mm: convert find_get_entry to return the head page

There are only four callers remaining of find_get_entry().
get_shadow_from_swap_cache() only wants to see shadow entries and doesn't
care about which page is returned.  Push the find_subpage() call into
find_lock_entry(), find_get_incore_page() and pagecache_get_page().

[willy@infradead.org: fix oops]
Link: https://lkml.kernel.org/r/20200914112738.GM6583@casper.infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Link: https://lkml.kernel.org/r/20200910183318.20139-7-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index 089a2f02067f371e4e380bf32ab96daf1524ad3c..9457d4f8b1c12fb8641015ce184c742d12c3d219 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1645,19 +1645,19 @@ 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();
@@ -1685,7 +1685,6 @@ repeat:
                put_page(page);
                goto repeat;
        }
-       page = find_subpage(page, offset);
 out:
        rcu_read_unlock();
 
@@ -1722,6 +1721,7 @@ repeat:
                        put_page(page);
                        goto repeat;
                }
+               page = find_subpage(page, offset);
                VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
        }
        return page;
@@ -1768,6 +1768,7 @@ repeat:
                page = NULL;
        if (!page)
                goto no_page;
+       page = find_subpage(page, index);
 
        if (fgp_flags & FGP_LOCK) {
                if (fgp_flags & FGP_NOWAIT) {

diff --git a/mm/swap_state.c b/mm/swap_state.c
index c79e2242dd04dcc5f3926d8e63e27469685a77ce..f24f2cea4238e1fe2c3b6f2937ee0c22e00b8b73 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -431,8 +431,10 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
        struct swap_info_struct *si;
        struct page *page = find_get_entry(mapping, index);
 
-       if (!xa_is_value(page))
+       if (!page)
                return page;
+       if (!xa_is_value(page))
+               return find_subpage(page, index);
        if (!shmem_mapping(mapping))
                return NULL;