dir_f.c
上传用户:jlfgdled
上传日期:2013-04-10
资源大小:33168k
文件大小:10k
- /*
- * linux/fs/adfs/dir_f.c
- *
- * Copyright (C) 1997-1999 Russell King
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * E and F format directory handling
- */
- #include <linux/version.h>
- #include <linux/errno.h>
- #include <linux/fs.h>
- #include <linux/adfs_fs.h>
- #include <linux/sched.h>
- #include <linux/stat.h>
- #include <linux/spinlock.h>
- #include "adfs.h"
- #include "dir_f.h"
- static void adfs_f_free(struct adfs_dir *dir);
- /*
- * Read an (unaligned) value of length 1..4 bytes
- */
- static inline unsigned int adfs_readval(unsigned char *p, int len)
- {
- unsigned int val = 0;
- switch (len) {
- case 4: val |= p[3] << 24;
- case 3: val |= p[2] << 16;
- case 2: val |= p[1] << 8;
- default: val |= p[0];
- }
- return val;
- }
- static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
- {
- switch (len) {
- case 4: p[3] = val >> 24;
- case 3: p[2] = val >> 16;
- case 2: p[1] = val >> 8;
- default: p[0] = val;
- }
- }
- static inline int adfs_readname(char *buf, char *ptr, int maxlen)
- {
- char *old_buf = buf;
- while (*ptr >= ' ' && maxlen--) {
- if (*ptr == '/')
- *buf++ = '.';
- else
- *buf++ = *ptr;
- ptr++;
- }
- *buf = ' ';
- return buf - old_buf;
- }
- static inline void adfs_writename(char *to, char *from, int maxlen)
- {
- int i;
- for (i = 0; i < maxlen; i++) {
- if (from[i] == ' ')
- break;
- if (from[i] == '.')
- to[i] = '/';
- else
- to[i] = from[i];
- }
- for (; i < maxlen; i++)
- to[i] = ' ';
- }
- #define ror13(v) ((v >> 13) | (v << 19))
- #define dir_u8(idx)
- ({ int _buf = idx >> blocksize_bits;
- int _off = idx - (_buf << blocksize_bits);
- *(u8 *)(bh[_buf]->b_data + _off);
- })
- #define dir_u32(idx)
- ({ int _buf = idx >> blocksize_bits;
- int _off = idx - (_buf << blocksize_bits);
- *(u32 *)(bh[_buf]->b_data + _off);
- })
- #define bufoff(_bh,_idx)
- ({ int _buf = _idx >> blocksize_bits;
- int _off = _idx - (_buf << blocksize_bits);
- (u8 *)(_bh[_buf]->b_data + _off);
- })
- /*
- * There are some algorithms that are nice in
- * assembler, but a bitch in C... This is one
- * of them.
- */
- static u8
- adfs_dir_checkbyte(const struct adfs_dir *dir)
- {
- struct buffer_head * const *bh = dir->bh;
- const int blocksize_bits = dir->sb->s_blocksize_bits;
- union { u32 *ptr32; u8 *ptr8; } ptr, end;
- u32 dircheck = 0;
- int last = 5 - 26;
- int i = 0;
- /*
- * Accumulate each word up to the last whole
- * word of the last directory entry. This
- * can spread across several buffer heads.
- */
- do {
- last += 26;
- do {
- dircheck = cpu_to_le32(dir_u32(i)) ^ ror13(dircheck);
- i += sizeof(u32);
- } while (i < (last & ~3));
- } while (dir_u8(last) != 0);
- /*
- * Accumulate the last few bytes. These
- * bytes will be within the same bh.
- */
- if (i != last) {
- ptr.ptr8 = bufoff(bh, i);
- end.ptr8 = ptr.ptr8 + last - i;
- do
- dircheck = *ptr.ptr8++ ^ ror13(dircheck);
- while (ptr.ptr8 < end.ptr8);
- }
- /*
- * The directory tail is in the final bh
- * Note that contary to the RISC OS PRMs,
- * the first few bytes are NOT included
- * in the check. All bytes are in the
- * same bh.
