text: // SPDX-License-Identifier: GPL-2.0
  /*
   *  linux/fs/pxt4/bitmap.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)
   */
  
  #include <linux/buffer_head.h>
  #include "pxt4.h"
  
  unsigned int pxt4_count_free(char *bitmap, unsigned int numchars)
  {
  	return numchars * BITS_PER_BYTE - memweight(bitmap, numchars);
  }
  
  int pxt4_inode_bitmap_csum_verify(struct super_block *sb, pxt4_group_t group,
  				  struct pxt4_group_desc *gdp,
  				  struct buffer_head *bh, int sz)
  {
  	__u32 hi;
  	__u32 provided, calculated;
  	struct pxt4_sb_info *sbi = PXT4_SB(sb);
  
  	if (!pxt4_has_metadata_csum(sb))
  		return 1;
  
  	provided = le16_to_cpu(gdp->bg_inode_bitmap_csum_lo);
  	calculated = pxt4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  	if (sbi->s_desc_size >= PXT4_BG_INODE_BITMAP_CSUM_HI_END) {
  		hi = le16_to_cpu(gdp->bg_inode_bitmap_csum_hi);
  		provided |= (hi << 16);
  	} else
  		calculated &= 0xFFFF;
  
  	return provided == calculated;
  }
  
  void pxt4_inode_bitmap_csum_set(struct super_block *sb, pxt4_group_t group,
  				struct pxt4_group_desc *gdp,
  				struct buffer_head *bh, int sz)
  {
  	__u32 csum;
  	struct pxt4_sb_info *sbi = PXT4_SB(sb);
  
  	if (!pxt4_has_metadata_csum(sb))
  		return;
  
  	csum = pxt4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  	gdp->bg_inode_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
  	if (sbi->s_desc_size >= PXT4_BG_INODE_BITMAP_CSUM_HI_END)
  		gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
  }
  
  int pxt4_block_bitmap_csum_verify(struct super_block *sb, pxt4_group_t group,
  				  struct pxt4_group_desc *gdp,
  				  struct buffer_head *bh)
  {
  	__u32 hi;
  	__u32 provided, calculated;
  	struct pxt4_sb_info *sbi = PXT4_SB(sb);
  	int sz = PXT4_CLUSTERS_PER_GROUP(sb) / 8;
  
  	if (!pxt4_has_metadata_csum(sb))
  		return 1;
  
  	provided = le16_to_cpu(gdp->bg_block_bitmap_csum_lo);
  	calculated = pxt4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  	if (sbi->s_desc_size >= PXT4_BG_BLOCK_BITMAP_CSUM_HI_END) {
  		hi = le16_to_cpu(gdp->bg_block_bitmap_csum_hi);
  		provided |= (hi << 16);
  	} else
  		calculated &= 0xFFFF;
  
  	if (provided == calculated)
  		return 1;
  
  	return 0;
  }
  
  void pxt4_block_bitmap_csum_set(struct super_block *sb, pxt4_group_t group,
  				struct pxt4_group_desc *gdp,
  				struct buffer_head *bh)
  {
  	int sz = PXT4_CLUSTERS_PER_GROUP(sb) / 8;
  	__u32 csum;
  	struct pxt4_sb_info *sbi = PXT4_SB(sb);
  
  	if (!pxt4_has_metadata_csum(sb))
  		return;
  
  	csum = pxt4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  	gdp->bg_block_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
  	if (sbi->s_desc_size >= PXT4_BG_BLOCK_BITMAP_CSUM_HI_END)
  		gdp->bg_block_bitmap_csum_hi = cpu_to_le16(csum >> 16);
  }
  