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Message-ID: <20200929082708.GA10896@quack2.suse.cz>
Date: Tue, 29 Sep 2020 10:27:08 +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 03/12] mm/filemap: Add helper for finding pages
On Mon 14-09-20 14:00:33, Matthew Wilcox (Oracle) wrote:
> There is a lot of common code in find_get_entries(),
> find_get_pages_range() and find_get_pages_range_tag(). Factor out
> xas_find_get_entry() which simplifies all three functions.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Looks good. You can add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> mm/filemap.c | 98 +++++++++++++++++++++++-----------------------------
> 1 file changed, 43 insertions(+), 55 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 7d8cf1a25628..d8f5ff07eb9c 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1758,6 +1758,43 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> }
> EXPORT_SYMBOL(pagecache_get_page);
>
> +static inline struct page *xas_find_get_entry(struct xa_state *xas,
> + pgoff_t max, xa_mark_t mark)
> +{
> + struct page *page;
> +
> +retry:
> + if (mark == XA_PRESENT)
> + page = xas_find(xas, max);
> + else
> + page = xas_find_marked(xas, max, mark);
> +
> + if (xas_retry(xas, page))
> + goto retry;
> + /*
> + * A shadow entry of a recently evicted page, a swap
> + * entry from shmem/tmpfs or a DAX entry. Return it
> + * without attempting to raise page count.
> + */
> + if (!page || xa_is_value(page))
> + return page;
> +
> + if (!page_cache_get_speculative(page))
> + goto reset;
> +
> + /* Has the page moved or been split? */
> + if (unlikely(page != xas_reload(xas))) {
> + put_page(page);
> + goto reset;
> + }
> + VM_BUG_ON_PAGE(!thp_contains(page, xas->xa_index), page);
> +
> + return page;
> +reset:
> + xas_reset(xas);
> + goto retry;
> +}
> +
> /**
> * find_get_entries - gang pagecache lookup
> * @mapping: The address_space to search
> @@ -1797,42 +1834,21 @@ unsigned find_get_entries(struct address_space *mapping,
> return 0;
>
> rcu_read_lock();
> - xas_for_each(&xas, page, ULONG_MAX) {
> - if (xas_retry(&xas, page))
> - continue;
> - /*
> - * A shadow entry of a recently evicted page, a swap
> - * entry from shmem/tmpfs or a DAX entry. Return it
> - * without attempting to raise page count.
> - */
> - if (xa_is_value(page))
> - goto export;
> -
> - if (!page_cache_get_speculative(page))
> - goto retry;
> -
> - /* Has the page moved or been split? */
> - if (unlikely(page != xas_reload(&xas)))
> - goto put_page;
> -
> + while ((page = xas_find_get_entry(&xas, ULONG_MAX, XA_PRESENT))) {
> /*
> * Terminate early on finding a THP, to allow the caller to
> * handle it all at once; but continue if this is hugetlbfs.
> */
> - if (PageTransHuge(page) && !PageHuge(page)) {
> + if (!xa_is_value(page) && PageTransHuge(page) &&
> + !PageHuge(page)) {
> page = find_subpage(page, xas.xa_index);
> nr_entries = ret + 1;
> }
> -export:
> +
> indices[ret] = xas.xa_index;
> entries[ret] = page;
> if (++ret == nr_entries)
> break;
> - continue;
> -put_page:
> - put_page(page);
> -retry:
> - xas_reset(&xas);
> }
> rcu_read_unlock();
> return ret;
> @@ -1871,30 +1887,16 @@ unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
> return 0;
>
> rcu_read_lock();
> - xas_for_each(&xas, page, end) {
> - if (xas_retry(&xas, page))
> - continue;
> + while ((page = xas_find_get_entry(&xas, end, XA_PRESENT))) {
> /* Skip over shadow, swap and DAX entries */
> if (xa_is_value(page))
> continue;
>
> - if (!page_cache_get_speculative(page))
> - goto retry;
> -
> - /* Has the page moved or been split? */
> - if (unlikely(page != xas_reload(&xas)))
> - goto put_page;
> -
> pages[ret] = find_subpage(page, xas.xa_index);
> if (++ret == nr_pages) {
> *start = xas.xa_index + 1;
> goto out;
> }
> - continue;
> -put_page:
> - put_page(page);
> -retry:
> - xas_reset(&xas);
> }
>
> /*
> @@ -1993,9 +1995,7 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
> return 0;
>
> rcu_read_lock();
> - xas_for_each_marked(&xas, page, end, tag) {
> - if (xas_retry(&xas, page))
> - continue;
> + while ((page = xas_find_get_entry(&xas, end, tag))) {
> /*
> * Shadow entries should never be tagged, but this iteration
> * is lockless so there is a window for page reclaim to evict
> @@ -2004,23 +2004,11 @@ unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
> if (xa_is_value(page))
> continue;
>
> - if (!page_cache_get_speculative(page))
> - goto retry;
> -
> - /* Has the page moved or been split? */
> - if (unlikely(page != xas_reload(&xas)))
> - goto put_page;
> -
> pages[ret] = page;
> if (++ret == nr_pages) {
> *index = page->index + thp_nr_pages(page);
> goto out;
> }
> - continue;
> -put_page:
> - put_page(page);
> -retry:
> - xas_reset(&xas);
> }
>
> /*
> --
> 2.28.0
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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