- */
- ptr.ptr8 = bufoff(bh, 2008);
- end.ptr8 = ptr.ptr8 + 36;
- do {
- unsigned int v = *ptr.ptr32++;
- dircheck = cpu_to_le32(v) ^ ror13(dircheck);
- } while (ptr.ptr32 < end.ptr32);
- return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
- }
- /*
- * Read and check that a directory is valid
- */
- int
- adfs_dir_read(struct super_block *sb, unsigned long object_id,
- unsigned int size, struct adfs_dir *dir)
- {
- const unsigned int blocksize_bits = sb->s_blocksize_bits;
- int blk = 0;
- /*
- * Directories which are not a multiple of 2048 bytes
- * are considered bad v2 [3.6]
- */
- if (size & 2047)
- goto bad_dir;
- size >>= blocksize_bits;
- dir->nr_buffers = 0;
- dir->sb = sb;
- for (blk = 0; blk < size; blk++) {
- int phys;
- phys = __adfs_block_map(sb, object_id, blk);
- if (!phys) {
- adfs_error(sb, "dir object %lX has a hole at offset %d",
- object_id, blk);
- goto release_buffers;
- }
- dir->bh[blk] = sb_bread(sb, phys);
- if (!dir->bh[blk])
- goto release_buffers;
- }
- memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
- memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
- if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
- memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
- goto bad_dir;
- if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
- memcmp(&dir->dirhead.startname, "Hugo", 4))
- goto bad_dir;
- if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
- goto bad_dir;
- dir->nr_buffers = blk;
- return 0;
- bad_dir:
- adfs_error(sb, "corrupted directory fragment %lX",
- object_id);
- release_buffers:
- for (blk -= 1; blk >= 0; blk -= 1)
- brelse(dir->bh[blk]);
- dir->sb = NULL;
- return -EIO;
- }
- /*
- * convert a disk-based directory entry to a Linux ADFS directory entry
- */
- static inline void
- adfs_dir2obj(struct object_info *obj, struct adfs_direntry *de)
- {
- obj->name_len = adfs_readname(obj->name, de->dirobname, ADFS_F_NAME_LEN);
- obj->file_id = adfs_readval(de->dirinddiscadd, 3);
- obj->loadaddr = adfs_readval(de->dirload, 4);
- obj->execaddr = adfs_readval(de->direxec, 4);
- obj->size = adfs_readval(de->dirlen, 4);
- obj->attr = de->newdiratts;
- }
- /*
- * convert a Linux ADFS directory entry to a disk-based directory entry
- */
- static inline void
- adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
- {
- adfs_writeval(de->dirinddiscadd, 3, obj->file_id);
- adfs_writeval(de->dirload, 4, obj->loadaddr);
- adfs_writeval(de->direxec, 4, obj->execaddr);
- adfs_writeval(de->dirlen, 4, obj->size);
- de->newdiratts = obj->attr;
- }
- /*
- * get a directory entry. Note that the caller is responsible
- * for holding the relevent locks.
- */
- int
- __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
- {
- struct super_block *sb = dir->sb;
- struct adfs_direntry de;
- int thissize, buffer, offset;
- buffer = pos >> sb->s_blocksize_bits;
- if (buffer > dir->nr_buffers)
- return -EINVAL;
- offset = pos & (sb->s_blocksize - 1);
- thissize = sb->s_blocksize - offset;
- if (thissize > 26)
- thissize = 26;
- memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
- if (thissize != 26)
- memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
- 26 - thissize);
- if (!de.dirobname[0])
- return -ENOENT;
- adfs_dir2obj(obj, &de);
- return 0;
- }
- int
- __adfs_dir_put(struct adfs_dir *dir, int pos, struct object_info *obj)
- {
- struct super_block *sb = dir->sb;
- struct adfs_direntry de;
- int thissize, buffer, offset;
- buffer = pos >> sb->s_blocksize_bits;
- if (buffer > dir->nr_buffers)
- return -EINVAL;
- offset = pos & (sb->s_blocksize - 1);
- thissize = sb->s_blocksize - offset;
- if (thissize > 26)
- thissize = 26;
- /*
- * Get the entry in total
- */
- memcpy(&de, dir->bh[buffer]->b_data + offset, thissize);
- if (thissize != 26)
- memcpy(((char *)&de) + thissize, dir->bh[buffer + 1]->b_data,
- 26 - thissize);
- /*
- * update it
- */
- adfs_obj2dir(&de, obj);
- /*
- * Put the new entry back
- */
- memcpy(dir->bh[buffer]->b_data + offset, &de, thissize);
- if (thissize != 26)
- memcpy(dir->bh[buffer + 1]->b_data, ((char *)&de) + thissize,
- 26 - thissize);
- return 0;
- }
- /*
- * the caller is responsible for holding the necessary
- * locks.
