F2FS Source Code Analysis (v) node management structure carding

Node is F2FS important management structure, it is very important! Once the system is mounted, there will be a node manager with the F2FS_NM_INFO structure to manage node allocations. The most puzzling of F2fs_nm_info is a few cardinal trees:

 490 structF2fs_nm_info {491block_t nat_blkaddr;/*base disk address of NAT*/ 492nid_t Max_nid;/*Maximum possible node IDs*/ 494nid_t Next_scan_nid;/*The next nid to be scanned*/ 497     /*NAT Cache Management*/ 498     structRadix_tree_root Nat_root;/*root of the NAT entry cache*/ 499     structRadix_tree_root Nat_set_root;/*root of the NAT set cache*/ 501     structList_head nat_entries;/*Cached NAT Entry List (clean)*/ 502Unsignedintnat_cnt;/*The # of cached NAT entries*/ 503Unsignedintdirty_nat_cnt;/*Total num of NAT entries in set*/ 505     /*Free node IDs management*/ 506     structRadix_tree_root Free_nid_root;/*root of the Free_nid cache*/ 507     structList_head free_nid_list;/*a list for free NIDs*/ 509Unsignedintfcnt;/*The number of the free node ID*/  +     /*For checkpoint*/ 513     Char*nat_bitmap;/*NAT Bitmap Pointer*/ 514     intBitmap_size;/*Bitmap Size*/ 515};

The three cardinal trees were: nat_root, Nat_set_root, Free_nid_root;

First, for the entire node manager, a core structure is node_info:

  $ structNode_info { -nid_t nid;/*Node ID*/  -nid_t ino;/*Inode number of the node ' s owner*/  theblock_t blk_addr;/*Block address of the node*/  -UnsignedCharVersion/*version of the node*/ WuyiUnsignedCharFlag/*For node information bits*/  the };  -   Wu structNat_entry { -     structList_head list;/*For clean or dirty NAT list*/  About     structNode_info ni;/*in-memory Node Information*/  $};

found that Node_info and f2fs_nat_entry "storage on disk" Look much like, even more than the struct f2fs_nat_entry a flag bit to represent some of the properties of this node!

266 struct F2fs_nat_entry {
267     __u8 version;       /*  */268     __le32 ino;     /*  */269     __le32 block_addr;  /*  * * __packed};

This core data structure is controlled by two structures: one is the cardinality tree "responsible for indexing" and the other is a linked list.

F2FS Source Code Analysis (v) node management structure carding