From d80172c2d85947efe285693c5cea9c8976f478bf Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Thu, 20 Feb 2020 09:03:08 +0200 Subject: ovl: strict upper fs requirements for remote upper fs Overlayfs works sub-optimally with upper fs that has no xattr/d_type/ RENAME_WHITEOUT support. We should basically deprecate support for those filesystems, but so far, we only issue a warning and don't fail the mount for the sake of backward compat. Some features are already being disabled with no xattr support. For newly supported remote upper fs, we do not need to worry about backward compatibility, so we can fail the mount if upper fs is a sub-optimal filesystem. This reduces the in-tree remote filesystems supported as upper to just FUSE, for which the remote upper fs support was added. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index b6ecaf95db9f..ac013ed97a53 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1136,6 +1136,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, { struct vfsmount *mnt = ofs->upper_mnt; struct dentry *temp; + bool rename_whiteout; + bool d_type; int fh_type; int err; @@ -1161,11 +1163,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, if (err < 0) goto out; - /* - * We allowed this configuration and don't want to break users over - * kernel upgrade. So warn instead of erroring out. - */ - if (!err) + d_type = err; + if (!d_type) pr_warn("upper fs needs to support d_type.\n"); /* Check if upper/work fs supports O_TMPFILE */ @@ -1182,7 +1181,8 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, if (err < 0) goto out; - if (!err) + rename_whiteout = err; + if (!rename_whiteout) pr_warn("upper fs does not support RENAME_WHITEOUT.\n"); /* @@ -1199,6 +1199,18 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs, vfs_removexattr(ofs->workdir, OVL_XATTR_OPAQUE); } + /* + * We allowed sub-optimal upper fs configuration and don't want to break + * users over kernel upgrade, but we never allowed remote upper fs, so + * we can enforce strict requirements for remote upper fs. + */ + if (ovl_dentry_remote(ofs->workdir) && + (!d_type || !rename_whiteout || ofs->noxattr)) { + pr_err("upper fs missing required features.\n"); + err = -EINVAL; + goto out; + } + /* Check if upper/work fs supports file handles */ fh_type = ovl_can_decode_fh(ofs->workdir->d_sb); if (ofs->config.index && !fh_type) { -- cgit