Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 72b608f0 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: constant st_ino/st_dev across copy up 



When all layers are on the same underlying filesystem, let stat(2) return
st_dev/st_ino values of the copy up origin inode if it is known.

This results in constant st_ino/st_dev representation of files in an
overlay mount before and after copy up.

When the underlying filesystem support NFS exportfs, the result is also
persistent st_ino/st_dev representation before and after mount cycle.

Lower hardlinks are broken on copy up to different upper files, so we
cannot use the lower origin st_ino for those different files, even for the
same fs case.

When all overlay layers are on the same fs, use overlay st_dev for non-dirs
to get the correct result from du -x.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent b7a807dc

fs/overlayfs/inode.c

+38 −1
Original line number Diff line number Diff line
@@ -61,14 +61,51 @@ static int ovl_getattr(const struct path *path, struct kstat *stat, 
		       u32 request_mask, unsigned int flags)

{

	struct dentry *dentry = path->dentry;

	enum ovl_path_type type;

	struct path realpath;

	const struct cred *old_cred;

	int err;



	ovl_path_real(dentry, &realpath);

	type = ovl_path_real(dentry, &realpath);

	old_cred = ovl_override_creds(dentry->d_sb);

	err = vfs_getattr(&realpath, stat, request_mask, flags);

	if (err)

		goto out;



	/*

	 * When all layers are on the same fs, all real inode number are

	 * unique, so we use the overlay st_dev, which is friendly to du -x.

	 *

	 * We also use st_ino of the copy up origin, if we know it.

	 * This guaranties constant st_dev/st_ino across copy up.

	 *

	 * If filesystem supports NFS export ops, this also guaranties

	 * persistent st_ino across mount cycle.

	 */

	if (ovl_same_sb(dentry->d_sb)) {

		if (OVL_TYPE_ORIGIN(type)) {

			struct kstat lowerstat;



			ovl_path_lower(dentry, &realpath);

			err = vfs_getattr(&realpath, &lowerstat,

					  STATX_INO | STATX_NLINK, flags);

			if (err)

				goto out;



			WARN_ON_ONCE(stat->dev != lowerstat.dev);

			/*

			 * Lower hardlinks are broken on copy up to different

			 * upper files, so we cannot use the lower origin st_ino

			 * for those different files, even for the same fs case.

			 */

			if (lowerstat.nlink == 1)

				stat->ino = lowerstat.ino;

		}

		stat->dev = dentry->d_sb->s_dev;

	}

out:

	revert_creds(old_cred);



	return err;

}