/* * linux/fs/befs/datastream.c * * Copyright (C) 2001 Will Dyson * * Based on portions of file.c by Makoto Kato * * Many thanks to Dominic Giampaolo, author of "Practical File System * Design with the Be File System", for such a helpful book. * */ #include #include #include #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, befs_data_stream * data, befs_blocknr_t blockno, befs_block_run * run); static int befs_find_brun_indirect(struct super_block *sb, befs_data_stream * data, befs_blocknr_t blockno, befs_block_run * run); static int befs_find_brun_dblindirect(struct super_block *sb, 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: datastrem 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, befs_data_stream * ds, befs_off_t pos, uint * off) { struct buffer_head *bh = NULL; 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; } /* * 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. * * 2001-11-15 Will Dyson */ int befs_fblock2brun(struct super_block *sb, 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: Datastrem 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, befs_data_stream * ds, void *buff, befs_off_t len) { befs_off_t bytes_read = 0; /* bytes readed */ u16 plen; struct buffer_head *bh = NULL; 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, 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 mapps 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; } /* 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. sb: the superblock data: the datastream blockno: the blocknumber to find run: The found run is passed back through this pointer 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). 2001-11-15 Will Dyson */ static int befs_find_brun_direct(struct super_block *sb, befs_data_stream * data, befs_blocknr_t blockno, befs_block_run * run) { int i; befs_block_run *array = data->direct; befs_blocknr_t sum; befs_blocknr_t max_block = data->max_direct_range >> BEFS_SB(sb)->block_shift; befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno); if (blockno > max_block) { befs_error(sb, "%s passed block outside of direct region", __func__); return BEFS_ERR; } 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_debug(sb, "---> %s ERROR", __func__); return BEFS_ERR; } /* 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. sb: the superblock data: the datastream blockno: the blocknumber to find run: The found run is passed back through this pointer 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. 2001-11-15 Will Dyson */ static int befs_find_brun_indirect(struct super_block *sb, 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