自学教程：C++ EXT2_DESC_PER_BLOCK函数代码示例

struct ext2_group_desc *get_group_desc(struct mount *mp, unsigned int block_group,	       struct buf **bh){	struct ext2_sb_info *sb = VFSTOEXT2(mp)->um_e2fs;	unsigned long group_desc;	unsigned long desc;	struct ext2_group_desc *gdp;	if (block_group >= sb->s_groups_count)		panic ("get_group_desc: "			    "block_group >= groups_count - "			    "block_group = %d, groups_count = %lu",			    block_group, sb->s_groups_count);	group_desc = block_group / EXT2_DESC_PER_BLOCK(sb);	desc = block_group % EXT2_DESC_PER_BLOCK(sb);	if (!sb->s_group_desc[group_desc])		panic ( "get_group_desc:"			    "Group descriptor not loaded - "			    "block_group = %d, group_desc = %lu, desc = %lu",			     block_group, group_desc, desc);	gdp = (struct ext2_group_desc *)		sb->s_group_desc[group_desc]->b_data;	if (bh)		*bh = sb->s_group_desc[group_desc];	return gdp + desc;}

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 - "			    "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 - "			    "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;}

int op_statfs (const char *path, struct statvfs *buf){	unsigned long long i;	unsigned long long s_gdb_count = 0;	unsigned long long s_groups_count = 0;	unsigned long long s_itb_per_group = 0;	unsigned long long s_overhead_last = 0;	unsigned long long s_inodes_per_block = 0;	ext2_filsys e2fs;	FUSE_EXT2_LOCK;	e2fs	= current_ext2fs();	debugf("enter");	memset(buf, 0, sizeof(struct statvfs));	if (e2fs->super->s_default_mount_opts & EXT2_MOUNT_MINIX_DF) {		s_overhead_last = 0;	} else {		s_overhead_last = e2fs->super->s_first_data_block;		s_groups_count = ((EXT2_BLOCKS_COUNT(e2fs->super) - e2fs->super->s_first_data_block - 1) / e2fs->super->s_blocks_per_group) + 1;		s_gdb_count = (s_groups_count + EXT2_DESC_PER_BLOCK(e2fs->super) - 1) / EXT2_DESC_PER_BLOCK(e2fs->super);		for (i = 0; i < s_groups_count; i++) {			s_overhead_last += ext2_bg_has_super(e2fs, i) + ((ext2_bg_num_gdb(e2fs, i) == 0) ? 0 : s_gdb_count);		}		s_inodes_per_block = EXT2_BLOCK_SIZE(e2fs->super) / EXT2_INODE_SIZE(e2fs->super);		s_itb_per_group = e2fs->super->s_inodes_per_group / s_inodes_per_block;		s_overhead_last += (s_groups_count * (2 +  s_itb_per_group));	}	buf->f_bsize = EXT2_BLOCK_SIZE(e2fs->super);	buf->f_frsize = /*EXT2_FRAG_SIZE(e2fs->super);*/ buf->f_bsize;	buf->f_blocks = EXT2_BLOCKS_COUNT(e2fs->super) - s_overhead_last;	buf->f_bfree = EXT2_FBLOCKS_COUNT(e2fs->super);	if (EXT2_FBLOCKS_COUNT(e2fs->super) < EXT2_RBLOCKS_COUNT(e2fs->super)) {		buf->f_bavail = 0;	} else {		buf->f_bavail = EXT2_FBLOCKS_COUNT(e2fs->super) - EXT2_RBLOCKS_COUNT(e2fs->super);	}	buf->f_files = e2fs->super->s_inodes_count;	buf->f_ffree = e2fs->super->s_free_inodes_count;	buf->f_favail = e2fs->super->s_free_inodes_count;	buf->f_namemax = EXT2_NAME_LEN;	debugf("leave");	FUSE_EXT2_UNLOCK;	return 0;}

/* * ext2fs_super_and_bgd_loc2() * @fs:			ext2 fs pointer * @group		given block group * @ret_super_blk:	if !NULL, returns super block location * @ret_old_desc_blk:	if !NULL, returns location of the old block *			group descriptor * @ret_new_desc_blk:	if !NULL, returns location of meta_bg block *			group descriptor * @ret_used_blks:	if !NULL, returns number of blocks used by *			super block and group_descriptors. * * Returns errcode_t of 0 */errcode_t ext2fs_super_and_bgd_loc2(ext2_filsys fs,					   dgrp_t group,					   blk64_t *ret_super_blk,					   blk64_t *ret_old_desc_blk,					   blk64_t *ret_new_desc_blk,					   blk_t *ret_used_blks){	blk64_t	group_block, super_blk = 0, old_desc_blk = 0, new_desc_blk = 0;	unsigned int meta_bg, meta_bg_size;	blk_t	numblocks = 0;	blk64_t old_desc_blocks;	int	has_super;	group_block = ext2fs_group_first_block2(fs, group);	if (group_block == 0 && fs->blocksize == 1024)		group_block = 1; /* Deal with 1024 blocksize && bigalloc */	if (ext2fs_has_feature_meta_bg(fs->super))		old_desc_blocks = fs->super->s_first_meta_bg;	else		old_desc_blocks =			fs->desc_blocks + fs->super->s_reserved_gdt_blocks;	has_super = ext2fs_bg_has_super(fs, group);	if (has_super) {		super_blk = group_block;		numblocks++;	}	meta_bg_size = EXT2_DESC_PER_BLOCK(fs->super);	meta_bg = group / meta_bg_size;	if (!ext2fs_has_feature_meta_bg(fs->super) ||	    (meta_bg < fs->super->s_first_meta_bg)) {		if (has_super) {			old_desc_blk = group_block + 1;			numblocks += old_desc_blocks;		}	} else {		if (((group % meta_bg_size) == 0) ||		    ((group % meta_bg_size) == 1) ||		    ((group % meta_bg_size) == (meta_bg_size-1))) {			if (has_super)				has_super = 1;			new_desc_blk = group_block + has_super;			numblocks++;		}	}	if (ret_super_blk)		*ret_super_blk = super_blk;	if (ret_old_desc_blk)		*ret_old_desc_blk = old_desc_blk;	if (ret_new_desc_blk)		*ret_new_desc_blk = new_desc_blk;	if (ret_used_blks)		*ret_used_blks = numblocks;	return 0;}

/* * Calculate the number of GDT blocks to reserve for online filesystem growth. * The absolute maximum number of GDT blocks we can reserve is determined by * the number of block pointers that can fit into a single block. */static unsigned int calc_reserved_gdt_blocks(ext2_filsys fs){	struct ext2_super_block *sb = fs->super;	unsigned long bpg = sb->s_blocks_per_group;	unsigned int gdpb = EXT2_DESC_PER_BLOCK(sb);	unsigned long max_blocks = 0xffffffff;	unsigned long rsv_groups;	unsigned int rsv_gdb;	/* We set it at 1024x the current filesystem size, or	 * the upper block count limit (2^32), whichever is lower.	 */	if (ext2fs_blocks_count(sb) < max_blocks / 1024)		max_blocks = ext2fs_blocks_count(sb) * 1024;	/*	 * ext2fs_div64_ceil() is unnecessary because max_blocks is	 * max _GDT_ blocks, which is limited to 32 bits.	 */	rsv_groups = ext2fs_div_ceil(max_blocks - sb->s_first_data_block, bpg);	rsv_gdb = ext2fs_div_ceil(rsv_groups, gdpb) - fs->desc_blocks;	if (rsv_gdb > EXT2_ADDR_PER_BLOCK(sb))		rsv_gdb = EXT2_ADDR_PER_BLOCK(sb);#ifdef RES_GDT_DEBUG	printf("max_blocks %lu, rsv_groups = %lu, rsv_gdb = %u/n",	       max_blocks, rsv_groups, rsv_gdb);#endif	return rsv_gdb;}

