inode.c

Linux 1.0 内核C源代码 Linux最早版本代码 由Linus Torvalds亲自书写的

/*
 *  linux/fs/ext2/inode.c
 *
 *  Copyright (C) 1992, 1993, 1994  Remy Card ([e-mail])
 *                                  Laboratoire MASI - Institut Blaise Pascal
 *                                  Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Goal-directed block allocation by Stephen Tweedie ([e-mail]), 1993
 */

#include <asm/segment.h>
#include <asm/system.h>

#include <linux/errno.h>
#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>

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

void ext2_put_inode (struct inode * inode)
{
	ext2_discard_prealloc (inode);
	if (inode->i_nlink || inode->i_ino == EXT2_ACL_IDX_INO ||
	    inode->i_ino == EXT2_ACL_DATA_INO)
		return;
	inode->i_size = 0;
	if (inode->i_blocks)
		ext2_truncate (inode);
	ext2_free_inode (inode);
}

#define inode_bmap(inode, nr) ((inode)->u.ext2_i.i_data[(nr)])

static int block_bmap (struct buffer_head * bh, int nr)
{
	int tmp;

	if (!bh)
		return 0;
	tmp = ((unsigned long *) bh->b_data)[nr];
	brelse (bh);
	return tmp;
}

/* 
 * ext2_discard_prealloc and ext2_alloc_block are atomic wrt. the
 * superblock in the same manner as are ext2_free_blocks and
 * ext2_new_block.  We just wait on the super rather than locking it
 * here, since ext2_new_block will do the necessary locking and we
 * can't block until then.
 */
void ext2_discard_prealloc (struct inode * inode)
{
#ifdef EXT2_PREALLOCATE
	if (inode->u.ext2_i.i_prealloc_count) {
		int i = inode->u.ext2_i.i_prealloc_count;
		inode->u.ext2_i.i_prealloc_count = 0;
		ext2_free_blocks (inode->i_sb,
				  inode->u.ext2_i.i_prealloc_block,
				  i);
	}
#endif
}

static int ext2_alloc_block (struct inode * inode, unsigned long goal)
{
#ifdef EXT2FS_DEBUG
	static unsigned long alloc_hits = 0, alloc_attempts = 0;
#endif
	unsigned long result;
	struct buffer_head * bh;

	wait_on_super (inode->i_sb);

#ifdef EXT2_PREALLOCATE
	if (inode->u.ext2_i.i_prealloc_count &&
	    (goal == inode->u.ext2_i.i_prealloc_block ||
	     goal + 1 == inode->u.ext2_i.i_prealloc_block))
	{		
		result = inode->u.ext2_i.i_prealloc_block++;
		inode->u.ext2_i.i_prealloc_count--;
		ext2_debug ("preallocation hit (%lu/%lu).\n",
			    ++alloc_hits, ++alloc_attempts);

		/* It doesn't matter if we block in getblk() since
		   we have already atomically allocated the block, and
		   are only clearing it now. */
		if (!(bh = getblk (inode->i_sb->s_dev, result,
				   inode->i_sb->s_blocksize))) {
			ext2_error (inode->i_sb, "ext2_alloc_block",
				    "cannot get block %lu", result);
			return 0;
		}
		clear_block (bh->b_data, inode->i_sb->s_blocksize);
		bh->b_uptodate = 1;
		bh->b_dirt = 1;
		brelse (bh);
	} else {
		ext2_discard_prealloc (inode);
		ext2_debug ("preallocation miss (%lu/%lu).\n",
			    alloc_hits, ++alloc_attempts);
		if (S_ISREG(inode->i_mode))
			result = ext2_new_block
				(inode->i_sb, goal,
				 &inode->u.ext2_i.i_prealloc_count,
				 &inode->u.ext2_i.i_prealloc_block);
		else
			result = ext2_new_block (inode->i_sb, goal, 0, 0);
	}
#else
	result = ext2_new_block (inode->i_sb, goal, 0, 0);
#endif

	return result;
}


int ext2_bmap (struct inode * inode, int block)
{
	int i;
	int addr_per_block = EXT2_ADDR_PER_BLOCK(inode->i_sb);

