530 lines
16 KiB
C
Executable File
530 lines
16 KiB
C
Executable File
/*
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* linux/fs/befs/datastream.c
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*
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* Copyright (C) 2001 Will Dyson <will_dyson@pobox.com>
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*
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* Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp>
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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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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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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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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: datastrem 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, 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 = NULL;
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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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* 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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* 2001-11-15 Will Dyson
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*/
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int
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befs_fblock2brun(struct super_block *sb, 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: Datastrem 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, befs_data_stream * ds, void *buff,
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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 = NULL;
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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, 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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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 mapps
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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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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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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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Return value is BEFS_OK if the blockrun is found, BEFS_ERR
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otherwise.
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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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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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2001-11-15 Will Dyson
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*/
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static int
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befs_find_brun_direct(struct super_block *sb, 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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befs_block_run *array = data->direct;
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befs_blocknr_t sum;
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befs_blocknr_t max_block =
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data->max_direct_range >> BEFS_SB(sb)->block_shift;
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befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
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if (blockno > max_block) {
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befs_error(sb, "%s passed block outside of direct region",
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__func__);
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return BEFS_ERR;
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}
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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_debug(sb, "---> %s ERROR", __func__);
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return BEFS_ERR;
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}
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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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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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Return value is BEFS_OK if the blockrun is found, BEFS_ERR
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otherwise.
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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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XXX:
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Really should check to make sure blockno is inside indirect
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region.
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2001-11-15 Will Dyson
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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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befs_data_stream * data, 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 = befs_bread(sb, indirblockno + i);
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if (indirblock == NULL) {
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befs_debug(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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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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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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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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Return value is BEFS_OK if the blockrun is found, BEFS_ERR
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otherwise.
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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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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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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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Then we offset the run as in befs_find_brun_array() and we are
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done.
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2001-11-15 Will Dyson
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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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befs_data_stream * data, 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 = NULL;
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befs_sb_info *befs_sb = BEFS_SB(sb);
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befs_blocknr_t indir_start_blk =
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data->max_indirect_range >> befs_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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/* 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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befs_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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brelse(dbl_indir_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]);
|
|
brelse(dbl_indir_block);
|
|
iaddr_array = NULL;
|
|
|
|
/* 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 =
|
|
befs_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);
|
|
brelse(indir_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);
|
|
iaddr_array = NULL;
|
|
|
|
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;
|
|
}
|