/*
* linux/fs/ext2/balloc.c
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card (card@masi.ibp.fr)
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller (davem@caip.rutgers.edu), 1995
*/
#include "ext2.h"
#include <linux/quotaops.h>
#include <linux/sched.h>
#include <linux/buffer_head.h>
#include <linux/capability.h>
/*
* balloc.c contains the blocks allocation and deallocation routines
*/
/*
* The free blocks 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_fill_super).
*/
#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
unsigned int block_group,
struct buffer_head ** bh)
{
unsigned long group_desc;
unsigned long offset;
struct ext2_group_desc * desc;
struct ext2_sb_info *sbi = EXT2_SB(sb);
if (block_group >= sbi->s_groups_count) {
ext2_error (sb, "ext2_get_group_desc",
"block_group >= groups_count - "
"block_group = %d, groups_count = %lu",
block_group, sbi->s_groups_count);
return NULL;
}
group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