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);	offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);	if (!sbi->s_group_desc[group_desc]) {		ext2_error (sb, "ext2_get_group_desc",			    "Group descriptor not loaded - "			    "block_group = %d, group_desc = %lu, desc = %lu",			     block_group, group_desc, offset);		return NULL;	}	desc = (struct ext2_group_desc *) sbi->s_group_desc[group_desc]->b_data;	if (bh)		*bh = sbi->s_group_desc[group_desc];	return desc + offset;}

/* * ext2fs_super_and_bgd_loc2() * @fs:			ext2 fs pointer * @group		given block group * @ret_super_blk:	if !NULL, returns super block location * @ret_old_desc_blk:	if !NULL, returns location of the old block *			group descriptor * @ret_new_desc_blk:	if !NULL, returns location of meta_bg block *			group descriptor * @ret_used_blks:	if !NULL, returns number of blocks used by *			super block and group_descriptors. * * Returns errcode_t of 0 */errcode_t ext2fs_super_and_bgd_loc2(ext2_filsys fs,					   dgrp_t group,					   blk64_t *ret_super_blk,					   blk64_t *ret_old_desc_blk,					   blk64_t *ret_new_desc_blk,					   blk_t *ret_used_blks){	blk64_t	group_block, super_blk = 0, old_desc_blk = 0, new_desc_blk = 0;	unsigned int meta_bg, meta_bg_size;	blk_t	numblocks = 0;	blk64_t old_desc_blocks;	int	has_super;	group_block = ext2fs_group_first_block2(fs, group);	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)		old_desc_blocks = fs->super->s_first_meta_bg;	else		old_desc_blocks =			fs->desc_blocks + fs->super->s_reserved_gdt_blocks;	has_super = ext2fs_bg_has_super(fs, group);	if (has_super) {		super_blk = group_block;		numblocks++;	}	meta_bg_size = EXT2_DESC_PER_BLOCK(fs->super);	meta_bg = group / meta_bg_size;	if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||	    (meta_bg < fs->super->s_first_meta_bg)) {		if (has_super) {			old_desc_blk = group_block + 1;			numblocks += old_desc_blocks;		}	} else {		if (((group % meta_bg_size) == 0) ||		    ((group % meta_bg_size) == 1) ||		    ((group % meta_bg_size) == (meta_bg_size-1))) {			if (has_super)				has_super = 1;			new_desc_blk = group_block + has_super;			numblocks++;		}	}	if (ret_super_blk)		*ret_super_blk = super_blk;	if (ret_old_desc_blk)		*ret_old_desc_blk = old_desc_blk;	if (ret_new_desc_blk)		*ret_new_desc_blk = new_desc_blk;	if (ret_used_blks)		*ret_used_blks = numblocks;	return 0;}

static int ext2_check_descriptors (struct super_block * sb){	int i;	int desc_block = 0;	struct ext2_sb_info *sbi = EXT2_SB(sb);	struct ext2_group_desc * gdp = NULL;	ext2_debug ("Checking group descriptors");	for (i = 0; i < sbi->s_groups_count; i++)	{		ext2_fsblk_t first_block = ext2_group_first_block_no(sb, i);		ext2_fsblk_t last_block;		if (i == sbi->s_groups_count - 1)			last_block = le32_to_cpu(sbi->s_es->s_blocks_count) - 1;		else			last_block = first_block +				(EXT2_BLOCKS_PER_GROUP(sb) - 1);		if ((i % EXT2_DESC_PER_BLOCK(sb)) == 0)			gdp = (struct ext2_group_desc *) sbi->s_group_desc[desc_block++]->b_data;		if (le32_to_cpu(gdp->bg_block_bitmap) < first_block ||		    le32_to_cpu(gdp->bg_block_bitmap) > last_block)		{			ext2_error (sb, "ext2_check_descriptors",				    "Block bitmap for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_block_bitmap));			return 0;		}		if (le32_to_cpu(gdp->bg_inode_bitmap) < first_block ||		    le32_to_cpu(gdp->bg_inode_bitmap) > last_block)		{			ext2_error (sb, "ext2_check_descriptors",				    "Inode bitmap for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_inode_bitmap));			return 0;		}		if (le32_to_cpu(gdp->bg_inode_table) < first_block ||		    le32_to_cpu(gdp->bg_inode_table) + sbi->s_itb_per_group - 1 >		    last_block)		{			ext2_error (sb, "ext2_check_descriptors",				    "Inode table for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_inode_table));			return 0;		}		gdp++;	}	return 1;}

void ext2_get_group_desc(ext2_VOLUME* volume,		   int group_id, struct ext2_group_desc *gdp){	unsigned int block, offset;	struct ext2_group_desc *le_gdp;	block = 1 + volume->super->s_first_data_block;	block += group_id / EXT2_DESC_PER_BLOCK(volume->super);	ext2_read_block(volume,  block);	offset = group_id % EXT2_DESC_PER_BLOCK(volume->super);	offset *= sizeof(*gdp);	le_gdp = (struct ext2_group_desc *)(volume->buffer + offset);	gdp->bg_block_bitmap = __le32_to_cpu(le_gdp->bg_block_bitmap);	gdp->bg_inode_bitmap = __le32_to_cpu(le_gdp->bg_inode_bitmap);	gdp->bg_inode_table = __le32_to_cpu(le_gdp->bg_inode_table);	gdp->bg_free_blocks_count = __le16_to_cpu(le_gdp->bg_free_blocks_count);	gdp->bg_free_inodes_count = __le16_to_cpu(le_gdp->bg_free_inodes_count);	gdp->bg_used_dirs_count = __le16_to_cpu(le_gdp->bg_used_dirs_count);}

/* * Checks that the data in the descriptor blocks make sense. */intext2_check_descriptors(struct ext2_sb_info *sb){        int i;        int desc_block = 0;        unsigned long block = sb->s_es->s_first_data_block;        struct ext2_group_desc *gdp = NULL;        /* ext2_debug ("Checking group descriptors"); */        for (i = 0; i < sb->s_groups_count; i++)        {		/* examine next descriptor block */                if ((i % EXT2_DESC_PER_BLOCK(sb)) == 0)                        gdp = (struct ext2_group_desc *)				sb->s_group_desc[desc_block++]->b_data;                if (gdp->bg_block_bitmap < block ||                    gdp->bg_block_bitmap >= block + EXT2_BLOCKS_PER_GROUP(sb))                {                        kprintf ("ext2_check_descriptors: "                                    "Block bitmap for group %d"                                    " not in group (block %lu)!/n",                                    i, (unsigned long) gdp->bg_block_bitmap);                        return 0;                }                if (gdp->bg_inode_bitmap < block ||                    gdp->bg_inode_bitmap >= block + EXT2_BLOCKS_PER_GROUP(sb))                {                        kprintf ("ext2_check_descriptors: "                                    "Inode bitmap for group %d"                                    " not in group (block %lu)!/n",                                    i, (unsigned long) gdp->bg_inode_bitmap);                        return 0;                }                if (gdp->bg_inode_table < block ||                    gdp->bg_inode_table + sb->s_itb_per_group >=                    block + EXT2_BLOCKS_PER_GROUP(sb))                {                        kprintf ("ext2_check_descriptors: "                                    "Inode table for group %d"                                    " not in group (block %lu)!/n",                                    i, (unsigned long) gdp->bg_inode_table);                        return 0;                }                block += EXT2_BLOCKS_PER_GROUP(sb);                gdp++;        }        return 1;}

