diff options
Diffstat (limited to 'fs/befs/datastream.c')
| -rw-r--r-- | fs/befs/datastream.c | 525 |
1 files changed, 525 insertions, 0 deletions
diff --git a/fs/befs/datastream.c b/fs/befs/datastream.c new file mode 100644 index 000000000..97719a7c7 --- /dev/null +++ b/fs/befs/datastream.c @@ -0,0 +1,525 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/befs/datastream.c + * + * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com> + * + * Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp> + * + * Many thanks to Dominic Giampaolo, author of "Practical File System + * Design with the Be File System", for such a helpful book. + * + */ + +#include <linux/kernel.h> +#include <linux/buffer_head.h> +#include <linux/string.h> + +#include "befs.h" +#include "datastream.h" +#include "io.h" + +const befs_inode_addr BAD_IADDR = { 0, 0, 0 }; + +static int befs_find_brun_direct(struct super_block *sb, + const befs_data_stream *data, + befs_blocknr_t blockno, befs_block_run *run); + +static int befs_find_brun_indirect(struct super_block *sb, + const befs_data_stream *data, + befs_blocknr_t blockno, + befs_block_run *run); + +static int befs_find_brun_dblindirect(struct super_block *sb, + const befs_data_stream *data, + befs_blocknr_t blockno, + befs_block_run *run); + +/** + * befs_read_datastream - get buffer_head containing data, starting from pos. + * @sb: Filesystem superblock + * @ds: datastream to find data with + * @pos: start of data + * @off: offset of data in buffer_head->b_data + * + * Returns pointer to buffer_head containing data starting with offset @off, + * if you don't need to know offset just set @off = NULL. + */ +struct buffer_head * +befs_read_datastream(struct super_block *sb, const befs_data_stream *ds, + befs_off_t pos, uint *off) +{ + struct buffer_head *bh; + befs_block_run run; + befs_blocknr_t block; /* block coresponding to pos */ + + befs_debug(sb, "---> %s %llu", __func__, pos); + block = pos >> BEFS_SB(sb)->block_shift; + if (off) + *off = pos - (block << BEFS_SB(sb)->block_shift); + + if (befs_fblock2brun(sb, ds, block, &run) != BEFS_OK) { + befs_error(sb, "BeFS: Error finding disk addr of block %lu", + (unsigned long)block); + befs_debug(sb, "<--- %s ERROR", __func__); + return NULL; + } + bh = befs_bread_iaddr(sb, run); + if (!bh) { + befs_error(sb, "BeFS: Error reading block %lu from datastream", + (unsigned long)block); + return NULL; + } + + befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos); + + return bh; +} + +/** + * befs_fblock2brun - give back block run for fblock + * @sb: the superblock + * @data: datastream to read from + * @fblock: the blocknumber with the file position to find + * @run: The found run is passed back through this pointer + * + * Takes a file position and gives back a brun who's starting block + * is block number fblock of the file. + * + * Returns BEFS_OK or BEFS_ERR. + * + * Calls specialized functions for each of the three possible + * datastream regions. + */ +int +befs_fblock2brun(struct super_block *sb, const befs_data_stream *data, + befs_blocknr_t fblock, befs_block_run *run) +{ + int err; + befs_off_t pos = fblock << BEFS_SB(sb)->block_shift; + + if (pos < data->max_direct_range) { + err = befs_find_brun_direct(sb, data, fblock, run); + + } else if (pos < data->max_indirect_range) { + err = befs_find_brun_indirect(sb, data, fblock, run); + + } else if (pos < data->max_double_indirect_range) { + err = befs_find_brun_dblindirect(sb, data, fblock, run); + + } else { + befs_error(sb, + "befs_fblock2brun() was asked to find block %lu, " + "which is not mapped by the datastream\n", + (unsigned long)fblock); + err = BEFS_ERR; + } + return err; +} + +/** + * befs_read_lsmylink - read long symlink from datastream. + * @sb: Filesystem superblock + * @ds: Datastream to read from + * @buff: Buffer in which to place long symlink data + * @len: Length of the long symlink in bytes + * + * Returns the number of bytes read + */ +size_t +befs_read_lsymlink(struct super_block *sb, const befs_data_stream *ds, + void *buff, befs_off_t len) +{ + befs_off_t bytes_read = 0; /* bytes readed */ + u16 plen; + struct