Re: [PATCH 21/22] xfs: %pF is only for function pointers

From: Dave Chinner
Date: Mon Aug 31 2015 - 04:07:10 EST

On Wed, Mar 11, 2015 at 10:13:56PM -0500, Scott Wood wrote:
> Use %pS for actual addresses, otherwise you'll get bad output
> on arches like ppc64 where %pF expects a function descriptor.
> Signed-off-by: Scott Wood <scottwood@xxxxxxxxxxxxx>
> Cc: xfs@xxxxxxxxxxx

Scott, I've just found that this change (commit 65dd297 "xfs: %pF is
only for function pointers") breaks the symbolic printing in XFS
trace events on x86_64. eg.

> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 51372e3..b5ac81e 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -115,7 +115,7 @@ DECLARE_EVENT_CLASS(xfs_perag_class,
> __entry->refcount = refcount;
> __entry->caller_ip = caller_ip;
> ),
> - TP_printk("dev %d:%d agno %u refcount %d caller %pf",
> + TP_printk("dev %d:%d agno %u refcount %d caller %ps",
> MAJOR(__entry->dev), MINOR(__entry->dev),
> __entry->agno,
> __entry->refcount,

This results in output like this:

760.828474: xfs_perag_get: dev 253:32 agno 13 refcount 10 caller 0xffffffff814eef02s
760.828476: xfs_perag_put: dev 253:32 agno 13 refcount 9 caller 0xffffffff814eefe8s

When I revert this commit, I get:

71.911265: xfs_perag_get: dev 253:32 agno 0 refcount 11 caller xfs_extent_busy_insert
71.911266: xfs_perag_put: dev 253:32 agno 0 refcount 10 caller xfs_extent_busy_insert

Which is exactly what we should be getting from the tracing. I'm
using trace-cmd to gather and print the events, and it breaks
both old and current versions of trace-cmd.

Can you please look into why this change broke the tracing output
on x86-64 - if there is no obvious/easy fix for it, then I'm simply
going to revert it because having the tracing work correctly on
x86-64 is far more important to us than ppc64 or ia64....


Dave Chinner
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at