Subject: Re: [PATCH kernel v7 2/7] powerpc/iommu: Stop using @current in mm_iommu_xxx

From: Alex Williamson <[email-masked]>
Date: Thu, 1 Dec 2016 12:44:51 -0700

On Wed, 30 Nov 2016 17:52:00 +1100
Alexey Kardashevskiy <[email-masked]> wrote:

> This changes mm_iommu_xxx helpers to take mm_struct as a parameter
> instead of getting it from @current which in some situations may
> not have a valid reference to mm.
> 
> This changes helpers to receive @mm and moves all references to @current
> to the caller, including checks for !current and !current->mm;
> checks in mm_iommu_preregistered() are removed as there is no caller
> yet.
> 
> This moves the mm_iommu_adjust_locked_vm() call to the caller as
> it receives mm_iommu_table_group_mem_t but it needs mm.
> 
> This should cause no behavioral change.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> Reviewed-by: David Gibson <[email-masked]>
> ---
>  arch/powerpc/include/asm/mmu_context.h | 16 ++++++------
>  arch/powerpc/mm/mmu_context_iommu.c    | 46 +++++++++++++---------------------
>  drivers/vfio/vfio_iommu_spapr_tce.c    | 14 ++++++++---
>  3 files changed, 36 insertions(+), 40 deletions(-)

