linux-kernel - Re: [RFC v5 PATCH] mm: shmem: make stat.st_blksize return huge page size if THP is on

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Date:   Tue, 01 May 2018 00:05:48 -0700
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     kirill.shutemov@...ux.intel.com, hughd@...gle.com,
        mhocko@...nel.org, hch@...radead.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v5 PATCH] mm: shmem: make stat.st_blksize return huge page
 size if THP is on

On Mon, 2018-04-30 at 16:40 -0700, Andrew Morton wrote:
> On Wed, 25 Apr 2018 22:13:53 +0800 Yang Shi <yang.shi@...ux.alibaba.com> wrote:
> 
> > Since tmpfs THP was supported in 4.8, hugetlbfs is not the only
> > filesystem with huge page support anymore. tmpfs can use huge page via
> > THP when mounting by "huge=" mount option.
[]
> > @@ -571,6 +571,16 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
> >  }
> >  #endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
> >  
> > +static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
> > +{
> > +	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
> > +	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
> > +	    shmem_huge != SHMEM_HUGE_DENY)
> > +		return true;
> > +	else
> > +		return false;
> > +}
> 
> Nit: we don't need that `else'.  Checkpatch normally warns about this,
> but not in this case.

because there are those that like symmetry.

> --- a/mm/shmem.c~mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on-fix
> +++ a/mm/shmem.c
> @@ -577,8 +577,7 @@ static inline bool is_huge_enabled(struc
>  	    (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
>  	    shmem_huge != SHMEM_HUGE_DENY)
>  		return true;
> -	else
> -		return false;
> +	return false;
>  }

Perhaps this case is better without the if/else as just

	return <logic>;