b1d068470b
isofs now uses an in-memory directory listing built on-the-fly instead of parsing the ISO 9660 data structures over and over for almost every request. This yields huge performance improvements. The directory listing is allocated dynamically, but Minix servers aren't normally supposed to do that because critical servers would crash if the system runs out of memory. isofs is quite frugal, won't allocate memory after having the whole directory tree cached and is not that critical (its most important job is to serve as a root file system during installation). The benefits and elegance of this scheme far outweights this small problem in practice. Change-Id: I13d070388c07d274cbee0645cbc50295c447c5b6
123 lines
3.1 KiB
C
123 lines
3.1 KiB
C
/*
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* Functions to manage the superblock of the filesystem. These functions are
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* are called at the beginning and at the end of the server.
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*/
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#include "inc.h"
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#include <string.h>
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#include <minix/com.h>
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#include <minix/u64.h>
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#include <minix/bdev.h>
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int release_vol_pri_desc(struct iso9660_vol_pri_desc *vol_pri)
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{
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/* Release the root dir root. */
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if (vol_pri->i_count > 0) {
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put_inode(vol_pri->inode_root);
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vol_pri->inode_root = NULL;
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vol_pri->i_count = 0;
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}
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return OK;
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}
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static int create_vol_pri_desc(struct iso9660_vol_pri_desc *vol_pri, char *buf)
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{
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/*
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* This function fullfill the super block data structure using the
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* information contained in the buffer.
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*/
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struct iso9660_dir_record *root_record;
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struct inode_dir_entry dir_entry;
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struct dir_extent extent;
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size_t dummy_offset = 0;
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if (vol_pri->i_count > 0)
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release_vol_pri_desc(vol_pri);
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memcpy(vol_pri, buf, 2048);
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/* Check various fields for consistency. */
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if ((memcmp(vol_pri->standard_id, "CD001",
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ISO9660_SIZE_STANDARD_ID) != 0)
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|| (vol_pri->vd_version != 1)
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|| (vol_pri->logical_block_size_l < 2048))
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return EINVAL;
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lmfs_set_blocksize(vol_pri->logical_block_size_l);
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lmfs_set_blockusage(vol_pri->volume_space_size_l,
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vol_pri->volume_space_size_l);
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/* Read root directory record. */
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root_record = (struct iso9660_dir_record *)vol_pri->root_directory;
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extent.location =
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root_record->loc_extent_l + root_record->ext_attr_rec_length;
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extent.length =
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root_record->data_length_l / vol_pri->logical_block_size_l;
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extent.next = NULL;
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if (root_record->data_length_l % vol_pri->logical_block_size_l)
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extent.length++;
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memset(&dir_entry, 0, sizeof(struct inode_dir_entry));
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if (read_inode(&dir_entry, &extent, &dummy_offset) != OK) {
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return EINVAL;
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}
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dir_entry.i_node->i_count = 1;
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vol_pri->inode_root = dir_entry.i_node;
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vol_pri->i_count = 1;
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return OK;
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}
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int read_vds(struct iso9660_vol_pri_desc *vol_pri, dev_t dev)
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{
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/*
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* This function reads from a ISO9660 filesystem (in the device dev)
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* the super block and saves it in vol_pri.
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*/
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size_t offset;
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int vol_ok = FALSE, vol_pri_flag = FALSE;
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int r;
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static char sbbuf[ISO9660_MIN_BLOCK_SIZE];
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int i = 0;
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for(offset = ISO9660_SUPER_BLOCK_POSITION;
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!vol_ok && i++ < MAX_ATTEMPTS;
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offset += ISO9660_MIN_BLOCK_SIZE) {
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/* Read the sector of the super block. */
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r = bdev_read(dev, offset, sbbuf, ISO9660_MIN_BLOCK_SIZE,
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BDEV_NOFLAGS);
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if (r != ISO9660_MIN_BLOCK_SIZE) {
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/* Damaged sector or what? */
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return EINVAL;
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}
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if ((sbbuf[0] & BYTE) == VD_PRIMARY) {
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/* Free already parsed descriptor, if any. */
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if (vol_pri_flag == TRUE) {
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release_vol_pri_desc(vol_pri);
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vol_pri_flag = FALSE;
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}
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/* Copy the buffer in the data structure. */
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if (create_vol_pri_desc(vol_pri, sbbuf) == OK) {
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vol_pri_flag = TRUE;
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}
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}
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if ((sbbuf[0] & BYTE) == VD_SET_TERM) {
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/* I dont need to save anything about it */
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vol_ok = TRUE;
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}
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}
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if (vol_ok == FALSE || vol_pri_flag == FALSE)
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return EINVAL; /* If no superblock was found... */
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else
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return OK; /* otherwise. */
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}
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