Acked-by: Alex Williamson <[email-masked]>

> diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> index 424844b..b9e3f0a 100644
> --- a/arch/powerpc/include/asm/mmu_context.h
> +++ b/arch/powerpc/include/asm/mmu_context.h
> @@ -19,16 +19,18 @@ extern void destroy_context(struct mm_struct *mm);
>  struct mm_iommu_table_group_mem_t;
>  
>  extern int isolate_lru_page(struct page *page);	/* from internal.h */
> -extern bool mm_iommu_preregistered(void);
> -extern long mm_iommu_get(unsigned long ua, unsigned long entries,
> +extern bool mm_iommu_preregistered(struct mm_struct *mm);
> +extern long mm_iommu_get(struct mm_struct *mm,
> +		unsigned long ua, unsigned long entries,
>  		struct mm_iommu_table_group_mem_t **pmem);
> -extern long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem);
> +extern long mm_iommu_put(struct mm_struct *mm,
> +		struct mm_iommu_table_group_mem_t *mem);
>  extern void mm_iommu_init(struct mm_struct *mm);
>  extern void mm_iommu_cleanup(struct mm_struct *mm);
> -extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(unsigned long ua,
> -		unsigned long size);
> -extern struct mm_iommu_table_group_mem_t *mm_iommu_find(unsigned long ua,
> -		unsigned long entries);
> +extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
> +		unsigned long ua, unsigned long size);
> +extern struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
> +		unsigned long ua, unsigned long entries);
>  extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
>  		unsigned long ua, unsigned long *hpa);
>  extern long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem);
> diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
> index ad2e575..4c6db09 100644
> --- a/arch/powerpc/mm/mmu_context_iommu.c
> +++ b/arch/powerpc/mm/mmu_context_iommu.c
> @@ -56,7 +56,7 @@ static long mm_iommu_adjust_locked_vm(struct mm_struct *mm,
>  	}
>  
>  	pr_debug("[%d] RLIMIT_MEMLOCK HASH64 %c%ld %ld/%ld\n",
> -			current->pid,
> +			current ? current->pid : 0,
>  			incr ? '+' : '-',
>  			npages << PAGE_SHIFT,
>  			mm->locked_vm << PAGE_SHIFT,
> @@ -66,12 +66,9 @@ static long mm_iommu_adjust_locked_vm(struct mm_struct *mm,
>  	return ret;
>  }
>  
> -bool mm_iommu_preregistered(void)
> +bool mm_iommu_preregistered(struct mm_struct *mm)
>  {
> -	if (!current || !current->mm)
> -		return false;
> -
> -	return !list_empty(&current->mm->context.iommu_group_mem_list);
> +	return !list_empty(&mm->context.iommu_group_mem_list);
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_preregistered);
>  
> @@ -124,19 +121,16 @@ static int mm_iommu_move_page_from_cma(struct page *page)
>  	return 0;
>  }
>  
> -long mm_iommu_get(unsigned long ua, unsigned long entries,
> +long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  		struct mm_iommu_table_group_mem_t **pmem)
>  {
>  	struct mm_iommu_table_group_mem_t *mem;
>  	long i, j, ret = 0, locked_entries = 0;
>  	struct page *page = NULL;
>  
> -	if (!current || !current->mm)
> -		return -ESRCH; /* process exited */
> -
>  	mutex_lock(&mem_list_mutex);
>  
> -	list_for_each_entry_rcu(mem, &current->mm->context.iommu_group_mem_list,
> +	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list,
>  			next) {
>  		if ((mem->ua == ua) && (mem->entries == entries)) {
>  			++mem->used;
> @@ -154,7 +148,7 @@ long mm_iommu_get(unsigned long ua, unsigned long entries,
>  
>  	}
>  
> -	ret = mm_iommu_adjust_locked_vm(current->mm, entries, true);
> +	ret = mm_iommu_adjust_locked_vm(mm, entries, true);
>  	if (ret)
>  		goto unlock_exit;
>  
> @@ -215,11 +209,11 @@ long mm_iommu_get(unsigned long ua, unsigned long entries,
>  	mem->entries = entries;
>  	*pmem = mem;
>  
> -	list_add_rcu(&mem->next, &current->mm->context.iommu_group_mem_list);
> +	list_add_rcu(&mem->next, &mm->context.iommu_group_mem_list);
>  
>  unlock_exit:
>  	if (locked_entries && ret)
> -		mm_iommu_adjust_locked_vm(current->mm, locked_entries, false);
> +		mm_iommu_adjust_locked_vm(mm, locked_entries, false);
>  
>  	mutex_unlock(&mem_list_mutex);
>  
> @@ -264,17 +258,13 @@ static void mm_iommu_free(struct rcu_head *head)
>  static void mm_iommu_release(struct mm_iommu_table_group_mem_t *mem)
>  {
>  	list_del_rcu(&mem->next);
> -	mm_iommu_adjust_locked_vm(current->mm, mem->entries, false);
>  	call_rcu(&mem->rcu, mm_iommu_free);
>  }
>  
> -long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem)
> +long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t *mem)
>  {
>  	long ret = 0;
>  
> -	if (!current || !current->mm)
> -		return -ESRCH; /* process exited */
> -
>  	mutex_lock(&mem_list_mutex);
>  
>  	if (mem->used == 0) {
> @@ -297,6 +287,8 @@ long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem)
>  	/* @mapped became 0 so now mappings are disabled, release the region */
>  	mm_iommu_release(mem);
>  
> +	mm_iommu_adjust_locked_vm(mm, mem->entries, false);
> +
>  unlock_exit:
>  	mutex_unlock(&mem_list_mutex);
>  
> @@ -304,14 +296,12 @@ long mm_iommu_put(struct mm_iommu_table_group_mem_t *mem)
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_put);
>  
> -struct mm_iommu_table_group_mem_t *mm_iommu_lookup(unsigned long ua,
> -		unsigned long size)
> +struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
> +		unsigned long ua, unsigned long size)
>  {
>  	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
>  
> -	list_for_each_entry_rcu(mem,
> -			&current->mm->context.iommu_group_mem_list,
> -			next) {
> +	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
>  		if ((mem->ua <= ua) &&
>  				(ua + size <= mem->ua +
>  				 (mem->entries << PAGE_SHIFT))) {
> @@ -324,14 +314,12 @@ struct mm_iommu_table_group_mem_t *mm_iommu_lookup(unsigned long ua,
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_lookup);
>  
> -struct mm_iommu_table_group_mem_t *mm_iommu_find(unsigned long ua,
> -		unsigned long entries)
> +struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
> +		unsigned long ua, unsigned long entries)
>  {
>  	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
>  
> -	list_for_each_entry_rcu(mem,
> -			&current->mm->context.iommu_group_mem_list,
> -			next) {
> +	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
>  		if ((mem->ua == ua) && (mem->entries == entries)) {
>  			ret = mem;
>  			break;
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 80378dd..d0c38b2 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -107,14 +107,17 @@ static long tce_iommu_unregister_pages(struct tce_container *container,
>  {
>  	struct mm_iommu_table_group_mem_t *mem;
>  
> +	if (!current || !current->mm)
> +		return -ESRCH; /* process exited */
> +
>  	if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
>  		return -EINVAL;
>  
> -	mem = mm_iommu_find(vaddr, size >> PAGE_SHIFT);
> +	mem = mm_iommu_find(current->mm, vaddr, size >> PAGE_SHIFT);
>  	if (!mem)
>  		return -ENOENT;
>  
> -	return mm_iommu_put(mem);
> +	return mm_iommu_put(current->mm, mem);
>  }
>  
>  static long tce_iommu_register_pages(struct tce_container *container,
> @@ -124,11 +127,14 @@ static long tce_iommu_register_pages(struct tce_container *container,
>  	struct mm_iommu_table_group_mem_t *mem = NULL;
>  	unsigned long entries = size >> PAGE_SHIFT;
>  
> +	if (!current || !current->mm)
> +		return -ESRCH; /* process exited */
> +
>  	if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK) ||
>  			((vaddr + size) < vaddr))
>  		return -EINVAL;
>  
> -	ret = mm_iommu_get(vaddr, entries, &mem);
> +	ret = mm_iommu_get(current->mm, vaddr, entries, &mem);
>  	if (ret)
>  		return ret;
>  
> @@ -375,7 +381,7 @@ static int tce_iommu_prereg_ua_to_hpa(unsigned long tce, unsigned long size,
>  	long ret = 0;
>  	struct mm_iommu_table_group_mem_t *mem;
>  
> -	mem = mm_iommu_lookup(tce, size);
> +	mem = mm_iommu_lookup(current->mm, tce, size);
>  	if (!mem)
>  		return -EINVAL;
>