Renaming an in-use directory results in access-denied error in 9p-mounted windows directory

[Amaranterre]

Windows Version

Microsoft Windows [Version10.0.22631.5189]

WSL Version

2.3.26.0

Are you using WSL 1 or WSL 2?

• [x] WSL 2
• [ ] WSL 1

Kernel Version

No response

Distro Version

No response

Other Software

No response

Repro Steps

Compile and run the code in linux-distro, expecting the error Permission denied

// repro_2.c
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int OPEN_DIR_FLAG = __O_DIRECTORY | O_RDONLY;
int CREATE_DIR_MDOE =
        S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IROTH;

int CREATE_FILE_FLAG = O_RDWR | O_CREAT | O_EXCL | O_SYNC | __O_DIRECT;
int CREATE_FILE_MDOE = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
char test_str[100] = "1e2d22";

int main() {
        // device "D" should be under-Windows device
        char log_pool_tmp_path[100] = "/d/tmp/log_pool.tmp";
        char log_pool_path[100] = "/d/tmp/log_pool";

        mkdir(log_pool_tmp_path, CREATE_DIR_MDOE);

        int tmp_dir_fd = -1;
        tmp_dir_fd = open(log_pool_tmp_path, OPEN_DIR_FLAG);

        int meta_fd_ = -1;
        meta_fd_ =
                openat(tmp_dir_fd, "meta", CREATE_FILE_FLAG, CREATE_FILE_MDOE);

        pwrite(meta_fd_, test_str, 2, 0);

        sleep(1);

        int ret = rename(log_pool_tmp_path, log_pool_path);
        if(ret == -1) {
                printf("error: %d, %s\n", errno, strerror(errno));
                return errno;
        }
        close(meta_fd_);

        return 0;
}

Expected Behavior

No error happens, as in linux-based distro like Ubuntu and CentOS which i have tested

Actual Behavior

Compile and run the code in linux-distro, expecting the error Permission denied

Diagnostic Logs

No response

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[Amaranterre]

#6664 reported similar problem long time ago.

Reasoning

i explore further and conclude that this issuse results from internel distinction in Windows file system, because when running similar code in original Windows environment same problems will be reproduced as well:

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <direct.h>    // for _mkdir
#include <io.h>        // for _open, _write, _lseek, _close
#include <fcntl.h>     // for _O_RDWR, etc.
#include <windows.h>   // for Sleep

int CREATE_FILE_FLAG = _O_RDWR | _O_CREAT | _O_EXCL;
int CREATE_FILE_MODE = 0;
// int CREATE_FILE_MODE = _S_IREAD | _S_IWRITE;
char test_str[100] = "1e2d22";

int main() {
    char log_pool_tmp_path[100] = "D:\\tmp\\log_pool.tmp";
    char log_pool_path[100] = "D:\\tmp\\log_pool";

    if (_mkdir(log_pool_tmp_path) != 0) {
        if (errno != EEXIST) {
            printf("mkdir failed: %s\n", strerror(errno));
            return errno;
        }
    }

    char meta_path[200];
    snprintf(meta_path, sizeof(meta_path), "%s\\meta", log_pool_tmp_path);

    int meta_fd = _open(meta_path, CREATE_FILE_FLAG, CREATE_FILE_MODE);
    if (meta_fd == -1) {
        printf("open meta failed: %s\n", strerror(errno));
        return errno;
    }

    if (_lseek(meta_fd, 0, SEEK_SET) == -1) {
        printf("lseek failed: %s\n", strerror(errno));
        _close(meta_fd);
        return errno;
    }

    if (_write(meta_fd, test_str, 2) == -1) {
        printf("write failed: %s\n", strerror(errno));
        _close(meta_fd);
        return errno;
    }

    Sleep(1000);  // sleep 1s

    if (rename(log_pool_tmp_path, log_pool_path) != 0) {
        printf("rename failed: %s\n", strerror(errno));
        _close(meta_fd);
        return errno;
    }

    _close(meta_fd);
    return 0;
}

So in my opinion the full process of this issue is that WSL2-9p-client request renameat to Windows-9p-Server, and because the server can't rename an directory if any file under this directory in use( while this is legal in linux-based system), it issued an error.

Possible way to fix

Though this issues appears to be distinctions between two file systems, i still think that WSL2 should implement the linux-semantics as complete as possible. One way to solve this is requiring software to close resources before renaming their parent directory. Another way to get around it is making WSL-9p-client do the manually-close-resources task( which may involve maintaining the directory tree in client-side and take care of any concurrent fault) and reopen these resources after ranaming.

[Khitiara]

running into this exact issue using the zig compiler - the deviation from linux behavior from this issue has made the compiler completely unusable on ReFS/9p drives on WSL