[PATCH] ceph: switch back to testing for NULL folio->private in ceph_dirty_folio

[Jeff Layton <jlayton@kernel.org>]

Willy requested that we change this back to warning on folio->private
being non-NULl. He's trying to kill off the PG_private flag, and so we'd
like to catch where it's non-NULL.

Add a VM_WARN_ON_FOLIO (since it doesn't exist yet) and change over to
using that instead of VM_BUG_ON_FOLIO along with testing the ->private
pointer.

Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/addr.c          | 2 +-
 include/linux/mmdebug.h | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index b43cc01a61db..b24d6bdb91db 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -122,7 +122,7 @@ static bool ceph_dirty_folio(struct address_space *mapping, struct folio *folio)
 	 * Reference snap context in folio->private.  Also set
 	 * PagePrivate so that we get invalidate_folio callback.
 	 */
-	VM_BUG_ON_FOLIO(folio_test_private(folio), folio);
+	VM_WARN_ON_FOLIO(folio->private, folio);
 	folio_attach_private(folio, snapc);
 
 	return ceph_fscache_dirty_folio(mapping, folio);
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index d7285f8148a3..5107bade2ab2 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -54,6 +54,15 @@ void dump_mm(const struct mm_struct *mm);
 	}								\
 	unlikely(__ret_warn_once);					\
 })
+#define VM_WARN_ON_FOLIO(cond, folio)		({			\
+	int __ret_warn = !!(cond);					\
+									\
+	if (unlikely(__ret_warn)) {					\
+		dump_page(&folio->page, "VM_WARN_ON_FOLIO(" __stringify(cond)")");\
+		WARN_ON(1);						\
+	}								\
+	unlikely(__ret_warn);						\
+})
 #define VM_WARN_ON_ONCE_FOLIO(cond, folio)	({			\
 	static bool __section(".data.once") __warned;			\
 	int __ret_warn_once = !!(cond);					\
-- 
2.36.1