blk64_t ext2fs_descriptor_block_loc2(ext2_filsys fs, blk64_t group_block,				     dgrp_t i){	int	bg;	int	has_super = 0, group_zero_adjust = 0;	blk64_t	ret_blk;	/*	 * On a bigalloc FS with 1K blocks, block 0 is reserved for non-ext4	 * stuff, so adjust for that if we're being asked for group 0.	 */	if (i == 0 && fs->blocksize == 1024 && EXT2FS_CLUSTER_RATIO(fs) > 1)		group_zero_adjust = 1;	if (!ext2fs_has_feature_meta_bg(fs->super) ||	    (i < fs->super->s_first_meta_bg))		return group_block + i + 1 + group_zero_adjust;	bg = EXT2_DESC_PER_BLOCK(fs->super) * i;	if (ext2fs_bg_has_super(fs, bg))		has_super = 1;	ret_blk = ext2fs_group_first_block2(fs, bg);	/*	 * If group_block is not the normal value, we're trying to use	 * the backup group descriptors and superblock --- so use the	 * alternate location of the second block group in the	 * metablock group.  Ideally we should be testing each bg	 * descriptor block individually for correctness, but we don't	 * have the infrastructure in place to do that.	 */	if (group_block != fs->super->s_first_data_block &&	    ((ret_blk + has_super + fs->super->s_blocks_per_group) <	     ext2fs_blocks_count(fs->super))) {		ret_blk += fs->super->s_blocks_per_group;		/*		 * If we're going to jump forward a block group, make sure		 * that we adjust has_super to account for the next group's		 * backup superblock (or lack thereof).		 */		if (ext2fs_bg_has_super(fs, bg + 1))			has_super = 1;		else			has_super = 0;	}	return ret_blk + has_super + group_zero_adjust;}

static int ext2_check_descriptors (struct super_block * sb){	int i;	int desc_block = 0;	unsigned long block = le32_to_cpu(sb->u.ext2_sb.s_es->s_first_data_block);	struct ext2_group_desc * gdp = NULL;	ext2_debug ("Checking group descriptors");	for (i = 0; i < sb->u.ext2_sb.s_groups_count; i++)	{		if ((i % EXT2_DESC_PER_BLOCK(sb)) == 0)			gdp = (struct ext2_group_desc *) sb->u.ext2_sb.s_group_desc[desc_block++]->b_data;		if (le32_to_cpu(gdp->bg_block_bitmap) < block ||		    le32_to_cpu(gdp->bg_block_bitmap) >= block + EXT2_BLOCKS_PER_GROUP(sb))		{			ext2_error (sb, "ext2_check_descriptors",				    "Block bitmap for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_block_bitmap));			return 0;		}		if (le32_to_cpu(gdp->bg_inode_bitmap) < block ||		    le32_to_cpu(gdp->bg_inode_bitmap) >= block + EXT2_BLOCKS_PER_GROUP(sb))		{			ext2_error (sb, "ext2_check_descriptors",				    "Inode bitmap for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_inode_bitmap));			return 0;		}		if (le32_to_cpu(gdp->bg_inode_table) < block ||		    le32_to_cpu(gdp->bg_inode_table) + sb->u.ext2_sb.s_itb_per_group >=		    block + EXT2_BLOCKS_PER_GROUP(sb))		{			ext2_error (sb, "ext2_check_descriptors",				    "Inode table for group %d"				    " not in group (block %lu)!",				    i, (unsigned long) le32_to_cpu(gdp->bg_inode_table));			return 0;		}		block += EXT2_BLOCKS_PER_GROUP(sb);		gdp++;	}	return 1;}

/* * This function returns the location of the superblock, block group * descriptors for a given block group.  It currently returns the * number of free blocks assuming that inode table and allocation * bitmaps will be in the group.  This is not necessarily the case * when the flex_bg feature is enabled, so callers should take care! * It was only really intended for use by mke2fs, and even there it's * not that useful. * * The ext2fs_super_and_bgd_loc2() function is 64-bit block number * capable and returns the number of blocks used by super block and * group descriptors. */int ext2fs_super_and_bgd_loc(ext2_filsys fs,			     dgrp_t group,			     blk_t *ret_super_blk,			     blk_t *ret_old_desc_blk,			     blk_t *ret_new_desc_blk,			     int *ret_meta_bg){	blk64_t ret_super_blk2;	blk64_t ret_old_desc_blk2;	blk64_t ret_new_desc_blk2;	blk_t ret_used_blks;	blk_t numblocks;	unsigned int meta_bg_size;	ext2fs_super_and_bgd_loc2(fs, group, &ret_super_blk2,					&ret_old_desc_blk2,					&ret_new_desc_blk2,					&ret_used_blks);	if (group == fs->group_desc_count-1) {		numblocks = (fs->super->s_blocks_count -			     fs->super->s_first_data_block) %			fs->super->s_blocks_per_group;		if (!numblocks)			numblocks = fs->super->s_blocks_per_group;	} else		numblocks = fs->super->s_blocks_per_group;	if (ret_super_blk)		*ret_super_blk = (blk_t)ret_super_blk2;	if (ret_old_desc_blk)		*ret_old_desc_blk = (blk_t)ret_old_desc_blk2;	if (ret_new_desc_blk)		*ret_new_desc_blk = (blk_t)ret_new_desc_blk2;	if (ret_meta_bg) {		meta_bg_size = EXT2_DESC_PER_BLOCK(fs->super);		*ret_meta_bg = group / meta_bg_size;	}	numblocks -= 2 + fs->inode_blocks_per_group + ret_used_blks;	return numblocks;}

static errcode_t adjust_fs_size(ext2_filsys fs, long long *new_size){    errcode_t	retval;    int    overhead = 0;    int    rem;    fs->super->s_blocks_count = (unsigned int)(*new_size / fs->blocksize);retry:    fs->group_desc_count = ext2fs_div_ceil(fs->super->s_blocks_count -			       fs->super->s_first_data_block, EXT2_BLOCKS_PER_GROUP(fs->super));    if (fs->group_desc_count == 0)        return EXT2_ET_TOOSMALL;    fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count, EXT2_DESC_PER_BLOCK(fs->super));    /*    * Overhead is the number of bookkeeping blocks per group.  It    * includes the superblock backup, the group descriptor    * backups, the inode bitmap, the block bitmap, and the inode    * table.    */    overhead = (int) (2 + fs->inode_blocks_per_group);    if (ext2fs_bg_has_super(fs, fs->group_desc_count - 1))        overhead += 1 + fs->desc_blocks + fs->super->s_reserved_gdt_blocks;    /*    * See if the last group is big enough to support the    * necessary data structures.  If not, we need to get rid of    * it.    */    rem = (fs->super->s_blocks_count - fs->super->s_first_data_block) % fs->super->s_blocks_per_group;    if ((fs->group_desc_count == 1) && rem && (rem < overhead))        return EXT2_ET_TOOSMALL;    if (rem && (rem < overhead+50)) {        fs->super->s_blocks_count -= rem;        goto retry;    }    *new_size = ((long long)fs->super->s_blocks_count * (long long)fs->blocksize);    return 0;}

