{"id":4476,"date":"2015-02-10T17:07:43","date_gmt":"2015-02-10T09:07:43","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=4476"},"modified":"2015-09-07T20:35:22","modified_gmt":"2015-09-07T12:35:22","slug":"open%e5%9c%a8linux%e5%86%85%e6%a0%b8%e7%9a%84%e5%ae%9e%e7%8e%b03-%e8%b7%af%e5%be%84%e6%9f%a5%e6%89%be","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/4476","title":{"rendered":"open()\u5728Linux\u5185\u6838\u7684\u5b9e\u73b0(2)-\u8def\u5f84\u67e5\u627e"},"content":{"rendered":"

1.\u57fa\u672c\u8bf4\u660e<\/h2>\n

\u6587\u4ef6\u7684\u6253\u5f00\u64cd\u4f5c\u5728\u5185\u6838\u4e2d\u7684\u5b9e\u73b0\u601d\u8def\u5f88\u7b80\u5355\uff1a\u5373\u901a\u8fc7\u7528\u6237\u6001\u4f20\u9012\u7684\u8def\u5f84\u9010\u9879\u67e5\u627e\u6587\u4ef6\uff1b\u5982\u679c\u8be5\u6587\u4ef6\u5b58\u5728\uff0c\u90a3\u4e48\u5185\u6838\u5c06\u4e3a\u8be5\u6587\u4ef6\u521b\u5efafile\u7ed3\u6784\uff1b\u540c\u65f6\u5c06\u8be5file\u7ed3\u6784\u4e0efiles\u6570\u7ec4\u5173\u8054\uff0c\u6700\u7ec8\u8fd4\u56de\u6570\u7ec4\u7684\u7d22\u5f15\u4f5c\u4e3a\u7528\u6237\u6001\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002<\/p>\n

\u8def\u5f84\u67e5\u627e\u662f\u5bf9\u7ed9\u5b9a\u7684\u6587\u4ef6\u8def\u5f84\u4ee5\u76ee\u5f55\u9879\u4e3a\u5355\u4f4d\u8fdb\u884c\u9010\u7ea7\u89e3\u6790\u3002\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u9879\u5185\u5bb9\uff1a<\/p>\n

1.\u786e\u5b9a\u8def\u5f84\u67e5\u627e\u7684\u8d77\u59cb\u4f4d\u7f6e\u3002\u6bd4\u5982\uff0c\u8d77\u59cb\u4f4d\u7f6e\u53ef\u80fd\u662fcurrent->fs->cwd\u6216current->fs->root\uff1b<\/p>\n

2.\u5f53\u524d\u8fdb\u7a0b\u662f\u5426\u6709\u5bf9\u76ee\u5f55\u9879\u5173\u8054\u7684inode\u8fdb\u884c\u8bbf\u95ee\u7684\u6743\u9650\uff1b<\/p>\n

3.\u6839\u636e\u5f53\u524d\u7684\u76ee\u5f55\u9879\uff0c\u5bf9\u4e0b\u4e00\u7ea7\u76ee\u5f55\u9879\u8fdb\u884c\u67e5\u627e\uff1b\u8fd9\u91cc\u7684\u67e5\u627e\u53ef\u80fd\u662f\u5411\u4e0b\u67e5\u627e\u5b50\u6587\u4ef6\uff0c\u4e5f\u53ef\u80fd\u662f\u5411\u4e0a\u53cd\u67e5\u7236\u76ee\u5f55\uff08\u6bd4\u5982\u4e0b\u4e00\u7ea7\u76ee\u5f55\u9879\u4e3a\u201c..\u201d\uff09\uff1b<\/p>\n

4.\u5904\u7406\u6302\u8f7d\u70b9\u95ee\u9898\uff1b\u5f53\u524d\u76ee\u5f55\u9879\u5982\u679c\u662f\u6302\u8f7d\u70b9\uff0c\u90a3\u4e48\u5fc5\u987b\u5904\u7406\u4e0d\u540c\u6587\u4ef6\u7cfb\u7edf\u4e4b\u95f4\u7684\u8de8\u8d8a\uff1b<\/p>\n

