Merge tag 'ovl-update-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "A mix of fixes and cleanups"

* tag 'ovl-update-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: automatically enable redirect_dir on metacopy=on
  ovl: check whiteout in ovl_create_over_whiteout()
  ovl: using posix_acl_xattr_size() to get size instead of posix_acl_to_xattr()
  ovl: abstract ovl_inode lock with a helper
  ovl: remove the 'locked' argument of ovl_nlink_{start,end}
  ovl: relax requirement for non null uuid of lower fs
  ovl: fold copy-up helpers into callers
  ovl: untangle copy up call chain
  ovl: relax permission checking on underlying layers
  ovl: fix recursive oi->lock in ovl_link()
  vfs: fix FIGETBSZ ioctl on an overlayfs file
  ovl: clean up error handling in ovl_get_tmpfile()
  ovl: fix error handling in ovl_verify_set_fh()

9 files changed, 260 insertions, 145 deletions

diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index 51c136c821bf..eef7d9d259e8 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -286,6 +286,12 @@ pointed by REDIRECT. This should not be possible on local system as setting
 "trusted." xattrs will require CAP_SYS_ADMIN. But it should be possible
 for untrusted layers like from a pen drive.
 
+Note: redirect_dir={off|nofollow|follow(*)} conflicts with metacopy=on, and
+results in an error.
+
+(*) redirect_dir=follow only conflicts with metacopy=on if upperdir=... is
+given.
+
 Sharing and copying layers
 --------------------------
 
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 2005529af560..0400297c8d72 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -669,6 +669,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
                 return ioctl_fiemap(filp, arg);
 
         case FIGETBSZ:
+                /* anon_bdev filesystems may not have a block size */
+                if (!inode->i_sb->s_blocksize)
+                        return -EINVAL;
                 return put_user(inode->i_sb->s_blocksize, argp);
 
         case FICLONE:
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 1cc797a08a5b..d6a3346e2672 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -395,7 +395,6 @@ struct ovl_copy_up_ctx {
         struct dentry *destdir;
         struct qstr destname;
         struct dentry *workdir;
-        bool tmpfile;
         bool origin;
         bool indexed;
         bool metacopy;
@@ -440,63 +439,6 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
         return err;
 }
 
-static int ovl_install_temp(struct ovl_copy_up_ctx *c, struct dentry *temp,
-                            struct dentry **newdentry)
-{
-        int err;
-        struct dentry *upper;
-        struct inode *udir = d_inode(c->destdir);
-
-        upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
-        if (IS_ERR(upper))
-                return PTR_ERR(upper);
-
-        if (c->tmpfile)
-                err = ovl_do_link(temp, udir, upper);
-        else
-                err = ovl_do_rename(d_inode(c->workdir), temp, udir, upper, 0);
-
-        if (!err)
-                *newdentry = dget(c->tmpfile ? upper : temp);
-        dput(upper);
-
-        return err;
-}
-
-static struct dentry *ovl_get_tmpfile(struct ovl_copy_up_ctx *c)
-{
-        int err;
-        struct dentry *temp;
-        const struct cred *old_creds = NULL;
-        struct cred *new_creds = NULL;
-        struct ovl_cattr cattr = {
-                /* Can't properly set mode on creation because of the umask */
-                .mode = c->stat.mode & S_IFMT,
-                .rdev = c->stat.rdev,
-                .link = c->link
-        };
-
-        err = security_inode_copy_up(c->dentry, &new_creds);
-        temp = ERR_PTR(err);
-        if (err < 0)
-                goto out;
-
-        if (new_creds)
-                old_creds = override_creds(new_creds);
-
-        if (c->tmpfile)
-                temp = ovl_do_tmpfile(c->workdir, c->stat.mode);
-        else
-                temp = ovl_create_temp(c->workdir, &cattr);
-out:
-        if (new_creds) {
-                revert_creds(old_creds);
-                put_cred(new_creds);
-        }
-
-        return temp;
-}
-
 static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
 {
         int err;
@@ -548,51 +490,148 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
         return err;
 }
 
