netfs, cifs: Fix mtime/ctime update for mmapped writes

The cifs flag CIFS_INO_MODIFIED_ATTR, which indicates that the mtime and
ctime need to be written back on close, got taken over by netfs as
NETFS_ICTX_MODIFIED_ATTR to avoid the need to call a function pointer to
set it.

The flag gets set correctly on buffered writes, but doesn't get set by
netfs_page_mkwrite(), leading to occasional failures in generic/080 and
generic/215.

Fix this by setting the flag in netfs_page_mkwrite().

Fixes: 7342580 ("netfs, cifs: Move CIFS_INO_MODIFIED_ATTR to netfs_inode")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202409161629.98887b2-oliver.sang@intel.com
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: dhowells

fs/netfs/buffered_write.c

@@ -552,6 +552,7 @@ vm_fault_t netfs_page_mkwrite(struct vm_fault *vmf, struct netfs_group *netfs_gr
 		trace_netfs_folio(folio, netfs_folio_trace_mkwrite);
 	netfs_set_group(folio, netfs_group);
 	file_update_time(file);
+	set_bit(NETFS_ICTX_MODIFIED_ATTR, &ictx->flags);
 	if (ictx->ops->post_modify)
 		ictx->ops->post_modify(inode);
 	ret = VM_FAULT_LOCKED;