/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *
 * Copyright (C) 2011 Novell Inc.
 * Copyright (C) 2016 Red Hat, Inc.
 */

struct ovl_config {
        char *upperdir;
        char *workdir;
        char **lowerdirs;
        bool default_permissions;
        int redirect_mode;
        int verity_mode;
        bool index;
        int uuid;
        bool nfs_export;
        int xino;
        bool metacopy;
        bool userxattr;
        int fsync_mode;
};

struct ovl_sb {
        struct super_block *sb;
        dev_t pseudo_dev;
        /* Unusable (conflicting) uuid */
        bool bad_uuid;
        /* Used as a lower layer (but maybe also as upper) */
        bool is_lower;
};

struct ovl_layer {
        /* ovl_free_fs() relies on @mnt being the first member! */
        struct vfsmount *mnt;
        /* Trap in ovl inode cache */
        struct inode *trap;
        struct ovl_sb *fs;
        /* Index of this layer in fs root (upper idx == 0) */
        int idx;
        /* One fsid per unique underlying sb (upper fsid == 0) */
        int fsid;
        /* xwhiteouts were found on this layer */
        bool has_xwhiteouts;
};

struct ovl_path {
        const struct ovl_layer *layer;
        struct dentry *dentry;
};

struct ovl_entry {
        unsigned int __numlower;
        struct ovl_path __lowerstack[] __counted_by(__numlower);
};

/* private information held for overlayfs's superblock */
struct ovl_fs {
        unsigned int numlayer;
        /* Number of unique fs among layers including upper fs */
        unsigned int numfs;
        /* Number of data-only lower layers */
        unsigned int numdatalayer;
        struct ovl_layer *layers;
        struct ovl_sb *fs;
        /* workbasedir is the path at workdir= mount option */
        struct dentry *workbasedir;
        /* workdir is the 'work' or 'index' directory under workbasedir */
        struct dentry *workdir;
        long namelen;
        /* pathnames of lower and upper dirs, for show_options */
        struct ovl_config config;
        /* creds of process who forced instantiation of super block */
        const struct cred *creator_cred;
        bool tmpfile;
        bool noxattr;
        bool nofh;
        /* Did we take the inuse lock? */
        bool upperdir_locked;
        bool workdir_locked;
        /* Traps in ovl inode cache */
        struct inode *workbasedir_trap;
        struct inode *workdir_trap;
        /* -1: disabled, 0: same fs, 1..32: number of unused ino bits */
        int xino_mode;
        /* For allocation of non-persistent inode numbers */
        atomic_long_t last_ino;
        /* Shared whiteout cache */
        struct dentry *whiteout;
        bool no_shared_whiteout;
        struct mutex whiteout_lock;
        /* r/o snapshot of upperdir sb's only taken on volatile mounts */
        errseq_t errseq;
        bool casefold;
};

/* Number of lower layers, not including data-only layers */
static inline unsigned int ovl_numlowerlayer(struct ovl_fs *ofs)
{
        return ofs->numlayer - ofs->numdatalayer - 1;
}

static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
{
        return ofs->layers[0].mnt;
}

static inline struct mnt_idmap *ovl_upper_mnt_idmap(struct ovl_fs *ofs)
{
        return mnt_idmap(ovl_upper_mnt(ofs));
}

extern struct file_system_type ovl_fs_type;

static inline struct ovl_fs *OVL_FS(struct super_block *sb)
{
        if (IS_ENABLED(CONFIG_OVERLAY_FS_DEBUG))
                WARN_ON_ONCE(sb->s_type != &ovl_fs_type);

        return (struct ovl_fs *)sb->s_fs_info;
}

static inline unsigned int ovl_numlower(struct ovl_entry *oe)
{
        return oe ? oe->__numlower : 0;
}

static inline struct ovl_path *ovl_lowerstack(struct ovl_entry *oe)
{
        return ovl_numlower(oe) ? oe->__lowerstack : NULL;
}

static inline struct ovl_path *ovl_lowerpath(struct ovl_entry *oe)
{
        return ovl_lowerstack(oe);
}

static inline struct ovl_path *ovl_lowerdata(struct ovl_entry *oe)
{
        struct ovl_path *lowerstack = ovl_lowerstack(oe);

        return lowerstack ? &lowerstack[oe->__numlower - 1] : NULL;
}

/* May return NULL if lazy lookup of lowerdata is needed */
static inline struct dentry *ovl_lowerdata_dentry(struct ovl_entry *oe)
{
        struct ovl_path *lowerdata = ovl_lowerdata(oe);

        return lowerdata ? READ_ONCE(lowerdata->dentry) : NULL;
}

/* private information held for every overlayfs dentry */
static inline unsigned long *OVL_E_FLAGS(struct dentry *dentry)
{
        return (unsigned long *) &dentry->d_fsdata;
}

struct ovl_inode {
        union {
                struct ovl_dir_cache *cache;    /* directory */
                const char *lowerdata_redirect; /* regular file */
        };
        const char *redirect;
        u64 version;
        unsigned long flags;
        struct inode vfs_inode;
        struct dentry *__upperdentry;
        struct ovl_entry *oe;

        /* synchronize copy up and more */
        struct mutex lock;
};

static inline struct ovl_inode *OVL_I(struct inode *inode)
{
        return container_of(inode, struct ovl_inode, vfs_inode);
}

static inline struct ovl_entry *OVL_I_E(struct inode *inode)
{
        return inode ? OVL_I(inode)->oe : NULL;
}

static inline struct ovl_entry *OVL_E(struct dentry *dentry)
{
        return OVL_I_E(d_inode(dentry));
}

static inline struct dentry *ovl_upperdentry_dereference(struct ovl_inode *oi)
{
        return READ_ONCE(oi->__upperdentry);
}