{"id":4506,"date":"2015-04-19T18:33:03","date_gmt":"2015-04-19T10:33:03","guid":{"rendered":"http:\/\/edsionte.com\/techblog\/?p=4506"},"modified":"2015-09-07T20:35:42","modified_gmt":"2015-09-07T12:35:42","slug":"open%e5%9c%a8linux%e5%86%85%e6%a0%b8%e7%9a%84%e5%ae%9e%e7%8e%b07-%e6%89%93%e5%bc%80%e6%93%8d%e4%bd%9c%e5%88%86%e6%9e%90","status":"publish","type":"post","link":"http:\/\/edsionte.com\/techblog\/archives\/4506","title":{"rendered":"open()\u5728Linux\u5185\u6838\u7684\u5b9e\u73b0(6)-\u6253\u5f00\u64cd\u4f5c\u5206\u6790"},"content":{"rendered":"

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

\u5f53link_path_walk()\u8fdb\u884c\u5b8c\u6bd5\u4e4b\u540e\uff0c\u4e5f\u5c31\u610f\u5473\u7740\u6587\u4ef6\u8def\u5f84\u7684\u67e5\u627e\u4f4d\u4e8e\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u4e2d\uff0c\u8fd9\u4e2a\u76ee\u5f55\u9879\u662f\u5426\u5b58\u5728\u76ee\u524d\u8fd8\u4e0d\u660e\u786e\uff0c\u56e0\u4e3a\u8fd8\u9700\u8981\u914d\u5408\u7528\u6237\u4f7f\u7528open()\u65f6\u6240\u4f20\u9012\u7684\u53c2\u6570\uff0c\u6709\u53ef\u80fd\u662f\u6253\u5f00\u5df2\u5b58\u5728\u6587\u4ef6\uff0c\u6709\u53ef\u80fd\u662f\u521b\u5efa\u65b0\u6587\u4ef6\u3002<\/p>\n

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

2.1.do_last()<\/h3>\n

\u5728path_openat()\u4e2d\uff0c\u7ecf\u8fc7link_path_walk()\u5bf9open\u8def\u5f84\u7684\u67e5\u627e\uff0c\u5c06\u8fdb\u5165do_last()\u5bf9\u8def\u5f84\u4e2d\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u505a\u5904\u7406\u3002\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u53ef\u80fd\u662f\u5404\u79cd\u7c7b\u578b\uff0c\u6bd4\u5982\u201c.\u201d\u6216\u8005\u201c..\u201d\uff0c\u4e5f\u53ef\u80fd\u662f\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\u6216\u8005\u662f\u201c\/\u201d\uff0c\u5728\u6b64\u5c06\u5bf9\u666e\u901a\u76ee\u5f55\u9879\uff08LAST_NORM\uff09\u6240\u8fdb\u884c\u7684\u5904\u7406\u8fdb\u884c\u8bf4\u660e\u3002<\/p>\n

\u5bf9\u4e8eopen\u7cfb\u7edf\u8c03\u7528\u6765\u8bf4\uff0cflags\u53c2\u6570\u901a\u8fc7\u53d6\u4e0d\u540c\u7684\u503c\u53ef\u4ee5\u8fdb\u884c\u4e0d\u540c\u7684\u64cd\u4f5c\uff0c\u4e0b\u9762\u5c06\u9488\u5bf9open\u6700\u5e38\u7528\u7684\u4e24\u79cd\u64cd\u4f5c\u8fdb\u884c\u8bf4\u660e\uff0c\u5373\u6253\u5f00\u6587\u4ef6\u548c\u521b\u5efa\u6587\u4ef6\u3002<\/p>\n

2.1.1.\u6253\u5f00\u6587\u4ef6<\/strong><\/p>\n

\u5982\u679c\u4f7f\u7528open\u7cfb\u7edf\u8c03\u7528\u7684\u4f5c\u7528\u4ec5\u4ec5\u662f\u6253\u5f00\u6587\u4ef6\uff0c\u90a3\u4e48flags\u4e2d\u5fc5\u7136\u4e0d\u4f1a\u5b58\u5728O_CREAT\u6807\u5fd7\uff0c\u57fa\u672c\u6b65\u9aa4\u5982\u4e0b\uff1a<\/p>\n

