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Subject[PATCH v2 03/12] mm/filemap: Add helper for finding pages
Date
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@infradead.org>
---
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
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