From 9df085f3c9a2d4658a9fe323d70c200aa00ede93 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Mon, 3 Sep 2018 09:12:09 +0300 Subject: [PATCH] ovl: relax requirement for non null uuid of lower fs We use uuid to associate an overlay lower file handle with a lower layer, so we can accept lower fs with null uuid as long as all lower layers with null uuid are on the same fs. This change allows enabling index and nfs_export features for the setup of single lower fs of type squashfs - squashfs supports file handles, but has a null uuid. This change also allows enabling index and nfs_export features for nested overlayfs, where the lower overlay has nfs_export enabled. Enabling the index feature with single lower squashfs fixes the unionmount-testsuite test: ./run --ov --squashfs --verify As a by-product, if, like the lower squashfs, upper fs also uses the generic export_encode_fh() implementation to export 32bit inode file handles (e.g. ext4), then the xino_auto config/module/mount option will enable unique overlay inode numbers. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 32 ++++++++++++++++++++++++++++++-- fs/overlayfs/util.c | 3 +-- 2 files changed, 31 insertions(+), 4 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 30adc9d..22ffb23 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1175,9 +1175,29 @@ out: return err; } +static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) +{ + unsigned int i; + + if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt)) + return true; + + for (i = 0; i < ofs->numlowerfs; i++) { + /* + * We use uuid to associate an overlay lower file handle with a + * lower layer, so we can accept lower fs with null uuid as long + * as all lower layers with null uuid are on the same fs. + */ + if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) + return false; + } + return true; +} + /* Get a unique fsid for the layer */ -static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb) +static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) { + struct super_block *sb = path->mnt->mnt_sb; unsigned int i; dev_t dev; int err; @@ -1191,6 +1211,14 @@ static int ovl_get_fsid(struct ovl_fs *ofs, struct super_block *sb) return i + 1; } + if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { + ofs->config.index = false; + ofs->config.nfs_export = false; + pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n", + uuid_is_null(&sb->s_uuid) ? "null" : "conflicting", + path->dentry); + } + err = get_anon_bdev(&dev); if (err) { pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n"); @@ -1225,7 +1253,7 @@ static int ovl_get_lower_layers(struct ovl_fs *ofs, struct path *stack, struct vfsmount *mnt; int fsid; - err = fsid = ovl_get_fsid(ofs, stack[i].mnt->mnt_sb); + err = fsid = ovl_get_fsid(ofs, &stack[i]); if (err < 0) goto out; diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index ace4fe4..8cd37ba 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -65,8 +65,7 @@ struct super_block *ovl_same_sb(struct super_block *sb) */ int ovl_can_decode_fh(struct super_block *sb) { - if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry || - uuid_is_null(&sb->s_uuid)) + if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry) return 0; return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN; -- 2.7.4