1.\u901a\u8fc7walk_component()\u5bf9\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u8fdb\u884c\u67e5\u627e\u3002walk_component()\u9996\u5148\u5728rcu\u6a21\u5f0f\u4e0b\u5bf9\u76ee\u5f55\u9879\u8fdb\u884c\u67e5\u627e\uff0c\u5982\u679c\u67e5\u627e\u5931\u8d25\u5219\u8fdb\u884cref\u6a21\u5f0f\u4e0b\u7684\u76ee\u5f55\u9879\u67e5\u627e\u3002\u5982\u679c\u4e24\u79cd\u65b9\u5f0f\u5747\u67e5\u627e\u5931\u8d25\uff0c\u5219\u8fd4\u56de\u503c\u5c0f\u4e8e0\uff1b\u5982\u679c\u5f53\u524d\u76ee\u5f55\u9879\u4e3a\u7b26\u53f7\u94fe\u63a5\u6587\u4ef6\uff0c\u5219\u8fd4\u56de1\uff0c\u8be5\u51fd\u6570\u5c06\u76f4\u63a5\u8fd4\u56de\u5230path_openat()\u4e2d\uff0c\u8fdb\u800c\u901a\u8fc7follow_link()\u8fdb\u884c\u5904\u7406\uff1b\u5982\u679c\u67e5\u627e\u6210\u529f\uff0c\u5219\u8df3\u81f3ok\u6807\u53f7\u5904\uff1b<\/p>\n

2.\u5b8c\u6210\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u7684\u67e5\u627e\u5de5\u4f5c\uff0c\u5373\u5c06\u8fdb\u884c\u771f\u6b63\u7684\u6253\u5f00\u64cd\u4f5c\u3002\u4e0d\u8fc7\uff0c\u5728\u8fd9\u4e4b\u524d\u8fd8\u9700\u8981\u901a\u8fc7may_open()\u5bf9\u5f53\u524dinode\u7684\u6743\u9650\u548c\u6807\u5fd7\u4f4d\u8fdb\u884c\u68c0\u67e5\uff1b<\/p>\n

3.\u5982\u679c\u4e00\u5207\u987a\u5229\uff0c\u5219\u901a\u8fc7nameidata_to_filp()\u6267\u884c\u6253\u5f00\u64cd\u4f5c\uff1b<\/p>\n

4.\u8fd4\u56defile\u7ed3\u6784\u3002<\/p>\n

2.1.2.\u521b\u5efa\u6587\u4ef6<\/strong><\/p>\n

\u5982\u679c\u521b\u5efa\u4e00\u4e2a\u6587\u4ef6\uff0c\u90a3\u4e48flags\u5fc5\u7136\u8bbe\u7f6e\u6807\u5fd7O_CREAT\u3002\u57fa\u672c\u6b65\u9aa4\u5982\u4e0b\uff1a<\/p>\n

1.\u9996\u5148\u4f1a\u68c0\u67e5\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u662f\u5426\u4ee5\u201c\/\u201d\u7ed3\u5c3e\uff0c\u5982\u679c\u662f\uff0c\u5219\u76f4\u63a5\u9519\u8bef\u8fd4\u56de\u3002\u5426\u5219\uff0c\u7ee7\u7eed\u8fdb\u884c\uff1b<\/p>\n

2.\u901a\u8fc7lookup_hash()\u5bf9\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u8fdb\u884c\u67e5\u627e\uff0c\u8fd9\u4e2a\u67e5\u627e\u51fd\u6570\u5c06\u8fd4\u56de\u4e00\u4e2adentry\u3002\u5982\u679c\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u786e\u5b9e\u5b58\u5728\uff0c\u90a3\u4e48dentry->d_inode\u4e0d\u4e3a\u7a7a\uff0c\u90a3\u4e48\u8bf4\u660e\u8981\u521b\u5efa\u7684\u8fd9\u4e2a\u6587\u4ef6\u4e8b\u5148\u662f\u5b58\u5728\u7684\u3002\u6b64\u65f6\u5148\u8fdb\u884c\u6807\u5fd7\u4f4d\u7684\u5224\u65ad\uff0c\u6bd4\u5982\u5982\u679c\u7528\u6237\u8bbe\u7f6e\u4e86O_EXCL\u6807\u5fd7\uff0c\u90a3\u4e48\u6b64\u65f6\u5c31\u4e0d\u5fc5\u7ee7\u7eed\u8fdb\u884c\u76f4\u63a5\u9519\u8bef\u8fd4\u56de\u3002\u5982\u679c\u6807\u5fd7\u68c0\u67e5\u4e00\u5207\u6210\u529f\uff0c\u5219\u8fdb\u884c\u6b65\u9aa44\uff1b\u5426\u5219\uff0cdentry->d_inode\u5c06\u4e3a\u7a7a\uff0c\u7ee7\u7eed\u8fdb\u884c\uff1b<\/p>\n

