linux/fs/adfs/inode.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  linux/fs/adfs/inode.c
   4 *
   5 *  Copyright (C) 1997-1999 Russell King
   6 */
   7#include <linux/buffer_head.h>
   8#include <linux/writeback.h>
   9#include "adfs.h"
  10
  11/*
  12 * Lookup/Create a block at offset 'block' into 'inode'.  We currently do
  13 * not support creation of new blocks, so we return -EIO for this case.
  14 */
  15static int
  16adfs_get_block(struct inode *inode, sector_t block, struct buffer_head *bh,
  17               int create)
  18{
  19        if (!create) {
  20                if (block >= inode->i_blocks)
  21                        goto abort_toobig;
  22
  23                block = __adfs_block_map(inode->i_sb, inode->i_ino, block);
  24                if (block)
  25                        map_bh(bh, inode->i_sb, block);
  26                return 0;
  27        }
  28        /* don't support allocation of blocks yet */
  29        return -EIO;
  30
  31abort_toobig:
  32        return 0;
  33}
  34
  35static int adfs_writepage(struct page *page, struct writeback_control *wbc)
  36{
  37        return block_write_full_page(page, adfs_get_block, wbc);
  38}
  39
  40static int adfs_readpage(struct file *file, struct page *page)
  41{
  42        return block_read_full_page(page, adfs_get_block);
  43}
  44
  45static void adfs_write_failed(struct address_space *mapping, loff_t to)
  46{
  47        struct inode *inode = mapping->host;
  48
  49        if (to > inode->i_size)
  50                truncate_pagecache(inode, inode->i_size);
  51}
  52
  53static int adfs_write_begin(struct file *file, struct address_space *mapping,
  54                        loff_t pos, unsigned len, unsigned flags,
  55                        struct page **pagep, void **fsdata)
  56{
  57        int ret;
  58
  59        *pagep = NULL;
  60        ret = cont_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
  61                                adfs_get_block,
  62                                &ADFS_I(mapping->host)->mmu_private);
  63        if (unlikely(ret))
  64                adfs_write_failed(mapping, pos + len);
  65
  66        return ret;
  67}
  68
  69static sector_t _adfs_bmap(struct address_space *mapping, sector_t block)
  70{
  71        return generic_block_bmap(mapping, block, adfs_get_block);
  72}
  73
  74static const struct address_space_operations adfs_aops = {
  75        .readpage       = adfs_readpage,
  76        .writepage      = adfs_writepage,
  77        .write_begin    = adfs_write_begin,
  78        .write_end      = generic_write_end,
  79        .bmap           = _adfs_bmap
  80};
  81
  82/*
  83 * Convert ADFS attributes and filetype to Linux permission.
  84 */
  85static umode_t
  86adfs_atts2mode(struct super_block *sb, struct inode *inode)
  87{
  88        unsigned int attr = ADFS_I(inode)->attr;
  89        umode_t mode, rmask;
  90        struct adfs_sb_info *asb = ADFS_SB(sb);
  91
  92        if (attr & ADFS_NDA_DIRECTORY) {
  93                mode = S_IRUGO & asb->s_owner_mask;
  94                return S_IFDIR | S_IXUGO | mode;
  95        }
  96
  97        switch (ADFS_I(inode)->filetype) {
  98        case 0xfc0:     /* LinkFS */
  99                return S_IFLNK|S_IRWXUGO;
 100
 101        case 0xfe6:     /* UnixExec */
 102                rmask = S_IRUGO | S_IXUGO;
 103                break;
 104
 105        default:
 106                rmask = S_IRUGO;
 107        }
 108
 109        mode = S_IFREG;
 110
 111        if (attr & ADFS_NDA_OWNER_READ)
 112                mode |= rmask & asb->s_owner_mask;
 113
 114        if (attr & ADFS_NDA_OWNER_WRITE)
 115                mode |= S_IWUGO & asb->s_owner_mask;
 116
 117        if (attr & ADFS_NDA_PUBLIC_READ)
 118                mode |= rmask & asb->s_other_mask;
 119
 120        if (attr & ADFS_NDA_PUBLIC_WRITE)
 121                mode |= S_IWUGO & asb->s_other_mask;
 122        return mode;
 123}
 124
 125/*
 126 * Convert Linux permission to ADFS attribute.  We try to do the reverse
 127 * of atts2mode, but there is not a 1:1 translation.
