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在之前 ls 命令 中我们可以看到, ls 命令的执行也是依赖于 opendir, readdir, stat, lstat 等相关操作系统提供的相关系统调用来处理业务
因此 我们这里来进一步看一下 更细节的这些 系统调用
我们这里关注的是 readdir 这个函数, 入口系统调用是 getdents 如下调试…前言
在之前 ls 命令 中我们可以看到, ls 命令的执行也是依赖于 opendir, readdir, stat, lstat 等相关操作系统提供的相关系统调用来处理业务
因此 我们这里来进一步看一下 更细节的这些 系统调用
我们这里关注的是 readdir 这个函数, 入口系统调用是 getdents 如下调试基于命令 ls -l /jerry
如下调试基于 linux 4.10 readdir 的词条 getdents
封装 getdents_callback, 然后 迭代 f 中的各个文件, getdents_callback 中藏有回调
将数据最终存放于 buf 中 ext4_dx_readdir
如下图 第一个 if block 为填充 info 用于迭代, 大致的工作是 将当前文件夹下的各个文件的相关信息填充到 info.root 中
然后 后面的处理为 迭代 info.root 的整棵树, 然后调用 call_filldir 来填充各个文件的信息, call_filldir 中会委托调用上面的 getdents_callback.ctx.actor htree_dirblock_to_tree
如下会 迭代 dir 中的各个文件, 然后调用 ext4_htree_store_dirent 将各个文件的信息放到 info.root 中 ext4_htree_store_dirent
复制给定的文件的相关信息到 info.root
这个 info.root 是基于 file-private_data 进行传输的, 具体的外面处理是在 ext4_dx_readdir 函数中
这里是 获取当前节点的 hash, minor_hash, inode, name, name_len, file_type 封装到 fname 中, 然后插入到 info.root[红黑树], 根据 hash, minor_hash 进行排序
关于这个顺序, 我们待会儿会有一个 case 来论证 call_filldir
接着来到外部 ext4_dx_readdir 中, 迭代目录中的各个文件信息, 调用回调填充 数据到 buf filldir
调用 filldir 向 buf.current_dir 中填充当前 dir 的各个文件信息
这个 buf.current_dir 是从参数传入的一个 用户空间的 dirent, 因此 这里使用了 __put_user 函数
这里向 dirent 中填充了 inode_no, record_len, d-name, 0[字符串结束符], file_type, offset 等相关信息 我们来看一下 填充之后的相关信息 内存中的数据 可以对号入座一下, 这里 省略
(gdb) x /30bc 0xaa3a40
0xaa3a40: 18 \022 0 \000 0 \000 0 \000 0 \000 0 \000 0 \000 0 \000
0xaa3a48: 0 \000 0 \000 0 \000 0 \000 0 \000 0 \000 0 \000 0 \000
0xaa3a50: 32 0 \000 84 T 101 e 115 s 116 t 48 0 50 2
0xaa3a58: 77 M 97 a 108 l 108 l 111 o 99 c确认一下 Test02Malloc 的 inode_no, 确实是 18
(initramfs) ls -ail /jerry/29 -rwxr-xr-x 1 8912 Test19UdpClient0232 -rw-r--r-- 1 860 Test19UdpServer.c21 -rw-r--r-- 1 1036 Test05SocketClient.c12 -rw-r--r-- 1 7 1.txt35 -rw-r--r-- 1 2 4.txt16 -rwxr-xr-x 1 913944 Test01SumStatic22 -rwxr-xr-x 1 9232 Test05SocketServer14 -rwxr-xr-x 1 9784 Test01Sum11 drwx------ 2 12288 lostfound2 drwxr-xr-x 3 1024 .25 -rw-r--r-- 1 2213 Test18UdpClient.c30 -rw-r--r-- 1 790 Test19UdpClient.c28 -rwxr-xr-x 1 8912 Test19UdpClient24 -rwxr-xr-x 1 13656 Test18UdpClient13 -rwxr-xr-x 1 44168 ping23 -rw-r--r-- 1 1839 Test05SocketServer.c34 -rw-r--r-- 1 2 3.txt17 -rw-r--r-- 1 8828 Test01Sum.txt19 -rw-r--r-- 1 112 Test02Malloc.c36 -rw-r--r-- 1 0 2.xml1 drwxr-xr-x 18 0 ..33 -rw-r--r-- 1 2 2.txt31 -rwxr-xr-x 1 9008 Test19UdpServer20 -rwxr-xr-x 1 9208 Test05SocketClient15 -rw-r--r-- 1 127 Test01Sum.c27 -rw-r--r-- 1 2139 Test18UdpServer.c26 -rwxr-xr-x 1 13656 Test18UdpServer18 -rwxr-xr-x 1 9898 Test02Malloc
(initramfs) 回顾一下 ls 中的使用
使用的是 系统调用获取到的 file_type, file_name, inode_no 等等 readdir 中获取的文件顺序
如下 摘录出 /jerry 中各个文件, 以及其 hash
然后根据 hash 进行排序, 输出各个文件的顺序, 我们比较一下 和 ls -l /jerry 的顺序的一下关系, 联系
/*** Test13ResolveFileAndHash** author Jerry.X.He 970655147qq.com* version 1.0* date 2022-08-06 10:58*/
public class Test13ResolveFileAndHash {// Test13ResolveFileAndHashpublic static void main(String[] args) {String lines (gdb) printf \%s %ld\, ent_name-name, hash\n . 2361201130\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash1798131950, minor_hash3795156168, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n .. 1798131950\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2638309314, minor_hash220112255, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n lostfound 2638309314\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash4147007512, minor_hash1467808689, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n 1.txt 4147007512\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2218817754, minor_hash2900089684, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n ping\u000E 2218817754\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2722591116, minor_hash3228507950, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Test01Sum 2722591116\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash582633220, minor_hash3262287479, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Test01Sum.c 582633220\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash3631608018, minor_hash2725415301, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Test01SumStatic 