file.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

					pbh = affs_bread(inode->i_dev,
							be32_to_cpu(k),
							AFFS_I2BSIZE(inode));
				} else
					pbh = affs_getblock(inode,inode->u.affs_i.i_lastblock);
				if (!pbh) {
					affs_error(sb,"getblock", "Cannot get last block in file");
					break;
				}
			}
			nkey = affs_new_data(inode);
			if (!nkey)
				break;
			inode->u.affs_i.i_lastblock++;
			if (AFFS_BLOCK(bh->b_data,inode,j)) {
				affs_warning(sb,"getblock","Block already allocated");
				affs_free_block(sb,nkey);
				continue;
			}
			AFFS_BLOCK(bh->b_data,inode,j) = cpu_to_be32(nkey);
			if (ofs) {
				ebh = affs_bread(inode->i_dev,nkey,AFFS_I2BSIZE(inode));
				if (!ebh) {
					affs_error(sb,"getblock", "Cannot get block %d",nkey);
					affs_free_block(sb,nkey);
					AFFS_BLOCK(bh->b_data,inode,j) = 0;
					break;
				}
				DATA_FRONT(ebh)->primary_type    = cpu_to_be32(T_DATA);
				DATA_FRONT(ebh)->header_key      = cpu_to_be32(inode->i_ino);
				DATA_FRONT(ebh)->sequence_number = cpu_to_be32(inode->u.affs_i.i_lastblock + 1);
				affs_fix_checksum(AFFS_I2BSIZE(inode), ebh->b_data, 5);
				mark_buffer_dirty(ebh);
				if (pbh) {
					DATA_FRONT(pbh)->data_size = cpu_to_be32(AFFS_I2BSIZE(inode) - 24);
					DATA_FRONT(pbh)->next_data = cpu_to_be32(nkey);
					affs_fix_checksum(AFFS_I2BSIZE(inode),pbh->b_data,5);
					mark_buffer_dirty(pbh);
					affs_brelse(pbh);
				}
				pbh = ebh;
			}
			cf = 1;
		}
		/* N.B. May need to release pbh after here */

		if (cf) {
			if (pt == T_SHORT)
				fdp->first_data = AFFS_BLOCK(bh->b_data,inode,0);
			fdp->block_count = cpu_to_be32(j);
			affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
			mark_buffer_dirty(bh);
		}

		if (block < j) {
			if (pbh)
				affs_brelse(pbh);
			break;
		}
		if (j < AFFS_I2HSIZE(inode)) {
			/* N.B. What about pbh here? */
			goto out_free_bh;
		}

		block -= AFFS_I2HSIZE(inode);
		key    = be32_to_cpu(FILE_END(bh->b_data,inode)->extension);
		if (!key) {
			key = affs_new_header(inode);
			if (!key)
				goto out_free_bh;
			ebh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
			if (!ebh) {
				/* N.B. must free bh here */
				goto out_free_block;
			}
			((struct file_front *)ebh->b_data)->primary_type = cpu_to_be32(T_LIST);
			((struct file_front *)ebh->b_data)->own_key      = cpu_to_be32(key);
			FILE_END(ebh->b_data,inode)->secondary_type      = cpu_to_be32(ST_FILE);
			FILE_END(ebh->b_data,inode)->parent              = cpu_to_be32(inode->i_ino);
			affs_fix_checksum(AFFS_I2BSIZE(inode),ebh->b_data,5);
			mark_buffer_dirty(ebh);
			FILE_END(bh->b_data,inode)->extension = cpu_to_be32(key);
			affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
			mark_buffer_dirty(bh);
			affs_brelse(bh);
			bh = ebh;
		}
		pt = T_LIST;
		ext++;
		index = seqnum_to_index(ext);
		if (index > inode->u.affs_i.i_ec->max_ext &&
		    AFFS_ISINDEX(ext)) {
			inode->u.affs_i.i_ec->ec[index] = key;
			inode->u.affs_i.i_ec->max_ext   = index;
		}
		affs_brelse(bh);
	}

	/* Invalidate key cache */
	for (j = 0; j < 4; j++) {
		kc = &inode->u.affs_i.i_ec->kc[j];
		kc->kc_last = -1;
	}
	key = be32_to_cpu(AFFS_BLOCK(bh->b_data,inode,block));
	affs_brelse(bh);
	if (!key)
		goto out_fail;

	bh = affs_bread(inode->i_dev, key, AFFS_I2BSIZE(inode));
	return bh;

out_free_block:
	affs_free_block(sb, key);
out_free_bh:
	affs_brelse(bh);
out_fail:
	return NULL;
}

static ssize_t
affs_file_read_ofs(struct file *filp, char *buf, size_t count, loff_t *ppos)
{
	struct inode		*inode = filp->f_dentry->d_inode;
	char			*start;
	ssize_t			 left, offset, size, sector;
	ssize_t			 blocksize;
	struct buffer_head	*bh;
	void			*data;
	loff_t		tmp;