5.\u5904\u7406\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff1b\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u4e00\u4e2a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u90a3\u4e48\u5fc5\u987b\u8ffd\u968f\uff08follow\uff09\u8be5\u6587\u4ef6\u6240\u6307\u5411\u7684\u771f\u5b9e\u6587\u4ef6\uff1b<\/p>\n

6.\u67e5\u627e\u5e76\u521b\u5efa\u6587\u4ef6\u8def\u5f84\u4e2d\u6240\u7f3a\u5931\u7684\u90e8\u5206\uff1b\u6bd4\u5982\uff0c\u901a\u8fc7open()\u521b\u5efa\u4e00\u4e2a\u65b0\u6587\u4ef6\u65f6\uff0c\u90a3\u4e48\u6240\u4f20\u9012\u7684\u8def\u5f84\u4e2d\u53ef\u80fd\u6709\u90e8\u5206\u76ee\u5f55\u9879\u5f53\u524d\u662f\u4e0d\u5b58\u5728\u7684\uff1b<\/p>\n

\u5176\u4e2d\uff0c\u7b2c1\u9879\u662f\u8def\u5f84\u67e5\u627e\u7684\u9996\u8981\u5de5\u4f5c\uff1b2~6\u9879\u662f\u5728\u8def\u5f84\u67e5\u627e\u8fc7\u7a0b\u4e2d\uff0c\u9488\u5bf9\u6bcf\u4e2a\u76ee\u5f55\u9879\u8fdb\u884c\u68c0\u67e5\u786e\u8ba4\u7684\u3002<\/p>\n

\u8d1f\u8d23open\u7cfb\u7edf\u8c03\u7528\u57fa\u672c\u5b9e\u73b0\u7684\u662fdo_sys_open()\uff0c\u5176\u5185\u90e8\u6240\u8c03\u7528\u7684do_filp_open\u51fd\u6570\u627f\u62c5\u4e86\u5927\u90e8\u5206open\u7684\u5b9e\u73b0\u8fc7\u7a0b\uff0c\u5176\u4e2d\u5c31\u5305\u62ec\u8def\u5f84\u67e5\u627e\u3002<\/p>\n

2.\u51fd\u6570\u5206\u6790<\/h2>\n

2.1.do_filp_open<\/h3>\n

open\u64cd\u4f5c\u7684\u6838\u5fc3\u51fd\u6570\u4e3ado_filp_open\uff0c\u5b83\u89e3\u6790\u6587\u4ef6\u8def\u5f84\u5e76\u65b0\u5efafile\u7ed3\u6784\u3002\u8be5\u51fd\u6570\u5185\u90e8\u521b\u5efand\u53d8\u91cf\uff0c\u4f20\u5165\u5e76\u8c03\u7528\u4e86path_openat()\u3002nameidata\u7c7b\u578b\u7684nd\u5728\u6574\u4e2a\u8def\u5f84\u67e5\u627e\u8fc7\u7a0b\u4e2d\u5145\u5f53\u4e2d\u95f4\u53d8\u91cf\uff0c\u5b83\u65e2\u53ef\u4ee5\u4e3a\u5f53\u524d\u67e5\u627e\u8f93\u5165\u6570\u636e\uff0c\u53c8\u53ef\u4ee5\u4fdd\u5b58\u672c\u6b21\u67e5\u627e\u7684\u7ed3\u679c\u3002<\/p>\n

