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cmd/link/internal/ld: fallocate_test.go failed test #50042

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devnull850 opened this issue Dec 8, 2021 · 1 comment
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cmd/link/internal/ld: fallocate_test.go failed test #50042

devnull850 opened this issue Dec 8, 2021 · 1 comment

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@devnull850
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devnull850 commented Dec 8, 2021

What version of Go are you using (go version)?

$ go version
go version go1.17.4 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOVERSION="go1.17.4"

What did you do?

I tried compiling Go off of current master on my machine. I followed the directions for compiling from source. I ran into an error when running all.bash in the fallocate_test.go file. I did a bit of research and it appears to be a problem with ZFS and nothing with the Go programming language.

#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

const char FILENAME[] = "/tmp/xxx";
const char FORMAT[] = "st_size/512 = %ld/512 = %ld, st_blocks = %ld\n";
const int FLAGS = O_RDWR | O_CREAT | O_TRUNC;
const mode_t MODE = 0666;

int main(void) {
    int e, fd;
    struct stat st;

    if ((fd = open(FILENAME, FLAGS, MODE)) == -1) {
        fprintf(stderr, "open failed: %d\n", fd);
        exit(EXIT_FAILURE);
    }

    if ((e = fallocate(fd, 0, 0, 1<<20)) == -1) {
        fprintf(stderr, "fallocate failed: %d\n", e);
        exit(EXIT_FAILURE);
    }

    if ((e = fstat(fd, &st)) == -1) {
        fprintf(stderr, "fstat failed: %d\n", e);
        exit(EXIT_FAILURE);
    }

    printf("%zu, %zu, %zu\n", sizeof(long int),
            sizeof(blkcnt_t), sizeof(off_t));
    printf("%zu\n", st.st_blksize);
    printf(FORMAT, st.st_size, st.st_size/512, st.st_blocks);
    printf("%lu, %lu\n", st.st_size, st.st_blksize * st.st_blocks);

    if (close(fd) == -1) {
        fprintf(stderr, "close failed: %d\n", fd);
        exit(EXIT_FAILURE);
    }

    if (remove(FILENAME) == -1) {
        fprintf(stderr, "error removing file [%s]\n", FILENAME);
        exit(EXIT_FAILURE);
    }

    return EXIT_SUCCESS;
}

Running the program above (recommended for debugging in a previous ticket related to this) resulted in

8, 8, 8
131072
st_size/512 = 1048576/512 = 2048, st_blocks = 2
1048576, 262144

The total size in bytes for the file is not equal to the number of 512 byte blocks allocated thus something weird is happening in reporting stats of a file descriptor back. Since this is an issue outside of Go, is there anyway a logic check could be done to not throw the failing test error?

// /src/cmd/link/internal/ld/fallocate_test.go [line 60]

if got, actual, want := stat.Sys().(*syscall.Stat_t).Blocks,
    stat.Sys().(*syscall.Stat_t).Size/512, (sz+511)/512; actual == got && got < want {
    t.Errorf("unexpected disk usage: got %d blocks, want at least %d", got, want)
}

Or leverage the os library to determine if the filesystem is ZFS or something that fallocate does not work well with but that fallocate does not fail with (return -1) as well?

What did you expect to see?

ALL TESTS PASSED

What did you see instead?

--- FAIL: TestFallocate (0.00s)
    fallocate_test.go:61: unexpected disk usage: got 2 blocks, want at least 2048
    fallocate_test.go:61: unexpected disk usage: got 2 blocks, want at least 4096
    fallocate_test.go:61: unexpected disk usage: got 2 blocks, want at least 6144
FAIL
FAIL	cmd/link/internal/ld	20.138s
@devnull850 devnull850 changed the title affected/package: ld cmd/link/internal/ld: fallocate_test.go failed test Dec 8, 2021
@cherrymui
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cherrymui commented Dec 8, 2021

Looks like a dup of #42005 . As you said, it is a problem with ZFS.

I tried compiling Go off of current master on my machine

If you just want to build the toolchain, you can just run make.bash instead of all.bash (which include tests).

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