fuse 文件系统无法更改 getattr 函数中 struct stat *stbuf 的值？

Question

问题已解决！ 感谢@basile-starynkevitch，我发现struct stat在不同文件中的大小不一样！

在<sys/stat.h> 中，sizeof(struct stat) 是 88 字节，但是使用 fuse 的库（我猜是因为 -D_FILE_OFFSET_BITS=64 标志），这是 96 字节。

所以当我将 fuse lib 添加到我的远程服务器（将 -D_FILE_OFFSET_BITS=64 /usr/local/lib/libfuse.so /usr/local/lib/libulockmgr.so 标志添加到 gcc）时，我的程序可以正常运行！

感谢您的帮助！

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我正在做一些关于 fuse 的项目，这让我发疯了。

我从远程服务器发送 struct stat *stbuf 的数据，并且数据在服务器和客户端都是正确的，但是当我使用 memcpy 将数据复制到 stbuf 时，似乎没有复制任何内容。我也尝试使用 read(socked,stbuf,sizeof(struct stat));直接，但这也不起作用。

这里是代码...（如果没有这个文件，远程服务器在st_ino中保存-ENOENT）

    static int rof_getattr(const char *path, struct stat *stbuf)

        {

    int res = 0;
    struct cmd sndcmd;
    struct stat buf;

    memset(&sndcmd, 0, sizeof(struct cmd));

    strcpy(sndcmd.cmd, "GETATTR");
    strcpy(sndcmd.str, path);
    memset(stbuf, 0, sizeof(struct stat));
GTTR_AGN:   
    memset(&buf, 0,sizeof(struct stat));
    write(sockfd, &sndcmd, sizeof(struct cmd));
    res=read(sockfd, &buf, sizeof(struct stat));

    if(res!=sizeof(struct stat))
        goto GTTR_AGN;

    memcpy(stbuf,&buf,sizeof(buf));
    if (buf.st_ino==-ENOENT)
        return -ENOENT;
return 0;
        }

我从 gdb 得到的数据：

39      res=read(sockfd, &buf, sizeof(struct stat));
3: (struct stat)stbuf = {st_dev = 694294557525955008, __pad1 = 0, __st_ino = 0, 
  st_mode = 0, st_nlink = 0, st_uid = 0, st_gid = 0, st_rdev = 0, __pad2 = 0, 
  st_size = 0, st_blksize = 0, st_blocks = 0, st_atim = {tv_sec = 0, tv_nsec = 0}, 
  st_mtim = {tv_sec = 0, tv_nsec = 0}, st_ctim = {tv_sec = 0, tv_nsec = 0}, 
  st_ino = 0}
1: buf = {st_dev = 0, __pad1 = 0, __st_ino = 0, st_mode = 0, st_nlink = 0, 
  st_uid = 0, st_gid = 0, st_rdev = 0, __pad2 = 0, st_size = 0, st_blksize = 0, 
  st_blocks = 0, st_atim = {tv_sec = 0, tv_nsec = 0}, st_mtim = {tv_sec = 0, 
    tv_nsec = 0}, st_ctim = {tv_sec = 0, tv_nsec = 0}, st_ino = 0}

read() 后，得到 buf 中的数据

(gdb) s
40      memcpy(stbuf,&buf,sizeof(buf));
3: (struct stat)stbuf = {st_dev = 694294557525955008, __pad1 = 2049, __st_ino = 0, 
  st_mode = 0, st_nlink = 943887, st_uid = 16877, st_gid = 2, 
  st_rdev = 4294967297000, __pad2 = 0, st_size = 0, st_blksize = 4096, 
  st_blocks = 34359742464, st_atim = {tv_sec = 1323833759, tv_nsec = 75415995}, 
  st_mtim = {tv_sec = 1323729515, tv_nsec = 6514929}, st_ctim = {
    tv_sec = 1323729515, tv_nsec = 6514929}, st_ino = 0}
1: buf = {st_dev = 2049, __pad1 = 0, __st_ino = 943887, st_mode = 16877, 
  st_nlink = 2, st_uid = 1000, st_gid = 1000, st_rdev = 0, __pad2 = 0, 
  st_size = 17592186048512, st_blksize = 8, st_blocks = 323909233444133279, 
  st_atim = {tv_sec = 1323729515, tv_nsec = 6514929}, st_mtim = {
    tv_sec = 1323729515, tv_nsec = 6514929}, st_ctim = {tv_sec = 0, tv_nsec = 0}, 
  st_ino = 0}
(gdb) s

复制数据到stbuf

41      if (stbuf->st_ino==-ENOENT)
3: (struct stat)stbuf = {st_dev = 694294557525955008, __pad1 = 2049, __st_ino = 0, 
  st_mode = 0, st_nlink = 943887, st_uid = 16877, st_gid = 2, 
  st_rdev = 4294967297000, __pad2 = 0, st_size = 0, st_blksize = 4096, 
  st_blocks = 34359742464, st_atim = {tv_sec = 1323833759, tv_nsec = 75415995}, 
  st_mtim = {tv_sec = 1323729515, tv_nsec = 6514929}, st_ctim = {
    tv_sec = 1323729515, tv_nsec = 6514929}, st_ino = 0}
1: buf = {st_dev = 2049, __pad1 = 0, __st_ino = 943887, st_mode = 16877, 
  st_nlink = 2, st_uid = 1000, st_gid = 1000, st_rdev = 0, __pad2 = 0, 
  st_size = 17592186048512, st_blksize = 8, st_blocks = 323909233444133279, 
  st_atim = {tv_sec = 1323729515, tv_nsec = 6514929}, st_mtim = {
    tv_sec = 1323729515, tv_nsec = 6514929}, st_ctim = {tv_sec = 0, tv_nsec = 0}, 
  st_ino = 0}

stbuf 完全没有变化。

谁能给我一些关于这种现象的建议？我做了一些工作，但仍然没有找到解决方案。

Answer 1

您没有在代码中检查读取字节数 res。

文件结尾可以是 0，错误可以是 -1，如果所有字节都没有被接收到，它可以小于 sizeof(struct stat)...

非常仔细地阅读（用你的眼睛和大脑）（并再次阅读两次）man page of read(2) 系统调用。