linux/fs/sysv/itree.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/sysv/itree.c
   4 *
   5 *  Handling of indirect blocks' trees.
   6 *  AV, Sep--Dec 2000
   7 */
   8
   9#include <linux/buffer_head.h>
  10#include <linux/mount.h>
  11#include <linux/string.h>
  12#include "sysv.h"
  13
  14enum {DIRECT = 10, DEPTH = 4};  /* Have triple indirect */
  15
  16static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
  17{
  18        mark_buffer_dirty_inode(bh, inode);
  19        if (IS_SYNC(inode))
  20                sync_dirty_buffer(bh);
  21}
  22
  23static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
  24{
  25        struct super_block *sb = inode->i_sb;
  26        struct sysv_sb_info *sbi = SYSV_SB(sb);
  27        int ptrs_bits = sbi->s_ind_per_block_bits;
  28        unsigned long   indirect_blocks = sbi->s_ind_per_block,
  29                        double_blocks = sbi->s_ind_per_block_2;
  30        int n = 0;
  31
  32        if (block < 0) {
  33                printk("sysv_block_map: block < 0\n");
  34        } else if (block < DIRECT) {
  35                offsets[n++] = block;
  36        } else if ( (block -= DIRECT) < indirect_blocks) {
  37                offsets[n++] = DIRECT;
  38                offsets[n++] = block;
  39        } else if ((block -= indirect_blocks) < double_blocks) {
  40                offsets[n++] = DIRECT+1;
  41                offsets[n++] = block >> ptrs_bits;
  42                offsets[n++] = block & (indirect_blocks - 1);
  43        } else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
  44                offsets[n++] = DIRECT+2;
  45                offsets[n++] = block >> (ptrs_bits * 2);
  46                offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
  47                offsets[n++] = block & (indirect_blocks - 1);
  48        } else {
  49                /* nothing */;
  50        }
  51        return n;
  52}
  53
  54static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr)
  55{
  56        return sbi->s_block_base + fs32_to_cpu(sbi, nr);
  57}
  58
  59typedef struct {
  60        sysv_zone_t     *p;
  61        sysv_zone_t     key;
  62        struct buffer_head *bh;
  63} Indirect;
  64
  65static DEFINE_RWLOCK(pointers_lock);
  66
  67static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_t *v)
  68{
  69        p->key = *(p->p = v);
  70        p->bh = bh;
  71}
  72
  73static inline int verify_chain(Indirect *from, Indirect *to)
  74{
  75        while (from <= to && from->key == *from->p)
  76                from++;
  77        return (from > to);
  78}
  79
  80static inline sysv_zone_t *block_end(struct buffer_head *bh)
  81{
  82        return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
  83}
  84
  85/*
  86 * Requires read_lock(&pointers_lock) or write_lock(&pointers_lock)
  87 */
  88static Indirect *get_branch(struct inode *inode,
  89                            int depth,
  90                            int offsets[],
  91                            Indirect chain[],
  92                            int *err)
  93{
  94        struct super_block *sb = inode->i_sb;
  95        Indirect *p = chain;
  96        struct buffer_head *bh;
  97
  98        *err = 0;
  99        add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
 100        if (!p->key)
 101                goto no_block;
 102        while (--depth) {
 103                int block = block_to_cpu(SYSV_SB(sb), p->key);
 104                bh = sb_bread(sb, block);
 105                if (!bh)
 106                        goto failure;
 107                if (!verify_chain(chain, p))
 108                        goto changed;
 109                add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
 110                if (!p->key)
 111                        goto no_block;
 112        }
 113        return NULL;
 114
 115changed:
 116        brelse(bh);
 117        *err = -EAGAIN;
 118        goto no_block;
 119failure:
 120        *err = -EIO;
 121no_block:
 122        return p;
 123}
 124
 125static int alloc_branch(struct inode *inode,
 126                        int num,
 127                        int *offsets,
 128                        Indirect *branch)
 129{
 130        int blocksize = inode->i_sb->s_blocksize;
 131        int n = 0;
 132        int i;
 133
 134        branch[0].key = sysv_new_block(inode->i_sb);
 135        if (branch[0].key) for (n = 1; n < num; n++) {
 136                struct buffer_head *bh;
 137                int parent;
 138                /* Allocate the next block */
 139                branch[n].key = sysv_new_block(inode->i_sb);
 140                if (!branch[n].key)
 141                        break;
 142                /*
 143                 * Get buffer_head for parent block, zero it out and set 
 144                 * the pointer to new one, then send parent to disk.
