Re: [f2fs-dev] [PATCH] f2fs: Eliminate usage of uninitialized_var() macro

[Jason Yan]

å 2020/6/15 16:26, Chao Yu åé:
> On 2020/6/15 12:02, Jason Yan wrote:
> > This is an effort to eliminate the uninitialized_var() macro[1].
> >
> > The use of this macro is the wrong solution because it forces off ANY
> > analysis by the compiler for a given variable. It even masks "unused
> > variable" warnings.
> >
> > Quoted from Linus[2]:
> >
> > "It's a horrible thing to use, in that it adds extra cruft to the
> > source code, and then shuts up a compiler warning (even the _reliable_
> > warnings from gcc)."
> >
> > The gcc option "-Wmaybe-uninitialized" has been disabled and this change
> > will not produce any warnnings even with "make W=1".
> >
> > [1] https://github.com/KSPP/linux/issues/81
> > [2] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@xxxxxxxxxxxxxx/
> >
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Signed-off-by: Jason Yan <yanaijie@xxxxxxxxxx>
> > ---
> >   fs/f2fs/data.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 326c63879ddc..e6ec61274d76 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -2856,7 +2856,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> >   	};
> >   #endif
> >   	int nr_pages;
> > -	pgoff_t uninitialized_var(writeback_index);
> > +	pgoff_t writeback_index;
>
> I suggest to delete this variable directly, as we did for mm in
> commit 28659cc8cc87 (mm/page-writeback.c: remove unused variable).

Good suggestion, I will send v2.

Thanks,
Jason

> Thanks,
>
> >   	pgoff_t index;
> >   	pgoff_t end;		/* Inclusive */
> >   	pgoff_t done_index;
>
> .