bitmap.c

早期linux0.95内核的源代码

/*
 *  linux/fs/bitmap.c
 *
 *  (C) 1991  Linus Torvalds
 */

/* bitmap.c contains the code that handles the inode and block bitmaps */
#include <string.h>

#include <linux/sched.h>
#include <linux/minix_fs.h>
#include <linux/kernel.h>

#define clear_block(addr) \
__asm__("cld\n\t" \
	"rep\n\t" \
	"stosl" \
	::"a" (0),"c" (BLOCK_SIZE/4),"D" ((long) (addr)):"cx","di")

#define set_bit(nr,addr) ({\
char res; \
__asm__ __volatile__("btsl %1,%2\n\tsetb %0": \
"=q" (res):"r" (nr),"m" (*(addr))); \
res;})

#define clear_bit(nr,addr) ({\
char res; \
__asm__ __volatile__("btrl %1,%2\n\tsetnb %0": \
"=q" (res):"r" (nr),"m" (*(addr))); \
res;})

#define find_first_zero(addr) ({ \
int __res; \
__asm__("cld\n" \
	"1:\tlodsl\n\t" \
	"notl %%eax\n\t" \
	"bsfl %%eax,%%edx\n\t" \
	"jne 2f\n\t" \
	"addl $32,%%ecx\n\t" \
	"cmpl $8192,%%ecx\n\t" \
	"jl 1b\n\t" \
	"xorl %%edx,%%edx\n" \
	"2:\taddl %%edx,%%ecx" \
	:"=c" (__res):"0" (0),"S" (addr):"ax","dx","si"); \
__res;})

int minix_free_block(int dev, int block)
{
	struct super_block * sb;
	struct buffer_head * bh;
	unsigned int bit,zone;

	if (!(sb = get_super(dev)))
		panic("trying to free block on nonexistent device");
	if (block < sb->s_firstdatazone || block >= sb->s_nzones)
		panic("trying to free block not in datazone");
	bh = get_hash_table(dev,block);
	if (bh) {
		if (bh->b_count > 1) {
			brelse(bh);
			return 0;
		}
		bh->b_dirt=0;
		bh->b_uptodate=0;
		if (bh->b_count)
			brelse(bh);
	}
	zone = block - sb->s_firstdatazone + 1;
	bit = zone & 8191;
	zone >>= 13;
	bh = sb->s_zmap[zone];
	if (clear_bit(bit,bh->b_data))
		printk("free_block (%04x:%d): bit already cleared\n",dev,block);
	bh->b_dirt = 1;
	return 1;
}

int minix_new_block(int dev)
{
	struct buffer_head * bh;
	struct super_block * sb;
	int i,j;

	if (!(sb = get_super(dev)))
		panic("trying to get new block from nonexistant device");
	j = 8192;
	for (i=0 ; i<8 ; i++)
		if (bh=sb->s_zmap[i])
			if ((j=find_first_zero(bh->b_data))<8192)
				break;
	if (i>=8 || !bh || j>=8192)
		return 0;
	if (set_bit(j,bh->b_data))
		panic("new_block: bit already set");
	bh->b_dirt = 1;
	j += i*8192 + sb->s_firstdatazone-1;
	if (j >= sb->s_nzones)
		return 0;
	if (!(bh=getblk(dev,j)))
		panic("new_block: cannot get block");
	if (bh->b_count != 1)
		panic("new block: count is != 1");
	clear_block(bh->b_data);
	bh->b_uptodate = 1;
	bh->b_dirt = 1;
	brelse(bh);
	return j;
}

void minix_free_inode(struct inode * inode)
{
	struct buffer_head * bh;

	if (!inode)
		return;
	if (!inode->i_dev) {
		memset(inode,0,sizeof(*inode));
		return;
	}
	if (inode->i_count>1) {
		printk("free_inode: inode has count=%d\n",inode->i_count);
		return;
	}
	if (inode->i_nlink) {
		printk("free_inode: inode has nlink=%d\n",inode->i_nlink);
		return;
	}
	if (!inode->i_sb) {
		printk("free_inode: inode on nonexistent device\n");
		return;
	}
	if (inode->i_ino < 1 || inode->i_ino > inode->i_sb->s_ninodes) {
		printk("free_inode: inode 0 or nonexistent inode\n");
		return;
	}
	if (!(bh=inode->i_sb->s_imap[inode->i_ino>>13])) {
		printk("free_inode: nonexistent imap in superblock\n");
		return;
	}
	if (clear_bit(inode->i_ino&8191,bh->b_data))
		printk("free_inode: bit already cleared.\n\r");
	bh->b_dirt = 1;
	memset(inode,0,sizeof(*inode));
}

struct inode * minix_new_inode(int dev)
{
	struct inode * inode;
	struct buffer_head * bh;
	int i,j;

	if (!(inode=get_empty_inode()))
		return NULL;
	if (!(inode->i_sb = get_super(dev))) {
		printk("new_inode: unknown device\n");
		iput(inode);
		return NULL;
	}
	j = 8192;
	for (i=0 ; i<8 ; i++)
		if (bh=inode->i_sb->s_imap[i])
			if ((j=find_first_zero(bh->b_data))<8192)
				break;
	if (!bh || j >= 8192 || j+i*8192 > inode->i_sb->s_ninodes) {
		iput(inode);
		return NULL;
	}
	if (set_bit(j,bh->b_data)) {	/* shouldn't happen */
		printk("new_inode: bit already set");
		iput(inode);
		return NULL;
	}
	bh->b_dirt = 1;
	inode->i_count = 1;
	inode->i_nlink = 1;
	inode->i_dev = dev;
	inode->i_uid = current->euid;
	inode->i_gid = current->egid;
	inode->i_dirt = 1;
	inode->i_ino = j + i*8192;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_op = &minix_inode_operations;
	return inode;
}