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x86/mm: Use mm_alloc() in poking_init()

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commit 3f4c8211d982099be693be9aa7d6fc4607dff290 upstream.

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>
Link: https://lkml.kernel.org/r/20221025201057.816175235@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra 2022-10-25 21:38:21 +02:00 committed by Greg Kroah-Hartman
parent f076d08178
commit 6ee042fd24
3 changed files with 2 additions and 7 deletions
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3
arch/x86/mm/init.c
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@ -7,6 +7,7 @@
#include <linux/swapops.h>
#include <linux/kmemleak.h>
#include <linux/sched/task.h>
#include <linux/sched/mm.h>
#include <asm/set_memory.h>
#include <asm/cpu_device_id.h>
@ -805,7 +806,7 @@ void __init poking_init(void)
spinlock_t *ptl;
pte_t *ptep;
poking_mm = copy_init_mm();
poking_mm = mm_alloc();
BUG_ON(!poking_mm);
/* Xen PV guests need the PGD to be pinned. */

1
include/linux/sched/task.h
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@ -89,7 +89,6 @@ extern void exit_itimers(struct task_struct *);
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 long kernel_wait4(pid_t, int __user *, int, struct rusage *);
int kernel_wait(pid_t pid, int *stat);

5
kernel/fork.c
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@ -2424,11 +2424,6 @@ struct task_struct * __init fork_idle(int cpu)
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.