/* * This function returns the location of the superblock, block group * descriptors for a given block group.  It currently returns the * number of free blocks assuming that inode table and allocation * bitmaps will be in the group.  This is not necessarily the case * when the flex_bg feature is enabled, so callers should take care! * It was only really intended for use by mke2fs, and even there it's * not that useful. * * The ext2fs_super_and_bgd_loc2() function is 64-bit block number * capable and returns the number of blocks used by super block and * group descriptors. */int ext2fs_super_and_bgd_loc(ext2_filsys fs,			     dgrp_t group,			     blk_t *ret_super_blk,			     blk_t *ret_old_desc_blk,			     blk_t *ret_new_desc_blk,			     int *ret_meta_bg){	blk64_t ret_super_blk2;	blk64_t ret_old_desc_blk2;	blk64_t ret_new_desc_blk2;	blk_t ret_used_blks;	blk_t numblocks;	unsigned int meta_bg_size;	ext2fs_super_and_bgd_loc2(fs, group, &ret_super_blk2,					&ret_old_desc_blk2,					&ret_new_desc_blk2,					&ret_used_blks);	numblocks = ext2fs_group_blocks_count(fs, group);	if (ret_super_blk)		*ret_super_blk = (blk_t)ret_super_blk2;	if (ret_old_desc_blk)		*ret_old_desc_blk = (blk_t)ret_old_desc_blk2;	if (ret_new_desc_blk)		*ret_new_desc_blk = (blk_t)ret_new_desc_blk2;	if (ret_meta_bg) {		meta_bg_size = EXT2_DESC_PER_BLOCK(fs->super);		*ret_meta_bg = group / meta_bg_size;	}	numblocks -= 2 + fs->inode_blocks_per_group + ret_used_blks;	return numblocks;}

//.........这里部分代码省略.........	/*	 * Check for feature set incompatibility	 */	if (!(flags & EXT2_FLAG_FORCE)) {		if (fs->super->s_feature_incompat &		    ~EXT2_LIB_FEATURE_INCOMPAT_SUPP) {			retval = EXT2_ET_UNSUPP_FEATURE;			goto cleanup;		}		if ((flags & EXT2_FLAG_RW) &&		    (fs->super->s_feature_ro_compat &		     ~EXT2_LIB_FEATURE_RO_COMPAT_SUPP)) {			retval = EXT2_ET_RO_UNSUPP_FEATURE;			goto cleanup;		}		if (!(flags & EXT2_FLAG_JOURNAL_DEV_OK) &&		    (fs->super->s_feature_incompat &		     EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)) {			retval = EXT2_ET_UNSUPP_FEATURE;			goto cleanup;		}	}		fs->blocksize = EXT2_BLOCK_SIZE(fs->super);	if (fs->blocksize == 0) {		retval = EXT2_ET_CORRUPT_SUPERBLOCK;		goto cleanup;	}	fs->fragsize = EXT2_FRAG_SIZE(fs->super);	fs->inode_blocks_per_group = ((fs->super->s_inodes_per_group *				       EXT2_INODE_SIZE(fs->super) +				       EXT2_BLOCK_SIZE(fs->super) - 1) /				      EXT2_BLOCK_SIZE(fs->super));	if (block_size) {		if (block_size != fs->blocksize) {			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;			goto cleanup;		}	}	/*	 * Set the blocksize to the filesystem's blocksize.	 */	io_channel_set_blksize(fs->io, fs->blocksize);	/*	 * If this is an external journal device, don't try to read	 * the group descriptors, because they're not there.	 */	if (fs->super->s_feature_incompat &	    EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {		fs->group_desc_count = 0;		*ret_fs = fs;		return 0;	}		/*	 * Read group descriptors	 */	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);	if (blocks_per_group == 0 ||	    blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||	    fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super)) {		retval = EXT2_ET_CORRUPT_SUPERBLOCK;		goto cleanup;	}	fs->group_desc_count = (fs->super->s_blocks_count -				fs->super->s_first_data_block +				blocks_per_group - 1) / blocks_per_group;	fs->desc_blocks = (fs->group_desc_count +			   EXT2_DESC_PER_BLOCK(fs->super) - 1)		/ EXT2_DESC_PER_BLOCK(fs->super);	retval = ext2fs_get_mem(fs->desc_blocks * fs->blocksize,				&fs->group_desc);	if (retval)		goto cleanup;	if (!group_block)		group_block = fs->super->s_first_data_block;	dest = (char *) fs->group_desc;	groups_per_block = fs->blocksize / sizeof(struct ext2_group_desc);	for (i=0 ; i < fs->desc_blocks; i++) {		blk = ext2fs_descriptor_block_loc(fs, group_block, i);		retval = io_channel_read_blk(fs->io, blk, 1, dest);		if (retval)			goto cleanup;#ifdef EXT2FS_ENABLE_SWAPFS		if (fs->flags & EXT2_FLAG_SWAP_BYTES) {			gdp = (struct ext2_group_desc *) dest;			for (j=0; j < groups_per_block; j++)				ext2fs_swap_group_desc(gdp++);		}#endif		dest += fs->blocksize;	}	*ret_fs = fs;	return 0;cleanup:	ext2fs_free(fs);	return retval;}

//.........这里部分代码省略.........	 * If this is an external journal device, don't write out the	 * block group descriptors or any of the backup superblocks	 */	if (ext2fs_has_feature_journal_dev(fs->super))		goto write_primary_superblock_only;	/*	 * Write out the master group descriptors, and the backup	 * superblocks and group descriptors.	 */	group_ptr = (char *) group_shadow;	if (ext2fs_has_feature_meta_bg(fs->super)) {		old_desc_blocks = fs->super->s_first_meta_bg;		if (old_desc_blocks > fs->desc_blocks)			old_desc_blocks = fs->desc_blocks;	} else		old_desc_blocks = fs->desc_blocks;	if (fs->progress_ops && fs->progress_ops->init)		(fs->progress_ops->init)(fs, &progress, NULL,					 fs->group_desc_count);	for (i = 0; i < fs->group_desc_count; i++) {		blk64_t	super_blk, old_desc_blk, new_desc_blk;		if (fs->progress_ops && fs->progress_ops->update)			(fs->progress_ops->update)(fs, &progress, i);		ext2fs_super_and_bgd_loc2(fs, i, &super_blk, &old_desc_blk,					 &new_desc_blk, 0);		if (!(fs->flags & EXT2_FLAG_MASTER_SB_ONLY) &&i && super_blk) {			retval = write_backup_super(fs, i, super_blk,						    super_shadow);			if (retval)				goto errout;		}		if (fs->flags & EXT2_FLAG_SUPER_ONLY)			continue;		if ((old_desc_blk) &&		    (!(fs->flags & EXT2_FLAG_MASTER_SB_ONLY) || (i == 0))) {			retval = io_channel_write_blk64(fs->io,			      old_desc_blk, old_desc_blocks, group_ptr);			if (retval)				goto errout;		}		if (new_desc_blk) {			int meta_bg = i / EXT2_DESC_PER_BLOCK(fs->super);			retval = io_channel_write_blk64(fs->io, new_desc_blk,				1, group_ptr + (meta_bg*fs->blocksize));			if (retval)				goto errout;		}	}	if (fs->progress_ops && fs->progress_ops->close)		(fs->progress_ops->close)(fs, &progress, NULL);write_primary_superblock_only:	/*	 * Write out master superblock.  This has to be done	 * separately, since it is located at a fixed location	 * (SUPERBLOCK_OFFSET).  We flush all other pending changes	 * out to disk first, just to avoid a race condition with an	 * insy-tinsy window....	 */	fs->super->s_block_group_nr = 0;	fs->super->s_state = fs_state;	fs->super->s_feature_incompat = feature_incompat;#ifdef WORDS_BIGENDIAN	*super_shadow = *fs->super;	ext2fs_swap_super(super_shadow);#endif	retval = ext2fs_superblock_csum_set(fs, super_shadow);	if (retval)		return retval;	if (!(flags & EXT2_FLAG_FLUSH_NO_SYNC))		retval = io_channel_flush(fs->io);	retval = write_primary_superblock(fs, super_shadow);	if (retval)		goto errout;	fs->flags &= ~EXT2_FLAG_DIRTY;	if (!(flags & EXT2_FLAG_FLUSH_NO_SYNC))		retval = io_channel_flush(fs->io);errout:	fs->super->s_state = fs_state;#ifdef WORDS_BIGENDIAN	if (super_shadow)		ext2fs_free_mem(&super_shadow);	if (group_shadow)		ext2fs_free_mem(&group_shadow);#endif	return retval;}