	pr_debug("AFFS: file_read_ofs(ino=%lu,pos=%lu,%d)\n",inode->i_ino,
		 (unsigned long)*ppos,count);

	if (!inode) {
		affs_error(inode->i_sb,"file_read_ofs","Inode = NULL");
		return -EINVAL;
	}
	blocksize = AFFS_I2BSIZE(inode) - 24;
	if (!(S_ISREG(inode->i_mode))) {
		pr_debug("AFFS: file_read: mode = %07o",inode->i_mode);
		return -EINVAL;
	}
	if (*ppos >= inode->i_size || count <= 0)
		return 0;

	start = buf;
	for (;;) {
		left = MIN (inode->i_size - *ppos,count - (buf - start));
		if (!left)
			break;
		tmp = *ppos;
		do_div(tmp, blocksize);
		sector = affs_bmap(inode, tmp);
		if (!sector)
			break;
		tmp = *ppos;
		offset = do_div(tmp, blocksize);
		bh = affs_bread(inode->i_dev,sector,AFFS_I2BSIZE(inode));
		if (!bh)
			break;
		data = bh->b_data + 24;
		size = MIN(blocksize - offset,left);
		*ppos += size;
		copy_to_user(buf,data + offset,size);
		buf += size;
		affs_brelse(bh);
	}
	if (start == buf)
		return -EIO;
	return buf - start;
}

static ssize_t
affs_file_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
	ssize_t retval;

	retval = generic_file_write (file, buf, count, ppos);
	if (retval >0) {
		struct inode *inode = file->f_dentry->d_inode;
		inode->i_ctime = inode->i_mtime = CURRENT_TIME;
		mark_inode_dirty(inode);
	}
	return retval;
}

static ssize_t
affs_file_write_ofs(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
	ssize_t retval;

	retval = generic_file_write (file, buf, count, ppos);
	if (retval >0) {
		struct inode *inode = file->f_dentry->d_inode;
		inode->i_ctime = inode->i_mtime = CURRENT_TIME;
		mark_inode_dirty(inode);
	}
	return retval;
}

/* Free any preallocated blocks. */

void
affs_free_prealloc(struct inode *inode)
{
	struct super_block	*sb = inode->i_sb;
	struct affs_zone	*zone;
	int block;

	pr_debug("AFFS: free_prealloc(ino=%lu)\n", inode->i_ino);

	while (inode->u.affs_i.i_pa_cnt) {	
		block = inode->u.affs_i.i_data[inode->u.affs_i.i_pa_next++];
		inode->u.affs_i.i_pa_next &= AFFS_MAX_PREALLOC - 1;
		inode->u.affs_i.i_pa_cnt--;
		affs_free_block(sb, block);
	}
	if (inode->u.affs_i.i_zone) {
		zone = &sb->u.affs_sb.s_zones[inode->u.affs_i.i_zone];
		if (zone->z_ino == inode->i_ino)
			zone->z_ino = 0;
	}
}

/* Truncate (or enlarge) a file to the requested size. */

void
affs_truncate(struct inode *inode)
{
	struct buffer_head	*bh = NULL;
	int	 first;			/* First block to be thrown away	*/
	int	 block;
	s32	 key;
	s32	*keyp;
	s32	 ekey;
	s32	 ptype, stype;
	int	 freethis;
	int	 net_blocksize;
	int	 blocksize = AFFS_I2BSIZE(inode);
	int	 rem;
	int	 ext;
	loff_t tmp;

	pr_debug("AFFS: truncate(inode=%ld,size=%lu)\n",inode->i_ino,inode->i_size);

	net_blocksize = blocksize - ((inode->i_sb->u.affs_sb.s_flags & SF_OFS) ? 24 : 0);
	first = inode->i_size + net_blocksize -1;
	do_div (first, net_blocksize);
	if (inode->u.affs_i.i_lastblock < first - 1) {
		/* There has to be at least one new block to be allocated */
		if (!inode->u.affs_i.i_ec && alloc_ext_cache(inode)) {
			/* XXX Fine! No way to indicate an error. */
			return /* -ENOSPC */;
		}
		bh = affs_getblock(inode,first - 1);
		if (!bh) {
			affs_warning(inode->i_sb,"truncate","Cannot extend file");
			inode->i_size = net_blocksize * (inode->u.affs_i.i_lastblock + 1);
		} else if (inode->i_sb->u.affs_sb.s_flags & SF_OFS) {
			tmp = inode->i_size;
			rem = do_div(tmp, net_blocksize);
			DATA_FRONT(bh)->data_size = cpu_to_be32(rem ? rem : net_blocksize);
			affs_fix_checksum(blocksize,bh->b_data,5);
			mark_buffer_dirty(bh);
		}
		goto out_truncate;
	}
	ekey = inode->i_ino;
	ext  = 0;

