Add a new FGP_HEAD flag which avoids calling find_subpage() and add a
convenience wrapper for it.
Signed-off-by: Matthew Wilcox (Oracle) <wi...@infradead.org>
---
include/linux/pagemap.h | 32 ++++++++++++++++++++++++++------
mm/filemap.c | 9 ++++++---
2 files changed, 32 insertions(+), 9 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index f374618b2c93..4e52a3ff92fb 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -278,6 +278,7 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping,
#define FGP_NOFS 0x00000010
#define FGP_NOWAIT 0x00000020
#define FGP_FOR_MMAP 0x00000040
+#define FGP_HEAD 0x00000080
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
int fgp_flags, gfp_t cache_gfp_mask);
@@ -309,18 +310,37 @@ static inline struct page *find_get_page_flags(struct
address_space *mapping,
* @mapping: the address_space to search
* @offset: the page index
*
- * Looks up the page cache slot at @mapping & @offset. If there is a
+ * Looks up the page cache entry at @mapping & @offset. If there is a
* page cache page, it is returned locked and with an increased
* refcount.
*
- * Otherwise, %NULL is returned.
- *
- * find_lock_page() may sleep.
+ * Context: May sleep.
+ * Return: A struct page or %NULL if there is no page in the cache for this
+ * index.
*/
static inline struct page *find_lock_page(struct address_space *mapping,
- pgoff_t offset)
+ pgoff_t index)
+{
+ 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.
+ * @offset: The page index.
+ *
+ * Looks up the page cache entry at @mapping & @offset. 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, offset, FGP_LOCK, 0);
+ return pagecache_get_page(mapping, index, FGP_LOCK | FGP_HEAD, 0);
}
/**
diff --git a/mm/filemap.c b/mm/filemap.c
index 453535170b8d..e429e02317ef 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1659,6 +1659,8 @@ struct page *find_lock_entry(struct address_space
*mapping, pgoff_t index)
*
* * %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_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.
* The page is returned locked and with an increased refcount.
@@ -1687,7 +1689,6 @@ 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) {
@@ -1700,12 +1701,12 @@ struct page *pagecache_get_page(struct address_space
*mapping, pgoff_t index,
}
/* Has the page been truncated? */
- if (unlikely(compound_head(page)->mapping != mapping)) {
+ if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
- VM_BUG_ON_PAGE(page->index != index, page);
+ VM_BUG_ON_PAGE(!thp_contains(page, index), page);
}
if (fgp_flags & FGP_ACCESSED)
@@ -1715,6 +1716,8 @@ struct page *pagecache_get_page(struct address_space
*mapping, pgoff_t index,
if (page_is_idle(page))
clear_page_idle(page);
}
+ if (!(fgp_flags & FGP_HEAD))
+ page = find_subpage(page, index);
no_page:
if (!page && (fgp_flags & FGP_CREAT)) {
--
2.28.0
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