/* * This function returns the location of the superblock, block group * descriptors for a given block group.  It currently returns the * number of free blocks assuming that inode table and allocation * bitmaps will be in the group.  This is not necessarily the case * when the flex_bg feature is enabled, so callers should take care! * It was only really intended for use by mke2fs, and even there it's * not that useful.  In the future, when we redo this function for * 64-bit block numbers, we should probably return the number of * blocks used by the super block and group descriptors instead. * * See also the comment for ext2fs_reserve_super_and_bgd() */int ext2fs_super_and_bgd_loc(ext2_filsys fs,			     dgrp_t group,			     blk_t *ret_super_blk,			     blk_t *ret_old_desc_blk,			     blk_t *ret_new_desc_blk,			     int *ret_meta_bg){	blk_t	group_block, super_blk = 0, old_desc_blk = 0, new_desc_blk = 0;	unsigned int meta_bg, meta_bg_size;	blk_t	numblocks, old_desc_blocks;	int	has_super;	group_block = ext2fs_group_first_block(fs, group);	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)		old_desc_blocks = fs->super->s_first_meta_bg;	else		old_desc_blocks =			fs->desc_blocks + fs->super->s_reserved_gdt_blocks;	if (group == fs->group_desc_count-1) {		numblocks = (fs->super->s_blocks_count -			     fs->super->s_first_data_block) %			fs->super->s_blocks_per_group;		if (!numblocks)			numblocks = fs->super->s_blocks_per_group;	} else		numblocks = fs->super->s_blocks_per_group;	has_super = ext2fs_bg_has_super(fs, group);	if (has_super) {		super_blk = group_block;		numblocks--;	}	meta_bg_size = EXT2_DESC_PER_BLOCK(fs->super);	meta_bg = group / meta_bg_size;	if (!(fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG) ||	    (meta_bg < fs->super->s_first_meta_bg)) {		if (has_super) {			old_desc_blk = group_block + 1;			numblocks -= old_desc_blocks;		}	} else {		if (((group % meta_bg_size) == 0) ||		    ((group % meta_bg_size) == 1) ||		    ((group % meta_bg_size) == (meta_bg_size-1))) {			if (has_super)				has_super = 1;			new_desc_blk = group_block + has_super;			numblocks--;		}	}	numblocks -= 2 + fs->inode_blocks_per_group;	if (ret_super_blk)		*ret_super_blk = super_blk;	if (ret_old_desc_blk)		*ret_old_desc_blk = old_desc_blk;	if (ret_new_desc_blk)		*ret_new_desc_blk = new_desc_blk;	if (ret_meta_bg)		*ret_meta_bg = meta_bg;	return (numblocks);}

//.........这里部分代码省略.........		    !is_power_of_2(sbi->s_inode_size) ||		    (sbi->s_inode_size > blocksize)) {			ext2_msg(sb, KERN_ERR,				"error: unsupported inode size: %d",				sbi->s_inode_size);			goto failed_mount;		}	}	sbi->s_frag_size = EXT2_MIN_FRAG_SIZE <<				   le32_to_cpu(es->s_log_frag_size);	if (sbi->s_frag_size == 0)		goto cantfind_ext2;	sbi->s_frags_per_block = sb->s_blocksize / sbi->s_frag_size;	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);	sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);	if (EXT2_INODE_SIZE(sb) == 0)		goto cantfind_ext2;	sbi->s_inodes_per_block = sb->s_blocksize / EXT2_INODE_SIZE(sb);	if (sbi->s_inodes_per_block == 0 || sbi->s_inodes_per_group == 0)		goto cantfind_ext2;	sbi->s_itb_per_group = sbi->s_inodes_per_group /					sbi->s_inodes_per_block;	sbi->s_desc_per_block = sb->s_blocksize /					sizeof (struct ext2_group_desc);	sbi->s_sbh = bh;	sbi->s_mount_state = le16_to_cpu(es->s_state);	sbi->s_addr_per_block_bits =		ilog2 (EXT2_ADDR_PER_BLOCK(sb));	sbi->s_desc_per_block_bits =		ilog2 (EXT2_DESC_PER_BLOCK(sb));	if (sb->s_magic != EXT2_SUPER_MAGIC)		goto cantfind_ext2;	if (sb->s_blocksize != bh->b_size) {		if (!silent)			ext2_msg(sb, KERN_ERR, "error: unsupported blocksize");		goto failed_mount;	}	if (sb->s_blocksize != sbi->s_frag_size) {		ext2_msg(sb, KERN_ERR,			"error: fragsize %lu != blocksize %lu"			"(not supported yet)",			sbi->s_frag_size, sb->s_blocksize);		goto failed_mount;	}	if (sbi->s_blocks_per_group > sb->s_blocksize * 8) {		ext2_msg(sb, KERN_ERR,			"error: #blocks per group too big: %lu",			sbi->s_blocks_per_group);		goto failed_mount;	}	if (sbi->s_frags_per_group > sb->s_blocksize * 8) {		ext2_msg(sb, KERN_ERR,			"error: #fragments per group too big: %lu",			sbi->s_frags_per_group);		goto failed_mount;	}	if (sbi->s_inodes_per_group > sb->s_blocksize * 8) {		ext2_msg(sb, KERN_ERR,

//.........这里部分代码省略.........		}	}	sb->u.ext2_sb.s_frag_size = EXT2_MIN_FRAG_SIZE <<				   es->s_log_frag_size;	if (sb->u.ext2_sb.s_frag_size)		sb->u.ext2_sb.s_frags_per_block = sb->s_blocksize /						  sb->u.ext2_sb.s_frag_size;	else		sb->s_magic = 0;	sb->u.ext2_sb.s_blocks_per_group = es->s_blocks_per_group;	sb->u.ext2_sb.s_frags_per_group = es->s_frags_per_group;	sb->u.ext2_sb.s_inodes_per_group = es->s_inodes_per_group;	sb->u.ext2_sb.s_inodes_per_block = sb->s_blocksize /					   EXT2_INODE_SIZE(sb);	sb->u.ext2_sb.s_itb_per_group = sb->u.ext2_sb.s_inodes_per_group /				        sb->u.ext2_sb.s_inodes_per_block;	sb->u.ext2_sb.s_desc_per_block = sb->s_blocksize /					 sizeof (struct ext2_group_desc);	sb->u.ext2_sb.s_sbh = bh;	if (resuid != EXT2_DEF_RESUID)		sb->u.ext2_sb.s_resuid = resuid;	else		sb->u.ext2_sb.s_resuid = es->s_def_resuid;	if (resgid != EXT2_DEF_RESGID)		sb->u.ext2_sb.s_resgid = resgid;	else		sb->u.ext2_sb.s_resgid = es->s_def_resgid;	sb->u.ext2_sb.s_mount_state = es->s_state;	sb->u.ext2_sb.s_rename_lock = 0;	sb->u.ext2_sb.s_rename_wait = NULL;	sb->u.ext2_sb.s_addr_per_block_bits =		log2 (EXT2_ADDR_PER_BLOCK(sb));	sb->u.ext2_sb.s_desc_per_block_bits =		log2 (EXT2_DESC_PER_BLOCK(sb));	if (sb->s_magic != EXT2_SUPER_MAGIC) {		if (!silent)			printk ("VFS: Can't find an ext2 filesystem on dev "				"%s./n",				kdevname(dev));		goto failed_mount;	}	if (sb->s_blocksize != bh->b_size) {		if (!silent)			printk ("VFS: Unsupported blocksize on dev "				"%s./n", kdevname(dev));		goto failed_mount;	}	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)/n",			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);		goto failed_mount;	}	if (sb->u.ext2_sb.s_blocks_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #blocks per group too big: %lu/n",			sb->u.ext2_sb.s_blocks_per_group);		goto failed_mount;	}	if (sb->u.ext2_sb.s_frags_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #fragments per group too big: %lu/n",			sb->u.ext2_sb.s_frags_per_group);		goto failed_mount;	}	if (sb->u.ext2_sb.s_inodes_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #inodes per group too big: %lu/n",

