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F2FS文件系统二实验分析f2fs文件系统

發布時間：2023/12/31 windows 42 豆豆

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一、環境準備：

1、ubuntu系統安裝f2fs-tools：sudo apt-get install -y f2fs-tools

2、使用系統loop設備進行實踐操作：

dd if=/dev/zero of=device bs=4K count=51200 //200M losetup /dev/loop0 device //尋址可用的loop設備 mkfs.f2fs -l f2fs /dev/loop0 //格式化此loop設備 mount -t f2fs /dev/loop0 ./f2fs_mp //掛載到f2fs_mp文件夾

3、獲取掛載初始狀態：dd if=/dev/loop0 of=f2fs_test，可以通過UE打開f2fs_test查看。

4、新建如下文件，以及對應的inode：

　　root@ubuntu:/home/yinpeng/f2fs_mp# ls -i

　　91 1.c? ???92 2.txt? ???87 a.txt? ???93 bio.c

二、磁盤布局分解：

1、superBlock：

　　F2FS文件的起始地址向后偏移0x400字節，尋址當前地址為所述超級塊SuperBlock的起始地址。

在內存的存儲方式是小端存儲，有兩個superblock如下：

對應的結構體信息如下：

struct f2fs_super_block {

__le32 magic;????????????????????????/* Magic Number */?? ??????????	0xF2F52010
__le16 major_ver;????????????????/* Major Version */?	0x01
__le16 minor_ver;????????????????/* Minor Version */?	0x0B
__le32 log_sectorsize;????????????????/* log2 sector size in bytes */????????	0x09
__le32 log_sectors_per_block;????????/* log2 # of sectors per block */??	0x03
__le32 log_blocksize;????????????????/* log2 block size in bytes */????????	?0x0C
__le32 log_blocks_per_seg;????????/* log2 # of blocks per segment */????	?0x09
__le32 segs_per_sec;????????????????/* # of segments per section */????????	0x01
__le32 secs_per_zone;????????????????/* # of sections per zone */??????????	?0x01
__le32 checksum_offset;????????????????/* checksum offset inside super block */	0x00
__le64 block_count;????????????????/* total # of user blocks */???????????????	0xC800
__le32 section_count;????????????????/* total # of sections */??????????????	0x5C
__le32 segment_count;????????????????/* total # of segments */?????????????	?0x63
__le32 segment_count_ckpt;????????/* # of segments for checkpoint */????	?0x02
__le32 segment_count_sit;????????/* # of segments for SIT */???????????	?0x02
__le32 segment_count_nat;????????/* # of segments for NAT */???????????	?0x02
__le32 segment_count_ssa;????????/* # of segments for SSA */????????????	0x01????????????
__le32 segment_count_main;????????/* # of segments for main area */????	0x5C
__le32 segment0_blkaddr;????????/* start block address of segment 0 */?	0x0200
__le32 cp_blkaddr;????????????????/* start block address of checkpoint */????	0x0200
__le32 sit_blkaddr;????????????????/* start block address of SIT */???????????	0x0600
__le32 nat_blkaddr;????????????????/* start block address of NAT */???????????	0x0A00
__le32 ssa_blkaddr;????????????????/* start block address of SSA */???????????	0x0E00
__le32 main_blkaddr;????????????????/* start block address of main area */?	0x1000
__le32 root_ino;????????????????/* root inode number */????????????????????	0x03
__le32 node_ino;????????????????/* node inode number */????????????????????	0x01
__le32 meta_ino;????????????????/* meta inode number */????????????????????	0x02
__u8 uuid[16];????????????????????????/* 128-bit uuid for volume */??????????????	***????????????????????
__le16 volume_name[MAX_VOLUME_NAME];????????/* volume name */??????????	F2FS???????
__le32 extension_count;????????????????/* # of extensions below */????????????	0X0001B???
__u8 extension_list[F2FS_MAX_EXTENSION][F2FS_EXTENSION_LEN];/* extension array */ ??	0x00
__le32 cp_payload;??????????????????????????????????????????????????	//0x0
__u8 version[VERSION_LEN];? /* the kernel version */???????????????????	//4.9.117+ #4 SMP PREEMPT Sat May 25 01:40:39 CST 2019
__u8 init_version[VERSION_LEN]; /* the initial kernel version */????????	//4.9.117+ #4 SMP PREEMPT Sat May 25 01:40:39 CST 2019
__le32 feature;???????? /* defined features */????????	//0x0
__u8 encryption_level;????? /* versioning level for encryption */????????	?//0x0
__u8 encrypt_pw_salt[16];?? /* Salt used for string2key algorithm */	?//0x0
struct f2fs_device devs[MAX_DEVICES];?? /* device list */????????????????	?//0x0
__le32 qf_ino[F2FS_MAX_QUOTAS]; /* quota inode numbers */???????????????	? //0x0
__u8 hot_ext_count;???? /* # of hot file extension */???????????????????	? //0x0
__u8 reserved[310];???? /* valid reserved region */???????????????????????	? //0x0??????????????????????????????????????????????????????????????????????????????????
__le32 crc;???????? /* checksum of superblock */????????????????????????	?//0x0

} __packed;

