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

From: "Darrick J. Wong" <[email-masked]>
Date: Mon, 21 Aug 2023 21:00:43 -0700

On Tue, Aug 22, 2023 at 02:34:06AM +0100, Matthew Wilcox wrote:
> On Tue, Aug 22, 2023 at 11:22:17AM +1000, Stephen Rothwell wrote:
> > Hi Matthew,
> > 
> > On Tue, 22 Aug 2023 02:11:44 +0100 Matthew Wilcox <[email-masked]> wrote:
> > >
> > > On Tue, Aug 22, 2023 at 09:55:37AM +1000, Stephen Rothwell wrote:
> > > > In file included from include/trace/trace_events.h:27,
> > > >                  from include/trace/define_trace.h:102,
> > > >                  from fs/xfs/xfs_trace.h:4428,
> > > >                  from fs/xfs/xfs_trace.c:45:
> > > > include/linux/pgtable.h:8:25: error: initializer element is not constant
> > > >     8 | #define PMD_ORDER       (PMD_SHIFT - PAGE_SHIFT)  
> > > 
> > > Ummm.  PowerPC doesn't have a compile-time constant PMD size?
> > 
> > Yeah, you are not the first (or probably the last) to be caught by that.
> 
> I think this will do the trick.  Any comments?
> 
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 1904eaf7a2e9..d5a4e6c2dcd1 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -796,15 +796,6 @@ DEFINE_INODE_EVENT(xfs_inode_reclaiming);
>  DEFINE_INODE_EVENT(xfs_inode_set_need_inactive);
>  DEFINE_INODE_EVENT(xfs_inode_inactivating);
>  
> -/*
> - * ftrace's __print_symbolic requires that all enum values be wrapped in the
> - * TRACE_DEFINE_ENUM macro so that the enum value can be encoded in the ftrace
> - * ring buffer.  Somehow this was only worth mentioning in the ftrace sample
> - * code.
> - */

Please leave this ^^^ comment, because the need for TRACE_DEFINE_ENUM to
make enums work in tracepoints is not at all obvious.

> -TRACE_DEFINE_ENUM(PMD_ORDER);
> -TRACE_DEFINE_ENUM(PUD_ORDER);
> -
>  TRACE_DEFINE_ENUM(XFS_REFC_DOMAIN_SHARED);
>  TRACE_DEFINE_ENUM(XFS_REFC_DOMAIN_COW);
>  
> @@ -823,13 +814,10 @@ TRACE_EVENT(xfs_filemap_fault,
>  		__entry->order = order;
>  		__entry->write_fault = write_fault;
>  	),
> -	TP_printk("dev %d:%d ino 0x%llx %s write_fault %d",
> +	TP_printk("dev %d:%d ino 0x%llx order:%u write_fault %d",

"order %u" to match the (non dev_t) style of the rest of the xfs
tracepoints.

--D

>  		  MAJOR(__entry->dev), MINOR(__entry->dev),
>  		  __entry->ino,
> -		  __print_symbolic(__entry->order,
> -			{ 0,		"PTE" },
> -			{ PMD_ORDER,	"PMD" },
> -			{ PUD_ORDER,	"PUD" }),
> +		  __entry->order,
>  		  __entry->write_fault)
>  )
>  
> 
>