 145                 */
 146                parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
 147                bh = sb_getblk(inode->i_sb, parent);
 148                lock_buffer(bh);
 149                memset(bh->b_data, 0, blocksize);
 150                branch[n].bh = bh;
 151                branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n];
 152                *branch[n].p = branch[n].key;
 153                set_buffer_uptodate(bh);
 154                unlock_buffer(bh);
 155                dirty_indirect(bh, inode);
 156        }
 157        if (n == num)
 158                return 0;
 159
 160        /* Allocation failed, free what we already allocated */
 161        for (i = 1; i < n; i++)
 162                bforget(branch[i].bh);
 163        for (i = 0; i < n; i++)
 164                sysv_free_block(inode->i_sb, branch[i].key);
 165        return -ENOSPC;
 166}
 167
 168static inline int splice_branch(struct inode *inode,
 169                                Indirect chain[],
 170                                Indirect *where,
 171                                int num)
 172{
 173        int i;
 174
 175        /* Verify that place we are splicing to is still there and vacant */
 176        write_lock(&pointers_lock);
 177        if (!verify_chain(chain, where-1) || *where->p)
 178                goto changed;
 179        *where->p = where->key;
 180        write_unlock(&pointers_lock);
 181
 182        inode->i_ctime = current_time(inode);
 183
 184        /* had we spliced it onto indirect block? */
 185        if (where->bh)
 186                dirty_indirect(where->bh, inode);
 187
 188        if (IS_SYNC(inode))
 189                sysv_sync_inode(inode);
 190        else
 191                mark_inode_dirty(inode);
 192        return 0;
 193
 194changed:
 195        write_unlock(&pointers_lock);
 196        for (i = 1; i < num; i++)
 197                bforget(where[i].bh);
 198        for (i = 0; i < num; i++)
 199                sysv_free_block(inode->i_sb, where[i].key);
 200        return -EAGAIN;
 201}
 202
 203static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
 204{
 205        int err = -EIO;
 206        int offsets[DEPTH];
 207        Indirect chain[DEPTH];
 208        struct super_block *sb = inode->i_sb;
 209        Indirect *partial;
 210        int left;
 211        int depth = block_to_path(inode, iblock, offsets);
 212
 213        if (depth == 0)
 214                goto out;
 215
 216reread:
 217        read_lock(&pointers_lock);
 218        partial = get_branch(inode, depth, offsets, chain, &err);
 219        read_unlock(&pointers_lock);
 220
 221        /* Simplest case - block found, no allocation needed */
 222        if (!partial) {
 223got_it:
 224                map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
 225                                        chain[depth-1].key));
 226                /* Clean up and exit */
 227                partial = chain+depth-1; /* the whole chain */
 228                goto cleanup;
 229        }
 230
 231        /* Next simple case - plain lookup or failed read of indirect block */
 232        if (!create || err == -EIO) {
 233cleanup:
 234                while (partial > chain) {
 235                        brelse(partial->bh);
 236                        partial--;
 237                }
 238out:
 239                return err;
 240        }
 241
 242        /*
 243         * Indirect block might be removed by truncate while we were
 244         * reading it. Handling of that case (forget what we've got and
 245         * reread) is taken out of the main path.