//.........这里部分代码省略.........	}#endif	if (sb->s_magic != EXT2_SUPER_MAGIC) {		sb->s_dev = 0;		unlock_super (sb);		brelse (bh);		if (!silent)			printk ("VFS: Can't find an ext2 filesystem on dev %d/%d./n",				MAJOR(dev), MINOR(dev));		return NULL;	}	if (sb->s_blocksize != bh->b_size) {		sb->s_dev = 0;		unlock_super (sb);		brelse (bh);		if (!silent)			printk ("VFS: Unsupported blocksize on dev 0x%04x./n",				dev);		return NULL;	}	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {		sb->s_dev = 0;		unlock_super (sb);		brelse (bh);		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)/n",			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);		return NULL;	}	sb->u.ext2_sb.s_groups_count = (es->s_blocks_count -				        es->s_first_data_block +				       EXT2_BLOCKS_PER_GROUP(sb) - 1) /				       EXT2_BLOCKS_PER_GROUP(sb);	for (i = 0; i < EXT2_MAX_GROUP_DESC; i++)		sb->u.ext2_sb.s_group_desc[i] = NULL;	bh_count = (sb->u.ext2_sb.s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /		   EXT2_DESC_PER_BLOCK(sb);	if (bh_count > EXT2_MAX_GROUP_DESC) {		sb->s_dev = 0;		unlock_super (sb);		brelse (bh);		printk ("EXT2-fs: file system is too big/n");		return NULL;	}	for (i = 0; i < bh_count; i++) {		sb->u.ext2_sb.s_group_desc[i] = bread (dev, logic_sb_block + i + 1,						       sb->s_blocksize);		if (!sb->u.ext2_sb.s_group_desc[i]) {			sb->s_dev = 0;			unlock_super (sb);			for (j = 0; j < i; j++)				brelse (sb->u.ext2_sb.s_group_desc[j]);			brelse (bh);			printk ("EXT2-fs: unable to read group descriptors/n");			return NULL;		}	}	if (!ext2_check_descriptors (sb)) {		sb->s_dev = 0;		unlock_super (sb);		for (j = 0; j < i; j++)			brelse (sb->u.ext2_sb.s_group_desc[j]);		brelse (bh);		printk ("EXT2-fs: group descriptors corrupted !/n");		return NULL;	}	for (i = 0; i < EXT2_MAX_GROUP_LOADED; i++) {		sb->u.ext2_sb.s_inode_bitmap_number[i] = 0;		sb->u.ext2_sb.s_inode_bitmap[i] = NULL;		sb->u.ext2_sb.s_block_bitmap_number[i] = 0;		sb->u.ext2_sb.s_block_bitmap[i] = NULL;	}	sb->u.ext2_sb.s_loaded_inode_bitmaps = 0;	sb->u.ext2_sb.s_loaded_block_bitmaps = 0;	unlock_super (sb);	/*	 * set up enough so that it can read an inode	 */	sb->s_dev = dev;	sb->s_op = &ext2_sops;	if (!(sb->s_mounted = iget (sb, EXT2_ROOT_INO))) {		sb->s_dev = 0;		for (i = 0; i < EXT2_MAX_GROUP_DESC; i++)			if (sb->u.ext2_sb.s_group_desc[i])				brelse (sb->u.ext2_sb.s_group_desc[i]);		brelse (bh);		printk ("EXT2-fs: get root inode failed/n");		return NULL;	}#ifdef EXT2FS_PRE_02B_COMPAT	if (fs_converted) {		for (i = 0; i < bh_count; i++)			sb->u.ext2_sb.s_group_desc[i]->b_dirt = 1;		sb->s_dirt = 1;	}#endif	ext2_setup_super (sb, es);	return sb;}

//.........这里部分代码省略.........				sbi->s_inode_size);			goto failed_mount;		}	}	sb->u.ext2_sb.s_frag_size = EXT2_MIN_FRAG_SIZE <<				   le32_to_cpu(es->s_log_frag_size);	if (sb->u.ext2_sb.s_frag_size)		sb->u.ext2_sb.s_frags_per_block = sb->s_blocksize /						  sb->u.ext2_sb.s_frag_size;	else		sb->s_magic = 0;	sb->u.ext2_sb.s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);	sb->u.ext2_sb.s_frags_per_group = le32_to_cpu(es->s_frags_per_group);	sb->u.ext2_sb.s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);	sb->u.ext2_sb.s_inodes_per_block = sb->s_blocksize /					   EXT2_INODE_SIZE(sb);	sb->u.ext2_sb.s_itb_per_group = sb->u.ext2_sb.s_inodes_per_group /				        sb->u.ext2_sb.s_inodes_per_block;	sb->u.ext2_sb.s_desc_per_block = sb->s_blocksize /					 sizeof (struct ext2_group_desc);	sb->u.ext2_sb.s_sbh = bh;	if (resuid != EXT2_DEF_RESUID)		sb->u.ext2_sb.s_resuid = resuid;	else		sb->u.ext2_sb.s_resuid = le16_to_cpu(es->s_def_resuid);	if (resgid != EXT2_DEF_RESGID)		sb->u.ext2_sb.s_resgid = resgid;	else		sb->u.ext2_sb.s_resgid = le16_to_cpu(es->s_def_resgid);	sb->u.ext2_sb.s_mount_state = le16_to_cpu(es->s_state);	sb->u.ext2_sb.s_addr_per_block_bits =		log2 (EXT2_ADDR_PER_BLOCK(sb));	sb->u.ext2_sb.s_desc_per_block_bits =		log2 (EXT2_DESC_PER_BLOCK(sb));	if (sb->s_magic != EXT2_SUPER_MAGIC) {		if (!silent)			printk ("VFS: Can't find an ext2 filesystem on dev "				"%s./n",				bdevname(dev));		goto failed_mount;	}	if (sb->s_blocksize != bh->b_size) {		if (!silent)			printk ("VFS: Unsupported blocksize on dev "				"%s./n", bdevname(dev));		goto failed_mount;	}	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)/n",			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);		goto failed_mount;	}	if (sb->u.ext2_sb.s_blocks_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #blocks per group too big: %lu/n",			sb->u.ext2_sb.s_blocks_per_group);		goto failed_mount;	}	if (sb->u.ext2_sb.s_frags_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #fragments per group too big: %lu/n",			sb->u.ext2_sb.s_frags_per_group);		goto failed_mount;	}	if (sb->u.ext2_sb.s_inodes_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #inodes per group too big: %lu/n",

