--- /dev/null
+/*
+ * 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,
+ 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 = 0; i < indirect.len; i++) {
+ indirblock = befs_bread(sb, indirblockno + i);
+ if (indirblock == NULL) {
+ befs_debug(sb, "---> %s failed to read "
+ "disk block %lu from the indirect brun",
+ __func__, (unsigned long)indirblockno + i);
+ 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;
+}
+
+/*
+ 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.
+
+ 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:
+ 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.
+
+ 2001-11-15 Will Dyson
+*/
+static int
+befs_find_brun_dblindirect(struct super_block *sb,
+ 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 = NULL;
+ struct befs_sb_info *befs_sb = BEFS_SB(sb);
+
+ befs_blocknr_t indir_start_blk =
+ data->max_indirect_range >> befs_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 =
+ befs_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);
+ brelse(dbl_indir_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);
+ 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;
+}
Code Review / kvmfornfv.git / blobdiff