\r\nstruct file *do_filp_open(int dfd, const char *pathname,\r\n\t\tconst struct open_flags *op, int flags)\r\n{\r\n\tstruct nameidata nd;\r\n\tstruct file *filp;\r\n\r\n\tfilp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);\r\n\tif (unlikely(filp == ERR_PTR(-ECHILD)))\r\n\t\tfilp = path_openat(dfd, pathname, &nd, op, flags);\r\n\tif (unlikely(filp == ERR_PTR(-ESTALE)))\r\n\t\tfilp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);\r\n\treturn filp;\r\n}\r\n<\/pre>\n
\u5728\u8fd9\u4e2a\u51fd\u6570\u4e2d\uff0cpath_openat\u6709\u53ef\u80fd\u4f1a\u88ab\u8c03\u7528\u4e09\u6b21\u3002\u901a\u5e38\u5185\u6838\u4e3a\u4e86\u63d0\u9ad8\u6548\u7387\uff0c\u4f1a\u9996\u5148\u5728RCU\u6a21\u5f0f\uff08rcu-walk\uff09\u4e0b\u8fdb\u884c\u6587\u4ef6\u6253\u5f00\u64cd\u4f5c\uff1b\u5982\u679c\u5728\u6b64\u65b9\u5f0f\u4e0b\u6253\u5f00\u5931\u8d25\uff0c\u5219\u8fdb\u5165\u666e\u901a\u6a21\u5f0f\uff08ref-walk\uff09\u3002\u7b2c\u4e09\u6b21\u8c03\u7528\u6bd4\u8f83\u5c11\u7528\uff0c\u76ee\u524d\u53ea\u6709\u5728nfs\u6587\u4ef6\u7cfb\u7edf\u624d\u6709\u53ef\u80fd\u4f1a\u88ab\u4f7f\u7528\u3002\u63a5\u4e0b\u6765\u5c06\u4e3b\u8981\u8bf4\u660e\u524d\u4e24\u79cd\u8c03\u7528\u65b9\u5f0f\u3002<\/p>\n
2.2.path_openat<\/h3>\n
path_openat()\u5176\u51fd\u6570\u58f0\u660e\u5982\u4e0b\uff1a<\/p>\n
\r\nstatic struct file *path_openat(int dfd, const char *pathname,\r\n\t\tstruct nameidata *nd, const struct open_flags *op, int flags);\r\n<\/pre>\n
\u8be5\u51fd\u6570\u63cf\u8ff0\u4e86\u6574\u4e2a\u8def\u5f84\u67e5\u627e\u8fc7\u7a0b\u7684\u57fa\u672c\u6b65\u9aa4\uff0c\u8fd9\u91cc\u505a\u7b80\u5355\u8bf4\u660e\u3002\u6bcf\u4e2a\u5177\u4f53\u6b65\u9aa4\u7684\u5b9e\u73b0\u8fc7\u7a0b\uff0c\u5c06\u5728\u672c\u6587\u4ee5\u53ca\u540e\u7eed\u6587\u7ae0\u4e2d\u505a\u8be6\u6790\u8bf4\u660e\u3002<\/p>\n
1.\u9996\u5148\u901a\u8fc7get_empty_flip()\u5206\u914d\u4e00\u4e2a\u65b0\u7684file\u7ed3\u6784\uff0c\u5206\u914d\u524d\u4f1a\u5bf9\u5f53\u524d\u8fdb\u7a0b\u7684\u6743\u9650\u548c\u6587\u4ef6\u6700\u5927\u6570\u8fdb\u884c\u5224\u65ad\uff1b<\/p>\n
2.path_init()\u5bf9\u63a5\u4e0b\u6765\u7684\u8def\u5f84\u904d\u5386\u505a\u4e00\u4e9b\u51c6\u5907\u5de5\u4f5c\uff0c\u4e3b\u8981\u7528\u4e8e\u5224\u65ad\u8def\u5f84\u904d\u5386\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u5373\u901a\u8fc7\u6839\u76ee\u5f55\/\uff0c\u6216\u5f53\u524d\u8def\u5f84\uff08pwd\uff09\uff0c\u6216\u6307\u5b9a\u8def\u5f84\uff08openat\u7cfb\u7edf\u8c03\u7528\u53ef\u4ee5\u6307\u5b9a\uff09\uff1b<\/p>\n
3.\u5c06\u5f53\u524d\u8fdb\u7a0b\u7684total_link_count\u7f6e\u4e3a0\uff1b<\/p>\n
