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发信人: GyeaonWoo (柏林恋人), 信区: Linux
标  题: Linus's Linux--fs/bitmap.c
发信站: 荔园晨风BBS站 (Mon Aug 25 20:01:27 2003), 站内信件

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

#include <linux/sched.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) ({\
register int res __asm__("ax"); \
__asm__("btsl %2,%3\n\tsetb %%al":"=a" (res):"0" (0),"r" (nr),"m"
(*(addr))); \
res;})

#define clear_bit(nr,addr) ({\
register int res __asm__("ax"); \
__asm__("btrl %2,%3\n\tsetnb %%al":"=a" (res):"0" (0),"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" \
        "je 2f\n\t" \
        "addl %%edx,%%ecx\n\t" \
        "jmp 3f\n" \
        "2:\taddl $32,%%ecx\n\t" \
        "cmpl $8192,%%ecx\n\t" \
        "jl 1b\n" \
        "3:" \
        :"=c" (__res):"c" (0),"S" (addr):"ax","dx","si"); \
__res;})

void free_block(int dev, int block)
{
        struct super_block * sb;
        struct buffer_head * bh;

        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) {
                        printk("trying to free block (%04x:%d), count=%d\n",
                                dev,block,bh->b_count);
                        return;
                }
                bh->b_dirt=0;
                bh->b_uptodate=0;
                brelse(bh);
        }
        block -= sb->s_firstdatazone - 1 ;
        if (clear_bit(block&8191,sb->s_zmap[block/8192]->b_data)) {
                printk("block (%04x:%d) ",dev,block+sb->s_firstdatazone-1);
                panic("free_block: bit already cleared");
        }
        sb->s_zmap[block/8192]->b_dirt = 1;
}

int 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 free_inode(struct m_inode * inode)
{
        struct super_block * sb;
        struct buffer_head * bh;

        if (!inode)
                return;
        if (!inode->i_dev) {
                memset(inode,0,sizeof(*inode));
                return;
        }
        if (inode->i_count>1) {
                printk("trying to free inode with count=%d\n",inode->i_count);
                panic("free_inode");
        }
        if (inode->i_nlinks)
                panic("trying to free inode with links");
        if (!(sb = get_super(inode->i_dev)))
                panic("trying to free inode on nonexistent device");
        if (inode->i_num < 1 || inode->i_num > sb->s_ninodes)
                panic("trying to free inode 0 or nonexistant inode");
        if (!(bh=sb->s_imap[inode->i_num>>13]))
                panic("nonexistent imap in superblock");
        if (clear_bit(inode->i_num&8191,bh->b_data))
                panic("free_inode: bit already cleared");
        bh->b_dirt = 1;
        memset(inode,0,sizeof(*inode));
}

struct m_inode * new_inode(int dev)
{
        struct m_inode * inode;
        struct super_block * sb;
        struct buffer_head * bh;
        int i,j;

        if (!(inode=get_empty_inode()))
                return NULL;
        if (!(sb = get_super(dev)))
                panic("new_inode with unknown device");
        j = 8192;
        for (i=0 ; i<8 ; i++)
                if (bh=sb->s_imap[i])
                        if ((j=find_first_zero(bh->b_data))<8192)
                                break;
        if (!bh || j >= 8192 || j+i*8192 > sb->s_ninodes) {
                iput(inode);
                return NULL;
        }
        if (set_bit(j,bh->b_data))
                panic("new_inode: bit already set");
        bh->b_dirt = 1;
        inode->i_count=1;
        inode->i_nlinks=1;
        inode->i_dev=dev;
        inode->i_dirt=1;
        inode->i_num = j + i*8192;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        return inode;
}

--
一个疯子的四大症状：
一、崇拜悲剧的力量，爱慕美狄亚
二、痛苦的时候不是发呆就是讲费话
三、看到有人在赞美肉麻就要发狂
四、像夸大自己的优点那样夸大自己的缺点活着就像皮影戏，一撤了幕，就什么都没了。

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