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SubjectRe: [PATCH v2] ovl: introduce new "index=nouuid" option for inodes index feature
On Wed, Sep 23, 2020 at 06:23:08PM +0300, Pavel Tikhomirov wrote:
> This relaxes uuid checks for overlay index feature. It is only possible
> in case there is only one filesystem for all the work/upper/lower
> directories and bare file handles from this backing filesystem are uniq.

Hi Pavel,

Wondering why upper/work has to be on same filesystem as lower for this to
work?

> In case we have multiple filesystems here just fall back to normal
> "index=on".
>
> This is needed when overlayfs is/was mounted in a container with
> index enabled (e.g.: to be able to resolve inotify watch file handles on
> it to paths in CRIU), and this container is copied and started alongside
> with the original one. This way the "copy" container can't have the same
> uuid on the superblock and mounting the overlayfs from it later would
> fail.
>
> That is an example of the problem on top of loop+ext4:
>
> dd if=/dev/zero of=loopbackfile.img bs=100M count=10
> losetup -fP loopbackfile.img
> losetup -a
> #/dev/loop0: [64768]:35 (/loop-test/loopbackfile.img)
> mkfs.ext4 loopbackfile.img
> mkdir loop-mp
> mount -o loop /dev/loop0 loop-mp
> mkdir loop-mp/{lower,upper,work,merged}
> mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
> upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
> umount loop-mp/merged
> umount loop-mp
> e2fsck -f /dev/loop0
> tune2fs -U random /dev/loop0
>
> mount -o loop /dev/loop0 loop-mp
> mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
> upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
> #mount: /loop-test/loop-mp/merged:
> #mount(2) system call failed: Stale file handle.
>
> mount -t overlay overlay -oindex=nouuid,lowerdir=loop-mp/lower,\
> upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
>
> If you just change the uuid of the backing filesystem, overlay is not
> mounting any more. In Virtuozzo we copy container disks (ploops) when
> crate the copy of container and we require fs uuid to be uniq for a new
> container.
>
> v2: in v1 I missed actual uuid check skip - add it
>
> CC: Amir Goldstein <amir73il@gmail.com>
> CC: Vivek Goyal <vgoyal@redhat.com>
> CC: Miklos Szeredi <miklos@szeredi.hu>
> CC: linux-unionfs@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
> ---
> fs/overlayfs/Kconfig | 16 +++++++++++
> fs/overlayfs/export.c | 6 ++--
> fs/overlayfs/namei.c | 35 +++++++++++++++--------
> fs/overlayfs/overlayfs.h | 23 +++++++++++----
> fs/overlayfs/ovl_entry.h | 2 +-
> fs/overlayfs/super.c | 61 +++++++++++++++++++++++++++++-----------
> 6 files changed, 106 insertions(+), 37 deletions(-)

Please put something in Documentation file to explain this option. Also
explain where it is safe to use and where it is not. I am concerned
about the case where recreating lower can result in file handle resolving
to a different file (as discusse in other thread). I think it would
be nice if we mention it explicitly.

Thanks
Vivek

>
> diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
> index dd188c7996b3..b00fd44006f9 100644
> --- a/fs/overlayfs/Kconfig
> +++ b/fs/overlayfs/Kconfig
> @@ -61,6 +61,22 @@ config OVERLAY_FS_INDEX
>
> If unsure, say N.
>
> +config OVERLAY_FS_INDEX_NOUUID
> + bool "Overlayfs: relax uuid checks of inodes index feature"
> + depends on OVERLAY_FS
> + depends on OVERLAY_FS_INDEX
> + help
> + If this config option is enabled then overlay will skip uuid checks
> + for index lower to upper inode map, this only can be done if all
> + upper and lower directories are on the same filesystem where basic
> + fhandles are uniq.
> +
> + It is needed to overcome possible change of uuid on superblock of the
> + backing filesystem, e.g. when you copied the virtual disk and mount
> + both the copy of the disk and the original one at the same time.
