Re: linux-next: build failure after merge of the bcachefs tree

[Kent Overstreet]

On Thu, Mar 27, 2025 at 11:54:03AM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> On Wed, 26 Mar 2025 13:28:19 +1100 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
> >
> > After merging the bcachefs tree, today's linux-next build (x86_64
> > allmodconfig) failed like this:
> > 
> > fs/bcachefs/time_stats.c: In function 'bch2_time_stats_reset':
> > fs/bcachefs/time_stats.c:165:27: error: comparison of pointers to disjoint address spaces
> >   165 |             stats->buffer != TIME_STATS_NONPCPU) {
> >       |                           ^~
> > fs/bcachefs/time_stats.c: In function 'bch2_time_stats_exit':
> > fs/bcachefs/time_stats.c:175:27: error: comparison of pointers to disjoint address spaces
> >   175 |         if (stats->buffer != TIME_STATS_NONPCPU) {
> >       |                           ^~
> > fs/bcachefs/time_stats.c: In function 'bch2_time_stats_init_no_pcpu':
> > fs/bcachefs/time_stats.c:192:23: error: assignment from pointer to non-enclosed address space
> >   192 |         stats->buffer = TIME_STATS_NONPCPU;
> >       |                       ^
> > fs/bcachefs/time_stats.c:192:23: note: expected '__seg_gs struct time_stat_buffer *' but pointer is of type 'struct time_stat_buffer *'
> > 
> > Caused by commit
> > 
> >   5490554cf06f ("bcachefs: bch2_time_stats_init_no_pcpu()")
> > 
> > interacting with commit
> > 
> >   6a367577153a ("percpu/x86: enable strict percpu checks via named AS qualifiers")
> > (or an associated one)
> > 
> > from the mm-stable tree.
> > 
> > I have applied the following merge fix patch for today (but I think it
> > could just be applied to the bcachefs tree).
> > 
> > From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Date: Wed, 26 Mar 2025 13:15:00 +1100
> > Subject: [PATCH] fix up for "bcachefs: bch2_time_stats_init_no_pcpu()"
> > 
> > interacting with "percpu/x86: enable strict percpu checks via named AS qualifiers"
> > 
> > Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > ---
> >  fs/bcachefs/time_stats.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/bcachefs/time_stats.c b/fs/bcachefs/time_stats.c
> > index a8382d876835..b16540aa9ca4 100644
> > --- a/fs/bcachefs/time_stats.c
> > +++ b/fs/bcachefs/time_stats.c
> > @@ -11,7 +11,7 @@
> >  #include "time_stats.h"
> >  
> >  /* disable automatic switching to percpu mode */
> > -#define TIME_STATS_NONPCPU	((struct time_stat_buffer *) 1)
> > +#define TIME_STATS_NONPCPU	((struct time_stat_buffer __percpu *) 1)
> >  
> >  static const struct time_unit time_units[] = {
> >  	{ "ns",		1		 },
> > -- 
> > 2.45.2
> 
> This now fails like this:
> 
> fs/bcachefs/time_stats.c: In function 'bch2_time_stats_init_no_pcpu':
> fs/bcachefs/time_stats.c:190:23: error: assignment from pointer to non-enclosed address space
>   190 |         stats->buffer = (struct time_stat_buffer __rcu *) TIME_STATS_NONPCPU;
>       |                       ^
> fs/bcachefs/time_stats.c:190:23: note: expected '__seg_gs struct time_stat_buffer *' but pointer is of type 'struct time_stat_buffer *'
> 
> I have now )instead of the above) applied the following merge fix patch (which should be able to be applied to the bcachefs tree directly):
> 
> From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Date: Thu, 27 Mar 2025 11:42:11 +1100
> Subject: [PATCH] fix up 2 for "bcachefs: bch2_time_stats_init_no_pcpu()"
> 
> Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> ---
>  fs/bcachefs/time_stats.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/bcachefs/time_stats.c b/fs/bcachefs/time_stats.c
> index 725d433a246f..2c34fe4be912 100644
> --- a/fs/bcachefs/time_stats.c
> +++ b/fs/bcachefs/time_stats.c
> @@ -187,5 +187,5 @@ void bch2_time_stats_init(struct bch2_time_stats *stats)
>  void bch2_time_stats_init_no_pcpu(struct bch2_time_stats *stats)
>  {
>  	bch2_time_stats_init(stats);
> -	stats->buffer = (struct time_stat_buffer __rcu *) TIME_STATS_NONPCPU;
> +	stats->buffer = (struct time_stat_buffer __percpu *) TIME_STATS_NONPCPU;

Thanks, late night brain fart...