	/* Free all blocks starting at 'first' and all then-empty
	 * extension blocks. Do not free the header block, though.
	 */
	while (ekey) {
		if (!(bh = affs_bread(inode->i_dev,ekey,blocksize))) {
			affs_error(inode->i_sb,"truncate","Cannot read block %d",ekey);
			goto out_truncate;
		}
		if (affs_checksum_block(blocksize,bh->b_data,&ptype,&stype)) {
			affs_error(inode->i_sb,"truncate","Checksum error in header/ext block %d",
				   ekey);
			goto out_truncate;
		}
		if (stype != ST_FILE || (ptype != T_SHORT && ptype != T_LIST)) {
			affs_error(inode->i_sb,"truncate",
				   "Bad block (key=%d, ptype=%d, stype=%d)",ekey,ptype,stype);
			goto out_truncate;
		}
		/* Do we have to free this extension block after
		 * freeing the data blocks pointed to?
		 */
		freethis = first == 0 && ekey != inode->i_ino;

		/* Free the data blocks. 'first' is relative to this
		 * extension block and may well lie behind this block.
		 */
		for (block = first; block < AFFS_I2HSIZE(inode); block++) {
			keyp = &AFFS_BLOCK(bh->b_data,inode,block);
			key  = be32_to_cpu(*keyp);
			if (key) {
				*keyp = 0;
				affs_free_block(inode->i_sb,key);
			} else
				break;
		}
		keyp = &GET_END_PTR(struct file_end,bh->b_data,blocksize)->extension;
		key  = be32_to_cpu(*keyp);

		/* If 'first' is in this block or is the first
		 * in the next one, this will be the last in
		 * the list, thus we have to adjust the count
		 * and zero the pointer to the next ext block.
		 */
		if (first <= AFFS_I2HSIZE(inode)) {
			((struct file_front *)bh->b_data)->block_count = cpu_to_be32(first);
			first = 0;
			*keyp = 0;
			affs_fix_checksum(blocksize,bh->b_data,5);
			mark_buffer_dirty(bh);
		} else
			first -= AFFS_I2HSIZE(inode);
		affs_brelse(bh);
		bh = NULL;
		if (freethis)			/* Don't bother fixing checksum */
			affs_free_block(inode->i_sb,ekey);
		ekey = key;
	}
	block = inode->i_size + net_blocksize - 1;
	do_div (block, net_blocksize);
	block--;
	inode->u.affs_i.i_lastblock = block;

	/* If the file is not truncated to a block boundary,
	 * the partial block after the EOF must be zeroed
	 * so it cannot become accessible again.
	 */

	tmp = inode->i_size;
	rem = do_div(tmp, net_blocksize);
	if (rem) {
		if ((inode->i_sb->u.affs_sb.s_flags & SF_OFS)) 
			rem += 24;
		pr_debug("AFFS: Zeroing from offset %d in block %d\n",rem,block);
		bh = affs_getblock(inode,block);
		if (bh) {
			memset(bh->b_data + rem,0,blocksize - rem);
			if ((inode->i_sb->u.affs_sb.s_flags & SF_OFS)) {
				((struct data_front *)bh->b_data)->data_size = cpu_to_be32(rem);
				((struct data_front *)bh->b_data)->next_data = 0;
				affs_fix_checksum(blocksize,bh->b_data,5);
			}
			mark_buffer_dirty(bh);
		} else 
			affs_error(inode->i_sb,"truncate","Cannot read block %d",block);
	}

out_truncate:
	affs_brelse(bh);
	/* Invalidate cache */
	if (inode->u.affs_i.i_ec) {
		inode->u.affs_i.i_ec->max_ext = 0;
		for (key = 0; key < 4; key++) {
			inode->u.affs_i.i_ec->kc[key].kc_next_key = 0;
			inode->u.affs_i.i_ec->kc[key].kc_last     = -1;
		}
	}
	mark_inode_dirty(inode);
}

/*
 * Called only when we need to allocate the extension cache.
 */

static int
alloc_ext_cache(struct inode *inode)
{
	s32	 key;
	int	 i;
	unsigned long cache_page;
	int      error = 0;

	pr_debug("AFFS: alloc_ext_cache(ino=%lu)\n",inode->i_ino);

	cache_page = get_free_page(GFP_KERNEL);
	/*
	 * Check whether somebody else allocated it for us ...
	 */
	if (inode->u.affs_i.i_ec)
		goto out_free;
	if (!cache_page)
		goto out_error;

	inode->u.affs_i.i_ec = (struct ext_cache *) cache_page;
	/* We only have to initialize non-zero values.
	 * get_free_page() zeroed the page already.
	 */
	key = inode->i_ino;
	inode->u.affs_i.i_ec->ec[0] = key;
	for (i = 0; i < 4; i++) {
		inode->u.affs_i.i_ec->kc[i].kc_this_key = key;
		inode->u.affs_i.i_ec->kc[i].kc_last     = -1;
	}
out:
	return error;

out_free:
	if (cache_page)
		free_page(cache_page);
	goto out;

out_error:
	affs_error(inode->i_sb,"alloc_ext_cache","Cache allocation failed");
	error = -ENOMEM;
	goto out;
}