buffer_head *bh; + + befs_debug(sb, "---> %s length: %llu", __func__, len); + + while (bytes_read < len) { + bh = befs_read_datastream(sb, ds, bytes_read, NULL); + if (!bh) { + befs_error(sb, "BeFS: Error reading datastream block " + "starting from %llu", bytes_read); + befs_debug(sb, "<--- %s ERROR", __func__); + return bytes_read; + + } + plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ? + BEFS_SB(sb)->block_size : len - bytes_read; + memcpy(buff + bytes_read, bh->b_data, plen); + brelse(bh); + bytes_read += plen; + } + + befs_debug(sb, "<--- %s read %u bytes", __func__, (unsigned int) + bytes_read); + return bytes_read; +} + +/** + * befs_count_blocks - blocks used by a file + * @sb: Filesystem superblock + * @ds: Datastream of the file + * + * Counts the number of fs blocks that the file represented by + * inode occupies on the filesystem, counting both regular file + * data and filesystem metadata (and eventually attribute data + * when we support attributes) +*/ + +befs_blocknr_t +befs_count_blocks(struct super_block *sb, const befs_data_stream *ds) +{ + befs_blocknr_t blocks; + befs_blocknr_t datablocks; /* File data blocks */ + befs_blocknr_t metablocks; /* FS metadata blocks */ + struct befs_sb_info *befs_sb = BEFS_SB(sb); + + befs_debug(sb, "---> %s", __func__); + + datablocks = ds->size >> befs_sb->block_shift; + if (ds->size & (befs_sb->block_size - 1)) + datablocks += 1; + + metablocks = 1; /* Start with 1 block for inode */ + + /* Size of indirect block */ + if (ds->size > ds->max_direct_range) + metablocks += ds->indirect.len; + + /* + * Double indir block, plus all the indirect blocks it maps. + * In the double-indirect range, all block runs of data are + * BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know + * how many data block runs are in the double-indirect region, + * and from that we know how many indirect blocks it takes to + * map them. We assume that the indirect blocks are also + * BEFS_DBLINDIR_BRUN_LEN blocks long. + */ + if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) { + uint dbl_bytes; + uint dbl_bruns; + uint indirblocks; + + dbl_bytes = + ds->max_double_indirect_range - ds->max_indirect_range; + dbl_bruns = + dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN); + indirblocks = dbl_bruns / befs_iaddrs_per_block(sb); + + metablocks += ds->double_indirect.len; + metablocks += indirblocks; + } + + blocks = datablocks + metablocks; + befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks); + + return blocks; +} + +/** + * befs_find_brun_direct - find a direct block run in the datastream + * @sb: the superblock + * @data: the datastream + * @blockno: the blocknumber to find + * @run: The found run is passed back through this pointer + * + * Finds the block run that starts at file block number blockno + * in the file represented by the datastream data, if that + * blockno is in the direct region of the datastream. + * + * Return value is BEFS_OK if the blockrun is found, BEFS_ERR + * otherwise. + * + * Algorithm: + * Linear search. Checks each element of array[] to see if it + * contains the blockno-th filesystem block. This is necessary + * because the block runs map variable amounts of data. Simply + * keeps a count of the number of blocks searched so far (sum), + * incrementing this by the length of each block run as we come + * across it. Adds sum to *count before returning (this is so + * you can search multiple arrays that are logicaly one array, + * as in the indirect region code). + * + * When/if blockno is found, if blockno is inside of a block + * run as stored on disk, we offset the start and length members + * of the block run, so that blockno is the start and len is + * still valid (the run ends in the same place). + */ +static int +befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data, + befs_blocknr_t blockno, befs_block_run *run) +{ + int i; + const befs_block_run *array = data->direct; + befs_blocknr_t sum; + + befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno); + + for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS; + sum += array[i].len, i++) { + if (blockno >= sum && blockno < sum + (array[i].len)) { + int offset = blockno - sum; + + run->allocation_group = array[i].allocation_group; + run->start = array[i].start + offset; + run->len = array[i].len - offset; + + befs_debug(sb, "---> %s, " + "found %lu at direct[%d]", __func__, + (unsigned long)blockno, i); + return BEFS_OK; + } + } + + befs_error(sb, "%s failed to find file block %lu", __func__, + (unsigned long)blockno); + befs_debug(sb, "---> %s ERROR", __func__); + return BEFS_ERR; +} + +/** + * befs_find_brun_indirect - find a block run in the datastream + * @sb: the superblock + * @data: the datastream + * @blockno: the blocknumber to find + * @run: The found run is passed back through this pointer + * + * Finds the block run that starts at file block number blockno + * in the file represented by the datastream data, if that + * blockno is in the indirect region of the datastream. + * + * Return value is BEFS_OK if the blockrun is found, BEFS_ERR + * otherwise. + * + * Algorithm: + * For each block in the indirect run of the datastream, read + * it in and search through it for search_blk. + * + * XXX: + * Really should check to make sure blockno is inside indirect + * region. + */ +static int +befs_find_brun_indirect(struct super_block *sb, + const befs_data_stream *data, + befs_blocknr_t blockno, + befs_block_run *run) +{ + int i, j; + befs_blocknr_t sum = 0; + befs_blocknr_t indir_start_blk; + befs_blocknr_t search_blk; + struct buffer_head *indirblock; + befs_disk_block_run *array; + + befs_block_run indirect = data->indirect; + befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect); + int arraylen = befs_iaddrs_per_block(sb); + + befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno); + + indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift; + search_blk = blockno - indir_start_blk; + + /* Examine blocks of the indirect run one at a time */ + for (i = 0; i < indirect.len; i++) { + indirblock = sb_bread(sb, indirblockno + i); + if (indirblock == NULL) { + befs_error(sb, "---> %s failed to read " + "disk block %lu from the indirect brun", + __func__, (unsigned long)indirblockno + i); + befs_debug(sb, "<--- %s ERROR", __func__); + return BEFS_ERR; + } + + array = (befs_disk_block_run *) indirblock->b_data; + + for (j = 0; j < arraylen; ++j) { + int len = fs16_to_cpu(sb, array[j].len); + + if (search_blk >= sum && search_blk < sum + len) { + int offset = search_blk - sum; + run->allocation_group = + fs32_to_cpu(sb, array[j].allocation_group); + run->start = + fs16_to_cpu(sb, array[j].start) + offset; + run->len = + fs16_to_cpu(sb, array[j].len) - offset; + + brelse(indirblock); + befs_debug(sb, + "<--- %s found file block " + "%lu at indirect[%d]", __func__, + (unsigned long)blockno, + j + (i * arraylen)); + return BEFS_OK; + } + sum += len; + } + + brelse(indirblock); + } + + /* Only fallthrough is an error */ + befs_error(sb, "BeFS: %s failed to find " + "file block %lu", __func__, (unsigned long)blockno); + + befs_debug(sb, "<--- %s ERROR", __func__); + return BEFS_ERR; +} + +/** + * befs_find_brun_dblindirect - find a block run in the datastream + * @sb: the superblock + * @data: the datastream + * @blockno: the blocknumber to find + * @run: The found run is passed back through this pointer + * + * Finds the block run that starts at file block number blockno + * in the file represented by the datastream data, if that + * blockno is in the double-indirect region of the datastream. + * + * Return value is BEFS_OK if the blockrun is found, BEFS_ERR + * otherwise. + * + * Algorithm: + * The block runs in the double-indirect region are different. + * They are always allocated 4 fs blocks at a time, so each + * block run maps a constant amount of file data. This means + * that we can directly calculate how many block runs into the + * double-indirect region we need to go to get to the one that + * maps a particular filesystem block. + * + * We do this in two stages. First we calculate which of the + * inode addresses in the double-indirect block will point us + * to the indirect block that contains the mapping for the data, + * then we calculate which of the