-static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)
+struct ovl_cu_creds {
+        const struct cred *old;
+        struct cred *new;
+};
+
+static int ovl_prep_cu_creds(struct dentry *dentry, struct ovl_cu_creds *cc)
+{
+        int err;
+
+        cc->old = cc->new = NULL;
+        err = security_inode_copy_up(dentry, &cc->new);
+        if (err < 0)
+                return err;
+
+        if (cc->new)
+                cc->old = override_creds(cc->new);
+
+        return 0;
+}
+
+static void ovl_revert_cu_creds(struct ovl_cu_creds *cc)
+{
+        if (cc->new) {
+                revert_creds(cc->old);
+                put_cred(cc->new);
+        }
+}
+
+/*
+ * Copyup using workdir to prepare temp file.  Used when copying up directories,
+ * special files or when upper fs doesn't support O_TMPFILE.
+ */
+static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
 {
-        struct inode *udir = c->destdir->d_inode;
         struct inode *inode;
-        struct dentry *newdentry = NULL;
-        struct dentry *temp;
+        struct inode *udir = d_inode(c->destdir), *wdir = d_inode(c->workdir);
+        struct dentry *temp, *upper;
+        struct ovl_cu_creds cc;
         int err;
+        struct ovl_cattr cattr = {
+                /* Can't properly set mode on creation because of the umask */
+                .mode = c->stat.mode & S_IFMT,
+                .rdev = c->stat.rdev,
+                .link = c->link
+        };
 
-        temp = ovl_get_tmpfile(c);
+        err = ovl_lock_rename_workdir(c->workdir, c->destdir);
+        if (err)
+                return err;
+
+        err = ovl_prep_cu_creds(c->dentry, &cc);
+        if (err)
+                goto unlock;
+
+        temp = ovl_create_temp(c->workdir, &cattr);
+        ovl_revert_cu_creds(&cc);
+
+        err = PTR_ERR(temp);
         if (IS_ERR(temp))
-                return PTR_ERR(temp);
+                goto unlock;
 
         err = ovl_copy_up_inode(c, temp);
         if (err)
-                goto out;
+                goto cleanup;
 
         if (S_ISDIR(c->stat.mode) && c->indexed) {
                 err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
                 if (err)
-                        goto out;
+                        goto cleanup;
         }
 
-        if (c->tmpfile) {
-                inode_lock_nested(udir, I_MUTEX_PARENT);
-                err = ovl_install_temp(c, temp, &newdentry);
-                inode_unlock(udir);
-        } else {
-                err = ovl_install_temp(c, temp, &newdentry);
-        }
+        upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
+        err = PTR_ERR(upper);
+        if (IS_ERR(upper))
+                goto cleanup;
+
+        err = ovl_do_rename(wdir, temp, udir, upper, 0);
+        dput(upper);
         if (err)
-                goto out;
+                goto cleanup;
 
         if (!c->metacopy)
                 ovl_set_upperdata(d_inode(c->dentry));
         inode = d_inode(c->dentry);
-        ovl_inode_update(inode, newdentry);
+        ovl_inode_update(inode, temp);
         if (S_ISDIR(inode->i_mode))
                 ovl_set_flag(OVL_WHITEOUTS, inode);
+unlock:
+        unlock_rename(c->workdir, c->destdir);
 
-out:
-        if (err && !c->tmpfile)
-                ovl_cleanup(d_inode(c->workdir), temp);
-        dput(temp);
         return err;
 
+cleanup:
+        ovl_cleanup(wdir, temp);
+        dput(temp);
+        goto unlock;
+}
+
+/* Copyup using O_TMPFILE which does not require cross dir locking */
+static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
+{
+        struct inode *udir = d_inode(c->destdir);
+        struct dentry *temp, *upper;
+        struct ovl_cu_creds cc;
+        int err;
+
+        err = ovl_prep_cu_creds(c->dentry, &cc);
+        if (err)
+                return err;
+
+        temp = ovl_do_tmpfile(c->workdir, c->stat.mode);
+        ovl_revert_cu_creds(&cc);
+
+        if (IS_ERR(temp))
+                return PTR_ERR(temp);
+
+        err = ovl_copy_up_inode(c, temp);
+        if (err)
+                goto out_dput;
+
+        inode_lock_nested(udir, I_MUTEX_PARENT);
+
+        upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
+        err = PTR_ERR(upper);
+        if (!IS_ERR(upper)) {
+                err = ovl_do_link(temp, udir, upper);
+                dput(upper);
+        }
+        inode_unlock(udir);
+
+        if (err)
+                goto out_dput;
+
+        if (!c->metacopy)
+                ovl_set_upperdata(d_inode(c->dentry));
+        ovl_inode_update(d_inode(c->dentry), temp);
+
+        return 0;
+
+out_dput:
+        dput(temp);
+        return err;
 }
 
 /*
@@ -646,18 +685,10 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
         }
 
