/*
 * fs/kernfs/inode.c - kernfs inode implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
 *
 * This file is released under the GPLv2.
 */

#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/security.h>

#include "kernfs-internal.h"

static const struct address_space_operations kernfs_aops = {
        .readpage       = simple_readpage,
        .write_begin    = simple_write_begin,
        .write_end      = simple_write_end,
};

static const struct inode_operations kernfs_iops = {
        .permission     = kernfs_iop_permission,
        .setattr        = kernfs_iop_setattr,
        .getattr        = kernfs_iop_getattr,
        .setxattr       = kernfs_iop_setxattr,
        .removexattr    = kernfs_iop_removexattr,
        .getxattr       = kernfs_iop_getxattr,
        .listxattr      = kernfs_iop_listxattr,
};

static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
{
        static DEFINE_MUTEX(iattr_mutex);
        struct kernfs_iattrs *ret;
        struct iattr *iattrs;

        mutex_lock(&iattr_mutex);

        if (kn->iattr)
                goto out_unlock;

        kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
        if (!kn->iattr)
                goto out_unlock;
        iattrs = &kn->iattr->ia_iattr;

        /* assign default attributes */
        iattrs->ia_mode = kn->mode;
        iattrs->ia_uid = GLOBAL_ROOT_UID;
        iattrs->ia_gid = GLOBAL_ROOT_GID;

        ktime_get_real_ts(&iattrs->ia_atime);
        iattrs->ia_mtime = iattrs->ia_atime;
        iattrs->ia_ctime = iattrs->ia_atime;

        simple_xattrs_init(&kn->iattr->xattrs);
out_unlock:
        ret = kn->iattr;
        mutex_unlock(&iattr_mutex);
        return ret;
}

static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
        struct kernfs_iattrs *attrs;
        struct iattr *iattrs;
        unsigned int ia_valid = iattr->ia_valid;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        iattrs = &attrs->ia_iattr;

        if (ia_valid & ATTR_UID)
                iattrs->ia_uid = iattr->ia_uid;
        if (ia_valid & ATTR_GID)
                iattrs->ia_gid = iattr->ia_gid;
        if (ia_valid & ATTR_ATIME)
                iattrs->ia_atime = iattr->ia_atime;
        if (ia_valid & ATTR_MTIME)
                iattrs->ia_mtime = iattr->ia_mtime;
        if (ia_valid & ATTR_CTIME)
                iattrs->ia_ctime = iattr->ia_ctime;
        if (ia_valid & ATTR_MODE) {
                umode_t mode = iattr->ia_mode;
                iattrs->ia_mode = kn->mode = mode;
        }
        return 0;
}

/**
 * kernfs_setattr - set iattr on a node
 * @kn: target node
 * @iattr: iattr to set
 *
 * Returns 0 on success, -errno on failure.
 */
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
{
        int ret;

        mutex_lock(&kernfs_mutex);
        ret = __kernfs_setattr(kn, iattr);
        mutex_unlock(&kernfs_mutex);
        return ret;
}

int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
{
        struct inode *inode = d_inode(dentry);
        struct kernfs_node *kn = dentry->d_fsdata;
        int error;

        if (!kn)
                return -EINVAL;

        mutex_lock(&kernfs_mutex);
        error = inode_change_ok(inode, iattr);
        if (error)
                goto out;

        error = __kernfs_setattr(kn, iattr);
        if (error)
                goto out;

        /* this ignores size changes */
        setattr_copy(inode, iattr);

out:
        mutex_unlock(&kernfs_mutex);
        return error;
}

static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
                                  u32 *secdata_len)
{
        struct kernfs_iattrs *attrs;
        void *old_secdata;
        size_t old_secdata_len;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        old_secdata = attrs->ia_secdata;
        old_secdata_len = attrs->ia_secdata_len;

        attrs->ia_secdata = *secdata;
        attrs->ia_secdata_len = *secdata_len;

        *secdata = old_secdata;
        *secdata_len = old_secdata_len;
        return 0;
}

int kernfs_iop_setxattr(struct dentry *unused, struct inode *inode,
                        const char *name, const void *value,
                        size_t size, int flags)
{
        struct kernfs_node *kn = inode->i_private;
        struct kernfs_iattrs *attrs;
        void *secdata;
        int error;
        u32 secdata_len = 0;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
                error = security_inode_setsecurity(inode, suffix,
                                                value, size, flags);
                if (error)
                        return error;
                error = security_inode_getsecctx(inode,
                                                &secdata, &secdata_len);
                if (error)
                        return error;

                mutex_lock(&kernfs_mutex);
                error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
                mutex_unlock(&kernfs_mutex);

                if (secdata)
                        security_release_secctx(secdata, secdata_len);
                return error;
        } else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
                return simple_xattr_set(&attrs->xattrs, name, value, size,
                                        flags);
        }

        return -EINVAL;
}

int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
{
        struct kernfs_node *kn = dentry->d_fsdata;
        struct kernfs_iattrs *attrs;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        return simple_xattr_set(&attrs->xattrs, name, NULL, 0, XATTR_REPLACE);
}

ssize_t kernfs_iop_getxattr(struct dentry *unused, struct inode *inode,
                            const char *name, void *buf, size_t size)
{
        struct kernfs_node *kn = inode->i_private;
        struct kernfs_iattrs *attrs;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        return simple_xattr_get(&attrs->xattrs, name, buf, size);
}

ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
{
        struct kernfs_node *kn = dentry->d_fsdata;
        struct kernfs_iattrs *attrs;

        attrs = kernfs_iattrs(kn);
        if (!attrs)
                return -ENOMEM;

        return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
}

static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
{
        inode->i_mode = mode;
        inode->i_atime = inode->i_mtime =
                inode->i_ctime = current_fs_time(inode->i_sb);
}

static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
{
        struct super_block *sb = inode->i_sb;
        inode->i_uid = iattr->ia_uid;
        inode->i_gid = iattr->ia_gid;
        inode->i_atime = timespec_trunc(iattr->ia_atime, sb->s_time_gran);
        inode->i_mtime = timespec_trunc(iattr->ia_mtime, sb->s_time_gran);
        inode->i_ctime = timespec_trunc(iattr->ia_ctime, sb->s_time_gran);
}

static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
{
        struct kernfs_iattrs *attrs = kn->iattr;

        inode->i_mode = kn->mode;
        if (attrs) {
                /*
                 * kernfs_node has non-default attributes get them from
                 * persistent copy in kernfs_node.
                 */
                set_inode_attr(inode, &attrs->ia_iattr);
                security_inode_notifysecctx(inode, attrs->ia_secdata,
                                            attrs->ia_secdata_len);
        }

        if (kernfs_type(kn) == KERNFS_DIR)
                set_nlink(inode, kn->dir.subdirs + 2);
}

int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
                   struct kstat *stat)
{
        struct kernfs_node *kn = dentry->d_fsdata;
        struct inode *inode = d_inode(dentry);

        mutex_lock(&kernfs_mutex);
        kernfs_refresh_inode(kn, inode);
        mutex_unlock(&kernfs_mutex);

        generic_fillattr(inode, stat);
        return 0;
}

static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
{
        kernfs_get(kn);
        inode->i_private = kn;
        inode->i_mapping->a_ops = &kernfs_aops;
        inode->i_op = &kernfs_iops;

        set_default_inode_attr(inode, kn->mode);
        kernfs_refresh_inode(kn, inode);

        /* initialize inode according to type */
        switch (kernfs_type(kn)) {
        case KERNFS_DIR:
                inode->i_op = &kernfs_dir_iops;
                inode->i_fop = &kernfs_dir_fops;
                if (kn->flags & KERNFS_EMPTY_DIR)
                        make_empty_dir_inode(inode);
                break;
        case KERNFS_FILE:
                inode->i_size = kn->attr.size;
                inode->i_fop = &kernfs_file_fops;
                break;
        case KERNFS_LINK:
                inode->i_op = &kernfs_symlink_iops;
                break;
        default:
                BUG();
        }

        unlock_new_inode(inode);
}

/**
 *      kernfs_get_inode - get inode for kernfs_node
 *      @sb: super block
 *      @kn: kernfs_node to allocate inode for
 *
 *      Get inode for @kn.  If such inode doesn't exist, a new inode is
 *      allocated and basics are initialized.  New inode is returned
 *      locked.
 *
 *      LOCKING:
 *      Kernel thread context (may sleep).
 *
 *      RETURNS:
 *      Pointer to allocated inode on success, NULL on failure.
 */
struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
{
        struct inode *inode;

        inode = iget_locked(sb, kn->ino);
        if (inode && (inode->i_state & I_NEW))
                kernfs_init_inode(kn, inode);

        return inode;
}

/*
 * The kernfs_node serves as both an inode and a directory entry for
 * kernfs.  To prevent the kernfs inode numbers from being freed
 * prematurely we take a reference to kernfs_node from the kernfs inode.  A
 * super_operations.evict_inode() implementation is needed to drop that
 * reference upon inode destruction.
 */
void kernfs_evict_inode(struct inode *inode)
{
        struct kernfs_node *kn = inode->i_private;

        truncate_inode_pages_final(&inode->i_data);
        clear_inode(inode);
        kernfs_put(kn);
}

int kernfs_iop_permission(struct inode *inode, int mask)
{
        struct kernfs_node *kn;

        if (mask & MAY_NOT_BLOCK)
                return -ECHILD;

        kn = inode->i_private;

        mutex_lock(&kernfs_mutex);
        kernfs_refresh_inode(kn, inode);
        mutex_unlock(&kernfs_mutex);

        return generic_permission(inode, mask);
}