3.link_path_walk()\u5bf9\u6240\u6253\u5f00\u6587\u4ef6\u8def\u5f84\u8fdb\u884c\u9010\u4e00\u89e3\u6790\uff0c\u6bcf\u4e2a\u76ee\u5f55\u9879\u7684\u89e3\u6790\u7ed3\u679c\u90fd\u5b58\u5728nd\u53c2\u6570\u4e2d\uff1b<\/p>\n
4.\u6839\u636e\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u7684\u7ed3\u679c\uff0cdo_last()\u5c06\u586b\u5145filp\u6240\u6307\u5411\u7684file\u7ed3\u6784\uff1b<\/p>\n
5.\u5982\u679c\u4e0a\u4e00\u6b65\u4e2d\u7684filp\u6240\u6307\u4e3a\u7a7a\uff0c\u5c06\u8bf4\u660e\u5f53\u524d\u6587\u4ef6\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff1b<\/p>\n
6.\u5982\u679c\u8bbe\u7f6e\u4e86LOOKUP_FOLLOW\u6807\u5fd7\uff0c\u5219\u901a\u8fc7follow_link()\u8fdb\u5165\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\u6240\u6307\u6587\u4ef6\uff0c\u586b\u5145file\uff1b\u5426\u5219\uff0c\u76f4\u63a5\u8fd4\u56de\u5f53\u524d\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\u7684filp\uff1b<\/p>\n
7.\u6700\u7ec8\u8fd4\u56defile\u7ed3\u6784\uff1b<\/p>\n
2.3.path_init<\/h3>\n
path_init()\u7528\u4e8e\u8bbe\u7f6e\u8def\u5f84\u641c\u5bfb\u7684\u8d77\u59cb\u4f4d\u7f6e\uff0c\u4e3b\u8981\u4f53\u73b0\u5728\u8bbe\u7f6end\u53d8\u91cf\u3002\u5176\u51fd\u6570\u58f0\u660e\u5982\u4e0b\uff1a<\/p>\n
\r\nstatic struct file *path_openat(int dfd, const char *pathname,\r\n\t\tstruct nameidata *nd, const struct open_flags *op, int flags);<\/pre>\n
\u5982\u679cflags\u8bbe\u7f6e\u4e86LOOKUP_ROOT\u6807\u5fd7\uff0c\u5219\u8868\u793a\u8be5\u51fd\u6570\u88abopen_by_handle_at\u51fd\u6570\u8c03\u7528\uff0c\u8be5\u51fd\u6570\u5c06\u6307\u5b9a\u4e00\u4e2a\u8def\u5f84\u4f5c\u4e3a\u6839\uff1b\u8fd9\u5c5e\u4e8e\u7279\u6b8a\u60c5\u51b5\uff0c\u8fd9\u91cc\u6682\u4e0d\u5206\u6790\uff1b\u63a5\u4e0b\u6765path_init\u4e3b\u8981\u5206\u4e09\u79cd\u60c5\u51b5\u8bbe\u7f6end\u3002<\/p>\n
1.\u5982\u679c\u8def\u5f84\u540dname\u4ee5\/\u4e3a\u8d77\u59cb\uff0c\u5219\u8868\u793a\u5f53\u524d\u8def\u5f84\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u901a\u8fc7set_root\u8bbe\u7f6end\uff1b\u5426\u5219\uff0c\u8868\u793a\u8def\u5f84name\u662f\u4e00\u4e2a\u76f8\u5bf9\u8def\u5f84\uff1b<\/p>\n
2.\u5982\u679cdfd\u4e3aAT_FDCWD\uff0c\u90a3\u4e48\u8868\u793a\u8fd9\u4e2a\u76f8\u5bf9\u8def\u5f84\u662f\u4ee5\u5f53\u524d\u8def\u5f84pwd\u4f5c\u4e3a\u8d77\u59cb\u7684\uff0c\u56e0\u6b64\u901a\u8fc7pwd\u8bbe\u7f6end\uff1b<\/p>\n
3.\u5982\u679cdfd\u4e0d\u662fAT_FDCWD\uff0c\u8868\u793a\u8fd9\u4e2a\u76f8\u5bf9\u8def\u5f84\u662f\u7528\u6237\u8bbe\u7f6e\u7684\uff0c\u9700\u8981\u901a\u8fc7dfd\u83b7\u53d6\u5177\u4f53\u76f8\u5bf9\u8def\u5f84\u4fe1\u606f\uff0c\u8fdb\u800c\u8bbe\u7f6end\uff1b<\/p>\n
