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Commit 41f727fd authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

fork/exec: cleanup mm initialization 



mm initialization on fork/exec is spread all over the place, which makes
the code look inconsistent.

We have mm_init(), which is supposed to init/nullify mm's internals, but
it doesn't init all the fields it should:

 - on fork ->mmap,mm_rb,vmacache_seqnum,map_count,mm_cpumask,locked_vm
   are zeroed in dup_mmap();

 - on fork ->pmd_huge_pte is zeroed in dup_mm(), immediately before
   calling mm_init();

 - ->cpu_vm_mask_var ptr is initialized by mm_init_cpumask(), which is
   called before mm_init() on both fork and exec;

 - ->context is initialized by init_new_context(), which is called after
   mm_init() on both fork and exec;

Let's consolidate all the initializations in mm_init() to make the code
look cleaner.

Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8f053ac1

fs/exec.c

+0 −4
Original line number Diff line number Diff line
@@ -368,10 +368,6 @@ static int bprm_mm_init(struct linux_binprm *bprm) 
	if (!mm)

		goto err;



	err = init_new_context(current, mm);

	if (err)

		goto err;



	err = __bprm_mm_init(bprm);

	if (err)

		goto err;

include/linux/mm_types.h

+1 −0
Original line number Diff line number Diff line
@@ -461,6 +461,7 @@ static inline void mm_init_cpumask(struct mm_struct *mm) 
#ifdef CONFIG_CPUMASK_OFFSTACK

	mm->cpu_vm_mask_var = &mm->cpumask_allocation;

#endif

	cpumask_clear(mm->cpu_vm_mask_var);

}



/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */

kernel/fork.c

+20 −27
Original line number Diff line number Diff line
@@ -374,12 +374,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 
	 */

	down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);



	mm->locked_vm = 0;

	mm->mmap = NULL;

	mm->vmacache_seqnum = 0;

	mm->map_count = 0;

	cpumask_clear(mm_cpumask(mm));

	mm->mm_rb = RB_ROOT;

	rb_link = &mm->mm_rb.rb_node;

	rb_parent = NULL;

	pprev = &mm->mmap;
@@ -538,17 +532,27 @@ static void mm_init_aio(struct mm_struct *mm) 


static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)

{

	mm->mmap = NULL;

	mm->mm_rb = RB_ROOT;

	mm->vmacache_seqnum = 0;

	atomic_set(&mm->mm_users, 1);

	atomic_set(&mm->mm_count, 1);

	init_rwsem(&mm->mmap_sem);

	INIT_LIST_HEAD(&mm->mmlist);

	mm->core_state = NULL;

	atomic_long_set(&mm->nr_ptes, 0);

	mm->map_count = 0;

	mm->locked_vm = 0;

	memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));

	spin_lock_init(&mm->page_table_lock);

	mm_init_cpumask(mm);

	mm_init_aio(mm);

	mm_init_owner(mm, p);

	mmu_notifier_mm_init(mm);

	clear_tlb_flush_pending(mm);

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS

	mm->pmd_huge_pte = NULL;

#endif



	if (current->mm) {

		mm->flags = current->mm->flags & MMF_INIT_MASK;
@@ -558,11 +562,17 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) 
		mm->def_flags = 0;

	}



	if (likely(!mm_alloc_pgd(mm))) {

		mmu_notifier_mm_init(mm);

	if (mm_alloc_pgd(mm))

		goto fail_nopgd;



	if (init_new_context(p, mm))

		goto fail_nocontext;



	return mm;

	}



fail_nocontext:

	mm_free_pgd(mm);

fail_nopgd:

	free_mm(mm);

	return NULL;

}
@@ -596,7 +606,6 @@ struct mm_struct *mm_alloc(void) 
		return NULL;



	memset(mm, 0, sizeof(*mm));

	mm_init_cpumask(mm);

	return mm_init(mm, current);

}
@@ -828,17 +837,10 @@ static struct mm_struct *dup_mm(struct task_struct *tsk) 
		goto fail_nomem;



	memcpy(mm, oldmm, sizeof(*mm));

	mm_init_cpumask(mm);



#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS

	mm->pmd_huge_pte = NULL;

#endif

	if (!mm_init(mm, tsk))

		goto fail_nomem;



	if (init_new_context(tsk, mm))

		goto fail_nocontext;



	dup_mm_exe_file(oldmm, mm);



	err = dup_mmap(mm, oldmm);
@@ -860,15 +862,6 @@ free_pt: 


fail_nomem:

	return NULL;



fail_nocontext:

	/*

	 * If init_new_context() failed, we cannot use mmput() to free the mm

	 * because it calls destroy_context()

	 */

	mm_free_pgd(mm);

	free_mm(mm);

	return NULL;

}



static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)