2、checkpoint：

checkpoint的數量也有兩個：

struct f2fs_checkpoint {

__le64 checkpoint_ver;????????????????/* checkpoint block version number */? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?	0x1052B10E
__le64 user_block_count;????????/* # of user blocks */?????????????????????	0x7A00
__le64 valid_block_count;????????/* # of valid blocks in main area */???????	0x13
__le32 rsvd_segment_count;????????/* # of reserved segments for gc */????????	0x15
__le32 overprov_segment_count;????????/* # of overprovision segments */??????	0x1F
__le32 free_segment_count;????????/* # of free segments in main area */??????	0x56
__le32 cur_node_segno[MAX_ACTIVE_NODE_LOGS];??????????????	?0x0.1.2.0xFFFFFFFF.FFFFFFFF.FFFFFFFF.FFFFFFFF.FFFFFFFF??
__le16 cur_node_blkoff[MAX_ACTIVE_NODE_LOGS];??????????????	0X2F.10.2.0x00. 0x00. 0x00. 0x00. 0x00. 0x00??????????????
__le32 cur_data_segno[MAX_ACTIVE_DATA_LOGS];???????????????	0x03. 0x47. 0x16. FFFFFFFF. FFFFFFFF. FFFFFFFF. FFFFFFFF. FFFFFFFF
__le16 cur_data_blkoff[MAX_ACTIVE_DATA_LOGS];???????????????????	0X85. 0x1AB. 0x00. 0x00. 0x00. 0x00. 0x00. 0x00
?__le32 ckpt_flags;????????????????/* Flags : umount and journal_present */???????	0x01C4
__le32 cp_pack_total_block_count;????????/* total # of one cp pack */???????	0x04
__le32 cp_pack_start_sum;????????/* start block number of data summary */???	0x01
__le32 valid_node_count;????????/* Total number of valid nodes */??????????	0x05
__le32 valid_inode_count;????????/* Total number of valid inodes */?????????	0x05
__le32 next_free_nid;????????????????/* Next free node number */???????????????	?0x61
__le32 sit_ver_bitmap_bytesize;????????/* Default value 64 */?????????????????	0x40
__le32 nat_ver_bitmap_bytesize; /* Default value 256 */????????????????	0x40
__le32 checksum_offset;????????????????/* checksum offset inside cp block */??????	0x0FF
__le64 elapsed_time;????????????????/* mounted time */?????????????????????????	0x019289
unsigned char alloc_type[MAX_ACTIVE_LOGS];?????????????????????????????	0x00
unsigned char sit_nat_version_bitmap[1];???????????????????????????????	0x00

} __packed;

3、SIT：

0xC01 >> 10 =? 3 type

0xC01 & 0x3FF =? 1

/** Note that f2fs_sit_entry->vblocks has the following bit-field information.* [15:10] : allocation type such as CURSEG_XXXX_TYPE* [9:0] : valid block count*/ struct f2fs_sit_entry {__le16 vblocks; /* reference above */__u8 valid_map[SIT_VBLOCK_MAP_SIZE]; /* bitmap for valid blocks */__le64 mtime; /* segment age for cleaning */ } __packed;

dump.f2fs ???-s ???0~-1 ???f2fs_test_2

root@ubuntu:/home/yinpeng# cat dump_sit

segment_type(0:HD, 1:WD, 2:CD, 3:HN, 4:WN, 5:CN)

segno:?????? 0????????vblocks:? 1????????seg_type:3????????sit_pack:2

//1segment = 512 block

? 00? 10? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00

? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00

segno:?????? 1????????vblocks:? 2????????seg_type:4????????sit_pack:2

用戶層的數據從0x100000開始：

1000000 + 1*2MB(segmet size) + (8*5 + 3) * 4Kb（block size） =

0x1000000 + 0x200000 + 0x2B000 = 0x122B000

0x18 = 0x00011000

? 00? 00? 00? 00? 00? 18? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00

? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00

segno:?????? 2????????vblocks:? 0????????seg_type:5????????sit_pack:2

segno:?????? 3????????vblocks:? 1????????seg_type:0????????sit_pack:2

0x1000000 + 3 * 2MB + (14*8 + 4) * 4kb = 74000

0x1000000 + 0x600000 + 74000

0x08 = 0x00001000

? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 08? 00

? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00? 00

segno:?????? 4????????vblocks:? 0????????seg_type:1????????sit_pack:2

segno:?????? 5????????vblocks:? 0????????seg_type:1????????sit_pack:2
?

從上面的分解，可以看到通過如下流程可以找到DataBlock的地址：

Superblock -> NAT -> inode number? ->? datablock

4.NAT

struct f2fs_nat_entry {__u8 version; /* latest version of cached nat entry */__le32 ino; /* inode number */__le32 block_addr; /* block address */ } __packed;struct f2fs_nat_block {struct f2fs_nat_entry entries[NAT_ENTRY_PER_BLOCK]; } __packed;

dump.f2fs ??-n ??0~-1 ???f2fs_test_2

root@ubuntu:/home/yinpeng# cat dump_nat

nid:??? 3????????ino:??? 3????????offset:??? 0????????blkaddr:????? 4111 //0x122A 000????????pack:2

nid:?? 87????????ino:?? 87????????offset:??? 0????????blkaddr:????? 4651 //0x122B????????pack:2

nid:?? 91????????ino:?? 91????????offset:??? 0????????blkaddr:????? 4652 //0x122C????????pack:2

nid:?? 92????????ino:?? 92????????offset:??? 0????????blkaddr:????? 4653 //0x122D????????pack:2

nid:?? 93????????ino:?? 93????????offset:??? 0????????blkaddr:????? 4654 //0x122E????????pack:2

5、DataBlock：

root@ubuntu:/home/yinpeng# dump.f2fs -a 0~-1 f2fs_test_2

root@ubuntu:/home/yinpeng# cat dump_ssa

/* a summary entry for a 4KB-sized block in a segment */ struct f2fs_summary {__le32 nid; /* parent node id */union {__u8 reserved[3];struct {__u8 version; /* node version number */__le16 ofs_in_node; /* block index in parent node */} __packed;}; } __packed;

參考博客：

https://blog.csdn.net/SweeNeil/article/details/91897016

作者：frank_zyp
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F2FS文件系统二 实验分析f2fs文件系统

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F2FS文件系统二实验分析f2fs文件系统