ialloc.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

/*
 *  linux/fs/ext2/ialloc.c
 *
 *  Copyright (C) 1992, 1993, 1994  Remy Card ([e-mail])
 *                                  Laboratoire MASI - Institut Blaise Pascal
 *                                  Universite Pierre et Marie Curie (Paris VI)
 *
 *  BSD ufs-inspired inode and directory allocation by 
 *  Stephen Tweedie ([e-mail]), 1993
 */

/*
 * ialloc.c contains the inodes allocation and deallocation routines
 */

/*
 * The free inodes are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.  The descriptors are loaded in memory
 * when a file system is mounted (see ext2_read_super).
 */

#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include <linux/sched.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/locks.h>

#include <asm/bitops.h>

static inline int find_first_zero_bit (unsigned long * addr, unsigned size)
{
	int res;

	if (!size)
		return 0;
	__asm__("
		cld
		movl $-1,%%eax
		repe; scasl
		je 1f
		subl $4,%%edi
		movl (%%edi),%%eax
		notl %%eax
		bsfl %%eax,%%edx
		jmp 2f
1:		xorl %%edx,%%edx
2:		subl %%ebx,%%edi
		shll $3,%%edi
		addl %%edi,%%edx"
		: "=d" (res)
		: "c" ((size + 31) >> 5), "D" (addr), "b" (addr)
		: "ax", "bx", "cx", "di");
	return res;
}

static struct ext2_group_desc * get_group_desc (struct super_block * sb,
						unsigned int block_group,
						struct buffer_head ** bh)
{
	unsigned long group_desc;
	unsigned long desc;
	struct ext2_group_desc * gdp;

	if (block_group >= sb->u.ext2_sb.s_groups_count)
		ext2_panic (sb, "get_group_desc",
			    "block_group >= groups_count\n"
			    "block_group = %d, groups_count = %lu",
			    block_group, sb->u.ext2_sb.s_groups_count);

	group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);
	desc = block_group % EXT2_DESC_PER_BLOCK(sb);
	if (!sb->u.ext2_sb.s_group_desc[group_desc])
		ext2_panic (sb, "get_group_desc",
			    "Group descriptor not loaded\n"
			    "block_group = %d, group_desc = %lu, desc = %lu",
			     block_group, group_desc, desc);
	gdp = (struct ext2_group_desc *) 
		sb->u.ext2_sb.s_group_desc[group_desc]->b_data;
	if (bh)
		*bh = sb->u.ext2_sb.s_group_desc[group_desc];
	return gdp + desc;
}

static void read_inode_bitmap (struct super_block * sb,
			       unsigned long block_group,
			       unsigned int bitmap_nr)
{
	struct ext2_group_desc * gdp;
	struct buffer_head * bh;

	gdp = get_group_desc (sb, block_group, NULL);
	bh = bread (sb->s_dev, gdp->bg_inode_bitmap, sb->s_blocksize);
	if (!bh)
		ext2_panic (sb, "read_inode_bitmap", "Cannot read inode bitmap\n"
			    "block_group = %lu, inode_bitmap = %lu",
			    block_group, gdp->bg_inode_bitmap);
	sb->u.ext2_sb.s_inode_bitmap_number[bitmap_nr] = block_group;
	sb->u.ext2_sb.s_inode_bitmap[bitmap_nr] = bh;
}

/*
 * load_inode_bitmap loads the inode bitmap for a blocks group
 *
 * It maintains a cache for the last bitmaps loaded.  This cache is managed
 * with a LRU algorithm.
 *
 * Notes:
 * 1/ There is one cache per mounted file system.
 * 2/ If the file system contains less than EXT2_MAX_GROUP_LOADED groups,
 *    this function reads the bitmap without maintaining a LRU cache.
 */
static int load_inode_bitmap (struct super_block * sb,
			      unsigned int block_group)
{
	int i, j;
	unsigned long inode_bitmap_number;
	struct buffer_head * inode_bitmap;

	if (block_group >= sb->u.ext2_sb.s_groups_count)
		ext2_panic (sb, "load_inode_bitmap",
			    "block_group >= groups_count\n"
			    "block_group = %d, groups_count = %lu",
			     block_group, sb->u.ext2_sb.s_groups_count);
	if (sb->u.ext2_sb.s_loaded_inode_bitmaps > 0 &&
	    sb->u.ext2_sb.s_inode_bitmap_number[0] == block_group)
		return 0;
	if (sb->u.ext2_sb.s_groups_count <= EXT2_MAX_GROUP_LOADED) {
		if (sb->u.ext2_sb.s_inode_bitmap[block_group]) {
			if (sb->u.ext2_sb.s_inode_bitmap_number[block_group] != block_group)
				ext2_panic (sb, "load_inode_bitmap",
					    "block_group != inode_bitmap_number");
			else
				return block_group;
		} else {
			read_inode_bitmap (sb, block_group, block_group);
			return block_group;
		}
	}