inode addresses in that + * indirect block maps the data block we are after. + * + * Oh, and once we've done that, we actually read in the blocks + * that contain the inode addresses we calculated above. Even + * though the double-indirect run may be several blocks long, + * we can calculate which of those blocks will contain the index + * we are after and only read that one. We then follow it to + * the indirect block and perform a similar process to find + * the actual block run that maps the data block we are interested + * in. + * + * Then we offset the run as in befs_find_brun_array() and we are + * done. + */ +static int +befs_find_brun_dblindirect(struct super_block *sb, + const befs_data_stream *data, + befs_blocknr_t blockno, + befs_block_run *run) +{ + int dblindir_indx; + int indir_indx; + int offset; + int dbl_which_block; + int which_block; + int dbl_block_indx; + int block_indx; + off_t dblindir_leftover; + befs_blocknr_t blockno_at_run_start; + struct buffer_head *dbl_indir_block; + struct buffer_head *indir_block; + befs_block_run indir_run; + befs_disk_inode_addr *iaddr_array; + + befs_blocknr_t indir_start_blk = + data->max_indirect_range >> BEFS_SB(sb)->block_shift; + + off_t dbl_indir_off = blockno - indir_start_blk; + + /* number of data blocks mapped by each of the iaddrs in + * the indirect block pointed to by the double indirect block + */ + size_t iblklen = BEFS_DBLINDIR_BRUN_LEN; + + /* number of data blocks mapped by each of the iaddrs in + * the double indirect block + */ + size_t diblklen = iblklen * befs_iaddrs_per_block(sb) + * BEFS_DBLINDIR_BRUN_LEN; + + befs_debug(sb, "---> %s find %lu", __func__, (unsigned long)blockno); + + /* First, discover which of the double_indir->indir blocks + * contains pos. Then figure out how much of pos that + * accounted for. Then discover which of the iaddrs in + * the indirect block contains pos. + */ + + dblindir_indx = dbl_indir_off / diblklen; + dblindir_leftover = dbl_indir_off % diblklen; + indir_indx = dblindir_leftover / diblklen; + + /* Read double indirect block */ + dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb); + if (dbl_which_block > data->double_indirect.len) { + befs_error(sb, "The double-indirect index calculated by " + "%s, %d, is outside the range " + "of the double-indirect block", __func__, + dblindir_indx); + return BEFS_ERR; + } + + dbl_indir_block = + sb_bread(sb, iaddr2blockno(sb, &data->double_indirect) + + dbl_which_block); + if (dbl_indir_block == NULL) { + befs_error(sb, "%s couldn't read the " + "double-indirect block at blockno %lu", __func__, + (unsigned long) + iaddr2blockno(sb, &data->double_indirect) + + dbl_which_block); + return BEFS_ERR; + } + + dbl_block_indx = + dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb)); + iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data; + indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]); + brelse(dbl_indir_block); + + /* Read indirect block */ + which_block = indir_indx / befs_iaddrs_per_block(sb); + if (which_block > indir_run.len) { + befs_error(sb, "The indirect index calculated by " + "%s, %d, is outside the range " + "of the indirect block", __func__, indir_indx); + return BEFS_ERR; + } + + indir_block = + sb_bread(sb, iaddr2blockno(sb, &indir_run) + which_block); + if (indir_block == NULL) { + befs_error(sb, "%s couldn't read the indirect block " + "at blockno %lu", __func__, (unsigned long) + iaddr2blockno(sb, &indir_run) + which_block); + return BEFS_ERR; + } + + block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb)); + iaddr_array = (befs_disk_inode_addr *) indir_block->b_data; + *run = fsrun_to_cpu(sb, iaddr_array[block_indx]); + brelse(indir_block); + + blockno_at_run_start = indir_start_blk; + blockno_at_run_start += diblklen * dblindir_indx; + blockno_at_run_start += iblklen * indir_indx; + offset = blockno - blockno_at_run_start; + + run->start += offset; + run->len -= offset; + + befs_debug(sb, "Found file block %lu in double_indirect[%d][%d]," + " double_indirect_leftover = %lu", (unsigned long) + blockno, dblindir_indx, indir_indx, dblindir_leftover); + + return BEFS_OK; +} |