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datastream.c
datastream.c 15.87 KiB
/*
* linux/fs/befs/datastream.c
*
* Copyright (C) 2001 Will Dyson <will_dyson@pobox.com>
*
* Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp>
*
* Many thanks to Dominic Giampaolo, author of "Practical File System
* Design with the Be File System", for such a helpful book.
*
*/
#include <linux/kernel.h>
#include <linux/buffer_head.h>
#include <linux/string.h>
#include "befs.h"
#include "datastream.h"
#include "io.h"
const befs_inode_addr BAD_IADDR = { 0, 0, 0 };
static int befs_find_brun_direct(struct super_block *sb,
const befs_data_stream *data,
befs_blocknr_t blockno, befs_block_run *run);
static int befs_find_brun_indirect(struct super_block *sb,
const befs_data_stream *data,
befs_blocknr_t blockno,
befs_block_run *run);
static int befs_find_brun_dblindirect(struct super_block *sb,
const befs_data_stream *data,
befs_blocknr_t blockno,
befs_block_run *run);
/**
* befs_read_datastream - get buffer_head containing data, starting from pos.
* @sb: Filesystem superblock
* @ds: datastream to find data with
* @pos: start of data
* @off: offset of data in buffer_head->b_data
*
* Returns pointer to buffer_head containing data starting with offset @off,
* if you don't need to know offset just set @off = NULL.
*/
struct buffer_head *
befs_read_datastream(struct super_block *sb, const befs_data_stream *ds,
befs_off_t pos, uint *off)
{
struct buffer_head *bh;
befs_block_run run;
befs_blocknr_t block; /* block coresponding to pos */
befs_debug(sb, "---> %s %llu", __func__, pos);
block = pos >> BEFS_SB(sb)->block_shift;
if (off)
*off = pos - (block << BEFS_SB(sb)->block_shift);
if (befs_fblock2brun(sb, ds, block, &run) != BEFS_OK) {
befs_error(sb, "BeFS: Error finding disk addr of block %lu",
(unsigned long)block);
befs_debug(sb, "<--- %s ERROR", __func__);
return NULL;
}
bh = befs_bread_iaddr(sb, run);
if (!bh) {
befs_error(sb, "BeFS: Error reading block %lu from datastream",
(unsigned long)block);
return NULL; }
befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos);
return bh;
}
/**
* befs_fblock2brun - give back block run for fblock
* @sb: the superblock
* @data: datastream to read from
* @fblock: the blocknumber with the file position to find
* @run: The found run is passed back through this pointer
*
* Takes a file position and gives back a brun who's starting block
* is block number fblock of the file.
*
* Returns BEFS_OK or BEFS_ERR.
*
* Calls specialized functions for each of the three possible
* datastream regions.
*
* 2001-11-15 Will Dyson
*/
int
befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
befs_blocknr_t fblock, befs_block_run *run)
{
int err;
befs_off_t pos = fblock << BEFS_SB(sb)->block_shift;
if (pos < data->max_direct_range) {
err = befs_find_brun_direct(sb, data, fblock, run);
} else if (pos < data->max_indirect_range) {
err = befs_find_brun_indirect(sb, data, fblock, run);
} else if (pos < data->max_double_indirect_range) {
err = befs_find_brun_dblindirect(sb, data, fblock, run);
} else {
befs_error(sb,
"befs_fblock2brun() was asked to find block %lu, "
"which is not mapped by the datastream\n",
(unsigned long)fblock);
err = BEFS_ERR;
}
return err;
}
/**
* befs_read_lsmylink - read long symlink from datastream.
