Implement overlayfs' ->writepages operation so that
we can sync dirty data/metadata to upper filesystem.
Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
---
fs/overlayfs/inode.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b584dca845ba..f27fc5be34df 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -11,6 +11,7 @@
#include <linux/posix_acl.h>
#include <linux/ratelimit.h>
#include <linux/fiemap.h>
+#include <linux/writeback.h>
#include "overlayfs.h"
@@ -516,7 +517,32 @@ static const struct inode_operations ovl_special_inode_operations = {
.update_time = ovl_update_time,
};
+static int ovl_writepages(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ struct inode *upper_inode = ovl_inode_upper(mapping->host);
+ struct ovl_fs *ofs = mapping->host->i_sb->s_fs_info;
+ struct writeback_control tmp_wbc = *wbc;
+
+ if (!ovl_should_sync(ofs))
+ return 0;
+
+ /*
+ * for sync(2) writeback, it has a separate external IO
+ * completion path by checking PAGECACHE_TAG_WRITEBACK
+ * in pagecache, we have to set for_sync to 0 in thie case,
+ * let writeback waits completion after syncing individual
+ * dirty inode, because we haven't implemented overlayfs'
+ * own pagecache yet.
+ */
+ if (wbc->for_sync && (wbc->sync_mode == WB_SYNC_ALL))
+ tmp_wbc.for_sync = 0;
+
+ return sync_inode(upper_inode, &tmp_wbc);
+}
+
static const struct address_space_operations ovl_aops = {
+ .writepages = ovl_writepages,
/* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
.direct_IO = noop_direct_IO,
};
--
2.26.2