         /* Should we copyup with O_TMPFILE or with workdir? */
-        if (S_ISREG(c->stat.mode) && ofs->tmpfile) {
-                c->tmpfile = true;
-                err = ovl_copy_up_locked(c);
-        } else {
-                err = ovl_lock_rename_workdir(c->workdir, c->destdir);
-                if (!err) {
-                        err = ovl_copy_up_locked(c);
-                        unlock_rename(c->workdir, c->destdir);
-                }
-        }
-
-
+        if (S_ISREG(c->stat.mode) && ofs->tmpfile)
+                err = ovl_copy_up_tmpfile(c);
+        else
+                err = ovl_copy_up_workdir(c);
         if (err)
                 goto out;
 
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 276914ae3c60..c6289147c787 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -414,13 +414,12 @@ static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
                 return 0;
 
-        size = posix_acl_to_xattr(NULL, acl, NULL, 0);
+        size = posix_acl_xattr_size(acl->a_count);
         buffer = kmalloc(size, GFP_KERNEL);
         if (!buffer)
                 return -ENOMEM;
 
-        size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
-        err = size;
+        err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
         if (err < 0)
                 goto out_free;
 
@@ -463,6 +462,10 @@ static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
         if (IS_ERR(upper))
                 goto out_unlock;
 
+        err = -ESTALE;
+        if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
+                goto out_dput;
+
         newdentry = ovl_create_temp(workdir, cattr);
         err = PTR_ERR(newdentry);
         if (IS_ERR(newdentry))
@@ -652,7 +655,6 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
                     struct dentry *new)
 {
         int err;
-        bool locked = false;
         struct inode *inode;
 
         err = ovl_want_write(old);
@@ -663,13 +665,17 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
         if (err)
                 goto out_drop_write;
 
+        err = ovl_copy_up(new->d_parent);
+        if (err)
+                goto out_drop_write;
+
         if (ovl_is_metacopy_dentry(old)) {
                 err = ovl_set_redirect(old, false);
                 if (err)
                         goto out_drop_write;
         }
 
-        err = ovl_nlink_start(old, &locked);
+        err = ovl_nlink_start(old);
         if (err)
                 goto out_drop_write;
 
@@ -682,7 +688,7 @@ static int ovl_link(struct dentry *old, struct inode *newdir,
         if (err)
                 iput(inode);
 
-        ovl_nlink_end(old, locked);
+        ovl_nlink_end(old);
 out_drop_write:
         ovl_drop_write(old);
 out:
@@ -807,7 +813,6 @@ static bool ovl_pure_upper(struct dentry *dentry)
 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
         int err;
-        bool locked = false;
         const struct cred *old_cred;
         struct dentry *upperdentry;
         bool lower_positive = ovl_lower_positive(dentry);
@@ -828,7 +833,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
         if (err)
                 goto out_drop_write;
 
-        err = ovl_nlink_start(dentry, &locked);
+        err = ovl_nlink_start(dentry);
         if (err)
                 goto out_drop_write;
 
@@ -844,7 +849,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
                 else
                         drop_nlink(dentry->d_inode);
         }
-        ovl_nlink_end(dentry, locked);
+        ovl_nlink_end(dentry);
 
         /*
          * Copy ctime
@@ -1008,7 +1013,6 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
                       unsigned int flags)
 {
         int err;
-        bool locked = false;
         struct dentry *old_upperdir;
         struct dentry *new_upperdir;
         struct dentry *olddentry;
@@ -1017,6 +1021,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
         bool old_opaque;
         bool new_opaque;
         bool cleanup_whiteout = false;
+        bool update_nlink = false;
         bool overwrite = !(flags & RENAME_EXCHANGE);
         bool is_dir = d_is_dir(old);
         bool new_is_dir = d_is_dir(new);
@@ -1074,10 +1079,12 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
                 err = ovl_copy_up(new);
                 if (err)
                         goto out_drop_write;
-        } else {
-                err = ovl_nlink_start(new, &locked);
+        } else if (d_inode(new)) {
+                err = ovl_nlink_start(new);
                 if (err)
                         goto out_drop_write;
+
+                update_nlink = true;
         }
 
         old_cred = ovl_override_creds(old->d_sb);
@@ -1206,7 +1213,8 @@ out_unlock:
         unlock_rename(new_upperdir, old_upperdir);
 out_revert_creds:
         revert_creds(old_cred);
-        ovl_nlink_end(new, locked);
+        if (update_nlink)
+                ovl_nlink_end(new);
 out_drop_write:
         ovl_drop_write(old);
 out:
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3b7ed5d2279c..6bcc9dedc342 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -286,13 +286,22 @@ int ovl_permission(struct inode *inode, int mask)
         if (err)
                 return err;
 
