[PATCH v13 087/137] mm/filemap: Add filemap_get_folio

Matthew Wilcox (Oracle)
2021-07-12T03:54:09Z

filemap_get_folio() is a replacement for find_get_page().
Turn pagecache_get_page() into a wrapper around __filemap_get_folio().
Remove find_lock_head() as this use case is now covered by
filemap_get_folio().

Reduces overall kernel size by 209 bytes. __filemap_get_folio() is
316 bytes shorter than pagecache_get_page() was, but the new
pagecache_get_page() is 99 bytes.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/pagemap.h | 41 +++++++++---------
mm/filemap.c | 92 ++++++++++++++++++++---------------------
mm/folio-compat.c | 12 ++++++
3 files changed, 76 insertions(+), 69 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 5a2ac2fc6dfa..5183e371e80f 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -302,8 +302,26 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
#define FGP_HEAD 0x00000080
#define FGP_ENTRY 0x00000100

-struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
- int fgp_flags, gfp_t cache_gfp_mask);
+struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
+ int fgp_flags, gfp_t gfp);
+struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
+ int fgp_flags, gfp_t gfp);
+
+/**
+ * filemap_get_folio - Find and get a folio.
+ * @mapping: The address_space to search.
+ * @index: The page index.
+ *
+ * Looks up the page cache entry at @mapping & @index. If a folio is
+ * present, it is returned with an increased refcount.
+ *
+ * Otherwise, %NULL is returned.
+ */
+static inline struct folio *filemap_get_folio(struct address_space *mapping,
+ pgoff_t index)
+{
+ return __filemap_get_folio(mapping, index, 0, 0);
+}

/**
* find_get_page - find and get a page reference
@@ -346,25 +364,6 @@ static inline struct page *find_lock_page(struct address_space *mapping,
return pagecache_get_page(mapping, index, FGP_LOCK, 0);
}

-/**
- * find_lock_head - Locate, pin and lock a pagecache page.
- * @mapping: The address_space to search.
- * @index: The page index.
- *
- * Looks up the page cache entry at @mapping & @index. If there is a
- * page cache page, its head page is returned locked and with an increased
- * refcount.
- *
- * Context: May sleep.
- * Return: A struct page which is !PageTail, or %NULL if there is no page
- * in the cache for this index.
- */
-static inline struct page *find_lock_head(struct address_space *mapping,
- pgoff_t index)
-{
- return pagecache_get_page(mapping, index, FGP_LOCK | FGP_HEAD, 0);
-}
-
/**
* find_or_create_page - locate or add a pagecache page
* @mapping: the page's address_space
diff --git a/mm/filemap.c b/mm/filemap.c
index 5e1e357ec43f..3487153c2630 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1794,93 +1794,89 @@ static void *mapping_get_entry(struct address_space *mapping, pgoff_t index)
}

/**
- * pagecache_get_page - Find and get a reference to a page.
+ * __filemap_get_folio - Find and get a reference to a folio.
* @mapping: The address_space to search.
* @index: The page index.
- * @fgp_flags: %FGP flags modify how the page is returned.
- * @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
+ * @fgp_flags: %FGP flags modify how the folio is returned.
+ * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
*
* Looks up the page cache entry at @mapping & @index.
*
* @fgp_flags can be zero or more of these flags:
*
- * * %FGP_ACCESSED - The page will be marked accessed.
- * * %FGP_LOCK - The page is returned locked.
- * * %FGP_HEAD - If the page is present and a THP, return the head page
- * rather than the exact page specified by the index.
+ * * %FGP_ACCESSED - The folio will be marked accessed.
+ * * %FGP_LOCK - The folio is returned locked.
* * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it
- * instead of allocating a new page to replace it.
+ * instead of allocating a new folio to replace it.
* * %FGP_CREAT - If no page is present then a new page is allocated using
- * @gfp_mask and added to the page cache and the VM's LRU list.
+ * @gfp and added to the page cache and the VM's LRU list.
* The page is returned locked and with an increased refcount.
* * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
* page is already in cache. If the page was allocated, unlock it before
* returning so the caller can do the same dance.
- * * %FGP_WRITE - The page will be written
- * * %FGP_NOFS - __GFP_FS will get cleared in gfp mask
- * * %FGP_NOWAIT - Don't get blocked by page lock
+ * * %FGP_WRITE - The page will be written to by the caller.
+ * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
+ * * %FGP_NOWAIT - Don't get blocked by page lock.
*
* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
* if the %GFP flags specified for %FGP_CREAT are atomic.
*
* If there is a page cache page, it is returned with an increased refcount.
*
- * Return: The found page or %NULL otherwise.
+ * Return: The found folio or %NULL otherwise.
*/
-struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
- int fgp_flags, gfp_t gfp_mask)
+struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
+ int fgp_flags, gfp_t gfp)
{
- struct page *page;
+ struct folio *folio;