3.\u5f53\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879inode\u4e3a\u7a7a\u65f6\uff0c\u90a3\u4e48\u9700\u8981\u901a\u8fc7vfs_create()\u8c03\u7528\u5177\u4f53\u6587\u4ef6\u7cfb\u7edf\u7684create\u94a9\u5b50\u51fd\u6570\u521b\u5efa\u8fd9\u4e2a\u6587\u4ef6\uff1b<\/p>\n

4.\u901a\u8fc7may_open()\u68c0\u67e5inode\u6807\u5fd7\u4f4d\u548c\u6743\u9650\u7684\u5408\u6cd5\u6027\uff1b<\/p>\n

5.\u901a\u8fc7nameidate_to_flip()\u8c03\u7528\u5177\u4f53\u6587\u4ef6\u7cfb\u7edf\u7684open\u94a9\u5b50\u51fd\u6570\u8fdb\u884c\u6587\u4ef6\u7684\u6253\u5f00\u5de5\u4f5c\uff1b<\/p>\n

6.\u8fd4\u56defile\u3002<\/p>\n

3.\u603b\u7ed3<\/h2>\n

\u901a\u8fc7\u524d\u9762\u7684\u7cfb\u5217\u6587\u7ae0\uff0c\u8bf4\u660e\u4e86open()\u5728Linux\u5185\u6838\u5b9e\u73b0\u3002\u4e8b\u5b9e\u4e0a\uff0c\u8fd9\u4ec5\u4ec5\u53cd\u6620\u7684\u662f\u5b83\u5728\u5728\u865a\u62df\u6587\u4ef6\u7cfb\u7edf\u7684\u5b9e\u73b0\u8fc7\u7a0b\uff0c\u4e3b\u8981\u6d89\u53ca\u7684\u5185\u5bb9\u4e3a\u5bf9\u8def\u5f84\u7684\u67e5\u627e\u3002\u6700\u7ec8\uff0c\u6587\u4ef6\u7684\u6253\u5f00\u64cd\u4f5c\u5fc5\u987b\u7ecf\u8fc7\u5177\u4f53\u6587\u4ef6\u7cfb\u7edf\u7684\u5b9e\u73b0\uff0c\u867d\u7136\u6bcf\u4e2a\u6587\u4ef6\u7cfb\u7edf\u5177\u4f53\u5b9e\u73b0\u4e0d\u540c\uff0c\u4f46\u662f\u4ed6\u4eec\u7684\u8f93\u5165\u8f93\u51fa\u90fd\u5c06\u53d7\u5230\u865a\u62df\u6587\u4ef6\u7cfb\u7edf\u7684\u9650\u5236\u4fdd\u6301\u4e00\u81f4\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 \u5f53link_path_walk()\u8fdb\u884c\u5b8c\u6bd5\u4e4b\u540e\uff0c\u4e5f\u5c31\u610f\u5473\u7740\u6587\u4ef6\u8def\u5f84\u7684\u67e5\u627e\u4f4d\u4e8e\u6700\u540e\u4e00\u4e2a\u76ee\u5f55\u9879\u4e2d\uff0c\u8fd9 […]<\/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":[],"class_list":["post-4506","post","type-post","status-publish","format-standard","hentry","category-linux","category-175"],"views":10068,"_links":{"self":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4506","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=4506"}],"version-history":[{"count":7,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4506\/revisions"}],"predecessor-version":[{"id":4546,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/posts\/4506\/revisions\/4546"}],"wp:attachment":[{"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/media?parent=4506"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/categories?post=4506"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/edsionte.com\/techblog\/wp-json\/wp\/v2\/tags?post=4506"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}