> +
> + If unsure, say N.
> +
> config OVERLAY_FS_NFS_EXPORT
> bool "Overlayfs: turn on NFS export feature by default"
> depends on OVERLAY_FS
> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
> index 0e696f72cf65..d53feb7547d9 100644
> --- a/fs/overlayfs/export.c
> +++ b/fs/overlayfs/export.c
> @@ -676,11 +676,12 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
> struct ovl_fs *ofs = sb->s_fs_info;
> struct dentry *dentry;
> struct dentry *upper;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> if (!ovl_upper_mnt(ofs))
> return ERR_PTR(-EACCES);
>
> - upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
> + upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true, nouuid);
> if (IS_ERR_OR_NULL(upper))
> return upper;
>
> @@ -700,6 +701,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
> struct dentry *index = NULL;
> struct inode *inode;
> int err;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> /* First lookup overlay inode in inode cache by origin fh */
> err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack);
> @@ -752,7 +754,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
> goto out_err;
> }
> if (index) {
> - err = ovl_verify_origin(index, origin.dentry, false);
> + err = ovl_verify_origin(index, origin.dentry, false, nouuid);
> if (err)
> goto out_err;
> }
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index f7d4358db637..676170d719f8 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -149,7 +149,7 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
> }
>
> struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
> - bool connected)
> + bool connected, bool nouuid)
> {
> struct dentry *real;
> int bytes;
> @@ -158,7 +158,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
> * Make sure that the stored uuid matches the uuid of the lower
> * layer where file handle will be decoded.
> */
> - if (!uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid))
> + if (!nouuid && !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid))
> return NULL;
>
> bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
> @@ -342,6 +342,7 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
> {
> struct dentry *origin = NULL;
> int i;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> for (i = 1; i < ofs->numlayer; i++) {
> /*
> @@ -353,7 +354,7 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
> continue;
>
> origin = ovl_decode_real_fh(fh, ofs->layers[i].mnt,
> - connected);
> + connected, nouuid);
> if (origin)
> break;
> }
> @@ -414,7 +415,7 @@ static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
> * Return 0 on match, -ESTALE on mismatch, < 0 on error.
> */
> static int ovl_verify_fh(struct dentry *dentry, const char *name,
> - const struct ovl_fh *fh)
> + const struct ovl_fh *fh, bool nouuid)
> {
> struct ovl_fh *ofh = ovl_get_fh(dentry, name);
> int err = 0;
> @@ -425,8 +426,14 @@ static int ovl_verify_fh(struct dentry *dentry, const char *name,
> if (IS_ERR(ofh))
> return PTR_ERR(ofh);
>
> - if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len))
> + if (fh->fb.len != ofh->fb.len) {
> err = -ESTALE;
> + } else {
> + if (nouuid && !uuid_equal(&fh->fb.uuid, &ofh->fb.uuid))
> + ofh->fb.uuid = fh->fb.uuid;
> + if (memcmp(&fh->fb, &ofh->fb, fh->fb.len))
> + err = -ESTALE;
> + }
>
> kfree(ofh);
> return err;
> @@ -441,7 +448,8 @@ static int ovl_verify_fh(struct dentry *dentry, const char *name,
> * Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
> */
> int ovl_verify_set_fh(struct dentry *dentry, const char *name,
> - struct dentry *real, bool is_upper, bool set)
> + struct dentry *real, bool is_upper, bool set,
> + bool nouuid)
> {
> struct inode *inode;
> struct ovl_fh *fh;
> @@ -454,7 +462,7 @@ int ovl_verify_set_fh(struct dentry *dentry, const char *name,
