linux-kernel - Re: [PATCH v2 09/12] mm: Pass pvec directly to find_get

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Date:   Tue, 29 Sep 2020 11:07:19 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        William Kucharski <william.kucharski@...cle.com>,
        Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Dave Chinner <dchinner@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 09/12] mm: Pass pvec directly to find_get_entries

On Mon 14-09-20 14:00:39, Matthew Wilcox (Oracle) wrote:
> All callers of find_get_entries() use a pvec, so pass it directly
> instead of manipulating it in the caller.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  include/linux/pagemap.h |  3 +--
>  mm/filemap.c            | 21 +++++++++------------
>  mm/shmem.c              |  5 ++---
>  mm/swap.c               |  4 +---
>  4 files changed, 13 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index d440c6750757..788c280737e0 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -414,8 +414,7 @@ static inline struct page *find_subpage(struct page *head, pgoff_t index)
>  }
>  
>  unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
> -		pgoff_t end, unsigned int nr_entries, struct page **entries,
> -		pgoff_t *indices);
> +		pgoff_t end, struct pagevec *pvec, pgoff_t *indices);
>  unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
>  			pgoff_t end, unsigned int nr_pages,
>  			struct page **pages);
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 6dc0a9b8c0fa..a4ad294a34dc 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1800,14 +1800,12 @@ static inline struct page *xas_find_get_entry(struct xa_state *xas,
>   * @mapping:	The address_space to search
>   * @start:	The starting page cache index
>   * @end:	The final page index (inclusive).
> - * @nr_entries:	The maximum number of entries
> - * @entries:	Where the resulting entries are placed
> + * @pvec:	Where the resulting entries are placed.
>   * @indices:	The cache indices corresponding to the entries in @entries
>   *
> - * find_get_entries() will search for and return a group of up to
> - * @nr_entries entries in the mapping.  The entries are placed at
> - * @entries.  find_get_entries() takes a reference against any actual
> - * pages it returns.
> + * find_get_entries() will search for and return a batch of entries in
> + * the mapping.  The entries are placed in @pvec.  find_get_entries()
> + * takes a reference on any actual pages it returns.
>   *
>   * The search returns a group of mapping-contiguous page cache entries
>   * with ascending indexes.  There may be holes in the indices due to
> @@ -1824,15 +1822,12 @@ static inline struct page *xas_find_get_entry(struct xa_state *xas,
>   * Return: the number of pages and shadow entries which were found.
>   */
>  unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
> -		pgoff_t end, unsigned int nr_entries, struct page **entries,
> -		pgoff_t *indices)
> +		pgoff_t end, struct pagevec *pvec, pgoff_t *indices)
>  {
>  	XA_STATE(xas, &mapping->i_pages, start);
>  	struct page *page;
>  	unsigned int ret = 0;
> -
> -	if (!nr_entries)
> -		return 0;
> +	unsigned nr_entries = PAGEVEC_SIZE;
>  
>  	rcu_read_lock();
>  	while ((page = xas_find_get_entry(&xas, end, XA_PRESENT))) {
> @@ -1847,11 +1842,13 @@ unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
>  		}
>  
>  		indices[ret] = xas.xa_index;
> -		entries[ret] = page;
> +		pvec->pages[ret] = page;
>  		if (++ret == nr_entries)
>  			break;
>  	}
>  	rcu_read_unlock();
> +
> +	pvec->nr = ret;
>  	return ret;
>  }
>  
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 404e45c285ca..b2b94025841a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -963,9 +963,8 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
>  	while (index < end) {
>  		cond_resched();
>  
> -		pvec.nr = find_get_entries(mapping, index, end - 1,
> -				PAGEVEC_SIZE, pvec.pages, indices);
> -		if (!pvec.nr) {
> +		if (!find_get_entries(mapping, index, end - 1, &pvec,
> +				indices)) {
>  			/* If all gone or hole-punch or unfalloc, we're done */
>  			if (index == start || end != -1)
>  				break;
> diff --git a/mm/swap.c b/mm/swap.c
> index d4e3ba4c967c..40b23300d353 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -1060,9 +1060,7 @@ unsigned pagevec_lookup_entries(struct pagevec *pvec,
>  		struct address_space *mapping, pgoff_t start, pgoff_t end,
>  		pgoff_t *indices)
>  {
> -	pvec->nr = find_get_entries(mapping, start, end, PAGEVEC_SIZE,
> -				    pvec->pages, indices);
> -	return pagevec_count(pvec);
> +	return find_get_entries(mapping, start, end, pvec, indices);
>  }
>  
>  /**
> -- 
> 2.28.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR