{"id":1659,"date":"2012-04-14T23:10:28","date_gmt":"2012-04-14T14:10:28","guid":{"rendered":"http:\/\/peta.okechan.net\/blog\/?p=1659"},"modified":"2012-04-14T23:13:37","modified_gmt":"2012-04-14T14:13:37","slug":"xv6-64-chapter-5-file-system-code-directory-layer","status":"publish","type":"post","link":"https:\/\/peta.okechan.net\/blog\/archives\/1659","title":{"rendered":"[xv6 #64] Chapter 5 – File system – Code: directory layer"},"content":{"rendered":"

\u30c6\u30ad\u30b9\u30c8\u306e71\u301c73\u30da\u30fc\u30b8<\/p>\n

\u672c\u6587<\/h3>\n

\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5c64\u306f\u30b7\u30f3\u30d7\u30eb\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306f\u3001\u4eca\u307e\u3067\u4ee5\u4e0a\u306b\u7279\u6b8a\u306a\u7a2e\u985e\u306e\u30d5\u30a1\u30a4\u30eb\u3001\u3067\u306f\u306a\u3044\u304b\u3089\u3067\u3042\u308b\u3002
\n\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306einode\u306fT_DIR\u3068\u3044\u3046\u30bf\u30a4\u30d7\u3092\u6301\u3061\u3001\u305d\u306e\u30c7\u30fc\u30bf\u306f\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306e\u9023\u306a\u308a\u3067\u3042\u308b\u3002
\n\u5404\u30a8\u30f3\u30c8\u30ea\u306f\u3001dirent\u69cb\u9020\u4f53\u3067\u3042\u308a\u3001\u540d\u524d\u3068inode\u756a\u53f7\u3092\u542b\u3080\u3002
\n\u540d\u524d\u306f\u3001\u6700\u5927\u3067DIRSIZ(14)\u6587\u5b57\u307e\u3067\u3067\u3042\u308a\u3001\u3082\u3057\u305d\u308c\u306b\u6e80\u305f\u306a\u304b\u3063\u305f\u3089\u3001NUL(0)\u3067\u7d42\u7aef\u3055\u308c\u308b\u3002
\ninode\u756a\u53f7\u30bc\u30ed\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306f\u3001\u7a7a\u304d\u3092\u793a\u3059\u3002<\/p>\n

fs.h<\/p>\n

\/\/ On-disk file system format. \r\n\/\/ Both the kernel and user programs use this header file.\r\n\r\n\/\/ Block 0 is unused.  Block 1 is super block.\r\n\/\/ Inodes start at block 2.\r\n\r\n#define ROOTINO 1  \/\/ root i-number\r\n#define BSIZE 512  \/\/ block size\r\n\r\n\/\/ File system super block\r\nstruct superblock {\r\n  uint size;         \/\/ Size of file system image (blocks)\r\n  uint nblocks;      \/\/ Number of data blocks\r\n  uint ninodes;      \/\/ Number of inodes.\r\n  uint nlog;         \/\/ Number of log blocks\r\n};\r\n\r\n#define NDIRECT 12\r\n#define NINDIRECT (BSIZE \/ sizeof(uint))\r\n#define MAXFILE (NDIRECT + NINDIRECT)\r\n\r\n\/\/ On-disk inode structure\r\nstruct dinode {\r\n  short type;           \/\/ File type\r\n  short major;          \/\/ Major device number (T_DEV only)\r\n  short minor;          \/\/ Minor device number (T_DEV only)\r\n  short nlink;          \/\/ Number of links to inode in file system\r\n  uint size;            \/\/ Size of file (bytes)\r\n  uint addrs[NDIRECT+1];   \/\/ Data block addresses\r\n};\r\n\r\n\/\/ Inodes per block.\r\n#define IPB           (BSIZE \/ sizeof(struct dinode))\r\n\r\n\/\/ Block containing inode i\r\n#define IBLOCK(i)     ((i) \/ IPB + 2)\r\n\r\n\/\/ Bitmap bits per block\r\n#define BPB           (BSIZE*8)\r\n\r\n\/\/ Block containing bit for block b\r\n#define BBLOCK(b, ninodes) (b\/BPB + (ninodes)\/IPB + 3)\r\n\r\n\/\/ Directory is a file containing a sequence of dirent structures.\r\n#define DIRSIZ 14\r\n\r\nstruct dirent {\r\n  ushort inum;\r\n  char name[DIRSIZ];\r\n};<\/pre>\n
dirlookup\u95a2\u6570\u306f\u3001\u5f15\u6570\u3067\u6e21\u3055\u308c\u305f\u540d\u524d\u306b\u5408\u81f4\u3059\u308b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u4e2d\u304b\u3089\u63a2\u3059\u3002
\n\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u3063\u305f\u5834\u5408\u3001\u305d\u308c\u306b\u5bfe\u5fdc\u3059\u308binode\u306e\u30dd\u30a4\u30f3\u30bf\uff08\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044\uff09\u3092\u8fd4\u3057\u3001\u305d\u3057\u3066\u3001\u547c\u3073\u51fa\u3057\u5074\u304c\u305d\u306e\u898b\u3064\u304b\u3063\u305f\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u7de8\u96c6\u3057\u305f\u3044\u5834\u5408\u306b\u5099\u3048\u3066\u3001*poff\u306b\u305d\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306e\u30aa\u30d5\u30bb\u30c3\u30c8\u3092\u683c\u7d0d\u3059\u308b\u3002
\ndirlookup\u95a2\u6570\u304c\u540d\u524d\u306b\u5bfe\u5fdc\u3059\u308b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u898b\u3064\u3051\u305f\u5834\u5408\u3001*poff\u3092\u66f4\u65b0\u3057\u3001\u305d\u306e\u30d6\u30ed\u30c3\u30af\u3092\u89e3\u653e\u3057\u3001\u305d\u3057\u3066iget\u95a2\u6570\u304b\u3089\u53d6\u5f97\u3057\u305f\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044inode\u3092\u8fd4\u3059\u3002\uff08\u3053\u3053\u3001\u4e00\u3064\u524d\u306e\u6587\u3068\u5185\u5bb9\u304c\u88ab\u3063\u3066\u308b\u4e0a\u306b\u3001\u30d6\u30ed\u30c3\u30af\u3092\u89e3\u653e\u3068\u304b\u3001\u30bd\u30fc\u30b9\u3068\u4e00\u81f4\u3057\u3066\u306a\u3044\u90e8\u5206\u304c\u3042\u308b\u305f\u3081\u3001\u3082\u3057\u304b\u3057\u305f\u3089\u6614\u306e\u30bd\u30fc\u30b9\u306b\u5bfe\u3059\u308b\u8aac\u660e\u306e\u6d88\u3057\u5fd8\u308c\u304b\u3082\u3057\u308c\u306a\u3044\u3002\uff09
\niget\u95a2\u6570\u306f\u3001\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044inode\u3092\u8fd4\u3059\u3068\u3044\u3046\u3053\u3068\u304c\u305d\u306e\u7406\u7531\u3067\u3042\u308b\u3002
\n\u547c\u3073\u51fa\u3057\u5074\u304c\u30ed\u30c3\u30af\u6e08\u307f\u306edp\u3092\u6301\u3063\u3066\u3044\u3066\u3001\u30ab\u30ec\u30f3\u30c8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5225\u540d\u3067\u3042\u308b\u300c.\u300d\u306b\u5bfe\u3057\u3066dirlookup\u95a2\u6570\u3092\u4f7f\u3063\u305f\u5834\u5408\u3001\u547c\u3073\u51fa\u3057\u5143\u306b\u623b\u308b\u307e\u3048\u306b\u305d\u306einode\u3092\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3057\u3066\u3001\u3064\u307e\u308adp\u3092\u518d\u5ea6\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3057\u3066\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u3092\u5f15\u304d\u8d77\u3053\u3059\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002\uff08\u8907\u6570\u306e\u30d7\u30ed\u30bb\u30b9\u3084\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5225\u540d\u300c..\u300d\u304c\u304b\u3089\u3093\u3067\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u3092\u5f15\u304d\u8d77\u3053\u3059\u3088\u3046\u306a\u3082\u3063\u3068\u8907\u96d1\u306a\u5834\u5408\u3082\u305f\u304f\u3055\u3093\u3042\u308b\u3002\u554f\u984c\u304c\u8d77\u304d\u308b\u306e\u306f\u300c.\u300d\u306e\u3068\u304d\u3060\u3051\u3067\u306f\u306a\u3044\u306e\u3067\u3042\u308b\u3002\uff09
\n\u547c\u3073\u51fa\u3057\u5074\u306f\u3001dp\u3092\u30a2\u30f3\u30ed\u30c3\u30af\u3057\u305d\u3057\u3066\u305d\u308c\u304b\u3089ip\u3092\u30ed\u30c3\u30af\u3059\u308b\u3053\u3068\u3067\u3001\u4e00\u5ea6\u306b\u4e00\u3064\u306e\u30ed\u30c3\u30af\u3060\u3051\u3092\u4fdd\u6301\u3059\u308b\u4e8b\u3092\u4fdd\u8a3c\u51fa\u6765\u308b\u3002
\n\uff08\u3068\u3001\u8aac\u660e\u3055\u308c\u3066\u307e\u3059\u304c\u3001dirlookup\u306e\u30b3\u30fc\u30c9\u30d1\u30b9\u3092\u8ffd\u3063\u3066\u307f\u305f\u3068\u3053\u308d\u3001inode\u5358\u4f4d\u3067\u30ed\u30c3\u30af\u3092\u53d6\u5f97\u3057\u3066\u308b\u3068\u3053\u308d\uff08ilock\u95a2\u6570\u3092\u547c\u3093\u3067\u308b\u3068\u3053\u308d\uff09\u306f\u898b\u5f53\u305f\u308a\u307e\u305b\u3093\u3067\u3057\u305f\u3002\u4f55\u306a\u3093\u3067\u3057\u3087\u3046\u30b3\u30ec\u3002\uff09<\/p>\n
fs.c\u306enamecmp, dirlookup, dirlink\u95a2\u6570<\/p>\n
\/\/ Directories\r\n\r\nint\r\nnamecmp(const char *s, const char *t)\r\n{\r\n  return strncmp(s, t, DIRSIZ);\r\n}\r\n\r\n\/\/ Look for a directory entry in a directory.\r\n\/\/ If found, set *poff to byte offset of entry.\r\n\/\/ Caller must have already locked dp.\r\nstruct inode*\r\ndirlookup(struct inode *dp, char *name, uint *poff)\r\n{\r\n  uint off, inum;\r\n  struct dirent de;\r\n\r\n  if(dp->type != T_DIR)\r\n    panic("dirlookup not DIR");\r\n\r\n  for(off = 0; off < dp->size; off += sizeof(de)){\r\n    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n      panic("dirlink read");\r\n    if(de.inum == 0)\r\n      continue;\r\n    if(namecmp(name, de.name) == 0){\r\n      \/\/ entry matches path element\r\n      if(poff)\r\n        *poff = off;\r\n      inum = de.inum;\r\n      return iget(dp->dev, inum);\r\n    }\r\n  }\r\n\r\n  return 0;\r\n}\r\n\r\n\/\/ Write a new directory entry (name, inum) into the directory dp.\r\nint\r\ndirlink(struct inode *dp, char *name, uint inum)\r\n{\r\n  int off;\r\n  struct dirent de;\r\n  struct inode *ip;\r\n\r\n  \/\/ Check that name is not present.\r\n  if((ip = dirlookup(dp, name, 0)) != 0){\r\n    iput(ip);\r\n    return -1;\r\n  }\r\n\r\n  \/\/ Look for an empty dirent.\r\n  for(off = 0; off < dp->size; off += sizeof(de)){\r\n    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n      panic("dirlink read");\r\n    if(de.inum == 0)\r\n      break;\r\n  }\r\n\r\n  strncpy(de.name, name, DIRSIZ);\r\n  de.inum = inum;\r\n  if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n    panic("dirlink");\r\n  \r\n  return 0;\r\n}<\/pre>\n
dirlink\u95a2\u6570\u306f\u3001\u5f15\u6570\u3067\u4e0e\u3048\u3089\u308c\u305f\u540d\u524d\u3068inode\u756a\u53f7\u3092\u5143\u306b\u3001\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30eadp\u306b\u66f8\u304d\u8fbc\u3080\u3002
\n\u3082\u3057\u540d\u524d\u304c\u65e2\u306b\u5b58\u5728\u3057\u305f\u5834\u5408\u3001dirlink\u95a2\u6570\u306f\u30a8\u30e9\u30fc\u3092\u8fd4\u3059\u3002
\n\u30e1\u30a4\u30f3\u306e\u30eb\u30fc\u30d7\u3067\u306f\u3001\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u3092\u63a2\u3059\u305f\u3081\u306b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u7fa4\u3092\u8d70\u67fb\u3059\u308b\u3002
\n\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u308c\u3070\u3001\u30eb\u30fc\u30d7\u3092\u7d42\u4e86\u3059\u308b\u3002
\n\u305d\u306e\u6642\u306eoff\u306b\u306f\u305d\u306e\u30a8\u30f3\u30c8\u30ea\u306e\u30aa\u30d5\u30bb\u30c3\u30c8\u304c\u683c\u7d0d\u3055\u308c\u3066\u3044\u308b\u3002
\n\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u3089\u306a\u3044\u5834\u5408\u3001off\u306bdp->size\u304c\u683c\u7d0d\u3055\u308c\u305f\u72b6\u614b\u3067\u30eb\u30fc\u30d7\u3092\u7d42\u3048\u308b\u3002
\n\u3069\u3061\u3089\u306b\u3057\u308d\u3001dirlink\u95a2\u6570\u306f\u305d\u308c\u304b\u3089\u30aa\u30d5\u30bb\u30c3\u30c8off\u306b\u66f8\u304d\u8fbc\u3080\u3053\u3068\u3067\u65b0\u3057\u3044\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b\u8ffd\u52a0\u3059\u308b\u3002<\/p>\n
\u611f\u60f3<\/h3>\n
\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u3067\u3059\u3002
\ninode\u306f\u3059\u3067\u306b\u81ea\u8eab\u306e\u7a2e\u985e\u3092\u8868\u3059\u30d3\u30c3\u30c8\u3092\u6301\u3064\u3053\u3068\u304c\u51fa\u6765\u308b\u3088\u3046\u306b\u306a\u3063\u3066\u308b\u306e\u3067\u3001inode\u306e\u5c64\u304b\u3089\u898b\u308b\u3068\u3059\u3067\u306b\u300c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30ec\u30c7\u30a3\u300d\u306a\u72b6\u614b\u3068\u8a00\u3048\u307e\u3059\u3002<\/p>\n
\u305d\u3057\u3066\u3001\u901a\u5e38\u306e\u30d5\u30a1\u30a4\u30eb\u306e\u5834\u5408\u306f\u30c7\u30fc\u30bf\u90e8\u5206\u306b\u5358\u306b\u305d\u306e\u5185\u5bb9\u3092\u6301\u3064\u308f\u3051\u3067\u3059\u304c\u3001\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5834\u5408\u306f\u30d5\u30a1\u30a4\u30eb\u540d\u3068\u305d\u308c\u306b\u5bfe\u5fdc\u3059\u308b\u30d5\u30a1\u30a4\u30eb\u306einode\u3092\u30c7\u30fc\u30bf\u3068\u3057\u3066\u6301\u3064\u308f\u3051\u3067\u3059\u3002<\/p>\n
\u672c\u6587\u306b\u3082\u62ec\u5f27\u4ed8\u304d\u3067\u66f8\u304d\u307e\u3057\u305f\u304c\u3001\u3061\u3087\u3063\u3068\u30bd\u30fc\u30b9\u3068\u5408\u81f4\u3057\u3066\u306a\u3044\u90e8\u5206\u304c\u898b\u53d7\u3051\u3089\u308c\u307e\u3059\u3002
\n\u300c\u30d6\u30ed\u30c3\u30af\u306e\u89e3\u653e\u300d\u306b\u3064\u3044\u3066\u306f\u3001\u6614\u306e\u30bd\u30fc\u30b9\u3092\u307f\u305f\u3089\u78ba\u304b\u306b\u30d6\u30ed\u30c3\u30af\u3092\u78ba\u4fdd\u3057\u3066\u3001\u6700\u5f8c\u306bbrelse\u3092\u547c\u3076\u3088\u3046\u306b\u306a\u3063\u3066\u308b\u6642\u671f\u304c\u3042\u3063\u305f\u306e\u306f\u78ba\u8a8d\u3057\u307e\u3057\u305f\u3002
\n\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306e\u65b9\u306b\u3064\u3044\u3066\u306f\u3001\u6614\u306e\u30bd\u30fc\u30b9\u3092\u3056\u3063\u3068\u898b\u305f\u3060\u3051\u3060\u3068\u307e\u3060\u8a72\u5f53\u3059\u308b\u3088\u3046\u306a\u3068\u3053\u308d\u306f\u898b\u3064\u3051\u3066\u306a\u3044\u306e\u3067\u3001\u3082\u3057\u304b\u3057\u305f\u3089\u3001\u3042\u306e\u8aac\u660e\u304c\u5408\u3063\u3066\u3066\u3001\u79c1\u306e\u8a8d\u8b58\u304c\u9593\u9055\u3063\u3066\u308b\u53ef\u80fd\u6027\u3082\u304a\u304a\u3044\u306b\u3042\u308a\u307e\u3059\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u30c6\u30ad\u30b9\u30c8\u306e71\u301c73\u30da\u30fc\u30b8<\/p>\n
\u672c\u6587<\/h3>\n
\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5c64\u306f\u30b7\u30f3\u30d7\u30eb\u3067\u3042\u308b\u3002
\n\u306a\u305c\u306a\u3089\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306f\u3001\u4eca\u307e\u3067\u4ee5\u4e0a\u306b\u7279\u6b8a\u306a\u7a2e\u985e\u306e\u30d5\u30a1\u30a4\u30eb\u3001\u3067\u306f\u306a\u3044\u304b\u3089\u3067\u3042\u308b\u3002
\n\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306einode\u306fT_DIR\u3068\u3044\u3046\u30bf\u30a4\u30d7\u3092\u6301\u3061\u3001\u305d\u306e\u30c7\u30fc\u30bf\u306f\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306e\u9023\u306a\u308a\u3067\u3042\u308b\u3002
\n\u5404\u30a8\u30f3\u30c8\u30ea\u306f\u3001dirent\u69cb\u9020\u4f53\u3067\u3042\u308a\u3001\u540d\u524d\u3068inode\u756a\u53f7\u3092\u542b\u3080\u3002
\n\u540d\u524d\u306f\u3001\u6700\u5927\u3067DIRSIZ(14)\u6587\u5b57\u307e\u3067\u3067\u3042\u308a\u3001\u3082\u3057\u305d\u308c\u306b\u6e80\u305f\u306a\u304b\u3063\u305f\u3089\u3001NUL(0)\u3067\u7d42\u7aef\u3055\u308c\u308b\u3002
\ninode\u756a\u53f7\u30bc\u30ed\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306f\u3001\u7a7a\u304d\u3092\u793a\u3059\u3002<\/p>\n
fs.h<\/p>\n
\/\/ On-disk file system format. \r\n\/\/ Both the kernel and user programs use this header file.\r\n\r\n\/\/ Block 0 is unused.  Block 1 is super block.\r\n\/\/ Inodes start at block 2.\r\n\r\n#define ROOTINO 1  \/\/ root i-number\r\n#define BSIZE 512  \/\/ block size\r\n\r\n\/\/ File system super block\r\nstruct superblock {\r\n  uint size;         \/\/ Size of file system image (blocks)\r\n  uint nblocks;      \/\/ Number of data blocks\r\n  uint ninodes;      \/\/ Number of inodes.\r\n  uint nlog;         \/\/ Number of log blocks\r\n};\r\n\r\n#define NDIRECT 12\r\n#define NINDIRECT (BSIZE \/ sizeof(uint))\r\n#define MAXFILE (NDIRECT + NINDIRECT)\r\n\r\n\/\/ On-disk inode structure\r\nstruct dinode {\r\n  short type;           \/\/ File type\r\n  short major;          \/\/ Major device number (T_DEV only)\r\n  short minor;          \/\/ Minor device number (T_DEV only)\r\n  short nlink;          \/\/ Number of links to inode in file system\r\n  uint size;            \/\/ Size of file (bytes)\r\n  uint addrs[NDIRECT+1];   \/\/ Data block addresses\r\n};\r\n\r\n\/\/ Inodes per block.\r\n#define IPB           (BSIZE \/ sizeof(struct dinode))\r\n\r\n\/\/ Block containing inode i\r\n#define IBLOCK(i)     ((i) \/ IPB + 2)\r\n\r\n\/\/ Bitmap bits per block\r\n#define BPB           (BSIZE*8)\r\n\r\n\/\/ Block containing bit for block b\r\n#define BBLOCK(b, ninodes) (b\/BPB + (ninodes)\/IPB + 3)\r\n\r\n\/\/ Directory is a file containing a sequence of dirent structures.\r\n#define DIRSIZ 14\r\n\r\nstruct dirent {\r\n  ushort inum;\r\n  char name[DIRSIZ];\r\n};<\/pre>\n
dirlookup\u95a2\u6570\u306f\u3001\u5f15\u6570\u3067\u6e21\u3055\u308c\u305f\u540d\u524d\u306b\u5408\u81f4\u3059\u308b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u4e2d\u304b\u3089\u63a2\u3059\u3002
\n\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u3063\u305f\u5834\u5408\u3001\u305d\u308c\u306b\u5bfe\u5fdc\u3059\u308binode\u306e\u30dd\u30a4\u30f3\u30bf\uff08\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044\uff09\u3092\u8fd4\u3057\u3001\u305d\u3057\u3066\u3001\u547c\u3073\u51fa\u3057\u5074\u304c\u305d\u306e\u898b\u3064\u304b\u3063\u305f\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u7de8\u96c6\u3057\u305f\u3044\u5834\u5408\u306b\u5099\u3048\u3066\u3001*poff\u306b\u305d\u306e\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u306e\u30aa\u30d5\u30bb\u30c3\u30c8\u3092\u683c\u7d0d\u3059\u308b\u3002
\ndirlookup\u95a2\u6570\u304c\u540d\u524d\u306b\u5bfe\u5fdc\u3059\u308b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u898b\u3064\u3051\u305f\u5834\u5408\u3001*poff\u3092\u66f4\u65b0\u3057\u3001\u305d\u306e\u30d6\u30ed\u30c3\u30af\u3092\u89e3\u653e\u3057\u3001\u305d\u3057\u3066iget\u95a2\u6570\u304b\u3089\u53d6\u5f97\u3057\u305f\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044inode\u3092\u8fd4\u3059\u3002\uff08\u3053\u3053\u3001\u4e00\u3064\u524d\u306e\u6587\u3068\u5185\u5bb9\u304c\u88ab\u3063\u3066\u308b\u4e0a\u306b\u3001\u30d6\u30ed\u30c3\u30af\u3092\u89e3\u653e\u3068\u304b\u3001\u30bd\u30fc\u30b9\u3068\u4e00\u81f4\u3057\u3066\u306a\u3044\u90e8\u5206\u304c\u3042\u308b\u305f\u3081\u3001\u3082\u3057\u304b\u3057\u305f\u3089\u6614\u306e\u30bd\u30fc\u30b9\u306b\u5bfe\u3059\u308b\u8aac\u660e\u306e\u6d88\u3057\u5fd8\u308c\u304b\u3082\u3057\u308c\u306a\u3044\u3002\uff09
\niget\u95a2\u6570\u306f\u3001\u30ed\u30c3\u30af\u3055\u308c\u3066\u3044\u306a\u3044inode\u3092\u8fd4\u3059\u3068\u3044\u3046\u3053\u3068\u304c\u305d\u306e\u7406\u7531\u3067\u3042\u308b\u3002
\n\u547c\u3073\u51fa\u3057\u5074\u304c\u30ed\u30c3\u30af\u6e08\u307f\u306edp\u3092\u6301\u3063\u3066\u3044\u3066\u3001\u30ab\u30ec\u30f3\u30c8\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5225\u540d\u3067\u3042\u308b\u300c.\u300d\u306b\u5bfe\u3057\u3066dirlookup\u95a2\u6570\u3092\u4f7f\u3063\u305f\u5834\u5408\u3001\u547c\u3073\u51fa\u3057\u5143\u306b\u623b\u308b\u307e\u3048\u306b\u305d\u306einode\u3092\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3057\u3066\u3001\u3064\u307e\u308adp\u3092\u518d\u5ea6\u30ed\u30c3\u30af\u3057\u3088\u3046\u3068\u3057\u3066\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u3092\u5f15\u304d\u8d77\u3053\u3059\u53ef\u80fd\u6027\u304c\u3042\u308b\u3002\uff08\u8907\u6570\u306e\u30d7\u30ed\u30bb\u30b9\u3084\u89aa\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5225\u540d\u300c..\u300d\u304c\u304b\u3089\u3093\u3067\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u3092\u5f15\u304d\u8d77\u3053\u3059\u3088\u3046\u306a\u3082\u3063\u3068\u8907\u96d1\u306a\u5834\u5408\u3082\u305f\u304f\u3055\u3093\u3042\u308b\u3002\u554f\u984c\u304c\u8d77\u304d\u308b\u306e\u306f\u300c.\u300d\u306e\u3068\u304d\u3060\u3051\u3067\u306f\u306a\u3044\u306e\u3067\u3042\u308b\u3002\uff09
\n\u547c\u3073\u51fa\u3057\u5074\u306f\u3001dp\u3092\u30a2\u30f3\u30ed\u30c3\u30af\u3057\u305d\u3057\u3066\u305d\u308c\u304b\u3089ip\u3092\u30ed\u30c3\u30af\u3059\u308b\u3053\u3068\u3067\u3001\u4e00\u5ea6\u306b\u4e00\u3064\u306e\u30ed\u30c3\u30af\u3060\u3051\u3092\u4fdd\u6301\u3059\u308b\u4e8b\u3092\u4fdd\u8a3c\u51fa\u6765\u308b\u3002
\n\uff08\u3068\u3001\u8aac\u660e\u3055\u308c\u3066\u307e\u3059\u304c\u3001dirlookup\u306e\u30b3\u30fc\u30c9\u30d1\u30b9\u3092\u8ffd\u3063\u3066\u307f\u305f\u3068\u3053\u308d\u3001inode\u5358\u4f4d\u3067\u30ed\u30c3\u30af\u3092\u53d6\u5f97\u3057\u3066\u308b\u3068\u3053\u308d\uff08ilock\u95a2\u6570\u3092\u547c\u3093\u3067\u308b\u3068\u3053\u308d\uff09\u306f\u898b\u5f53\u305f\u308a\u307e\u305b\u3093\u3067\u3057\u305f\u3002\u4f55\u306a\u3093\u3067\u3057\u3087\u3046\u30b3\u30ec\u3002\uff09<\/p>\n
fs.c\u306enamecmp, dirlookup, dirlink\u95a2\u6570<\/p>\n
\/\/ Directories\r\n\r\nint\r\nnamecmp(const char *s, const char *t)\r\n{\r\n  return strncmp(s, t, DIRSIZ);\r\n}\r\n\r\n\/\/ Look for a directory entry in a directory.\r\n\/\/ If found, set *poff to byte offset of entry.\r\n\/\/ Caller must have already locked dp.\r\nstruct inode*\r\ndirlookup(struct inode *dp, char *name, uint *poff)\r\n{\r\n  uint off, inum;\r\n  struct dirent de;\r\n\r\n  if(dp->type != T_DIR)\r\n    panic("dirlookup not DIR");\r\n\r\n  for(off = 0; off < dp->size; off += sizeof(de)){\r\n    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n      panic("dirlink read");\r\n    if(de.inum == 0)\r\n      continue;\r\n    if(namecmp(name, de.name) == 0){\r\n      \/\/ entry matches path element\r\n      if(poff)\r\n        *poff = off;\r\n      inum = de.inum;\r\n      return iget(dp->dev, inum);\r\n    }\r\n  }\r\n\r\n  return 0;\r\n}\r\n\r\n\/\/ Write a new directory entry (name, inum) into the directory dp.\r\nint\r\ndirlink(struct inode *dp, char *name, uint inum)\r\n{\r\n  int off;\r\n  struct dirent de;\r\n  struct inode *ip;\r\n\r\n  \/\/ Check that name is not present.\r\n  if((ip = dirlookup(dp, name, 0)) != 0){\r\n    iput(ip);\r\n    return -1;\r\n  }\r\n\r\n  \/\/ Look for an empty dirent.\r\n  for(off = 0; off < dp->size; off += sizeof(de)){\r\n    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n      panic("dirlink read");\r\n    if(de.inum == 0)\r\n      break;\r\n  }\r\n\r\n  strncpy(de.name, name, DIRSIZ);\r\n  de.inum = inum;\r\n  if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))\r\n    panic("dirlink");\r\n  \r\n  return 0;\r\n}<\/pre>\n
dirlink\u95a2\u6570\u306f\u3001\u5f15\u6570\u3067\u4e0e\u3048\u3089\u308c\u305f\u540d\u524d\u3068inode\u756a\u53f7\u3092\u5143\u306b\u3001\u65b0\u3057\u3044\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30eadp\u306b\u66f8\u304d\u8fbc\u3080\u3002
\n\u3082\u3057\u540d\u524d\u304c\u65e2\u306b\u5b58\u5728\u3057\u305f\u5834\u5408\u3001dirlink\u95a2\u6570\u306f\u30a8\u30e9\u30fc\u3092\u8fd4\u3059\u3002
\n\u30e1\u30a4\u30f3\u306e\u30eb\u30fc\u30d7\u3067\u306f\u3001\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u3092\u63a2\u3059\u305f\u3081\u306b\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30a8\u30f3\u30c8\u30ea\u7fa4\u3092\u8d70\u67fb\u3059\u308b\u3002
\n\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u308c\u3070\u3001\u30eb\u30fc\u30d7\u3092\u7d42\u4e86\u3059\u308b\u3002
\n\u305d\u306e\u6642\u306eoff\u306b\u306f\u305d\u306e\u30a8\u30f3\u30c8\u30ea\u306e\u30aa\u30d5\u30bb\u30c3\u30c8\u304c\u683c\u7d0d\u3055\u308c\u3066\u3044\u308b\u3002
\n\u672a\u5272\u308a\u5f53\u3066\u306e\u30a8\u30f3\u30c8\u30ea\u304c\u898b\u3064\u304b\u3089\u306a\u3044\u5834\u5408\u3001off\u306bdp->size\u304c\u683c\u7d0d\u3055\u308c\u305f\u72b6\u614b\u3067\u30eb\u30fc\u30d7\u3092\u7d42\u3048\u308b\u3002