> goto fail;
> }
>
> - err = ovl_verify_fh(dentry, name, fh);
> + err = ovl_verify_fh(dentry, name, fh, nouuid);
> if (set && err == -ENODATA)
> err = ovl_do_setxattr(dentry, name, fh->buf, fh->fb.len, 0);
> if (err)
> @@ -477,6 +485,7 @@ struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
> {
> struct ovl_fh *fh;
> struct dentry *upper;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> if (!d_is_dir(index))
> return dget(index);
> @@ -485,7 +494,7 @@ struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index)
> if (IS_ERR_OR_NULL(fh))
> return ERR_CAST(fh);
>
> - upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true);
> + upper = ovl_decode_real_fh(fh, ovl_upper_mnt(ofs), true, nouuid);
> kfree(fh);
>
> if (IS_ERR_OR_NULL(upper))
> @@ -514,6 +523,7 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
> struct ovl_path *stack = &origin;
> struct dentry *upper = NULL;
> int err;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> if (!d_inode(index))
> return 0;
> @@ -574,7 +584,7 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
> goto fail;
> }
>
> - err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh);
> + err = ovl_verify_fh(upper, OVL_XATTR_ORIGIN, fh, nouuid);
> dput(upper);
> if (err)
> goto fail;
> @@ -690,6 +700,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
> struct qstr name;
> bool is_dir = d_is_dir(origin);
> int err;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> err = ovl_get_index_name(origin, &name);
> if (err)
> @@ -741,7 +752,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
> }
>
> /* Verify that dir index 'upper' xattr points to upper dir */
> - err = ovl_verify_upper(index, upper, false);
> + err = ovl_verify_upper(index, upper, false, nouuid);
> if (err) {
> if (err == -ESTALE) {
> pr_warn_ratelimited("suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n",
> @@ -840,6 +851,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> .redirect = NULL,
> .metacopy = false,
> };
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> if (dentry->d_name.len > ofs->namelen)
> return ERR_PTR(-ENAMETOOLONG);
> @@ -939,7 +951,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> if (upperdentry && !ctr &&
> ((d.is_dir && ovl_verify_lower(dentry->d_sb)) ||
> (!d.is_dir && ofs->config.index && origin_path))) {
> - err = ovl_verify_origin(upperdentry, this, false);
> + err = ovl_verify_origin(upperdentry, this, false,
> + nouuid);
> if (err) {
> dput(this);
> if (d.is_dir)
> diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
> index 29bc1ec699e7..2aacfa42bb12 100644
> --- a/fs/overlayfs/overlayfs.h
> +++ b/fs/overlayfs/overlayfs.h
> @@ -18,6 +18,12 @@ enum ovl_path_type {
> __OVL_PATH_ORIGIN = (1 << 2),
> };
>
> +enum ovl_index_type {
> + OVL_INDEX_OFF = 0,
> + OVL_INDEX_ON,
> + OVL_INDEX_NOUUID,
> +};
> +
> #define OVL_TYPE_UPPER(type) ((type) & __OVL_PATH_UPPER)
> #define OVL_TYPE_MERGE(type) ((type) & __OVL_PATH_MERGE)
> #define OVL_TYPE_ORIGIN(type) ((type) & __OVL_PATH_ORIGIN)
> @@ -362,11 +368,12 @@ static inline int ovl_check_fh_len(struct ovl_fh *fh, int fh_len)
> }
>
> struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,
> - bool connected);
> + bool connected, bool nouuid);
> int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
> struct dentry *upperdentry, struct ovl_path **stackp);
> int ovl_verify_set_fh(struct dentry *dentry, const char *name,
> - struct dentry *real, bool is_upper, bool set);
> + struct dentry *real, bool is_upper, bool set,
> + bool nouuid);
> struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index);
> int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index);
> int ovl_get_index_name(struct dentry *origin, struct qstr *name);
> @@ -379,15 +386,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
