[PATCH 6/8] mm: Convert find_get_entry to return the head page

Matthew Wilcox (Oracle)
2020-08-19T18:48:48Z

There are only three callers remaining of find_get_entry().
find_get_swap_page() is happy to get the head page instead of the subpage.
Add find_subpage() calls to find_lock_entry() and pagecache_get_page()
to avoid auditing all their callers.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/pagemap.h | 4 ++--
mm/filemap.c | 13 +++++++------
2 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7de11dcd534d..8261c64f592d 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -384,8 +384,8 @@ static inline struct page *find_subpage(struct page *head, pgoff_t index)
return head + (index & (thp_nr_pages(head) - 1));
}

-struct page *find_get_entry(struct address_space *mapping, pgoff_t offset);
-struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset);
+struct page *find_get_entry(struct address_space *mapping, pgoff_t index);
+struct page *find_lock_entry(struct address_space *mapping, pgoff_t index);
unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
unsigned int nr_entries, struct page **entries,
pgoff_t *indices);
diff --git a/mm/filemap.c b/mm/filemap.c
index 36067cf7f8c5..5a87e1bdddd6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1547,19 +1547,19 @@ EXPORT_SYMBOL(page_cache_prev_miss);
/**
* find_get_entry - find and get a page cache entry
* @mapping: the address_space to search
- * @offset: the page cache index
+ * @index: The page cache index.
*
* Looks up the page cache slot at @mapping & @offset. If there is a
- * page cache page, it is returned with an increased refcount.
+ * page cache page, the head page is returned with an increased refcount.
*
* If the slot holds a shadow entry of a previously evicted page, or a
* swap entry from shmem/tmpfs, it is returned.
*
- * Return: the found page or shadow entry, %NULL if nothing is found.
+ * Return: The head page or shadow entry, %NULL if nothing is found.
*/
-struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
+struct page *find_get_entry(struct address_space *mapping, pgoff_t index)
{
- XA_STATE(xas, &mapping->i_pages, offset);
+ XA_STATE(xas, &mapping->i_pages, index);
struct page *page;

rcu_read_lock();
@@ -1587,7 +1587,6 @@ struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
put_page(page);
goto repeat;
}
- page = find_subpage(page, offset);
out:
rcu_read_unlock();

@@ -1624,6 +1623,7 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
put_page(page);
goto repeat;
}
+ page = find_subpage(page, offset);
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
}
return page;
@@ -1670,6 +1670,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
page = NULL;
if (!page)
goto no_page;
+ page = find_subpage(page, index);

if (fgp_flags & FGP_LOCK) {
if (fgp_flags & FGP_NOWAIT) {
--
2.28.0