\n\u3069\u3061\u3089\u306b\u3057\u308d\u3001dirlink\u95a2\u6570\u306f\u305d\u308c\u304b\u3089\u30aa\u30d5\u30bb\u30c3\u30c8off\u306b\u66f8\u304d\u8fbc\u3080\u3053\u3068\u3067\u65b0\u3057\u3044\u30a8\u30f3\u30c8\u30ea\u3092\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306b\u8ffd\u52a0\u3059\u308b\u3002<\/p>\n
\u611f\u60f3<\/h3>\n
\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5b9f\u88c5\u306b\u3064\u3044\u3066\u3067\u3059\u3002
\ninode\u306f\u3059\u3067\u306b\u81ea\u8eab\u306e\u7a2e\u985e\u3092\u8868\u3059\u30d3\u30c3\u30c8\u3092\u6301\u3064\u3053\u3068\u304c\u51fa\u6765\u308b\u3088\u3046\u306b\u306a\u3063\u3066\u308b\u306e\u3067\u3001inode\u306e\u5c64\u304b\u3089\u898b\u308b\u3068\u3059\u3067\u306b\u300c\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u30ec\u30c7\u30a3\u300d\u306a\u72b6\u614b\u3068\u8a00\u3048\u307e\u3059\u3002<\/p>\n
\u305d\u3057\u3066\u3001\u901a\u5e38\u306e\u30d5\u30a1\u30a4\u30eb\u306e\u5834\u5408\u306f\u30c7\u30fc\u30bf\u90e8\u5206\u306b\u5358\u306b\u305d\u306e\u5185\u5bb9\u3092\u6301\u3064\u308f\u3051\u3067\u3059\u304c\u3001\u30c7\u30a3\u30ec\u30af\u30c8\u30ea\u306e\u5834\u5408\u306f\u30d5\u30a1\u30a4\u30eb\u540d\u3068\u305d\u308c\u306b\u5bfe\u5fdc\u3059\u308b\u30d5\u30a1\u30a4\u30eb\u306einode\u3092\u30c7\u30fc\u30bf\u3068\u3057\u3066\u6301\u3064\u308f\u3051\u3067\u3059\u3002<\/p>\n
\u672c\u6587\u306b\u3082\u62ec\u5f27\u4ed8\u304d\u3067\u66f8\u304d\u307e\u3057\u305f\u304c\u3001\u3061\u3087\u3063\u3068\u30bd\u30fc\u30b9\u3068\u5408\u81f4\u3057\u3066\u306a\u3044\u90e8\u5206\u304c\u898b\u53d7\u3051\u3089\u308c\u307e\u3059\u3002
\n\u300c\u30d6\u30ed\u30c3\u30af\u306e\u89e3\u653e\u300d\u306b\u3064\u3044\u3066\u306f\u3001\u6614\u306e\u30bd\u30fc\u30b9\u3092\u307f\u305f\u3089\u78ba\u304b\u306b\u30d6\u30ed\u30c3\u30af\u3092\u78ba\u4fdd\u3057\u3066\u3001\u6700\u5f8c\u306bbrelse\u3092\u547c\u3076\u3088\u3046\u306b\u306a\u3063\u3066\u308b\u6642\u671f\u304c\u3042\u3063\u305f\u306e\u306f\u78ba\u8a8d\u3057\u307e\u3057\u305f\u3002
\n\u30c7\u30c3\u30c9\u30ed\u30c3\u30af\u306e\u65b9\u306b\u3064\u3044\u3066\u306f\u3001\u6614\u306e\u30bd\u30fc\u30b9\u3092\u3056\u3063\u3068\u898b\u305f\u3060\u3051\u3060\u3068\u307e\u3060\u8a72\u5f53\u3059\u308b\u3088\u3046\u306a\u3068\u3053\u308d\u306f\u898b\u3064\u3051\u3066\u306a\u3044\u306e\u3067\u3001\u3082\u3057\u304b\u3057\u305f\u3089\u3001\u3042\u306e\u8aac\u660e\u304c\u5408\u3063\u3066\u3066\u3001\u79c1\u306e\u8a8d\u8b58\u304c\u9593\u9055\u3063\u3066\u308b\u53ef\u80fd\u6027\u3082\u304a\u304a\u3044\u306b\u3042\u308a\u307e\u3059\u3002<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32],"tags":[405],"class_list":["post-1659","post","type-post","status-publish","format-standard","hentry","category-tech","tag-xv6"],"_links":{"self":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1659","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/comments?post=1659"}],"version-history":[{"count":0,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/posts\/1659\/revisions"}],"wp:attachment":[{"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/media?parent=1659"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/categories?post=1659"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peta.okechan.net\/blog\/wp-json\/wp\/v2\/tags?post=1659"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}