> bool ovl_lower_positive(struct dentry *dentry);
>
> static inline int ovl_verify_origin(struct dentry *upper,
> - struct dentry *origin, bool set)
> + struct dentry *origin, bool set,
> + bool nouuid)
> {
> - return ovl_verify_set_fh(upper, OVL_XATTR_ORIGIN, origin, false, set);
> + return ovl_verify_set_fh(upper, OVL_XATTR_ORIGIN, origin, false, set,
> + nouuid);
> }
>
> static inline int ovl_verify_upper(struct dentry *index,
> - struct dentry *upper, bool set)
> + struct dentry *upper, bool set,
> + bool nouuid)
> {
> - return ovl_verify_set_fh(index, OVL_XATTR_UPPER, upper, true, set);
> + return ovl_verify_set_fh(index, OVL_XATTR_UPPER, upper, true, set,
> + nouuid);
> }
>
> /* readdir.c */
> diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
> index b429c80879ee..2fd2cc515ad2 100644
> --- a/fs/overlayfs/ovl_entry.h
> +++ b/fs/overlayfs/ovl_entry.h
> @@ -13,7 +13,7 @@ struct ovl_config {
> bool redirect_dir;
> bool redirect_follow;
> const char *redirect_mode;
> - bool index;
> + int index;
> bool nfs_export;
> int xino;
> bool metacopy;
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index 4b38141c2985..d1ed580f24b7 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -38,10 +38,12 @@ module_param_named(redirect_always_follow, ovl_redirect_always_follow,
> MODULE_PARM_DESC(redirect_always_follow,
> "Follow redirects even if redirect_dir feature is turned off");
>
> -static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
> -module_param_named(index, ovl_index_def, bool, 0644);
> +static int ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX_NOUUID) ?
> + OVL_INDEX_NOUUID :
> + IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
> +module_param_named(index, ovl_index_def, int, 0644);
> MODULE_PARM_DESC(index,
> - "Default to on or off for the inodes index feature");
> + "Default to on, off or nouuid for the inodes index feature");
>
> static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
> module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
> @@ -352,8 +354,18 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
> seq_puts(m, ",default_permissions");
> if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
> seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
> - if (ofs->config.index != ovl_index_def)
> - seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
> + if (ofs->config.index != ovl_index_def) {
> + switch (ofs->config.index) {
> + case OVL_INDEX_OFF:
> + seq_puts(m, ",index=off");
> + break;
> + case OVL_INDEX_NOUUID:
> + seq_puts(m, ",index=nouuid");
> + break;
> + default:
> + seq_puts(m, ",index=on");
> + }
> + }
> if (ofs->config.nfs_export != ovl_nfs_export_def)
> seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
> "on" : "off");
> @@ -404,6 +416,7 @@ enum {
> OPT_REDIRECT_DIR,
> OPT_INDEX_ON,
> OPT_INDEX_OFF,
> + OPT_INDEX_NOUUID,
> OPT_NFS_EXPORT_ON,
> OPT_NFS_EXPORT_OFF,
> OPT_XINO_ON,
> @@ -422,6 +435,7 @@ static const match_table_t ovl_tokens = {
> {OPT_REDIRECT_DIR, "redirect_dir=%s"},
> {OPT_INDEX_ON, "index=on"},
> {OPT_INDEX_OFF, "index=off"},
> + {OPT_INDEX_NOUUID, "index=nouuid"},
> {OPT_NFS_EXPORT_ON, "nfs_export=on"},
> {OPT_NFS_EXPORT_OFF, "nfs_export=off"},
> {OPT_XINO_ON, "xino=on"},
> @@ -532,12 +546,17 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
> break;
>
> case OPT_INDEX_ON:
> - config->index = true;
> + config->index = OVL_INDEX_ON;
> index_opt = true;
> break;
>
> case OPT_INDEX_OFF:
> - config->index = false;
> + config->index = OVL_INDEX_OFF;
> + index_opt = true;
> + break;
> +
> + case OPT_INDEX_NOUUID:
> + config->index = OVL_INDEX_NOUUID;
> index_opt = true;
> break;
>
> @@ -592,7 +611,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
> pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