3631608018\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2142992528, minor_hash928223017, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Test01Sum.txt 2142992528\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash220227180, minor_hash2471538305, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Test02Malloc\u0013 220227180\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash1840751322, minor_hash137392396, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n (gdb) printf \%s %ld\, ent_name-name, hash\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash857331192, minor_hash434642936, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test05SocketClient 857331192\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash4158704484, minor_hash312643960, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test05SocketClient.c\u0016 4158704484\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash3462659828, minor_hash2883930437, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test05SocketServer 3462659828\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2205009970, minor_hash314116339, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test05SocketServer.c\u0018 2205009970\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2263127060, minor_hash2266183803, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test18UdpClient 2263127060\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2342703042, minor_hash2944388140, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test18UdpClient.c 2342703042\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash428460190, minor_hash2134201002, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test18UdpServer 428460190\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash493987328, minor_hash2169830099, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test18UdpServer.c 493987328\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2302229242, minor_hash322069301, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test19UdpClient 2302229242\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash4262479554, minor_hash1848801320, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test19UdpClient02 4262479554\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2304662458, minor_hash1793028086, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test19UdpClient.c 2304662458\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash888054094, minor_hash304564512, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test19UdpServer 888054094\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash4198063328, minor_hash3673609025, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n Test19UdpServer.c 4198063328\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash1673380854, minor_hash394531314, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n 2.txt 1673380854\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash2170292718, minor_hash758117636, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n 3.txt 2170292718\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash4053642864, minor_hash2642363966, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n 4.txt 4053642864\n Breakpoint 6, ext4_htree_store_dirent (dir_fileoptimized out, hash1832402012, minor_hash2399099147, direntoptimized out, ent_name0xffffc9000074bcb8) at fs/ext4/dir.c:459\n 459\t\tnew_fn-name[ent_name-len] 0;\n 2.xml 1832402012 \n;MapLong, String hash2FileName new TreeMap();for (String line : lines.split(\n)) {if (line.contains(ext4_htree_store_dirent)) {continue;}if (line.contains(new_fn-name)) {continue;}if (line.contains(printf)) {continue;}// System.out.println(line);String[] splits line.split(\\s);hash2FileName.put(Long.parseLong(splits[1]), splits[0]);}for (Map.EntryLong, String entry : hash2FileName.entrySet()) {System.out.println(entry.getValue());}}}文件顺序如下, 呵呵 是不是和 ls -l /jerry 的顺序差不多, 只是顺序是反的
从 readdir 中读取的文件的顺序和 上面的 Test13ResolveFileAndHash 的顺序一致, 那就是 外围的 ls 的处理可能导致的这个顺序上的差异
类似于 coreutils 中 ls 是有 根据文件名排序, 根据扩展名排序, 根据文件大小排序, 根据版本排序, 根据时间排序
只是 qemu虚拟机中的 ls 的排序 是另外一种排序, 并且有一些 奇怪
Test02Malloc
Test18UdpServer
Test18UdpServer.c
Test01Sum.c
Test05SocketClient
Test19UdpServer
2.txt
..
2.xml
Test01Sum.txt
3.txt
Test05SocketServer.c
ping
Test18UdpClient
Test19UdpClient
Test19UdpClient.c
Test18UdpClient.c
.
