[PATCH v14 026/138] mm/writeback: Add folio_wait_stable()

Matthew Wilcox (Oracle)
2021-07-15T03:59:53Z

Move wait_for_stable_page() into the folio compatibility file.
folio_wait_stable() avoids a call to compound_head() and is 14 bytes
smaller than wait_for_stable_page() was. The net text size grows by 16
bytes as a result of this patch. We can also remove thp_head() as this
was the last user.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: David Howells <dhowells@redhat.com>
---
include/linux/huge_mm.h | 15 ---------------
include/linux/pagemap.h | 1 +
mm/folio-compat.c | 6 ++++++
mm/page-writeback.c | 24 ++++++++++++++----------
4 files changed, 21 insertions(+), 25 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index f123e15d966e..f280f33ff223 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -250,15 +250,6 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud,
return NULL;
}

-/**
- * thp_head - Head page of a transparent huge page.
- * @page: Any page (tail, head or regular) found in the page cache.
- */
-static inline struct page *thp_head(struct page *page)
-{
- return compound_head(page);
-}
-
/**
* thp_order - Order of a transparent huge page.
* @page: Head page of a transparent huge page.
@@ -336,12 +327,6 @@ static inline struct list_head *page_deferred_list(struct page *page)
#define HPAGE_PUD_MASK ({ BUILD_BUG(); 0; })
#define HPAGE_PUD_SIZE ({ BUILD_BUG(); 0; })

-static inline struct page *thp_head(struct page *page)
-{
- VM_BUG_ON_PGFLAGS(PageTail(page), page);
- return page;
-}
-
static inline unsigned int thp_order(struct page *page)
{
VM_BUG_ON_PGFLAGS(PageTail(page), page);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 0c5f53368fe9..96b62a2331fb 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -772,6 +772,7 @@ int folio_wait_writeback_killable(struct folio *folio);
void end_page_writeback(struct page *page);
void folio_end_writeback(struct folio *folio);
void wait_for_stable_page(struct page *page);
+void folio_wait_stable(struct folio *folio);

void __set_page_dirty(struct page *, struct address_space *, int warn);
int __set_page_dirty_nobuffers(struct page *page);
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 41275dac7a92..3c83f03b80d7 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -29,3 +29,9 @@ void wait_on_page_writeback(struct page *page)
return folio_wait_writeback(page_folio(page));
}
EXPORT_SYMBOL_GPL(wait_on_page_writeback);
+
+void wait_for_stable_page(struct page *page)
+{
+ return folio_wait_stable(page_folio(page));
+}
+EXPORT_SYMBOL_GPL(wait_for_stable_page);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c2c00e1533ad..a078e9786cc4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2877,17 +2877,21 @@ int folio_wait_writeback_killable(struct folio *folio)
EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);

/**
- * wait_for_stable_page() - wait for writeback to finish, if necessary.
- * @page: The page to wait on.
+ * folio_wait_stable() - wait for writeback to finish, if necessary.
+ * @folio: The folio to wait on.
*
- * This function determines if the given page is related to a backing device
- * that requires page contents to be held stable during writeback. If so, then
- * it will wait for any pending writeback to complete.
+ * This function determines if the given folio is related to a backing
+ * device that requires folio contents to be held stable during writeback.
+ * If so, then it will wait for any pending writeback to complete.
+ *
+ * Context: Sleeps. Must be called in process context and with
+ * no spinlocks held. Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
*/
-void wait_for_stable_page(struct page *page)
+void folio_wait_stable(struct folio *folio)
{
- page = thp_head(page);
- if (page->mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
- wait_on_page_writeback(page);
+ if (folio->mapping->host->i_sb->s_iflags & SB_I_STABLE_WRITES)
+ folio_wait_writeback(folio);
}
-EXPORT_SYMBOL_GPL(wait_for_stable_page);
+EXPORT_SYMBOL_GPL(folio_wait_stable);
--
2.30.2