errcode_t online_resize_fs(ext2_filsys fs, const char *mtpt,			   blk64_t *new_size, int flags EXT2FS_ATTR((unused))){#ifdef __linux__	struct ext2_new_group_input input;	struct ext4_new_group_input input64;	struct ext2_super_block *sb = fs->super;	unsigned long		new_desc_blocks;	ext2_filsys 		new_fs;	errcode_t 		retval;	double			percent;	dgrp_t			i;	blk_t			size;	int			fd, overhead;	int			use_old_ioctl = 1;	int			no_meta_bg_resize = 0;	int			no_resize_ioctl = 0;	if (getenv("RESIZE2FS_KERNEL_VERSION")) {		char *version_to_emulate = getenv("RESIZE2FS_KERNEL_VERSION");		int kvers = parse_version_number(version_to_emulate);		if (kvers < VERSION_CODE(3, 7, 0))			no_meta_bg_resize = 1;		if (kvers < VERSION_CODE(3, 3, 0))			no_resize_ioctl = 1;	}	if (ext2fs_has_feature_sparse_super2(fs->super) &&	    (access("/sys/fs/ext4/features/sparse_super2", R_OK) != 0)) {		com_err(program_name, 0, _("kernel does not support online "					   "resize with sparse_super2"));		exit(1);	}	printf(_("Filesystem at %s is mounted on %s; "		 "on-line resizing required/n"), fs->device_name, mtpt);	if (*new_size < ext2fs_blocks_count(sb)) {		com_err(program_name, 0, _("On-line shrinking not supported"));		exit(1);	}	/*	 * If the number of descriptor blocks is going to increase,	 * the on-line resizing inode must be present.	 */	new_desc_blocks = ext2fs_div_ceil(		ext2fs_div64_ceil(*new_size -				  fs->super->s_first_data_block,				  EXT2_BLOCKS_PER_GROUP(fs->super)),		EXT2_DESC_PER_BLOCK(fs->super));	printf("old_desc_blocks = %lu, new_desc_blocks = %lu/n",	       fs->desc_blocks, new_desc_blocks);	/*	 * Do error checking to make sure the resize will be successful.	 */	if ((access("/sys/fs/ext4/features/meta_bg_resize", R_OK) != 0) ||	    no_meta_bg_resize) {		if (!ext2fs_has_feature_resize_inode(fs->super) &&		    (new_desc_blocks != fs->desc_blocks)) {			com_err(program_name, 0,				_("Filesystem does not support online resizing"));			exit(1);		}		if (ext2fs_has_feature_resize_inode(fs->super) &&		    new_desc_blocks > (fs->desc_blocks +				       fs->super->s_reserved_gdt_blocks)) {			com_err(program_name, 0,				_("Not enough reserved gdt blocks for resizing"));			exit(1);		}		if ((ext2fs_blocks_count(sb) > MAX_32_NUM) ||		    (*new_size > MAX_32_NUM)) {			com_err(program_name, 0,				_("Kernel does not support resizing a file system this large"));			exit(1);		}	}	fd = open(mtpt, O_RDONLY);	if (fd < 0) {		com_err(program_name, errno,			_("while trying to open mountpoint %s"), mtpt);		exit(1);	}	if (no_resize_ioctl) {		printf(_("Old resize interface requested./n"));	} else if (ioctl(fd, EXT4_IOC_RESIZE_FS, new_size)) {		/*		 * If kernel does not support EXT4_IOC_RESIZE_FS, use the		 * old online resize. Note that the old approach does not		 * handle >32 bit file systems		 *		 * Sigh, if we are running a 32-bit binary on a 64-bit		 * kernel (which happens all the time on the MIPS//.........这里部分代码省略.........

//.........这里部分代码省略.........			retval = EXT2_ET_UNEXPECTED_BLOCK_SIZE;			goto cleanup;		}	}	/*	 * Set the blocksize to the filesystem's blocksize.	 */	io_channel_set_blksize(fs->io, fs->blocksize);	/*	 * If this is an external journal device, don't try to read	 * the group descriptors, because they're not there.	 */	if (ext2fs_has_feature_journal_dev(fs->super)) {		fs->group_desc_count = 0;		*ret_fs = fs;		return 0;	}	if (EXT2_INODES_PER_GROUP(fs->super) == 0) {		retval = EXT2_ET_CORRUPT_SUPERBLOCK;		goto cleanup;	}	/* Precompute the FS UUID to seed other checksums */	ext2fs_init_csum_seed(fs);	/*	 * Read group descriptors	 */	blocks_per_group = EXT2_BLOCKS_PER_GROUP(fs->super);	if (blocks_per_group == 0 ||	    blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(fs->super) ||	    fs->inode_blocks_per_group > EXT2_MAX_INODES_PER_GROUP(fs->super) ||           EXT2_DESC_PER_BLOCK(fs->super) == 0 ||           fs->super->s_first_data_block >= ext2fs_blocks_count(fs->super)) {		retval = EXT2_ET_CORRUPT_SUPERBLOCK;		goto cleanup;	}	fs->group_desc_count = ext2fs_div64_ceil(ext2fs_blocks_count(fs->super) -						 fs->super->s_first_data_block,						 blocks_per_group);	if (fs->group_desc_count * EXT2_INODES_PER_GROUP(fs->super) !=	    fs->super->s_inodes_count) {		retval = EXT2_ET_CORRUPT_SUPERBLOCK;		goto cleanup;	}	fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,					  EXT2_DESC_PER_BLOCK(fs->super));	retval = ext2fs_get_array(fs->desc_blocks, fs->blocksize,				&fs->group_desc);	if (retval)		goto cleanup;	if (!group_block)		group_block = fs->super->s_first_data_block;	/*	 * On a FS with a 1K blocksize, block 0 is reserved for bootloaders	 * so we must increment block numbers to any group 0 items.	 *	 * However, we cannot touch group_block directly because in the meta_bg	 * case, the ext2fs_descriptor_block_loc2() function will interpret	 * group_block != s_first_data_block to mean that we want to access the	 * backup group descriptors.  This is not what we want if the caller	 * set superblock == 0 (i.e. auto-detect the superblock), which is	 * what's going on here.	 */	if (group_block == 0 && fs->blocksize == 1024)