lostfound
Test01Sum
Test05SocketServer
Test01SumStatic
4.txt
1.txt
Test05SocketClient.c
Test19UdpServer.c
Test19UdpClient02 readdir 的顺序, 抽样前两个 ls -ail /jerry 的顺序
(initramfs) ls -ail /jerry29 -rwxr-xr-x 1 8912 Test19UdpClient0232 -rw-r--r-- 1 860 Test19UdpServer.c21 -rw-r--r-- 1 1036 Test05SocketClient.c12 -rw-r--r-- 1 7 1.txt35 -rw-r--r-- 1 2 4.txt16 -rwxr-xr-x 1 913944 Test01SumStatic22 -rwxr-xr-x 1 9232 Test05SocketServer14 -rwxr-xr-x 1 9784 Test01Sum11 drwx------ 2 12288 lostfound2 drwxr-xr-x 3 1024 .25 -rw-r--r-- 1 2213 Test18UdpClient.c30 -rw-r--r-- 1 790 Test19UdpClient.c28 -rwxr-xr-x 1 8912 Test19UdpClient24 -rwxr-xr-x 1 13656 Test18UdpClient13 -rwxr-xr-x 1 44168 ping23 -rw-r--r-- 1 1839 Test05SocketServer.c34 -rw-r--r-- 1 2 3.txt17 -rw-r--r-- 1 8828 Test01Sum.txt19 -rw-r--r-- 1 112 Test02Malloc.c36 -rw-r--r-- 1 0 2.xml1 drwxr-xr-x 18 0 ..33 -rw-r--r-- 1 2 2.txt31 -rwxr-xr-x 1 9008 Test19UdpServer20 -rwxr-xr-x 1 9208 Test05SocketClient15 -rw-r--r-- 1 127 Test01Sum.c27 -rw-r--r-- 1 2139 Test18UdpServer.c26 -rwxr-xr-x 1 13656 Test18UdpServer18 -rwxr-xr-x 1 9898 Test02Malloc 调试虚拟机 ls 命令帮助文档如下
(initramfs) ls -help
ls: invalid option -- h
BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) multi-call binary.Usage: ls [-1AaCxdLHFplins] [FILE]...List directory contents-1 One column output-a Include entries which start with .-A Like -a, but exclude . and ..-C List by columns-x List by lines-d List directory entries instead of contents-L Follow symlinks-H Follow symlinks on command line-p Append / to dir entries-F Append indicator (one of */|) to entries-l Long listing format-i List inode numbers-n List numeric UIDs and GIDs instead of names-s List allocated blocks 呵呵 从宿主机 ubuntu 拿到的顺序又不一样
rootubuntu:/jerryDisk/linux-4.10.14# ls -ail images/share/
total 10752 drwxr-xr-x 3 root root 1024 May 4 00:57 .
414752 drwxr-xr-x 5 root root 4096 May 4 00:58 ..12 -rw-r--r-- 1 root root 7 May 4 00:57 1.txt33 -rw-r--r-- 1 root root 2 Jul 30 19:03 2.txt36 -rw-r--r-- 1 root root 0 Jul 30 20:13 2.xml34 -rw-r--r-- 1 root root 2 Jul 30 19:03 3.txt35 -rw-r--r-- 1 root root 2 Jul 30 19:03 4.txt14 -rwxr-xr-x 1 root root 9784 May 4 00:57 Test01Sum15 -rw-r--r-- 1 root root 127 May 4 00:57 Test01Sum.c17 -rw-r--r-- 1 root root 8828 May 4 00:57 Test01Sum.txt16 -rwxr-xr-x 1 root root 913944 May 4 00:57 Test01SumStatic18 -rwxr-xr-x 1 root root 9898 Jul 30 19:05 Test02Malloc19 -rw-r--r-- 1 root root 112 May 4 00:57 Test02Malloc.c20 -rwxr-xr-x 1 root root 9208 May 4 00:57 Test05SocketClient21 -rw-r--r-- 1 root root 1036 May 4 00:57 Test05SocketClient.c22 -rwxr-xr-x 1 root root 9232 May 4 00:57 Test05SocketServer23 -rw-r--r-- 1 root root 1839 May 4 00:57 Test05SocketServer.c24 -rwxr-xr-x 1 root root 13656 May 4 00:57 Test18UdpClient25 -rw-r--r-- 1 root root 2213 May 4 00:57 Test18UdpClient.c26 -rwxr-xr-x 1 root root 13656 May 4 00:57 Test18UdpServer27 -rw-r--r-- 1 root root 2139 May 4 00:57 Test18UdpServer.c28 -rwxr-xr-x 1 root root 8912 May 4 00:57 Test19UdpClient30 -rw-r--r-- 1 root root 790 May 4 00:57 Test19UdpClient.c29 -rwxr-xr-x 1 root root 8912 May 4 00:57 Test19UdpClient0231 -rwxr-xr-x 1 root root 9008 May 4 00:57 Test19UdpServer32 -rw-r--r-- 1 root root 860 May 4 00:57 Test19UdpServer.c11 drwx------ 2 root root 12288 May 4 00:56 lostfound13 -rwxr-xr-x 1 root root 44168 May 4 00:57 ping上面提到的 hash 的计算方式存在于 hash.ext4fs_dirhash 中 readdir/ls 中的文件顺序关联的问题?
可以关联到如下问题中的 WebappClassloader 如何加载 ?, 它的类加载顺序 依赖于 File.list
40 classpath中存在多个jar存在同限定名的class classloader会如何加载_蓝风9的博客-CSDN博客_xbootclasspath 多个jar File.list 实现来自于 FileSystem.list
其实现 也取决于 readdir 相关具体的实现 完