-        old_cred = ovl_override_creds(inode->i_sb);
-        if (!upperinode &&
-            !special_file(realinode->i_mode) && mask & MAY_WRITE) {
+        /* No need to do any access on underlying for special files */
+        if (special_file(realinode->i_mode))
+                return 0;
+
+        /* No need to access underlying for execute */
+        mask &= ~MAY_EXEC;
+        if ((mask & (MAY_READ | MAY_WRITE)) == 0)
+                return 0;
+
+        /* Lower files get copied up, so turn write access into read */
+        if (!upperinode && mask & MAY_WRITE) {
                 mask &= ~(MAY_WRITE | MAY_APPEND);
-                /* Make sure mounter can read file for copy up later */
                 mask |= MAY_READ;
         }
+
+        old_cred = ovl_override_creds(inode->i_sb);
         err = inode_permission(realinode, mask);
         revert_creds(old_cred);
 
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 9c0ca6a7becf..efd372312ef1 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -422,8 +422,10 @@ int ovl_verify_set_fh(struct dentry *dentry, const char *name,
 
         fh = ovl_encode_real_fh(real, is_upper);
         err = PTR_ERR(fh);
-        if (IS_ERR(fh))
+        if (IS_ERR(fh)) {
+                fh = NULL;
                 goto fail;
+        }
 
         err = ovl_verify_fh(dentry, name, fh);
         if (set && err == -ENODATA)
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index a3c0d9584312..5e45cb3630a0 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -271,8 +271,8 @@ bool ovl_test_flag(unsigned long flag, struct inode *inode);
 bool ovl_inuse_trylock(struct dentry *dentry);
 void ovl_inuse_unlock(struct dentry *dentry);
 bool ovl_need_index(struct dentry *dentry);
-int ovl_nlink_start(struct dentry *dentry, bool *locked);
-void ovl_nlink_end(struct dentry *dentry, bool locked);
+int ovl_nlink_start(struct dentry *dentry);
+void ovl_nlink_end(struct dentry *dentry);
 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
 int ovl_check_metacopy_xattr(struct dentry *dentry);
 bool ovl_is_metacopy_dentry(struct dentry *dentry);
@@ -290,6 +290,16 @@ static inline unsigned int ovl_xino_bits(struct super_block *sb)
         return ofs->xino_bits;
 }
 
+static inline int ovl_inode_lock(struct inode *inode)
+{
+        return mutex_lock_interruptible(&OVL_I(inode)->lock);
+}
+
+static inline void ovl_inode_unlock(struct inode *inode)
+{
+        mutex_unlock(&OVL_I(inode)->lock);
+}
+
 
 /* namei.c */
 int ovl_check_fh_len(struct ovl_fh *fh, int fh_len);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 30adc9d408a0..0116735cc321 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -472,6 +472,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 {
         char *p;
         int err;
+        bool metacopy_opt = false, redirect_opt = false;
 
         config->redirect_mode = kstrdup(ovl_redirect_mode_def(), GFP_KERNEL);
         if (!config->redirect_mode)
@@ -516,6 +517,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
                         config->redirect_mode = match_strdup(&args[0]);
                         if (!config->redirect_mode)
                                 return -ENOMEM;
+                        redirect_opt = true;
                         break;
 
                 case OPT_INDEX_ON:
@@ -548,6 +550,7 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
 
                 case OPT_METACOPY_ON:
                         config->metacopy = true;
+                        metacopy_opt = true;
                         break;
 
                 case OPT_METACOPY_OFF:
@@ -572,13 +575,32 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
         if (err)
                 return err;
 