 246         */
 247        if (err == -EAGAIN)
 248                goto changed;
 249
 250        left = (chain + depth) - partial;
 251        err = alloc_branch(inode, left, offsets+(partial-chain), partial);
 252        if (err)
 253                goto cleanup;
 254
 255        if (splice_branch(inode, chain, partial, left) < 0)
 256                goto changed;
 257
 258        set_buffer_new(bh_result);
 259        goto got_it;
 260
 261changed:
 262        while (partial > chain) {
 263                brelse(partial->bh);
 264                partial--;
 265        }
 266        goto reread;
 267}
 268
 269static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
 270{
 271        while (p < q)
 272                if (*p++)
 273                        return 0;
 274        return 1;
 275}
 276
 277static Indirect *find_shared(struct inode *inode,
 278                                int depth,
 279                                int offsets[],
 280                                Indirect chain[],
 281                                sysv_zone_t *top)
 282{
 283        Indirect *partial, *p;
 284        int k, err;
 285
 286        *top = 0;
 287        for (k = depth; k > 1 && !offsets[k-1]; k--)
 288                ;
 289
 290        write_lock(&pointers_lock);
 291        partial = get_branch(inode, k, offsets, chain, &err);
 292        if (!partial)
 293                partial = chain + k-1;
 294        /*
 295         * If the branch acquired continuation since we've looked at it -
 296         * fine, it should all survive and (new) top doesn't belong to us.
 297         */
 298        if (!partial->key && *partial->p) {
 299                write_unlock(&pointers_lock);
 300                goto no_top;
 301        }
 302        for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
 303                ;
 304        /*
 305         * OK, we've found the last block that must survive. The rest of our
 306         * branch should be detached before unlocking. However, if that rest
 307         * of branch is all ours and does not grow immediately from the inode
 308         * it's easier to cheat and just decrement partial->p.
 309         */
 310        if (p == chain + k - 1 && p > chain) {
 311                p->p--;
 312        } else {
 313                *top = *p->p;
 314                *p->p = 0;
 315        }
 316        write_unlock(&pointers_lock);
 317
 318        while (partial > p) {
 319                brelse(partial->bh);
 320                partial--;
 321        }
 322no_top:
 323        return partial;
 324}
 325
 326static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q)
 327{
 328        for ( ; p < q ; p++) {
 329                sysv_zone_t nr = *p;
 330                if (nr) {
 331                        *p = 0;
 332                        sysv_free_block(inode->i_sb, nr);
 333                        mark_inode_dirty(inode);
 334                }
 335        }
 336}
 337
 338static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
 339{
 340        struct buffer_head * bh;
 341        struct super_block *sb = inode->i_sb;
 342
 343        if (depth--) {
 344                for ( ; p < q ; p++) {
 345                        int block;
 346                        sysv_zone_t nr = *p;
 347                        if (!nr)
 348                                continue;
 349                        *p = 0;
 350                        block = block_to_cpu(SYSV_SB(sb), nr);
 351                        bh = sb_bread(sb, block);
 352                        if (!bh)
 353                                continue;
 354                        free_branches(inode, (sysv_zone_t*)bh->b_data,
 355                                        block_end(bh), depth);
 356                        bforget(bh);
 357                        sysv_free_block(sb, nr);
 358                        mark_inode_dirty(inode);
 359                }
 360        } else
 361                free_data(inode, p, q);
 362}
 363
 364void sysv_truncate (struct inode * inode)
 365{
 366        sysv_zone_t *i_data = SYSV_I(inode)->i_data;
 367        int offsets[DEPTH];
 368        Indirect chain[DEPTH];
 369        Indirect *partial;
 370        sysv_zone_t nr = 0;
 371        int n;
 372        long iblock;
 373        unsigned blocksize;
 374
 375        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
 376            S_ISLNK(inode->i_mode)))
 377                return;
 378
 379        blocksize = inode->i_sb->s_blocksize;