\u4e0a\u8ff0\u6b65\u9aa42\u548c3\u90fd\u8868\u793a\u8981\u6253\u5f00\u7684\u6587\u4ef6\u8def\u5f84\u662f\u4ee5\u76f8\u5bf9\u8def\u5f84\u4e3a\u8d77\u59cb\u7684\uff0c\u4f46\u662f\u4e24\u8005\u7a0d\u6709\u4e0d\u540c\u3002\u6b65\u9aa42\u4e3a\u6211\u4eec\u901a\u5e38\u9ed8\u8ba4\u7684open\u64cd\u4f5c\uff0c\u800c\u6b65\u9aa43\u5177\u4f53\u6307\u7684\u662fopenat\u7cfb\u7edf\u8c03\u7528\uff0c\u8fd9\u4e00\u70b9\u4f53\u73b0\u5728\u4e0d\u540c\u6253\u5f00\u7cfb\u7edf\u8c03\u7528\u5411do_sys_open\u4e2ddfd\u53c2\u6570\u6240\u4f20\u9012\u7684\u503c\u3002<\/p>\n
\u4e0d\u7ba1\u4e0a\u8ff0\u54ea\u4e00\u79cd\u6253\u5f00\u60c5\u51b5\uff0c\u5747\u8981\u8bbe\u7f6end\u53d8\u91cf\uff0c\u5b83\u662f\u4e00\u4e2anameidata\u7c7b\u578b\u3002\u5728path_init\u4e2d\uff0cnd\u7684last_type\u90fd\u88ab\u9ed8\u8ba4\u8bbe\u7f6e\u6210\u4e86LAST_ROOT\u3002<\/p>\n
\u5728path_init\u4e2d\uff0c\u5982\u679c\u4e3a\u4e0a\u8ff0\u6b65\u9aa41\uff0c\u5219\u901a\u8fc7\u5f53\u524d\u8fdb\u7a0b\u7684fs->root\u5b57\u6bb5\u66f4\u65b0nd\u7684root\u5b57\u6bb5\uff0c\u5e76\u4e14nd\u7684path\u5b57\u6bb5\u4e5f\u6307\u5411root\u5b57\u6bb5\uff1b\u5982\u679c\u4e3a\u6b65\u9aa42\uff0c\u5219\u901a\u5f53\u524d\u8fdb\u7a0bfs->pwd\u66f4\u65b0nd\u7684path\u5b57\u6bb5\uff1b\u5982\u679c\u4e3a\u6b65\u9aa43\uff0c\u5219\u5148\u901a\u8fc7\u6587\u4ef6\u63cf\u8ff0\u7b26dfd\u83b7\u53d6\u7528\u6237\u6307\u5b9a\u7684\u5de5\u4f5c\u76ee\u5f55file\u7ed3\u6784\uff0c\u7136\u540e\u901a\u8fc7file\u7684f_path\u5b57\u6bb5\u66f4\u65b0nd\u7684path\u5b57\u6bb5\u3002\u9700\u8981\u6ce8\u610f\u7684\uff0c\u6b65\u9aa42\u548c\u6b65\u9aa43\u5747\u672a\u8bbe\u7f6eroot\u5b57\u6bb5\u3002\u6700\u7ec8\uff0cnd\u4e2d\u7684inode\u5b57\u6bb5\u5747\u7531path.dentry->d_inode\u66f4\u65b0\u3002<\/p>\n
2.4.link_path_walk<\/h3>\n
link_path_walk()\u4e3b\u8981\u7528\u4e8e\u5bf9\u5404\u76ee\u5f55\u9879\u9010\u7ea7\u904d\u5386\u3002\u5176\u51fd\u6570\u58f0\u660e\u5982\u4e0b\uff1a<\/p>\n
static int link_path_walk(const char *name, struct nameidata *nd);<\/pre>\n
\u8be5\u51fd\u6570\u6838\u5fc3\u90e8\u5206\u662f\u901a\u8fc7\u4e00\u4e2a\u5faa\u73af\u5b8c\u6210\u7684\u3002\u5728\u8fdb\u5165\u8fd9\u4e2a\u5faa\u73af\u4e4b\u524d\uff0c\u5982\u679c\u8def\u5f84name\u662f\u4e00\u4e2a\u7edd\u5bf9\u8def\u5f84\uff0c\u90a3\u4e48\u8be5\u51fd\u6570\u8fd8\u5bf9\u8def\u5f84\u8fdb\u884c\u4e86\u4e00\u4e9b\u5904\u7406\uff0c\u5373\u8fc7\u6ee4\u6389\u7edd\u5bf9\u8def\u5f84\/\u524d\u591a\u4f59\u7684\u7b26\u53f7\/\u3002<\/p>\n