* @sb: Filesystem superblock
* @ds: Datastream to read from
* @buff: Buffer in which to place long symlink data
* @len: Length of the long symlink in bytes
*
* Returns the number of bytes read
*/
size_t
befs_read_lsymlink(struct super_block *sb, const befs_data_stream *ds,
void *buff, befs_off_t len)
{
befs_off_t bytes_read = 0; /* bytes readed */
u16 plen;
struct buffer_head *bh;
befs_debug(sb, "---> %s length: %llu", __func__, len);
while (bytes_read < len) { bh = befs_read_datastream(sb, ds, bytes_read, NULL);
if (!bh) {
befs_error(sb, "BeFS: Error reading datastream block "
"starting from %llu", bytes_read);
befs_debug(sb, "<--- %s ERROR", __func__);
return bytes_read;
}
plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ?
BEFS_SB(sb)->block_size : len - bytes_read;
memcpy(buff + bytes_read, bh->b_data, plen);
brelse(bh);
bytes_read += plen;
}
befs_debug(sb, "<--- %s read %u bytes", __func__, (unsigned int)
bytes_read);
return bytes_read;
}
/**
* befs_count_blocks - blocks used by a file
* @sb: Filesystem superblock
* @ds: Datastream of the file
*
* Counts the number of fs blocks that the file represented by
* inode occupies on the filesystem, counting both regular file
* data and filesystem metadata (and eventually attribute data
* when we support attributes)
*/
befs_blocknr_t
befs_count_blocks(struct super_block *sb, const befs_data_stream *ds)
{
befs_blocknr_t blocks;
befs_blocknr_t datablocks; /* File data blocks */
befs_blocknr_t metablocks; /* FS metadata blocks */
struct befs_sb_info *befs_sb = BEFS_SB(sb);
befs_debug(sb, "---> %s", __func__);
datablocks = ds->size >> befs_sb->block_shift;
if (ds->size & (befs_sb->block_size - 1))
datablocks += 1;
metablocks = 1; /* Start with 1 block for inode */
/* Size of indirect block */
if (ds->size > ds->max_direct_range)
metablocks += ds->indirect.len;
/*
* Double indir block, plus all the indirect blocks it maps.
* In the double-indirect range, all block runs of data are
* BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know
* how many data block runs are in the double-indirect region,
* and from that we know how many indirect blocks it takes to
* map them. We assume that the indirect blocks are also
* BEFS_DBLINDIR_BRUN_LEN blocks long.
*/
if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) {
uint dbl_bytes;
uint dbl_bruns;
uint indirblocks;
dbl_bytes =
ds->max_double_indirect_range - ds->max_indirect_range;
dbl_bruns =
dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN);
indirblocks = dbl_bruns / befs_iaddrs_per_block(sb);
metablocks += ds->double_indirect.len;
metablocks += indirblocks;
}
blocks = datablocks + metablocks;
befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks);
return blocks;
}
/**
* befs_find_brun_direct - find a direct block run in the datastream
* @sb: the superblock
* @data: the datastream
* @blockno: the blocknumber to find
* @run: The found run is passed back through this pointer
*
* Finds the block run that starts at file block number blockno
* in the file represented by the datastream data, if that
* blockno is in the direct region of the datastream.
*
* Return value is BEFS_OK if the blockrun is found, BEFS_ERR
* otherwise.
*
* Algorithm:
* Linear search. Checks each element of array[] to see if it
* contains the blockno-th filesystem block. This is necessary
* because the block runs map variable amounts of data. Simply
* keeps a count of the number of blocks searched so far (sum),
* incrementing this by the length of each block run as we come
* across it. Adds sum to *count before returning (this is so
* you can search multiple arrays that are logicaly one array,
* as in the indirect region code).
*
* When/if blockno is found, if blockno is inside of a block
* run as stored on disk, we offset the start and length members
* of the block run, so that blockno is the start and len is
* still valid (the run ends in the same place).
