filemap: Add a version of folio_end_writeback that ignores dropbehind

Filesystems such as NFS may need to defer dropbehind until after their
2-stage writes are done. This adds a helper
folio_end_writeback_no_dropbehind() that allows them to release the
writeback flag without immediately dropping the folio.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 201b7c6f64415abdfbfed64d55d3ee53b69215ed..5b26465358ce88c8a71ea551f0effc242151e881 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1221,6 +1221,7 @@ void folio_wait_writeback(struct folio *folio);
 int folio_wait_writeback_killable(struct folio *folio);
 void end_page_writeback(struct page *page);
 void folio_end_writeback(struct folio *folio);
+void folio_end_writeback_no_dropbehind(struct folio *folio);
 void folio_end_dropbehind(struct folio *folio);
 void folio_wait_stable(struct folio *folio);
 void __folio_mark_dirty(struct folio *folio, struct address_space *, int warn);

diff --git a/mm/filemap.c b/mm/filemap.c
index 66cec689bec4f39aaa5c205872392a46fc682ea8..d12bbb4c9d8a1667d8ad54068adb87f39329001b 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1628,14 +1628,15 @@ void folio_end_dropbehind(struct folio *folio)
 EXPORT_SYMBOL_GPL(folio_end_dropbehind);
 
 /**
- * folio_end_writeback - End writeback against a folio.
+ * folio_end_writeback_no_dropbehind - End writeback against a folio.
  * @folio: The folio.
  *
  * The folio must actually be under writeback.
+ * This call is intended for filesystems that need to defer dropbehind.
  *
  * Context: May be called from process or interrupt context.
  */
-void folio_end_writeback(struct folio *folio)
+void folio_end_writeback_no_dropbehind(struct folio *folio)
 {
        VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);
 
@@ -1651,6 +1652,25 @@ void folio_end_writeback(struct folio *folio)
                folio_rotate_reclaimable(folio);
        }
 
+       if (__folio_end_writeback(folio))
+               folio_wake_bit(folio, PG_writeback);
+
+       acct_reclaim_writeback(folio);
+}
+EXPORT_SYMBOL_GPL(folio_end_writeback_no_dropbehind);
+
+/**
+ * folio_end_writeback - End writeback against a folio.
+ * @folio: The folio.
+ *
+ * The folio must actually be under writeback.
+ *
+ * Context: May be called from process or interrupt context.
+ */
+void folio_end_writeback(struct folio *folio)
+{
+       VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);
+
        /*
         * Writeback does not hold a folio reference of its own, relying
         * on truncation to wait for the clearing of PG_writeback.
@@ -1658,11 +1678,8 @@ void folio_end_writeback(struct folio *folio)
         * reused before the folio_wake_bit().
         */
        folio_get(folio);
-       if (__folio_end_writeback(folio))
-               folio_wake_bit(folio, PG_writeback);
-
+       folio_end_writeback_no_dropbehind(folio);
        folio_end_dropbehind(folio);
-       acct_reclaim_writeback(folio);
        folio_put(folio);
 }
 EXPORT_SYMBOL(folio_end_writeback);