\u5728\u5faa\u73af\u4e2d\uff0c\u6240\u8981\u505a\u7684\u5de5\u4f5c\u5305\u542b\u5982\u4e0b\uff1a<\/p>\n
1.next\u4e3apath\u7c7b\u578b\u7684\u53d8\u91cf\uff0c\u6307\u5411\u4e0b\u4e00\u4e2a\u76ee\u5f55\u9879\uff1bname\u6307\u5411\u88ab\u641c\u7d22\u7684\u8def\u5f84\uff1bthis\u4e3aqstr\u7c7b\u578b\u53d8\u91cf\uff0c\u8868\u793a\u5f53\u524d\u641c\u7d22\u8def\u5f84\u6240\u5904\u76ee\u5f55\u9879\u7684\u54c8\u5e0c\u503c\uff0c\u7528type\u6307\u660e\u5f53\u524d\u76ee\u5f55\u9879\u7c7b\u578b\uff1b<\/p>\n
2.\u5982\u679c\u6709\u5fc5\u8981\uff0c\u4e3a\u5f53\u524d\u76ee\u5f55\u9879\u66f4\u65b0\u54c8\u5e0c\u503c\uff0c\u5e76\u4fdd\u5b58\u5728this\u4e2d\uff1b<\/p>\n
3.\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u201c.\u201d\uff0c\u5219type\u4e3aLAST_DOT\uff1b\u5982\u679c\u76ee\u5f55\u9879\u4e3a\u201c..\u201d\uff0c\u5219type\u4e3aLAST_DOTDOT\uff1b\u5426\u5219\uff0ctype\u9ed8\u8ba4\u4e3aLAST_NORM\uff1b<\/p>\n
4.\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u7d27\u90bb\u7684\u5206\u9694\u7b26\/\u6709\u591a\u4e2a\uff08\u6bd4\u5982\/home\/\/\/edsionte\uff09\uff0c\u5219\u5c06\u5176\u8fc7\u6ee4\uff0c\u5373\u4f7fname\u6307\u5411\u6700\u540e\u4e00\u4e2a\/\uff1b<\/p>\n
5.\u901a\u8fc7walk_component()\u5904\u7406\u5f53\u524d\u76ee\u5f55\u9879\uff0c\u66f4\u65b0nd\u548cnext\uff1b\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u5219\u53ea\u66f4\u65b0next\uff1b<\/p>\n
6.\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u5219\u901a\u8fc7nested_symlink()\u8fdb\u884c\u5904\u7406\uff0c\u66f4\u65b0nd\uff1b<\/p>\n
7.\u5982\u679cname\u4e2d\u7684\u76ee\u5f55\u9879\u904d\u5386\u5b8c\u6bd5\uff0c\u5219\u7ed3\u675f\uff1b\u5426\u5219\u8fdb\u884c\u4e0b\u4e00\u8f6e\u5faa\u73af\uff1b<\/p>\n
\u901a\u8fc7\u4e0a\u8ff0\u5faa\u73af\uff0c\u5c06\u7528\u6237\u6240\u6307\u5b9a\u7684\u8def\u5f84name\u4ece\u5934\u81f3\u5c3e\u8fdb\u884c\u4e86\u641c\u7d22\uff0c\u81f3\u6b64nd\u4fdd\u5b58\u4e86\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u7684\u4fe1\u606f\uff0c\u4f46\u662f\u5185\u6838\u5e76\u6ca1\u6709\u786e\u5b9a\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u662f\u5426\u771f\u7684\u5b58\u5728\uff0c\u8fd9\u4e9b\u5de5\u4f5c\u5c06\u5728do_last()\u4e2d\u8fdb\u884c\u3002<\/p>\n
2.5.walk_component<\/h3>\n
walk_component()\u4f4d\u4e8elink_path_walk\u51fd\u6570\u4e4b\u4e2d\u3002\u8be5\u51fd\u6570\u58f0\u660e\u5982\u4e0b\uff1a<\/p>\n
static inline int walk_component(struct nameidata *nd, struct path *path,\r\n\t\tstruct qstr *name, int type, int follow)\r\n<\/pre>\n
