[RFC PATCH v5 04/10] ovl: mark overlayfs' inode dirty on modification

[Chengguang Xu]

Mark overlayfs' inode dirty on modification so that
we can recognize and collect target inodes for syncfs.

Signed-off-by: Chengguang Xu <cgxu519@xxxxxxxxxxxx>
---
 fs/overlayfs/inode.c     |  1 +
 fs/overlayfs/overlayfs.h |  4 ++++
 fs/overlayfs/util.c      | 21 +++++++++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index d854e59a3710..4a03aceaeedc 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -478,6 +478,7 @@ int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
 		if (upperpath.dentry) {
 			touch_atime(&upperpath);
 			inode->i_atime = d_inode(upperpath.dentry)->i_atime;
+			ovl_mark_inode_dirty(inode);
 		}
 	}
 	return 0;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 3894f3347955..5a016baa06dd 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -276,6 +276,7 @@ static inline bool ovl_allow_offline_changes(struct ovl_fs *ofs)
 
 
 /* util.c */
+void ovl_mark_inode_dirty(struct inode *inode);
 int ovl_want_write(struct dentry *dentry);
 void ovl_drop_write(struct dentry *dentry);
 struct dentry *ovl_workdir(struct dentry *dentry);
@@ -529,6 +530,9 @@ static inline void ovl_copyattr(struct inode *from, struct inode *to)
 	to->i_mtime = from->i_mtime;
 	to->i_ctime = from->i_ctime;
 	i_size_write(to, i_size_read(from));
+
+	if (ovl_inode_upper(to) && from->i_state & I_DIRTY_ALL)
+		ovl_mark_inode_dirty(to);
 }
 
 /* vfs inode flags copied from real to ovl inode */
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index f48284a2a896..5441eae2e345 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -25,7 +25,14 @@ int ovl_want_write(struct dentry *dentry)
 void ovl_drop_write(struct dentry *dentry)
 {
 	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct dentry *upper;
+
 	mnt_drop_write(ovl_upper_mnt(ofs));
+	if (d_inode(dentry)) {
+		upper = ovl_dentry_upper(dentry);
+		if (upper && d_inode(upper) && d_inode(upper)->i_state & I_DIRTY_ALL)
+			ovl_mark_inode_dirty(d_inode(dentry));
+	}
 }
 
 struct dentry *ovl_workdir(struct dentry *dentry)
@@ -1060,3 +1067,17 @@ int ovl_sync_status(struct ovl_fs *ofs)
 
 	return errseq_check(&mnt->mnt_sb->s_wb_err, ofs->errseq);
 }
+
+/*
+ * We intentionally add I_DIRTY_SYNC flag regardless dirty flag
+ * of upper inode so that we have chance to invoke ->write_inode
+ * to re-dirty overlayfs' inode during writeback process.
+ */
+void ovl_mark_inode_dirty(struct inode *inode)
+{
+	struct inode *upper = ovl_inode_upper(inode);
+	unsigned long iflag = I_DIRTY_SYNC;
+
+	iflag |= upper->i_state & I_DIRTY_ALL;
+	__mark_inode_dirty(inode, iflag);
+}
-- 
2.27.0