patch-2.4.20 linux-2.4.20/fs/befs/datastream.c

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diff -urN linux-2.4.19/fs/befs/datastream.c linux-2.4.20/fs/befs/datastream.c
@@ -0,0 +1,527 @@
+/*
+ * 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/version.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+#include "befs_fs.h"
+#include "endian.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, "---> befs_read_datastream() %Lu", 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",
+			   block);
+		befs_debug(sb, "<--- befs_read_datastream() ERROR");
+		return NULL;
+	}
+	bh = befs_bread_iaddr(sb, run);
+	if (!bh) {
+		befs_error(sb, "BeFS: Error reading block %lu from datastream",
+			   block);
+		return NULL;
+	}
+
+	befs_debug(sb, "<--- befs_read_datastream() read data, starting at %Lu",
+		   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", fblock);
+		err = BEFS_ERR;
+	}
+	return err;
+}
+
+/**
+ * befs_read_lsmylink - read long symlink from datastream.
+ * @sb: Filesystem superblock 
+ * @ds: Datastrem to read from
+ * @buf: Buffer in wich 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, "---> befs_read_lsymlink() length: %Lu", 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 %Lu", bytes_read);
+			befs_debug(sb, "<--- befs_read_lsymlink() ERROR");
+			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, "<--- befs_read_lsymlink() read %u bytes", 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 */
+	befs_sb_info *befs_sb = BEFS_SB(sb);
+
+	befs_debug(sb, "---> befs_count_blocks()");
+
+	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, "<--- befs_count_blocks() %u blocks", 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 nessisary
+	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 lenght 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, "---> befs_find_brun_direct(), find %lu", blockno);
+
+	if (blockno > max_block) {
+		befs_error(sb, "befs_find_brun_direct() passed block outside of"
+			   "direct region");
+		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, "---> befs_find_brun_direct(), "
+				   "found %lu at direct[%d]", blockno, i);
+			return BEFS_OK;
+		}
+	}
+
+	befs_debug(sb, "---> befs_find_brun_direct() ERROR");
+	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_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, "---> befs_find_brun_indirect(), find %lu", 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,
+				   "---> befs_find_brun_indirect() failed to "
+				   "read disk block %lu from the indirect brun",
+				   indirblockno + i);
+			return BEFS_ERR;
+		}
+
+		array = (befs_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,
+					   "<--- befs_find_brun_indirect() found "
+					   "file block %lu at indirect[%d]",
+					   blockno, j + (i * arraylen));
+				return BEFS_OK;
+			}
+			sum += len;
+		}
+
+		brelse(indirblock);
+	}
+
+	/* Only fallthrough is an error */
+	befs_error(sb, "BeFS: befs_find_brun_indirect() failed to find "
+		   "file block %lu", blockno);
+
+	befs_debug(sb, "<--- befs_find_brun_indirect() ERROR");
+	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_inode_addr *iaddr_array = NULL;
+	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, "---> befs_find_brun_dblindirect() find %lu", 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 "
+			   "befs_read_brun_dblindirect(), %d, is outside the range "
+			   "of the double-indirect block", 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, "befs_read_brun_dblindirect() couldn't read the "
+			   "double-indirect block at blockno %lu",
+			   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_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 "
+			   "befs_read_brun_dblindirect(), %d, is outside the range "
+			   "of the indirect block", indir_indx);
+		return BEFS_ERR;
+	}
+
+	indir_block =
+	    befs_bread(sb, iaddr2blockno(sb, &indir_run) + which_block);
+	if (indir_block == NULL) {
+		befs_error(sb, "befs_read_brun_dblindirect() couldn't read the "
+			   "indirect block at blockno %lu",
+			   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_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",
+		   blockno, dblindir_indx, indir_indx, dblindir_leftover);
+
+	return BEFS_OK;
+}
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