\u5728\u6bcf\u6b21\u5faa\u73af\u4e2d\uff0c\u5b83\u5c06\u83b7\u53d6\u5f53\u524d\u76ee\u5f55\u9879\u7684dentry\u7ed3\u6784\u4ee5\u53cainode\u7ed3\u6784\u7b49\u4fe1\u606f\uff0c\u5373\u66f4\u65b0nd\u3002\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u5bf9\u5e94\u7684inode\u4e0d\u5b58\u5728\uff0c\u90a3\u4e48\u5c06\u5411\u7528\u6237\u6001\u8fd4\u56deENOENT\uff1b\u5728\u8be5\u51fd\u6570\u4e2d\uff0c\u5b9a\u4e49\u4e86\u53d8\u91cfinode\uff0c\u5b83\u5c06\u4fdd\u5b58\u5f53\u524d\u76ee\u5f55\u9879\u5bf9\u5e94\u7684\u7d22\u5f15\u8282\u70b9\u3002<\/p>\n
\u6839\u636e\u5f53\u524d\u76ee\u5f55\u9879\u7c7b\u578b\u7684\u4e0d\u540c\uff0c\u5bf9\u76ee\u5f55\u9879\u7684\u5904\u7406\u6d41\u7a0b\u4e5f\u4e0d\u540c\u3002\u8be5\u51fd\u6570\u7684\u5177\u4f53\u6d41\u7a0b\u5982\u4e0b\uff1a<\/p>\n
1.\u5982\u679ctype\u4e3aLAST_DOT\u548cLAST_DOTDOT\uff0c\u5c06\u8fdb\u5165handle_dots()\u5bf9\u5f53\u524d\u76ee\u5f55\u9879\u8fdb\u884c\u201cwalk\u201d\uff1b<\/p>\n
2.\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u666e\u901a\u76ee\u5f55\u9879\uff0c\u5219\u901a\u8fc7do_lookup()\u5bf9\u5176\u8fdb\u884c\u5904\u7406\uff1b<\/p>\n
3.\u5982\u679cshould_follow_link()\u83b7\u77e5\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u5219\u9000\u51fa\u5f53\u524d\u51fd\u6570\u3002\u5177\u4f53\u7684\uff0c\u5982\u679c\u5f53\u524dwalk\u6a21\u5f0f\u4e3arcu\uff0c\u5219\u76f4\u63a5\u8fd4\u56de-ECHILD\uff0c\u5426\u5219\u8fd4\u56de1\u3002\u8fd4\u56de-ECHILD\u65f6\u5019\uff0c\u5c06\u76f4\u63a5\u8fd4\u56de\u5230do_filp_open()\uff0c\u8fdb\u884cref-walk\u6a21\u5f0f\u91cd\u65b0\u67e5\u627e\uff1b\u5982\u679c\u8fd4\u56de1\uff0c\u5219\u8fd4\u56de\u81f3\u4e0a\u5c42\u51fd\u6570link_path_walk()\uff0c\u8fdb\u5165netsted_symlink()\u8fdb\u884c\u7b26\u53f7\u94fe\u63a5\u76ee\u5f55\u9879\u7684\u5904\u7406\uff1b<\/p>\n
\u4e5f\u5c31\u662f\u8bf4\uff0c\u4e00\u65e6\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u5219\u9700\u8981\u901a\u8fc7ref-walk\u8fdb\u884c\u5904\u7406\u3002\u8fd9\u662f\u56e0\u4e3a\u5904\u7406\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\u9700\u8981\u901a\u8fc7\u5177\u4f53\u6587\u4ef6\u7684\u5904\u7406\u51fd\u6570\u8fdb\u884c\u5b9e\u73b0\uff0c\u8fd9\u4e2a\u8fc7\u7a0b\u53ef\u80fd\u4f1a\u5bfc\u81f4\u963b\u585e\uff0c\u8fd9\u4e0ercu\u65b9\u5f0f\u662f\u8fdd\u80cc\u7684\uff0c\u56e0\u6b64\u9700\u8981\u5148\u8f6c\u6362\u5230ref-walk\uff1b<\/p>\n
4.\u81f3\u6b64\uff0c\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u67e5\u627e\u6210\u529f\uff0c\u5219\u901a\u8fc7path_to_nameidata()\u66f4\u65b0nd\uff1b<\/p>\n
