adding linux syscall fallocate

[r0ller <r0ller%freemail.hu@localhost>]

Hi All,

I'm trying to add and map the linux syscall fallocate to posix_fallocate so I modified sys/compat/linux/common/linux_file.c like:

int linux_sys_fallocate(struct lwp *l, const struct linux_sys_fallocate_args *uap, register_t *retval){
    int mode = SCARG(uap, mode);
    printf("\nCalling linux_sys_fallocate, mode is:%d\n",mode);
    if(mode == 0){
        struct sys_posix_fallocate_args fall;
        SCARG(&fall, fd) = SCARG(uap, fd);
        // Is PAD necessary? Compiles with and without as well but it's there in sys/kern/syscalls.master
        // and sys/kern/systrace_args.c but not in sys/kern/vfs_syscalls.c
        SCARG(&fall, PAD) = 0;
        SCARG(&fall, pos) = SCARG(uap, offset);
        SCARG(&fall, len) = SCARG(uap, len);
        int result = sys_posix_fallocate(l, &fall, retval);
        printf("result:%d\n",result);
        return result;
    }
    return EOPNOTSUPP;
}

This seems to compile but when tested it didn't work out so I added some printfs to sys/kern/vfs_syscalls.c:

int sys_posix_fallocate(struct lwp *l, const struct sys_posix_fallocate_args *uap,
        register_t *retval)
{
    /* {
        syscallarg(int) fd;
        syscallarg(off_t) pos;
        syscallarg(off_t) len;
    } */
    int fd;
    off_t pos, len;
    struct file *fp;
    struct vnode *vp;
    int error;

    fd = SCARG(uap, fd);
    pos = SCARG(uap, pos);
    len = SCARG(uap, len);
    
    if (pos < 0 || len < 0 || len > OFF_T_MAX - pos) {
        printf("posix_fallocate line 4718\n");
        *retval = EINVAL;
        return 0;
    }
    
    error = fd_getvnode(fd, &fp);
    if (error) {
        printf("posix_fallocate line 4725\n");
        *retval = error;
        return 0;
    }
    if ((fp->f_flag & FWRITE) == 0) {
        printf("posix_fallocate line 4730\n");
        error = EBADF;
        goto fail;
    }
    vp = fp->f_vnode;

    vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
    if (vp->v_type == VDIR) {
        printf("posix_fallocate line 4738\n");
        error = EISDIR;
    } else {
        printf("posix_fallocate line 4741\n");
        error = VOP_FALLOCATE(vp, pos, len);
    }
    VOP_UNLOCK(vp);

fail:
    fd_putfile(fd);
    *retval = error;
    return 0;
}

As you can see on the attached screenshot, "line 4741" gets printed out. So I went on to check what happens in VOP_FALLOCATE but it gets really internal there.

Does anyone have any hint?

Thanks,
r0ller

Attachment: fallocate_result2.JPG
Description: JPEG image