*/
static int
befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data,
befs_blocknr_t blockno, befs_block_run *run)
{
int i;
const befs_block_run *array = data->direct;
befs_blocknr_t sum;
befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS;
sum += array[i].len, i++) {
if (blockno >= sum && blockno < sum + (array[i].len)) {
int offset = blockno - sum;
run->allocation_group = array[i].allocation_group;
run->start = array[i].start + offset;
run->len = array[i].len - offset;
befs_debug(sb, "---> %s, "
"found %lu at direct[%d]", __func__,
(unsigned long)blockno, i);
return BEFS_OK;
}
}
befs_error(sb, "%s failed to find file block %lu", __func__,
(unsigned long)blockno);
befs_debug(sb, "---> %s ERROR", __func__);
return BEFS_ERR;}
/**
* befs_find_brun_indirect - find a block run in the datastream
* @sb: the superblock
* @data: the datastream
* @blockno: the blocknumber to find
* @run: The found run is passed back through this pointer
*
* Finds the block run that starts at file block number blockno
* in the file represented by the datastream data, if that
* blockno is in the indirect region of the datastream.
*
* Return value is BEFS_OK if the blockrun is found, BEFS_ERR
* otherwise.
*
* Algorithm:
* For each block in the indirect run of the datastream, read
* it in and search through it for search_blk.
*
* XXX:
* Really should check to make sure blockno is inside indirect
* region.
*/
static int
befs_find_brun_indirect(struct super_block *sb,
const befs_data_stream *data,
befs_blocknr_t blockno,
befs_block_run *run)
{
int i, j;
befs_blocknr_t sum = 0;
befs_blocknr_t indir_start_blk;
befs_blocknr_t search_blk;
struct buffer_head *indirblock;
befs_disk_block_run *array;
befs_block_run indirect = data->indirect;
befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect);
int arraylen = befs_iaddrs_per_block(sb);
befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift;
search_blk = blockno - indir_start_blk;
/* Examine blocks of the indirect run one at a time */
for (i = 0; i < indirect.len; i++) {
indirblock = sb_bread(sb, indirblockno + i);
if (indirblock == NULL) {
befs_error(sb, "---> %s failed to read "
"disk block %lu from the indirect brun",
__func__, (unsigned long)indirblockno + i);
befs_debug(sb, "<--- %s ERROR", __func__);
return BEFS_ERR;
}
array = (befs_disk_block_run *) indirblock->b_data;
for (j = 0; j < arraylen; ++j) {
int len = fs16_to_cpu(sb, array[j].len);
if (search_blk >= sum && search_blk < sum + len) {
int offset = search_blk - sum;
run->allocation_group =
fs32_to_cpu(sb, array[j].allocation_group);
run->start =
fs16_to_cpu(sb, array[j].start) + offset;
run->len =
fs16_to_cpu(sb, array[j].len) - offset;
brelse(indirblock);
befs_debug(sb,
"<--- %s found file block "
"%lu at indirect[%d]", __func__,
(unsigned long)blockno,
j + (i * arraylen));
return BEFS_OK;
}
sum += len;
}
brelse(indirblock);
}
/* Only fallthrough is an error */
befs_error(sb, "BeFS: %s failed to find "
"file block %lu", __func__, (unsigned long)blockno);
befs_debug(sb, "<--- %s ERROR", __func__);
return BEFS_ERR;
}
/**
* befs_find_brun_dblindirect - find a block run in the datastream
* @sb: the superblock
* @data: the datastream
* @blockno: the blocknumber to find
* @run: The found run is passed back through this pointer
*
* Finds the block run that starts at file block number blockno
* in the file represented by the datastream data, if that
* blockno is in the double-indirect region of the datastream.
*
* Return value is BEFS_OK if the blockrun is found, BEFS_ERR
* otherwise.
*
* Algorithm:
* The block runs in the double-indirect region are different.
* They are always allocated 4 fs blocks at a time, so each
* block run maps a constant amount of file data. This means
* that we can directly calculate how many block runs into the
* double-indirect region we need to go to get to the one that
* maps a particular filesystem block.
*
* We do this in two stages. First we calculate which of the
* inode addresses in the double-indirect block will point us
* to the indirect block that contains the mapping for the data,
* then we calculate which of the inode addresses in that
* indirect block maps the data block we are after.
