Re: [PATCH] wil6210: fix debugfs_simple_attr.cocci warnings

[Julia Lawall <julia.lawall-L2FTfq7BK8M@public.gmane.org>]

On Fri, 5 Oct 2018, Kalle Valo wrote:

> YueHaibing <yuehaibing-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> writes:
>
> > Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE
> > for debugfs files.
> >
> > Semantic patch information:
> > Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file()
> > imposes some significant overhead as compared to
> > DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe().
> >
> > Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci
>
> Just out of curiosity, what kind of overhead are we talking about here?

The log message on the commit introducing the semantic patch says the
following:

    In order to protect against file removal races, debugfs files created via
    debugfs_create_file() now get wrapped by a struct file_operations at their
    opening.

    If the original struct file_operations are known to be safe against removal
    races by themselves already, the proxy creation may be bypassed by creating
    the files through debugfs_create_file_unsafe().

    In order to help debugfs users who use the common
      DEFINE_SIMPLE_ATTRIBUTE() + debugfs_create_file()
    idiom to transition to removal safe struct file_operations, the helper
    macro DEFINE_DEBUGFS_ATTRIBUTE() has been introduced.

    Thus, the preferred strategy is to use
      DEFINE_DEBUGFS_ATTRIBUTE() + debugfs_create_file_unsafe()
    now.

julia

>
> --
> Kalle Valo
>