	if (block < 0) {
		ext2_warning (inode->i_sb, "ext2_bmap", "block < 0");
		return 0;
	}
	if (block >= EXT2_NDIR_BLOCKS + addr_per_block +
		     addr_per_block * addr_per_block +
		     addr_per_block * addr_per_block * addr_per_block) {
		ext2_warning (inode->i_sb, "ext2_bmap", "block > big");
		return 0;
	}
	if (block < EXT2_NDIR_BLOCKS)
		return inode_bmap (inode, block);
	block -= EXT2_NDIR_BLOCKS;
	if (block < addr_per_block) {
		i = inode_bmap (inode, EXT2_IND_BLOCK);
		if (!i)
			return 0;
		return block_bmap (bread (inode->i_dev, i,
					  inode->i_sb->s_blocksize), block);
	}
	block -= addr_per_block;
	if (block < addr_per_block * addr_per_block) {
		i = inode_bmap (inode, EXT2_DIND_BLOCK);
		if (!i)
			return 0;
		i = block_bmap (bread (inode->i_dev, i,
				       inode->i_sb->s_blocksize),
				block / addr_per_block);
		if (!i)
			return 0;
		return block_bmap (bread (inode->i_dev, i,
					  inode->i_sb->s_blocksize),
				   block & (addr_per_block - 1));
	}
	block -= addr_per_block * addr_per_block;
	i = inode_bmap (inode, EXT2_TIND_BLOCK);
	if (!i)
		return 0;
	i = block_bmap (bread (inode->i_dev, i, inode->i_sb->s_blocksize),
			block / (addr_per_block * addr_per_block));
	if (!i)
		return 0;
	i = block_bmap (bread (inode->i_dev, i, inode->i_sb->s_blocksize),
			(block / addr_per_block) & (addr_per_block - 1));
	if (!i)
		return 0;
	return block_bmap (bread (inode->i_dev, i, inode->i_sb->s_blocksize),
			   block & (addr_per_block - 1));
}

static struct buffer_head * inode_getblk (struct inode * inode, int nr,
					  int create, int new_block, int * err)
{
	int tmp, goal = 0;
	unsigned long * p;
	struct buffer_head * result;
	int blocks = inode->i_sb->s_blocksize / 512;

	p = inode->u.ext2_i.i_data + nr;
repeat:
	tmp = *p;
	if (tmp) {
		result = getblk (inode->i_dev, tmp, inode->i_sb->s_blocksize);
		if (tmp == *p)
			return result;
		brelse (result);
		goto repeat;
	}
	if (!create || new_block >= 
	    (current->rlim[RLIMIT_FSIZE].rlim_cur >>
	     EXT2_BLOCK_SIZE_BITS(inode->i_sb))) {
		*err = -EFBIG;
		return NULL;
	}
	if (inode->u.ext2_i.i_next_alloc_block == new_block)
		goal = inode->u.ext2_i.i_next_alloc_goal;

	ext2_debug ("hint = %d,", goal);

	if (!goal) {
		for (tmp = nr - 1; tmp >= 0; tmp--) {
			if (inode->u.ext2_i.i_data[tmp]) {
				goal = inode->u.ext2_i.i_data[tmp];
				break;
			}
		}
		if (!goal)
			goal = (inode->u.ext2_i.i_block_group * 
				EXT2_BLOCKS_PER_GROUP(inode->i_sb)) +
			       inode->i_sb->u.ext2_sb.s_es->s_first_data_block;
	}

	ext2_debug ("goal = %d.\n", goal);

	tmp = ext2_alloc_block (inode, goal);
	if (!tmp)
		return NULL;
	result = getblk (inode->i_dev, tmp, inode->i_sb->s_blocksize);
	if (*p) {
		ext2_free_blocks (inode->i_sb, tmp, 1);
		brelse (result);
		goto repeat;
	}
	*p = tmp;
	inode->u.ext2_i.i_next_alloc_block = new_block;
	inode->u.ext2_i.i_next_alloc_goal = tmp;
	inode->i_ctime = CURRENT_TIME;
	inode->i_blocks += blocks;
	if (IS_SYNC(inode))
		ext2_sync_inode (inode);
	else
		inode->i_dirt = 1;
	return result;
}

static struct buffer_head * block_getblk (struct inode * inode,
					  struct buffer_head * bh, int nr,
					  int create, int blocksize, 
					  int new_block, int * err)
{
	int tmp, goal = 0;
	unsigned long * p;
	struct buffer_head * result;
	int blocks = inode->i_sb->s_blocksize / 512;

	if (!bh)
		return NULL;
	if (!bh->b_uptodate) {
		ll_rw_block (READ, 1, &bh);
		wait_on_buffer (bh);
		if (!bh->b_uptodate) {
			brelse (bh);
			return NULL;
		}
	}
	p = (unsigned long *) bh->b_data + nr;
repeat:
	tmp = *p;
	if (tmp) {
		result = getblk (bh->b_dev, tmp, blocksize);
		if (tmp == *p) {
			brelse (bh);
			return result;
		}
		brelse (result);
		goto repeat;
	}
	if (!create || new_block >= 
	    (current->rlim[RLIMIT_FSIZE].rlim_cur >> 
	     EXT2_BLOCK_SIZE_BITS(inode->i_sb))) {
		brelse (bh);
		*err = -EFBIG;
		return NULL;
	}
	if (inode->u.ext2_i.i_next_alloc_block == new_block)