- */
- static int
- adfs_dir_find_entry(struct adfs_dir *dir, unsigned long object_id)
- {
- int pos, ret;
- ret = -ENOENT;
- for (pos = 5; pos < ADFS_NUM_DIR_ENTRIES * 26 + 5; pos += 26) {
- struct object_info obj;
- if (!__adfs_dir_get(dir, pos, &obj))
- break;
- if (obj.file_id == object_id) {
- ret = pos;
- break;
- }
- }
- return ret;
- }
- static int
- adfs_f_read(struct super_block *sb, unsigned int id, unsigned int sz, struct adfs_dir *dir)
- {
- int ret;
- if (sz != ADFS_NEWDIR_SIZE)
- return -EIO;
- ret = adfs_dir_read(sb, id, sz, dir);
- if (ret)
- adfs_error(sb, "unable to read directory");
- else
- dir->parent_id = adfs_readval(dir->dirtail.new.dirparent, 3);
- return ret;
- }
- static int
- adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
- {
- if (fpos >= ADFS_NUM_DIR_ENTRIES)
- return -ENOENT;
- dir->pos = 5 + fpos * 26;
- return 0;
- }
- static int
- adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
- {
- unsigned int ret;
- ret = __adfs_dir_get(dir, dir->pos, obj);
- if (ret == 0)
- dir->pos += 26;
- return ret;
- }
- static int
- adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
- {
- struct super_block *sb = dir->sb;
- int ret, i;
- ret = adfs_dir_find_entry(dir, obj->file_id);
- if (ret < 0) {
- adfs_error(dir->sb, "unable to locate entry to update");
- goto out;
- }
- __adfs_dir_put(dir, ret, obj);
-
- /*
- * Increment directory sequence number
- */
- dir->bh[0]->b_data[0] += 1;
- dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 6] += 1;
- ret = adfs_dir_checkbyte(dir);
- /*
- * Update directory check byte
- */
- dir->bh[dir->nr_buffers - 1]->b_data[sb->s_blocksize - 1] = ret;
- #if 1
- {
- const unsigned int blocksize_bits = sb->s_blocksize_bits;
- memcpy(&dir->dirhead, bufoff(dir->bh, 0), sizeof(dir->dirhead));
- memcpy(&dir->dirtail, bufoff(dir->bh, 2007), sizeof(dir->dirtail));
- if (dir->dirhead.startmasseq != dir->dirtail.new.endmasseq ||
- memcmp(&dir->dirhead.startname, &dir->dirtail.new.endname, 4))
- goto bad_dir;
- if (memcmp(&dir->dirhead.startname, "Nick", 4) &&
- memcmp(&dir->dirhead.startname, "Hugo", 4))
- goto bad_dir;
- if (adfs_dir_checkbyte(dir) != dir->dirtail.new.dircheckbyte)
- goto bad_dir;
- }
- #endif
- for (i = dir->nr_buffers - 1; i >= 0; i--)
- mark_buffer_dirty(dir->bh[i]);
- ret = 0;
- out:
- return ret;
- #if 1
- bad_dir:
- adfs_error(dir->sb, "whoops! I broke a directory!");
- return -EIO;
- #endif
- }
- static void
- adfs_f_free(struct adfs_dir *dir)
- {
- int i;
- for (i = dir->nr_buffers - 1; i >= 0; i--) {
- brelse(dir->bh[i]);
- dir->bh[i] = NULL;
- }
- dir->nr_buffers = 0;
- dir->sb = NULL;
- }
- struct adfs_dir_ops adfs_f_dir_ops = {
- adfs_f_read,
- adfs_f_setpos,
- adfs_f_getnext,
- adfs_f_update,
- NULL,
- NULL,
- adfs_f_free
- };