ovl: update atime on upper

Fix atime update logic in overlayfs.

This patch adds an i_op->update_time() handler to overlayfs inodes.  This
forwards atime updates to the upper layer only.  No atime updates are done
on lower layers.

Remove implicit atime updates to underlying files and directories with
O_NOATIME.  Remove explicit atime update in ovl_readlink().

Clear atime related mnt flags from cloned upper mount.  This means atime
updates are controlled purely by overlayfs mount options.

Reported-by: Konstantin Khlebnikov <koct9i@gmail.com> 
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 26 insertions, 3 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 66f42f5cf705..041db9c6621c 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -185,8 +185,6 @@ static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
 	if (!realinode->i_op->readlink)
 		return -EINVAL;
 
-	touch_atime(&realpath);
-
 	old_cred = ovl_override_creds(dentry->d_sb);
 	err = realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
 	revert_creds(old_cred);
@@ -367,6 +365,29 @@ int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
 	return err;
 }
 
+int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
+{
+	struct dentry *alias;
+	struct path upperpath;
+
+	if (!(flags & S_ATIME))
+		return 0;
+
+	alias = d_find_any_alias(inode);
+	if (!alias)
+		return 0;
+
+	ovl_path_upper(alias, &upperpath);
+	if (upperpath.dentry) {
+		touch_atime(&upperpath);
+		inode->i_atime = d_inode(upperpath.dentry)->i_atime;
+	}
+
+	dput(alias);
+
+	return 0;
+}
+
 static const struct inode_operations ovl_file_inode_operations = {
 	.setattr	= ovl_setattr,
 	.permission	= ovl_permission,
@@ -376,6 +397,7 @@ static const struct inode_operations ovl_file_inode_operations = {
 	.listxattr	= ovl_listxattr,
 	.removexattr	= ovl_removexattr,
 	.get_acl	= ovl_get_acl,
+	.update_time	= ovl_update_time,
 };
 
 static const struct inode_operations ovl_symlink_inode_operations = {
@@ -387,6 +409,7 @@ static const struct inode_operations ovl_symlink_inode_operations = {
 	.getxattr	= ovl_getxattr,
 	.listxattr	= ovl_listxattr,
 	.removexattr	= ovl_removexattr,
+	.update_time	= ovl_update_time,
 };
 
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
@@ -400,7 +423,7 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
 
 	inode->i_ino = get_next_ino();
 	inode->i_mode = mode;
-	inode->i_flags |= S_NOATIME | S_NOCMTIME;
+	inode->i_flags |= S_NOCMTIME;
 	inode->i_private = oe;
 
 	mode &= S_IFMT;