	for (i = 0; i < sb->u.ext2_sb.s_loaded_inode_bitmaps &&
		    sb->u.ext2_sb.s_inode_bitmap_number[i] != block_group;
	     i++)
		;
	if (i < sb->u.ext2_sb.s_loaded_inode_bitmaps &&
  	    sb->u.ext2_sb.s_inode_bitmap_number[i] == block_group) {
		inode_bitmap_number = sb->u.ext2_sb.s_inode_bitmap_number[i];
		inode_bitmap = sb->u.ext2_sb.s_inode_bitmap[i];
		for (j = i; j > 0; j--) {
			sb->u.ext2_sb.s_inode_bitmap_number[j] =
				sb->u.ext2_sb.s_inode_bitmap_number[j - 1];
			sb->u.ext2_sb.s_inode_bitmap[j] =
				sb->u.ext2_sb.s_inode_bitmap[j - 1];
		}
		sb->u.ext2_sb.s_inode_bitmap_number[0] = inode_bitmap_number;
		sb->u.ext2_sb.s_inode_bitmap[0] = inode_bitmap;
	} else {
		if (sb->u.ext2_sb.s_loaded_inode_bitmaps < EXT2_MAX_GROUP_LOADED)
			sb->u.ext2_sb.s_loaded_inode_bitmaps++;
		else
			brelse (sb->u.ext2_sb.s_inode_bitmap[EXT2_MAX_GROUP_LOADED - 1]);
		for (j = sb->u.ext2_sb.s_loaded_inode_bitmaps - 1; j > 0; j--) {
			sb->u.ext2_sb.s_inode_bitmap_number[j] =
				sb->u.ext2_sb.s_inode_bitmap_number[j - 1];
			sb->u.ext2_sb.s_inode_bitmap[j] =
				sb->u.ext2_sb.s_inode_bitmap[j - 1];
		}
		read_inode_bitmap (sb, block_group, 0);
	}
	return 0;
}

/*
 * This function sets the deletion time for the inode
 *
 * This may be used one day by an 'undelete' program
 */
static void set_inode_dtime (struct inode * inode,
			     struct ext2_group_desc * gdp)
{
	unsigned long inode_block;
	struct buffer_head * bh;
	struct ext2_inode * raw_inode;

	inode_block = gdp->bg_inode_table + (((inode->i_ino - 1) %
			EXT2_INODES_PER_GROUP(inode->i_sb)) /
			EXT2_INODES_PER_BLOCK(inode->i_sb));
	bh = bread (inode->i_sb->s_dev, inode_block, inode->i_sb->s_blocksize);
	if (!bh)
		ext2_panic (inode->i_sb, "set_inode_dtime",
			    "Cannot load inode table block\n"
			    "inode=%lu, inode_block=%lu",
			    inode->i_ino, inode_block);
	raw_inode = ((struct ext2_inode *) bh->b_data) +
			(((inode->i_ino - 1) %
			EXT2_INODES_PER_GROUP(inode->i_sb)) %
			EXT2_INODES_PER_BLOCK(inode->i_sb));
	raw_inode->i_links_count = 0;
	raw_inode->i_dtime = CURRENT_TIME;
	bh->b_dirt = 1;
	if (IS_SYNC(inode)) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}
	brelse (bh);
}

void ext2_free_inode (struct inode * inode)
{
	struct super_block * sb;
	struct buffer_head * bh;
	struct buffer_head * bh2;
	unsigned long block_group;
	unsigned long bit;
	int bitmap_nr;
	struct ext2_group_desc * gdp;
	struct ext2_super_block * es;

	if (!inode)
		return;
	if (!inode->i_dev) {
		printk ("ext2_free_inode: inode has no device\n");
		return;
	}
	if (inode->i_count > 1) {
		printk ("ext2_free_inode: inode has count=%d\n",
			inode->i_count);
		return;
	}
	if (inode->i_nlink) {
		printk ("ext2_free_inode: inode has nlink=%d\n",
			inode->i_nlink);
		return;
	}
	if (!inode->i_sb) {
		printk("ext2_free_inode: inode on nonexistent device\n");
		return;
	}

	ext2_debug ("freeing inode %lu\n", inode->i_ino);

	sb = inode->i_sb;
	lock_super (sb);
	if (inode->i_ino < EXT2_FIRST_INO ||
	    inode->i_ino > sb->u.ext2_sb.s_es->s_inodes_count) {
		ext2_error (sb, "free_inode",
			    "reserved inode or nonexistent inode");
		unlock_super (sb);
		return;
	}
	es = sb->u.ext2_sb.s_es;
	block_group = (inode->i_ino - 1) / EXT2_INODES_PER_GROUP(sb);
	bit = (inode->i_ino - 1) % EXT2_INODES_PER_GROUP(sb);
	bitmap_nr = load_inode_bitmap (sb, block_group);
	bh = sb->u.ext2_sb.s_inode_bitmap[bitmap_nr];
	if (!clear_bit (bit, bh->b_data))
		ext2_warning (sb, "ext2_free_inode",
			      "bit already cleared for inode %lu", inode->i_ino);
	else {
		gdp = get_group_desc (sb, block_group, &bh2);
		gdp->bg_free_inodes_count++;
		if (S_ISDIR(inode->i_mode))
			gdp->bg_used_dirs_count--;
		bh2->b_dirt = 1;
		es->s_free_inodes_count++;
		sb->u.ext2_sb.s_sbh->b_dirt = 1;
		set_inode_dtime (inode, gdp);
	}
	bh->b_dirt = 1;
	if (sb->s_flags & MS_SYNC) {
		ll_rw_block (WRITE, 1, &bh);
		wait_on_buffer (bh);
	}

	sb->s_dirt = 1;
	clear_inode (inode);
	unlock_super (sb);
}

/*
 * This function increments the inode version number
 *
 * This may be used one day by the NFS server
 */