 128 */
 129static int
 130adfs_mode2atts(struct super_block *sb, struct inode *inode)
 131{
 132        umode_t mode;
 133        int attr;
 134        struct adfs_sb_info *asb = ADFS_SB(sb);
 135
 136        /* FIXME: should we be able to alter a link? */
 137        if (S_ISLNK(inode->i_mode))
 138                return ADFS_I(inode)->attr;
 139
 140        if (S_ISDIR(inode->i_mode))
 141                attr = ADFS_NDA_DIRECTORY;
 142        else
 143                attr = 0;
 144
 145        mode = inode->i_mode & asb->s_owner_mask;
 146        if (mode & S_IRUGO)
 147                attr |= ADFS_NDA_OWNER_READ;
 148        if (mode & S_IWUGO)
 149                attr |= ADFS_NDA_OWNER_WRITE;
 150
 151        mode = inode->i_mode & asb->s_other_mask;
 152        mode &= ~asb->s_owner_mask;
 153        if (mode & S_IRUGO)
 154                attr |= ADFS_NDA_PUBLIC_READ;
 155        if (mode & S_IWUGO)
 156                attr |= ADFS_NDA_PUBLIC_WRITE;
 157
 158        return attr;
 159}
 160
 161/*
 162 * Convert an ADFS time to Unix time.  ADFS has a 40-bit centi-second time
 163 * referenced to 1 Jan 1900 (til 2248) so we need to discard 2208988800 seconds
 164 * of time to convert from RISC OS epoch to Unix epoch.
 165 */
 166static void
 167adfs_adfs2unix_time(struct timespec64 *tv, struct inode *inode)
 168{
 169        unsigned int high, low;
 170        /* 01 Jan 1970 00:00:00 (Unix epoch) as nanoseconds since
 171         * 01 Jan 1900 00:00:00 (RISC OS epoch)
 172         */
 173        static const s64 nsec_unix_epoch_diff_risc_os_epoch =
 174                                                        2208988800000000000LL;
 175        s64 nsec;
 176
 177        if (ADFS_I(inode)->stamped == 0)
 178                goto cur_time;
 179
 180        high = ADFS_I(inode)->loadaddr & 0xFF; /* top 8 bits of timestamp */
 181        low  = ADFS_I(inode)->execaddr;    /* bottom 32 bits of timestamp */
 182
 183        /* convert 40-bit centi-seconds to 32-bit seconds
 184         * going via nanoseconds to retain precision
 185         */
 186        nsec = (((s64) high << 32) | (s64) low) * 10000000; /* cs to ns */
 187
 188        /* Files dated pre  01 Jan 1970 00:00:00. */
 189        if (nsec < nsec_unix_epoch_diff_risc_os_epoch)
 190                goto too_early;
 191
 192        /* convert from RISC OS to Unix epoch */
 193        nsec -= nsec_unix_epoch_diff_risc_os_epoch;
 194
 195        *tv = ns_to_timespec64(nsec);
 196        return;
 197
 198 cur_time:
 199        *tv = current_time(inode);
 200        return;
 201
 202 too_early:
 203        tv->tv_sec = tv->tv_nsec = 0;
 204        return;
 205}
 206
 207/*
 208 * Convert an Unix time to ADFS time.  We only do this if the entry has a
 209 * time/date stamp already.
 210 */
 211static void
 212adfs_unix2adfs_time(struct inode *inode, unsigned int secs)
 213{
 214        unsigned int high, low;
 215
 216        if (ADFS_I(inode)->stamped) {
 217                /* convert 32-bit seconds to 40-bit centi-seconds */
 218                low  = (secs & 255) * 100;
 219                high = (secs / 256) * 100 + (low >> 8) + 0x336e996a;
 220
 221                ADFS_I(inode)->loadaddr = (high >> 24) |
 222                                (ADFS_I(inode)->loadaddr & ~0xff);
 223                ADFS_I(inode)->execaddr = (low & 255) | (high << 8);
 224        }
 225}
 226
 227/*
 228 * Fill in the inode information from the object information.
 229 *
 230 * Note that this is an inode-less filesystem, so we can't use the inode
 231 * number to reference the metadata on the media.  Instead, we use the
 232 * inode number to hold the object ID, which in turn will tell us where
 233 * the data is held.  We also save the parent object ID, and with these
 234 * two, we can locate the metadata.
 235 *
 236 * This does mean that we rely on an objects parent remaining the same at
 237 * all times - we cannot cope with a cross-directory rename (yet).
 238 */
 239struct inode *
 240adfs_iget(struct super_block *sb, struct object_info *obj)
 241{
 242        struct inode *inode;
 243
 244        inode = new_inode(sb);
 245        if (!inode)
 246                goto out;
 247
 248        inode->i_uid     = ADFS_SB(sb)->s_uid;
 249        inode->i_gid     = ADFS_SB(sb)->s_gid;
 250        inode->i_ino     = obj->file_id;
 251        inode->i_size    = obj->size;
 252        set_nlink(inode, 2);
 253        inode->i_blocks  = (inode->i_size + sb->s_blocksize - 1) >>
 254                            sb->s_blocksize_bits;
 255
 256        /*
 257         * we need to save the parent directory ID so that
 258         * write_inode can update the directory information
 259         * for this file.  This will need special handling
 260         * for cross-directory renames.