3.\u603b\u7ed3<\/h2>\n
\u672c\u6587\u91cd\u70b9\u8bf4\u660e\u4e86open\u5b9e\u73b0\u8fc7\u7a0b\u4e2d\u7684\u8def\u5f84\u67e5\u627e\u8fc7\u7a0b\u3002open\u4e2d\u7684\u8def\u5f84\u67e5\u627e\u662f\u9488\u5bf9\u7528\u6237\u6240\u4f20\u9012\u8def\u5f84\uff0c\u6309\u7167\u76ee\u5f55\u9879\u9010\u7ea7\u8fdb\u884c\u904d\u5386\u67e5\u627e\uff1b\u5bf9\u4e8e\u8def\u5f84\u4e2d\u7684\u6bcf\u4e2a\u76ee\u5f55\u9879\uff0c\u4e0d\u540c\u7c7b\u578b\u7684\u76ee\u5f55\u9879\u6709\u4e0d\u540c\u7684\u5904\u7406\u65b9\u6cd5\u3002\u5982\u679c\u9700\u8981\u4e86\u89e3\u5bf9\u201c.\u201d\u3001\u201c..\u201d\u4ee5\u53ca\u7b26\u53f7\u8fde\u63a5\u6587\u4ef6\u7684\u5904\u7406\u65b9\u6cd5\uff0c\u53ef\u4ee5\u9605\u8bfb\u672c\u7cfb\u5217\u540e\u7eed\u6587\u7ae0\u3002<\/p>\n
\u53c2\u8003\u8d44\u6599\uff1a<\/strong><\/p>\n
1.Linux\u6e90\u78013.2.69\uff1b<\/strong><\/p>\n
2.Linux\u7cfb\u7edf\u8c03\u7528open\u4e03\u65e5\u6e38\uff1ahttp:\/\/blog.chinaunix.net\/uid-20522771-id-4419666.html<\/strong><\/p>\n
3.\u6df1\u5165\u7406\u89e3Linux\u5185\u6838\uff1ahttp:\/\/book.douban.com\/subject\/2287506\/\uff1b<\/strong><\/p>\n
4.\u6df1\u5165Linux\u5185\u6838\u67b6\u6784\uff1ahttp:\/\/book.douban.com\/subject\/4843567\/\uff1b<\/strong><\/p>\n
5.Linux\u5185\u6838\u63a2\u79d8\uff1ahttp:\/\/book.douban.com\/subject\/25817503\/\uff1b<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"
1.\u57fa\u672c\u8bf4\u660e \u6587\u4ef6\u7684\u6253\u5f00\u64cd\u4f5c\u5728\u5185\u6838\u4e2d\u7684\u5b9e\u73b0\u601d\u8def\u5f88\u7b80\u5355\uff1a\u5373\u901a\u8fc7\u7528\u6237\u6001\u4f20\u9012\u7684\u8def\u5f84\u9010\u9879\u67e5\u627e\u6587\u4ef6\uff1b\u5982\u679c\u8be5\u6587\u4ef6\u5b58\u5728\uff0c\u90a3\u4e48 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[110,175],"tags":[394,151,393],"class_list":["post-4476","post","type-post","status-publish","format-standard","hentry","category-linux","category-175","tag-path_walk","tag-151","tag-393"],"views":18366,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4476","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/comments?post=4476"}],"version-history":[{"count":11,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4476\/revisions"}],"predecessor-version":[{"id":4548,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4476\/revisions\/4548"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=4476"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=4476"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=4476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}