linux-kernel - Re: [PATCH 09/16] huge tmpfs: decide stat.st_blksize by shmem_is

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Date:   Fri, 30 Jul 2021 16:40:54 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexey Gladkov <legion@...nel.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH 09/16] huge tmpfs: decide stat.st_blksize by shmem_is_huge()

On Fri, Jul 30, 2021 at 12:51 AM Hugh Dickins <hughd@...gle.com> wrote:
>
> 4.18 commit 89fdcd262fd4 ("mm: shmem: make stat.st_blksize return huge
> page size if THP is on") added is_huge_enabled() to decide st_blksize:
> now that hugeness can be defined per file, that too needs to be replaced
> by shmem_is_huge().
>
> Unless they have been fcntl'ed F_HUGEPAGE, this does give a different
> answer (No) for small files on a "huge=within_size" mount: but that can
> be considered a minor bugfix.  And a different answer (No) for unfcntl'ed
> files on a "huge=advise" mount: I'm reluctant to complicate it, just to
> reproduce the same debatable answer as before.
>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>

Reviewed-by: Yang Shi <shy828301@...il.com>

> ---
>  mm/shmem.c | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 67a4b7a4849b..f50f2ede71da 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -712,15 +712,6 @@ static unsigned long shmem_unused_huge_shrink(struct shmem_sb_info *sbinfo,
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>
> -static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
> -{
> -       if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
> -           (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
> -           shmem_huge != SHMEM_HUGE_DENY)
> -               return true;
> -       return false;
> -}
> -
>  /*
>   * Like add_to_page_cache_locked, but error if expected item has gone.
>   */
> @@ -1101,7 +1092,6 @@ static int shmem_getattr(struct user_namespace *mnt_userns,
>  {
>         struct inode *inode = path->dentry->d_inode;
>         struct shmem_inode_info *info = SHMEM_I(inode);
> -       struct shmem_sb_info *sb_info = SHMEM_SB(inode->i_sb);
>
>         if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
>                 spin_lock_irq(&info->lock);
> @@ -1110,7 +1100,7 @@ static int shmem_getattr(struct user_namespace *mnt_userns,
>         }
>         generic_fillattr(&init_user_ns, inode, stat);
>
> -       if (is_huge_enabled(sb_info))
> +       if (shmem_is_huge(NULL, inode, 0))
>                 stat->blksize = HPAGE_PMD_SIZE;
>
>         return 0;
> --
> 2.26.2
>