// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/fs/adfs/inode.c
 *
 *  Copyright (C) 1997-1999 Russell King
 */
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include "adfs.h"

/*
 * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
 * not support creation of new blocks, so we return -EIO for this case.
 */
static int
adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
               int create)
{
        if (!create) {
                if (block >= inode->i_blocks)
                        goto abort_toobig;

                block = __adfs_block_map(inode->i_sb, ADFS_I(inode)->indaddr,
                                         block);
                if (block)
                        map_bh(bh, inode->i_sb, block);
                return 0;
        }
        /* don't support allocation of blocks yet */
        return -EIO;

abort_toobig:
        return 0;
}

static int adfs_writepage(struct page *page, struct writeback_control *wbc)
{
        return block_write_full_page(page, adfs_get_block, wbc);
}

static int adfs_readpage(struct file *file, struct page *page)
{
        return block_read_full_page(page, adfs_get_block);
}

static void adfs_write_failed(struct address_space *mapping, loff_t to)
{
        struct inode *inode = mapping->host;

        if (to > inode->i_size)
                truncate_pagecache(inode, inode->i_size);
}

static int adfs_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
                        struct page **pagep, void **fsdata)
{
        int ret;

        *pagep = NULL;
        ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
                                adfs_get_block,
                                &ADFS_I(mapping->host)->mmu_private);
        if (unlikely(ret))
                adfs_write_failed(mapping, pos + len);

        return ret;
}

static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
{
        return generic_block_bmap(mapping, block, adfs_get_block);
}

static const struct address_space_operations adfs_aops = {
        .readpage       = adfs_readpage,
        .writepage      = adfs_writepage,
        .write_begin    = adfs_write_begin,
        .write_end      = generic_write_end,
        .bmap           = _adfs_bmap
};

/*
 * Convert ADFS attributes and filetype to Linux permission.
 */
static umode_t
adfs_atts2mode(struct super_block *sb, struct inode *inode)
{
        unsigned int attr = ADFS_I(inode)->attr;
        umode_t mode, rmask;
        struct adfs_sb_info *asb = ADFS_SB(sb);

        if (attr & ADFS_NDA_DIRECTORY) {
                mode = S_IRUGO & asb->s_owner_mask;
                return S_IFDIR | S_IXUGO | mode;
        }

        switch (adfs_filetype(ADFS_I(inode)->loadaddr)) {
        case 0xfc0:     /* LinkFS */
                return S_IFLNK|S_IRWXUGO;

        case 0xfe6:     /* UnixExec */
                rmask = S_IRUGO | S_IXUGO;
                break;

        default:
                rmask = S_IRUGO;
        }

        mode = S_IFREG;

        if (attr & ADFS_NDA_OWNER_READ)
                mode |= rmask & asb->s_owner_mask;

        if (attr & ADFS_NDA_OWNER_WRITE)
                mode |= S_IWUGO & asb->s_owner_mask;

        if (attr & ADFS_NDA_PUBLIC_READ)
                mode |= rmask & asb->s_other_mask;

        if (attr & ADFS_NDA_PUBLIC_WRITE)
                mode |= S_IWUGO & asb->s_other_mask;
        return mode;
}

/*
 * Convert Linux permission to ADFS attribute.  We try to do the reverse
 * of atts2mode, but there is not a 1:1 translation.
 */
static int adfs_mode2atts(struct super_block *sb, struct inode *inode,
                          umode_t ia_mode)
{
        struct adfs_sb_info *asb = ADFS_SB(sb);
        umode_t mode;
        int attr;

        /* FIXME: should we be able to alter a link? */
        if (S_ISLNK(inode->i_mode))
                return ADFS_I(inode)->attr;

        /* Directories do not have read/write permissions on the media */
        if (S_ISDIR(inode->i_mode))
                return ADFS_NDA_DIRECTORY;

        attr = 0;
        mode = ia_mode & asb->s_owner_mask;
        if (mode & S_IRUGO)
                attr |= ADFS_NDA_OWNER_READ;
        if (mode & S_IWUGO)
                attr |= ADFS_NDA_OWNER_WRITE;

        mode = ia_mode & asb->s_other_mask;
        mode &= ~asb->s_owner_mask;
        if (mode & S_IRUGO)
                attr |= ADFS_NDA_PUBLIC_READ;
        if (mode & S_IWUGO)
                attr |= ADFS_NDA_PUBLIC_WRITE;

        return attr;
}

static const s64 nsec_unix_epoch_diff_risc_os_epoch = 2208988800000000000LL;

/*
 * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
 * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
 * of time to convert from RISC OS epoch to Unix epoch.
 */
static void
adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
{
        unsigned int high, low;
        /* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
         * 01 Jan 1900 00:00:00 (RISC OS epoch)
         */
        s64 nsec;

        if (!adfs_inode_is_stamped(inode))
                goto cur_time;

        high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
        low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */

        /* convert 40-bit centi-seconds to 32-bit seconds
         * going via nanoseconds to retain precision
         */
        nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */

        /* Files dated pre  01 Jan 1970 00:00:00. */
        if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
                goto too_early;

        /* convert from RISC OS to Unix epoch */
        nsec -= nsec_unix_epoch_diff_risc_os_epoch;

        *tv = ns_to_timespec64(nsec);
        return;

 cur_time:
        *tv = current_time(inode);
        return;

 too_early:
        tv->tv_sec = tv->tv_nsec = 0;
        return;
}

/* Convert an Unix time to ADFS time for an entry that is already stamped. */
static void adfs_unix2adfs_time(struct inode *inode,
                                const struct timespec64 *ts)
{
        s64 cs, nsec = timespec64_to_ns(ts);

