore_zone(struct pstore_zone_info *info)
> > {
> >        int err = -EINVAL;
> >        struct psz_context *cxt = &pstore_zone_cxt;
> > +      char buf[256] = "";
> > +      size_t len = 0;
>
> Please use a seq_buf backed by a stack array instead of the scnprintf calls.
>
> Otherwise, yes, seems good to keep this all on one line.
>
> Thanks!
>
> -Kees

ACK. I will push v2 to use seq_buf instead of scnprintf calls.

Thanks,
Kartik