//.........这里部分代码省略.........    /* default: (fs->blocksize*8) blocks/group, up to 2^16 (GDT limit) */    set_field(s_blocks_per_group, fs->blocksize * 8);    if (super->s_blocks_per_group > EXT2_MAX_BLOCKS_PER_GROUP(super))        super->s_blocks_per_group = EXT2_MAX_BLOCKS_PER_GROUP(super);    super->s_frags_per_group = super->s_blocks_per_group * frags_per_block;    super->s_blocks_count = param->s_blocks_count;    super->s_r_blocks_count = param->s_r_blocks_count;    if (super->s_r_blocks_count >= param->s_blocks_count) {        retval = EXT2_ET_INVALID_ARGUMENT;        goto cleanup;    }    /*     * If we're creating an external journal device, we don't need     * to bother with the rest.     */    if (super->s_feature_incompat & EXT3_FEATURE_INCOMPAT_JOURNAL_DEV) {        fs->group_desc_count = 0;        ext2fs_mark_super_dirty(fs);        *ret_fs = fs;        return 0;    }retry:    fs->group_desc_count = ext2fs_div_ceil(super->s_blocks_count -                                           super->s_first_data_block,                                           EXT2_BLOCKS_PER_GROUP(super));    if (fs->group_desc_count == 0) {        retval = EXT2_ET_TOOSMALL;        goto cleanup;    }    fs->desc_blocks = ext2fs_div_ceil(fs->group_desc_count,                                      EXT2_DESC_PER_BLOCK(super));    i = fs->blocksize >= 4096 ? 1 : 4096 / fs->blocksize;    set_field(s_inodes_count, super->s_blocks_count / i);    /*     * Make sure we have at least EXT2_FIRST_INO + 1 inodes, so     * that we have enough inodes for the filesystem(!)     */    if (super->s_inodes_count < EXT2_FIRST_INODE(super)+1)        super->s_inodes_count = EXT2_FIRST_INODE(super)+1;    /*     * There should be at least as many inodes as the user     * requested.  Figure out how many inodes per group that     * should be.  But make sure that we don't allocate more than     * one bitmap's worth of inodes each group.     */    ipg = ext2fs_div_ceil(super->s_inodes_count, fs->group_desc_count);    if (ipg > fs->blocksize * 8) {        if (super->s_blocks_per_group >= 256) {            /* Try again with slightly different parameters */            super->s_blocks_per_group -= 8;            super->s_blocks_count = param->s_blocks_count;            super->s_frags_per_group = super->s_blocks_per_group *                                       frags_per_block;            goto retry;        } else            return EXT2_ET_TOO_MANY_INODES;    }    if (ipg > (unsigned) EXT2_MAX_INODES_PER_GROUP(super))        ipg = EXT2_MAX_INODES_PER_GROUP(super);

errcode_t ext2fs_flush(ext2_filsys fs){	dgrp_t		i;	errcode_t	retval;	unsigned long	fs_state;	__u32		feature_incompat;	struct ext2_super_block *super_shadow = 0;	struct ext2_group_desc *group_shadow = 0;#ifdef WORDS_BIGENDIAN	struct ext2_group_desc *s, *t;	dgrp_t		j;#endif	char	*group_ptr;	int	old_desc_blocks;	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);	fs_state = fs->super->s_state;	feature_incompat = fs->super->s_feature_incompat;	fs->super->s_wtime = fs->now ? fs->now : time(NULL);	fs->super->s_block_group_nr = 0;#ifdef WORDS_BIGENDIAN	retval = EXT2_ET_NO_MEMORY;	retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &super_shadow);	if (retval)		goto errout;	retval = ext2fs_get_array(fs->desc_blocks, fs->blocksize,				  &group_shadow);	if (retval)		goto errout;	memset(group_shadow, 0, (size_t) fs->blocksize *	       fs->desc_blocks);	/* swap the group descriptors */	for (j=0, s=fs->group_desc, t=group_shadow;	     j < fs->group_desc_count; j++, t++, s++) {		*t = *s;		ext2fs_swap_group_desc(t);	}#else	super_shadow = fs->super;	group_shadow = fs->group_desc;#endif	/*	 * Set the state of the FS to be non-valid.  (The state has	 * already been backed up earlier, and will be restored after	 * we write out the backup superblocks.)	 */	fs->super->s_state &= ~EXT2_VALID_FS;	fs->super->s_feature_incompat &= ~EXT3_FEATURE_INCOMPAT_RECOVER;#ifdef WORDS_BIGENDIAN	*super_shadow = *fs->super;	ext2fs_swap_super(super_shadow);#endif	/*	 * If this is an external journal device, don't write out the	 * block group descriptors or any of the backup superblocks	 */	if (fs->super->s_feature_incompat &	    EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)		goto write_primary_superblock_only;	/*	 * Write out the master group descriptors, and the backup	 * superblocks and group descriptors.	 */	group_ptr = (char *) group_shadow;	if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)		old_desc_blocks = fs->super->s_first_meta_bg;	else		old_desc_blocks = fs->desc_blocks;	for (i = 0; i < fs->group_desc_count; i++) {		blk64_t	super_blk, old_desc_blk, new_desc_blk;		ext2fs_super_and_bgd_loc2(fs, i, &super_blk, &old_desc_blk,					 &new_desc_blk, 0);		if (!(fs->flags & EXT2_FLAG_MASTER_SB_ONLY) &&i && super_blk) {			retval = write_backup_super(fs, i, super_blk,						    super_shadow);			if (retval)				goto errout;		}		if (fs->flags & EXT2_FLAG_SUPER_ONLY)			continue;		if ((old_desc_blk) &&		    (!(fs->flags & EXT2_FLAG_MASTER_SB_ONLY) || (i == 0))) {			retval = io_channel_write_blk(fs->io,			      old_desc_blk, old_desc_blocks, group_ptr);			if (retval)				goto errout;		}		if (new_desc_blk) {			int meta_bg = i / EXT2_DESC_PER_BLOCK(fs->super);			retval = io_channel_write_blk(fs->io, new_desc_blk,//.........这里部分代码省略.........

//.........这里部分代码省略.........		if ((sbi->s_inode_size < EXT2_GOOD_OLD_INODE_SIZE) ||		    !is_power_of_2(sbi->s_inode_size) ||		    (sbi->s_inode_size > blocksize)) {			printk ("EXT2-fs: unsupported inode size: %d/n",				sbi->s_inode_size);			goto failed_mount;		}	}	sbi->s_frag_size = EXT2_MIN_FRAG_SIZE <<				   le32_to_cpu(es->s_log_frag_size);	if (sbi->s_frag_size == 0)		goto cantfind_ext2;	sbi->s_frags_per_block = sb->s_blocksize / sbi->s_frag_size;	sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);	sbi->s_frags_per_group = le32_to_cpu(es->s_frags_per_group);	sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);	if (EXT2_INODE_SIZE(sb) == 0)		goto cantfind_ext2;	sbi->s_inodes_per_block = sb->s_blocksize / EXT2_INODE_SIZE(sb);	if (sbi->s_inodes_per_block == 0 || sbi->s_inodes_per_group == 0)		goto cantfind_ext2;	sbi->s_itb_per_group = sbi->s_inodes_per_group /					sbi->s_inodes_per_block;	sbi->s_desc_per_block = sb->s_blocksize /					sizeof (struct ext2_group_desc);	sbi->s_sbh = bh;	sbi->s_mount_state = le16_to_cpu(es->s_state);	sbi->s_addr_per_block_bits =		ilog2 (EXT2_ADDR_PER_BLOCK(sb));	sbi->s_desc_per_block_bits =		ilog2 (EXT2_DESC_PER_BLOCK(sb));	if (sb->s_magic != EXT2_SUPER_MAGIC)		goto cantfind_ext2;	if (sb->s_blocksize != bh->b_size) {		if (!silent)			printk ("VFS: Unsupported blocksize on dev "				"%s./n", sb->s_id);		goto failed_mount;	}	if (sb->s_blocksize != sbi->s_frag_size) {		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)/n",			sbi->s_frag_size, sb->s_blocksize);		goto failed_mount;	}	if (sbi->s_blocks_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #blocks per group too big: %lu/n",			sbi->s_blocks_per_group);		goto failed_mount;	}	if (sbi->s_frags_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #fragments per group too big: %lu/n",			sbi->s_frags_per_group);		goto failed_mount;	}	if (sbi->s_inodes_per_group > sb->s_blocksize * 8) {		printk ("EXT2-fs: #inodes per group too big: %lu/n",			sbi->s_inodes_per_group);		goto failed_mount;	}