 261         */
 262        ADFS_I(inode)->parent_id = obj->parent_id;
 263        ADFS_I(inode)->loadaddr  = obj->loadaddr;
 264        ADFS_I(inode)->execaddr  = obj->execaddr;
 265        ADFS_I(inode)->attr      = obj->attr;
 266        ADFS_I(inode)->filetype  = obj->filetype;
 267        ADFS_I(inode)->stamped   = ((obj->loadaddr & 0xfff00000) == 0xfff00000);
 268
 269        inode->i_mode    = adfs_atts2mode(sb, inode);
 270        adfs_adfs2unix_time(&inode->i_mtime, inode);
 271        inode->i_atime = inode->i_mtime;
 272        inode->i_ctime = inode->i_mtime;
 273
 274        if (S_ISDIR(inode->i_mode)) {
 275                inode->i_op     = &adfs_dir_inode_operations;
 276                inode->i_fop    = &adfs_dir_operations;
 277        } else if (S_ISREG(inode->i_mode)) {
 278                inode->i_op     = &adfs_file_inode_operations;
 279                inode->i_fop    = &adfs_file_operations;
 280                inode->i_mapping->a_ops = &adfs_aops;
 281                ADFS_I(inode)->mmu_private = inode->i_size;
 282        }
 283
 284        inode_fake_hash(inode);
 285
 286out:
 287        return inode;
 288}
 289
 290/*
 291 * Validate and convert a changed access mode/time to their ADFS equivalents.
 292 * adfs_write_inode will actually write the information back to the directory
 293 * later.
 294 */
 295int
 296adfs_notify_change(struct dentry *dentry, struct iattr *attr)
 297{
 298        struct inode *inode = d_inode(dentry);
 299        struct super_block *sb = inode->i_sb;
 300        unsigned int ia_valid = attr->ia_valid;
 301        int error;
 302        
 303        error = setattr_prepare(dentry, attr);
 304
 305        /*
 306         * we can't change the UID or GID of any file -
 307         * we have a global UID/GID in the superblock
 308         */
 309        if ((ia_valid & ATTR_UID && !uid_eq(attr->ia_uid, ADFS_SB(sb)->s_uid)) ||
 310            (ia_valid & ATTR_GID && !gid_eq(attr->ia_gid, ADFS_SB(sb)->s_gid)))
 311                error = -EPERM;
 312
 313        if (error)
 314                goto out;
 315
 316        /* XXX: this is missing some actual on-disk truncation.. */
 317        if (ia_valid & ATTR_SIZE)
 318                truncate_setsize(inode, attr->ia_size);
 319
 320        if (ia_valid & ATTR_MTIME) {
 321                inode->i_mtime = attr->ia_mtime;
 322                adfs_unix2adfs_time(inode, attr->ia_mtime.tv_sec);
 323        }
 324        /*
 325         * FIXME: should we make these == to i_mtime since we don't
 326         * have the ability to represent them in our filesystem?
 327         */
 328        if (ia_valid & ATTR_ATIME)
 329                inode->i_atime = attr->ia_atime;
 330        if (ia_valid & ATTR_CTIME)
 331                inode->i_ctime = attr->ia_ctime;
 332        if (ia_valid & ATTR_MODE) {
 333                ADFS_I(inode)->attr = adfs_mode2atts(sb, inode);
 334                inode->i_mode = adfs_atts2mode(sb, inode);
 335        }
 336
 337        /*
 338         * FIXME: should we be marking this inode dirty even if
 339         * we don't have any metadata to write back?
 340         */
 341        if (ia_valid & (ATTR_SIZE | ATTR_MTIME | ATTR_MODE))
 342                mark_inode_dirty(inode);
 343out:
 344        return error;
 345}
 346
 347/*
 348 * write an existing inode back to the directory, and therefore the disk.
 349 * The adfs-specific inode data has already been updated by
 350 * adfs_notify_change()
 351 */
 352int adfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 353{
 354        struct super_block *sb = inode->i_sb;
 355        struct object_info obj;
 356        int ret;
 357
 358        obj.file_id     = inode->i_ino;
 359        obj.name_len    = 0;
 360        obj.parent_id   = ADFS_I(inode)->parent_id;
 361        obj.loadaddr    = ADFS_I(inode)->loadaddr;
 362        obj.execaddr    = ADFS_I(inode)->execaddr;
 363        obj.attr        = ADFS_I(inode)->attr;
 364        obj.size        = inode->i_size;
 365
 366        ret = adfs_dir_update(sb, &obj, wbc->sync_mode == WB_SYNC_ALL);
 367        return ret;
 368}
 369