diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/befs/datastream.c | 193 |
1 files changed, 98 insertions, 95 deletions
diff --git a/fs/befs/datastream.c b/fs/befs/datastream.c index b2eb5b5cdff2..5ce85cfd8ae1 100644 --- a/fs/befs/datastream.c +++ b/fs/befs/datastream.c @@ -75,7 +75,13 @@ befs_read_datastream(struct super_block *sb, const befs_data_stream *ds, 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. * @@ -212,36 +218,35 @@ befs_count_blocks(struct super_block *sb, const befs_data_stream *ds) 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 -*/ +/** + * 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) @@ -273,29 +278,28 @@ befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data, 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 -*/ +/** + * 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, @@ -365,47 +369,46 @@ befs_find_brun_indirect(struct super_block *sb, 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 -*/ +/** + * 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, |