        /* convert from Unix to RISC OS epoch */
        nsec += nsec_unix_epoch_diff_risc_os_epoch;

        /* convert from nanoseconds to centiseconds */
        cs = div_s64(nsec, 10000000);

        cs = clamp_t(s64, cs, 0, 0xffffffffff);

        ADFS_I(inode)->loadaddr &= ~0xff;
        ADFS_I(inode)->loadaddr |= (cs >> 32) & 0xff;
        ADFS_I(inode)->execaddr = cs;
}

/*
 * Fill in the inode information from the object information.
 *
 * Note that this is an inode-less filesystem, so we can't use the inode
 * number to reference the metadata on the media.  Instead, we use the
 * inode number to hold the object ID, which in turn will tell us where
 * the data is held.  We also save the parent object ID, and with these
 * two, we can locate the metadata.
 *
 * This does mean that we rely on an objects parent remaining the same at
 * all times - we cannot cope with a cross-directory rename (yet).
 */
struct inode *
adfs_iget(struct super_block *sb, struct object_info *obj)
{
        struct inode *inode;

        inode = new_inode(sb);
        if (!inode)
                goto out;

        inode->i_uid     = ADFS_SB(sb)->s_uid;
        inode->i_gid     = ADFS_SB(sb)->s_gid;
        inode->i_ino     = obj->indaddr;
        inode->i_size    = obj->size;
        set_nlink(inode, 2);
        inode->i_blocks  = (inode->i_size + sb->s_blocksize - 1) >>
                            sb->s_blocksize_bits;

        /*
         * we need to save the parent directory ID so that
         * write_inode can update the directory information
         * for this file.  This will need special handling
         * for cross-directory renames.
         */
        ADFS_I(inode)->parent_id = obj->parent_id;
        ADFS_I(inode)->indaddr   = obj->indaddr;
        ADFS_I(inode)->loadaddr  = obj->loadaddr;
        ADFS_I(inode)->execaddr  = obj->execaddr;
        ADFS_I(inode)->attr      = obj->attr;

        inode->i_mode    = adfs_atts2mode(sb, inode);
        adfs_adfs2unix_time(&inode->i_mtime, inode);
        inode->i_atime = inode->i_mtime;
        inode->i_ctime = inode->i_mtime;

        if (S_ISDIR(inode->i_mode)) {
                inode->i_op     = &adfs_dir_inode_operations;
                inode->i_fop    = &adfs_dir_operations;
        } else if (S_ISREG(inode->i_mode)) {
                inode->i_op     = &adfs_file_inode_operations;
                inode->i_fop    = &adfs_file_operations;
                inode->i_mapping->a_ops = &adfs_aops;
                ADFS_I(inode)->mmu_private = inode->i_size;
        }

        inode_fake_hash(inode);

out:
        return inode;
}

/*
 * Validate and convert a changed access mode/time to their ADFS equivalents.
 * adfs_write_inode will actually write the information back to the directory
 * later.
 */
int
adfs_notify_change(struct user_namespace *mnt_userns, struct dentry *dentry,
                   struct iattr *attr)
{
        struct inode *inode = d_inode(dentry);
        struct super_block *sb = inode->i_sb;
        unsigned int ia_valid = attr->ia_valid;
        int error;
        
        error = setattr_prepare(&init_user_ns, dentry, attr);

        /*
         * we can't change the UID or GID of any file -
         * we have a global UID/GID in the superblock
         */
        if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
            (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
                error = -EPERM;

        if (error)
                goto out;

        /* XXX: this is missing some actual on-disk truncation.. */
        if (ia_valid & ATTR_SIZE)
                truncate_setsize(inode, attr->ia_size);

        if (ia_valid & ATTR_MTIME && adfs_inode_is_stamped(inode)) {
                adfs_unix2adfs_time(inode, &attr->ia_mtime);
                adfs_adfs2unix_time(&inode->i_mtime, inode);
        }

        /*
         * FIXME: should we make these == to i_mtime since we don't
         * have the ability to represent them in our filesystem?
         */
        if (ia_valid & ATTR_ATIME)
                inode->i_atime = attr->ia_atime;
        if (ia_valid & ATTR_CTIME)
                inode->i_ctime = attr->ia_ctime;
        if (ia_valid & ATTR_MODE) {
                ADFS_I(inode)->attr = adfs_mode2atts(sb, inode, attr->ia_mode);
                inode->i_mode = adfs_atts2mode(sb, inode);
        }

        /*
         * FIXME: should we be marking this inode dirty even if
         * we don't have any metadata to write back?
         */
        if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
                mark_inode_dirty(inode);
out:
        return error;
}

/*
 * write an existing inode back to the directory, and therefore the disk.
 * The adfs-specific inode data has already been updated by
 * adfs_notify_change()
 */
int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        struct super_block *sb = inode->i_sb;
        struct object_info obj;
        int ret;

        obj.indaddr     = ADFS_I(inode)->indaddr;
        obj.name_len    = 0;
        obj.parent_id   = ADFS_I(inode)->parent_id;
        obj.loadaddr    = ADFS_I(inode)->loadaddr;
        obj.execaddr    = ADFS_I(inode)->execaddr;
        obj.attr        = ADFS_I(inode)->attr;
        obj.size        = inode->i_size;

        ret = adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
        return ret;
}