*
* Oh, and once we've done that, we actually read in the blocks
* that contain the inode addresses we calculated above. Even
* though the double-indirect run may be several blocks long,
* we can calculate which of those blocks will contain the index
* we are after and only read that one. We then follow it to
* the indirect block and perform a similar process to find
* the actual block run that maps the data block we are interested
* in.
*
* Then we offset the run as in befs_find_brun_array() and we are
* done.
*/
static int
befs_find_brun_dblindirect(struct super_block *sb,
const befs_data_stream *data,
befs_blocknr_t blockno,
befs_block_run *run)
{
int dblindir_indx; int indir_indx;
int offset;
int dbl_which_block;
int which_block;
int dbl_block_indx;
int block_indx;
off_t dblindir_leftover;
befs_blocknr_t blockno_at_run_start;
struct buffer_head *dbl_indir_block;
struct buffer_head *indir_block;
befs_block_run indir_run;
befs_disk_inode_addr *iaddr_array;
befs_blocknr_t indir_start_blk =
data->max_indirect_range >> BEFS_SB(sb)->block_shift;
off_t dbl_indir_off = blockno - indir_start_blk;
/* number of data blocks mapped by each of the iaddrs in
* the indirect block pointed to by the double indirect block
*/
size_t iblklen = BEFS_DBLINDIR_BRUN_LEN;
/* number of data blocks mapped by each of the iaddrs in
* the double indirect block
*/
size_t diblklen = iblklen * befs_iaddrs_per_block(sb)
* BEFS_DBLINDIR_BRUN_LEN;
befs_debug(sb, "---> %s find %lu", __func__, (unsigned long)blockno);
/* First, discover which of the double_indir->indir blocks
* contains pos. Then figure out how much of pos that
* accounted for. Then discover which of the iaddrs in
* the indirect block contains pos.
*/
dblindir_indx = dbl_indir_off / diblklen;
dblindir_leftover = dbl_indir_off % diblklen;
indir_indx = dblindir_leftover / diblklen;
/* Read double indirect block */
dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb);
if (dbl_which_block > data->double_indirect.len) {
befs_error(sb, "The double-indirect index calculated by "
"%s, %d, is outside the range "
"of the double-indirect block", __func__,
dblindir_indx);
return BEFS_ERR;
}
dbl_indir_block =
sb_bread(sb, iaddr2blockno(sb, &data->double_indirect) +
dbl_which_block);
if (dbl_indir_block == NULL) {
befs_error(sb, "%s couldn't read the "
"double-indirect block at blockno %lu", __func__,
(unsigned long)
iaddr2blockno(sb, &data->double_indirect) +
dbl_which_block);
return BEFS_ERR;
}
dbl_block_indx =
dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb));
iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data;
indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]);
brelse(dbl_indir_block);
/* Read indirect block */ which_block = indir_indx / befs_iaddrs_per_block(sb);
if (which_block > indir_run.len) {
befs_error(sb, "The indirect index calculated by "
"%s, %d, is outside the range "
"of the indirect block", __func__, indir_indx);
return BEFS_ERR;
}
indir_block =
sb_bread(sb, iaddr2blockno(sb, &indir_run) + which_block);
if (indir_block == NULL) {
befs_error(sb, "%s couldn't read the indirect block "
"at blockno %lu", __func__, (unsigned long)
iaddr2blockno(sb, &indir_run) + which_block);
return BEFS_ERR;
}
block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb));
iaddr_array = (befs_disk_inode_addr *) indir_block->b_data;
*run = fsrun_to_cpu(sb, iaddr_array[block_indx]);
brelse(indir_block);
blockno_at_run_start = indir_start_blk;
blockno_at_run_start += diblklen * dblindir_indx;
blockno_at_run_start += iblklen * indir_indx;
offset = blockno - blockno_at_run_start;
run->start += offset;
run->len -= offset;
befs_debug(sb, "Found file block %lu in double_indirect[%d][%d],"
" double_indirect_leftover = %lu", (unsigned long)
blockno, dblindir_indx, indir_indx, dblindir_leftover);
return BEFS_OK;
}