F2FS文件系统二 实验分析f2fs文件系统
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
? 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? 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
? 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? 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
? 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? 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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