> index_opt = false;
> }
> - config->index = false;
> + config->index = OVL_INDEX_OFF;
> }
>
> err = ovl_parse_redirect_mode(config, config->redirect_mode);
> @@ -644,7 +663,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
> config->nfs_export = false;
> } else {
> /* Automatically enable index otherwise. */
> - config->index = true;
> + config->index = OVL_INDEX_ON;
> }
> }
>
> @@ -859,7 +878,7 @@ static int ovl_lower_dir(const char *name, struct path *path,
> fh_type = ovl_can_decode_fh(path->dentry->d_sb);
> if ((ofs->config.nfs_export ||
> (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
> - ofs->config.index = false;
> + ofs->config.index = OVL_INDEX_OFF;
> ofs->config.nfs_export = false;
> pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
> name);
> @@ -1259,7 +1278,7 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
> err = ovl_do_setxattr(ofs->workdir, OVL_XATTR_OPAQUE, "0", 1, 0);
> if (err) {
> ofs->noxattr = true;
> - ofs->config.index = false;
> + ofs->config.index = OVL_INDEX_OFF;
> ofs->config.metacopy = false;
> pr_warn("upper fs does not support xattr, falling back to index=off and metacopy=off.\n");
> err = 0;
> @@ -1282,7 +1301,7 @@ static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
> /* Check if upper/work fs supports file handles */
> fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
> if (ofs->config.index && !fh_type) {
> - ofs->config.index = false;
> + ofs->config.index = OVL_INDEX_OFF;
> pr_warn("upper fs does not support file handles, falling back to index=off.\n");
> }
>
> @@ -1348,6 +1367,7 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
> {
> struct vfsmount *mnt = ovl_upper_mnt(ofs);
> int err;
> + bool nouuid = ofs->config.index == OVL_INDEX_NOUUID;
>
> err = mnt_want_write(mnt);
> if (err)
> @@ -1355,7 +1375,7 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
>
> /* Verify lower root is upper root origin */
> err = ovl_verify_origin(upperpath->dentry, oe->lowerstack[0].dentry,
> - true);
> + true, nouuid);
> if (err) {
> pr_err("failed to verify upper root origin\n");
> goto out;
> @@ -1385,11 +1405,13 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
> */
> if (ovl_check_origin_xattr(ofs->indexdir)) {
> err = ovl_verify_set_fh(ofs->indexdir, OVL_XATTR_ORIGIN,
> - upperpath->dentry, true, false);
> + upperpath->dentry, true, false,
> + nouuid);
> if (err)
> pr_err("failed to verify index dir 'origin' xattr\n");
> }
> - err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true);
> + err = ovl_verify_upper(ofs->indexdir, upperpath->dentry, true,
> + nouuid);
> if (err)
> pr_err("failed to verify index dir 'upper' xattr\n");
>
> @@ -1458,7 +1480,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
> if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
> bad_uuid = true;
> if (ofs->config.index || ofs->config.nfs_export) {
> - ofs->config.index = false;
> + ofs->config.index = OVL_INDEX_OFF;
> ofs->config.nfs_export = false;
> pr_warn("%s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n",
> uuid_is_null(&sb->s_uuid) ? "null" :
> @@ -1889,9 +1911,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
> if (err)
> goto out_free_oe;
>
> + if (ofs->config.index == OVL_INDEX_NOUUID && ofs->numfs > 1) {
> + pr_warn("The index=nouuid requires a single fs for lower and upper, falling back to index=on.\n");
> + ofs->config.index = OVL_INDEX_ON;
> + }
> +
> /* Show index=off in /proc/mounts for forced r/o mount */
> if (!ofs->indexdir) {
> - ofs->config.index = false;
> + ofs->config.index = OVL_INDEX_OFF;
> if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
> pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
> ofs->config.nfs_export = false;
> --
> 2.26.2
>

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