afs: Fix to take ref on page when PG_private is set

Fix afs to take a ref on a page when it sets PG_private on it and to drop
the ref when removing the flag.

Note that in afs_write_begin(), a lot of the time, PG_private is already
set on a page to which we're going to add some data.  In such a case, we
leave the bit set and mustn't increment the page count.

As suggested by Matthew Wilcox, use attach/detach_page_private() where
possible.

Fixes: 31143d5d515e ("AFS: implement basic file write support")
Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/fs/afs/dir_edit.c b/fs/afs/dir_edit.c
index b108528bf010..2ffe09abae7f 100644
--- a/fs/afs/dir_edit.c
+++ b/fs/afs/dir_edit.c
@@ -243,10 +243,8 @@ void afs_edit_dir_add(struct afs_vnode *vnode,
 						   index, gfp);
 			if (!page)
 				goto error;
-			if (!PagePrivate(page)) {
-				set_page_private(page, 1);
-				SetPagePrivate(page);
-			}
+			if (!PagePrivate(page))
+				attach_page_private(page, (void *)1);
 			dir_page = kmap(page);
 		}