 380        iblock = (inode->i_size + blocksize-1)
 381                                        >> inode->i_sb->s_blocksize_bits;
 382
 383        block_truncate_page(inode->i_mapping, inode->i_size, get_block);
 384
 385        n = block_to_path(inode, iblock, offsets);
 386        if (n == 0)
 387                return;
 388
 389        if (n == 1) {
 390                free_data(inode, i_data+offsets[0], i_data + DIRECT);
 391                goto do_indirects;
 392        }
 393
 394        partial = find_shared(inode, n, offsets, chain, &nr);
 395        /* Kill the top of shared branch (already detached) */
 396        if (nr) {
 397                if (partial == chain)
 398                        mark_inode_dirty(inode);
 399                else
 400                        dirty_indirect(partial->bh, inode);
 401                free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
 402        }
 403        /* Clear the ends of indirect blocks on the shared branch */
 404        while (partial > chain) {
 405                free_branches(inode, partial->p + 1, block_end(partial->bh),
 406                                (chain+n-1) - partial);
 407                dirty_indirect(partial->bh, inode);
 408                brelse (partial->bh);
 409                partial--;
 410        }
 411do_indirects:
 412        /* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
 413        while (n < DEPTH) {
 414                nr = i_data[DIRECT + n - 1];
 415                if (nr) {
 416                        i_data[DIRECT + n - 1] = 0;
 417                        mark_inode_dirty(inode);
 418                        free_branches(inode, &nr, &nr+1, n);
 419                }
 420                n++;
 421        }
 422        inode->i_mtime = inode->i_ctime = current_time(inode);
 423        if (IS_SYNC(inode))
 424                sysv_sync_inode (inode);
 425        else
 426                mark_inode_dirty(inode);
 427}
 428
 429static unsigned sysv_nblocks(struct super_block *s, loff_t size)
 430{
 431        struct sysv_sb_info *sbi = SYSV_SB(s);
 432        int ptrs_bits = sbi->s_ind_per_block_bits;
 433        unsigned blocks, res, direct = DIRECT, i = DEPTH;
 434        blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
 435        res = blocks;
 436        while (--i && blocks > direct) {
 437                blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
 438                res += blocks;
 439                direct = 1;
 440        }
 441        return blocks;
 442}
 443
 444int sysv_getattr(const struct path *path, struct kstat *stat,
 445                 u32 request_mask, unsigned int flags)
 446{
 447        struct super_block *s = path->dentry->d_sb;
 448        generic_fillattr(d_inode(path->dentry), stat);
 449        stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
 450        stat->blksize = s->s_blocksize;
 451        return 0;
 452}
 453
 454static int sysv_writepage(struct page *page, struct writeback_control *wbc)
 455{
 456        return block_write_full_page(page,get_block,wbc);
 457}
 458
 459static int sysv_readpage(struct file *file, struct page *page)
 460{
 461        return block_read_full_page(page,get_block);
 462}
 463
 464int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
 465{
 466        return __block_write_begin(page, pos, len, get_block);
 467}
 468
 469static void sysv_write_failed(struct address_space *mapping, loff_t to)
 470{
 471        struct inode *inode = mapping->host;
 472
 473        if (to > inode->i_size) {
 474                truncate_pagecache(inode, inode->i_size);
 475                sysv_truncate(inode);
 476        }
 477}
 478
 479static int sysv_write_begin(struct file *file, struct address_space *mapping,
 480                        loff_t pos, unsigned len, unsigned flags,
 481                        struct page **pagep, void **fsdata)
 482{
 483        int ret;
 484
 485        ret = block_write_begin(mapping, pos, len, flags, pagep, get_block);
 486        if (unlikely(ret))
 487                sysv_write_failed(mapping, pos + len);
 488
 489        return ret;
 490}
 491
 492static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
 493{
 494        return generic_block_bmap(mapping,block,get_block);
 495}
 496
 497const struct address_space_operations sysv_aops = {
 498        .readpage = sysv_readpage,
 499        .writepage = sysv_writepage,
 500        .write_begin = sysv_write_begin,
 501        .write_end = generic_write_end,
 502        .bmap = sysv_bmap
 503};
 504