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