[v10,27/33] mm/writeback: Add folio_wait_stable

Commit Message

Matthew Wilcox May 11, 2021, 9:47 p.m. UTC

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 24
bytes as a result of this patch.

Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: Jeff Layton <[e-mail]>
---
 include/linux/pagemap.h |  1 +
 mm/folio-compat.c       |  6 ++++++
 mm/page-writeback.c     | 24 ++++++++++++++----------
 3 files changed, 21 insertions(+), 10 deletions(-)

Comments

Vlastimil Babka May 18, 2021, 11:42 a.m. UTC | #1

On 5/11/21 11:47 PM, Matthew Wilcox (Oracle) wrote:
> 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 24
> bytes as a result of this patch.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
> Reviewed-by: Christoph Hellwig <[e-mail]>
> Acked-by: Jeff Layton <[e-mail]>

Acked-by: Vlastimil Babka <[e-mail]>

This seems to remove last user of thp_head(). Remove it as obsolete?

Matthew Wilcox May 18, 2021, 1:55 p.m. UTC | #2

On Tue, May 18, 2021 at 01:42:04PM +0200, Vlastimil Babka wrote:
> On 5/11/21 11:47 PM, Matthew Wilcox (Oracle) wrote:
> > 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 24
> > bytes as a result of this patch.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
> > Reviewed-by: Christoph Hellwig <[e-mail]>
> > Acked-by: Jeff Layton <[e-mail]>
> 
> Acked-by: Vlastimil Babka <[e-mail]>
> 
> This seems to remove last user of thp_head(). Remove it as obsolete?

Good catch!  I'll squash that in.  We're down to just one user of
thp_order in my tree ...

Patch

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 417efd7edd19..06b69cd03da3 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -757,6 +757,7 @@  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 page_endio(struct page *page, bool is_write, int err);
 
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 d7ac428df68a..003b85813f7c 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2860,17 +2860,21 @@  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);