-        /* metacopy feature with upper requires redirect_dir=on */
-        if (config->upperdir && config->metacopy && !config->redirect_dir) {
-                pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=on\", falling back to metacopy=off.\n");
-                config->metacopy = false;
-        } else if (config->metacopy && !config->redirect_follow) {
-                pr_warn("overlayfs: metadata only copy up requires \"redirect_dir=follow\" on non-upper mount, falling back to metacopy=off.\n");
-                config->metacopy = false;
+        /*
+         * This is to make the logic below simpler.  It doesn't make any other
+         * difference, since config->redirect_dir is only used for upper.
+         */
+        if (!config->upperdir && config->redirect_follow)
+                config->redirect_dir = true;
+
+        /* Resolve metacopy -> redirect_dir dependency */
+        if (config->metacopy && !config->redirect_dir) {
+                if (metacopy_opt && redirect_opt) {
+                        pr_err("overlayfs: conflicting options: metacopy=on,redirect_dir=%s\n",
+                               config->redirect_mode);
+                        return -EINVAL;
+                }
+                if (redirect_opt) {
+                        /*
+                         * There was an explicit redirect_dir=... that resulted
+                         * in this conflict.
+                         */
+                        pr_info("overlayfs: disabling metacopy due to redirect_dir=%s\n",
+                                config->redirect_mode);
+                        config->metacopy = false;
+                } else {
+                        /* Automatically enable redirect otherwise. */
+                        config->redirect_follow = config->redirect_dir = true;
+                }
         }
 
         return 0;
@@ -1175,9 +1197,29 @@ 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 +1233,14 @@ 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 +1275,7 @@ 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 ace4fe4c39a9..7c01327b1852 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;
@@ -522,13 +521,13 @@ bool ovl_already_copied_up(struct dentry *dentry, int flags)
 
 int ovl_copy_up_start(struct dentry *dentry, int flags)
 {
-        struct ovl_inode *oi = OVL_I(d_inode(dentry));
+        struct inode *inode = d_inode(dentry);
         int err;
 
-        err = mutex_lock_interruptible(&oi->lock);
+        err = ovl_inode_lock(inode);
         if (!err && ovl_already_copied_up_locked(dentry, flags)) {
                 err = 1; /* Already copied up */
-                mutex_unlock(&oi->lock);
+                ovl_inode_unlock(inode);
         }
 
         return err;
@@ -536,7 +535,7 @@ int ovl_copy_up_start(struct dentry *dentry, int flags)
 
 void ovl_copy_up_end(struct dentry *dentry)
 {
-        mutex_unlock(&OVL_I(d_inode(dentry))->lock);
+        ovl_inode_unlock(d_inode(dentry));
 }
 
 bool ovl_check_origin_xattr(struct dentry *dentry)
@@ -739,14 +738,14 @@ fail:
  * Operations that change overlay inode and upper inode nlink need to be
  * synchronized with copy up for persistent nlink accounting.
  */
-int ovl_nlink_start(struct dentry *dentry, bool *locked)
+int ovl_nlink_start(struct dentry *dentry)
 {
-        struct ovl_inode *oi = OVL_I(d_inode(dentry));
+        struct inode *inode = d_inode(dentry);
         const struct cred *old_cred;
         int err;
 
-        if (!d_inode(dentry))
-                return 0;
+        if (WARN_ON(!inode))
+                return -ENOENT;
 
         /*
          * With inodes index is enabled, we store the union overlay nlink
@@ -768,11 +767,11 @@ int ovl_nlink_start(struct dentry *dentry, bool *locked)
                         return err;
         }
 
-        err = mutex_lock_interruptible(&oi->lock);
+        err = ovl_inode_lock(inode);
         if (err)
                 return err;
 
-        if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+        if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, inode))
                 goto out;
 
         old_cred = ovl_override_creds(dentry->d_sb);
@@ -787,27 +786,24 @@ int ovl_nlink_start(struct dentry *dentry, bool *locked)
 
 out:
         if (err)
-                mutex_unlock(&oi->lock);
-        else
-                *locked = true;
+                ovl_inode_unlock(inode);
 
         return err;
 }
 
-void ovl_nlink_end(struct dentry *dentry, bool locked)
+void ovl_nlink_end(struct dentry *dentry)
 {
-        if (locked) {
-                if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
-                    d_inode(dentry)->i_nlink == 0) {
-                        const struct cred *old_cred;
+        struct inode *inode = d_inode(dentry);
 
-                        old_cred = ovl_override_creds(dentry->d_sb);
-                        ovl_cleanup_index(dentry);
-                        revert_creds(old_cred);
-                }
+        if (ovl_test_flag(OVL_INDEX, inode) && inode->i_nlink == 0) {
+                const struct cred *old_cred;
 
-                mutex_unlock(&OVL_I(d_inode(dentry))->lock);
+                old_cred = ovl_override_creds(dentry->d_sb);
+                ovl_cleanup_index(dentry);
+                revert_creds(old_cred);
         }
+
+        ovl_inode_unlock(inode);
 }
 
 int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)