repeat:
- page = mapping_get_entry(mapping, index);
- if (xa_is_value(page)) {
+ folio = mapping_get_entry(mapping, index);
+ if (xa_is_value(folio)) {
if (fgp_flags & FGP_ENTRY)
- return page;
- page = NULL;
+ return folio;
+ folio = NULL;
}
- if (!page)
+ if (!folio)
goto no_page;

if (fgp_flags & FGP_LOCK) {
if (fgp_flags & FGP_NOWAIT) {
- if (!trylock_page(page)) {
- put_page(page);
+ if (!folio_trylock(folio)) {
+ folio_put(folio);
return NULL;
}
} else {
- lock_page(page);
+ folio_lock(folio);
}

/* Has the page been truncated? */
- if (unlikely(page->mapping != mapping)) {
- unlock_page(page);
- put_page(page);
+ if (unlikely(folio->mapping != mapping)) {
+ folio_unlock(folio);
+ folio_put(folio);
goto repeat;
}
- VM_BUG_ON_PAGE(!thp_contains(page, index), page);
+ VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
}

if (fgp_flags & FGP_ACCESSED)
- mark_page_accessed(page);
+ folio_mark_accessed(folio);
else if (fgp_flags & FGP_WRITE) {
/* Clear idle flag for buffer write */
- if (page_is_idle(page))
- clear_page_idle(page);
+ if (folio_idle(folio))
+ folio_clear_idle_flag(folio);
}
- if (!(fgp_flags & FGP_HEAD))
- page = find_subpage(page, index);

no_page:
- if (!page && (fgp_flags & FGP_CREAT)) {
+ if (!folio && (fgp_flags & FGP_CREAT)) {
int err;
if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
- gfp_mask |= __GFP_WRITE;
+ gfp |= __GFP_WRITE;
if (fgp_flags & FGP_NOFS)
- gfp_mask &= ~__GFP_FS;
+ gfp &= ~__GFP_FS;

- page = __page_cache_alloc(gfp_mask);
- if (!page)
+ folio = filemap_alloc_folio(gfp, 0);
+ if (!folio)
return NULL;

if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
@@ -1888,27 +1884,27 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,

/* Init accessed so avoid atomic mark_page_accessed later */
if (fgp_flags & FGP_ACCESSED)
- __SetPageReferenced(page);
+ __folio_set_referenced_flag(folio);

- err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
+ err = filemap_add_folio(mapping, folio, index, gfp);
if (unlikely(err)) {
- put_page(page);
- page = NULL;
+ folio_put(folio);
+ folio = NULL;
if (err == -EEXIST)
goto repeat;
}

/*
- * add_to_page_cache_lru locks the page, and for mmap we expect
- * an unlocked page.
+ * filemap_add_folio locks the page, and for mmap
+ * we expect an unlocked page.
*/
- if (page && (fgp_flags & FGP_FOR_MMAP))
- unlock_page(page);
+ if (folio && (fgp_flags & FGP_FOR_MMAP))
+ folio_unlock(folio);
}

- return page;
+ return folio;
}
-EXPORT_SYMBOL(pagecache_get_page);
+EXPORT_SYMBOL(__filemap_get_folio);

static inline struct page *find_get_entry(struct xa_state *xas, pgoff_t max,
xa_mark_t mark)
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 6b19bc4ed6b0..e833e680e944 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -115,3 +115,15 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
return filemap_add_folio(mapping, page_folio(page), index, gfp);
}
EXPORT_SYMBOL(add_to_page_cache_lru);
+
+struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
+ int fgp_flags, gfp_t gfp)
+{
+ struct folio *folio;
+
+ folio = __filemap_get_folio(mapping, index, fgp_flags, gfp);
+ if ((fgp_flags & FGP_HEAD) || !folio || xa_is_value(folio))
+ return &folio->page;
+ return folio_file_page(folio, index);
+}
+EXPORT_SYMBOL(pagecache_get_page);
--
2.30.2