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    Subject[PATCH 2/5] x86/mm: Use mm_alloc() in poking_init()
    Instead of duplicating init_mm, allocate a fresh mm. The advantage is
    that mm_alloc() has much simpler dependencies. Additionally it makes
    more conceptual sense, init_mm has no (and must not have) user state
    to duplicate.

    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    ---
    arch/x86/mm/init.c | 2 +-
    include/linux/sched/task.h | 1 -
    kernel/fork.c | 5 -----
    3 files changed, 1 insertion(+), 7 deletions(-)

    --- a/arch/x86/mm/init.c
    +++ b/arch/x86/mm/init.c
    @@ -801,7 +801,7 @@ void __init poking_init(void)
    spinlock_t *ptl;
    pte_t *ptep;

    - poking_mm = copy_init_mm();
    + poking_mm = mm_alloc();
    BUG_ON(!poking_mm);

    /*
    --- a/include/linux/sched/task.h
    +++ b/include/linux/sched/task.h
    @@ -91,7 +91,6 @@ extern void exit_itimers(struct task_str
    extern pid_t kernel_clone(struct kernel_clone_args *kargs);
    struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
    struct task_struct *fork_idle(int);
    -struct mm_struct *copy_init_mm(void);
    extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
    extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
    extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
    --- a/kernel/fork.c
    +++ b/kernel/fork.c
    @@ -2592,11 +2592,6 @@ struct task_struct * __init fork_idle(in
    return task;
    }

    -struct mm_struct *copy_init_mm(void)
    -{
    - return dup_mm(NULL, &init_mm);
    -}
    -
    /*
    * This is like kernel_clone(), but shaved down and tailored to just
    * creating io_uring workers. It returns a created task, or an error pointer.

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