Re: [PATCH hmm 01/15] mm/mmu_notifier: define the header pre-processor parts even if disabled

[Jerome Glisse <jglisse@redhat.com>]

On Tue, Oct 15, 2019 at 03:12:28PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
> 
> Now that we have KERNEL_HEADER_TEST all headers are generally compile
> tested, so relying on makefile tricks to avoid compiling code that depends
> on CONFIG_MMU_NOTIFIER is more annoying.
> 
> Instead follow the usual pattern and provide most of the header with only
> the functions stubbed out when CONFIG_MMU_NOTIFIER is disabled. This
> ensures code compiles no matter what the config setting is.
> 
> While here, struct mmu_notifier_mm is private to mmu_notifier.c, move it.
> 
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

Reviewed-by: Jérôme Glisse <jglisse@redhat.com>

> ---
>  include/linux/mmu_notifier.h | 46 +++++++++++++-----------------------
>  mm/mmu_notifier.c            | 13 ++++++++++
>  2 files changed, 30 insertions(+), 29 deletions(-)
> 
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index 1bd8e6a09a3c27..12bd603d318ce7 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -7,8 +7,9 @@
>  #include <linux/mm_types.h>
>  #include <linux/srcu.h>
>  
> +struct mmu_notifier_mm;
>  struct mmu_notifier;
> -struct mmu_notifier_ops;
> +struct mmu_notifier_range;
>  
>  /**
>   * enum mmu_notifier_event - reason for the mmu notifier callback
> @@ -40,36 +41,8 @@ enum mmu_notifier_event {
>  	MMU_NOTIFY_SOFT_DIRTY,
>  };
>  
> -#ifdef CONFIG_MMU_NOTIFIER
> -
> -#ifdef CONFIG_LOCKDEP
> -extern struct lockdep_map __mmu_notifier_invalidate_range_start_map;
> -#endif
> -
> -/*
> - * The mmu notifier_mm structure is allocated and installed in
> - * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
> - * critical section and it's released only when mm_count reaches zero
> - * in mmdrop().
> - */
> -struct mmu_notifier_mm {
> -	/* all mmu notifiers registerd in this mm are queued in this list */
> -	struct hlist_head list;
> -	/* to serialize the list modifications and hlist_unhashed */
> -	spinlock_t lock;
> -};
> -
>  #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
>  
> -struct mmu_notifier_range {
> -	struct vm_area_struct *vma;
> -	struct mm_struct *mm;
> -	unsigned long start;
> -	unsigned long end;
> -	unsigned flags;
> -	enum mmu_notifier_event event;
> -};
> -
>  struct mmu_notifier_ops {
>  	/*
>  	 * Called either by mmu_notifier_unregister or when the mm is
> @@ -249,6 +222,21 @@ struct mmu_notifier {
>  	unsigned int users;
>  };
>  
> +#ifdef CONFIG_MMU_NOTIFIER
> +
> +#ifdef CONFIG_LOCKDEP
> +extern struct lockdep_map __mmu_notifier_invalidate_range_start_map;
> +#endif
> +
> +struct mmu_notifier_range {
> +	struct vm_area_struct *vma;
> +	struct mm_struct *mm;
> +	unsigned long start;
> +	unsigned long end;
> +	unsigned flags;
> +	enum mmu_notifier_event event;
> +};
> +
>  static inline int mm_has_notifiers(struct mm_struct *mm)
>  {
>  	return unlikely(mm->mmu_notifier_mm);
> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> index 7fde88695f35d6..367670cfd02b7b 100644
> --- a/mm/mmu_notifier.c
> +++ b/mm/mmu_notifier.c
> @@ -27,6 +27,19 @@ struct lockdep_map __mmu_notifier_invalidate_range_start_map = {
>  };
>  #endif
>  
> +/*
> + * The mmu notifier_mm structure is allocated and installed in
> + * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
> + * critical section and it's released only when mm_count reaches zero
> + * in mmdrop().
> + */
> +struct mmu_notifier_mm {
> +	/* all mmu notifiers registered in this mm are queued in this list */
> +	struct hlist_head list;
> +	/* to serialize the list modifications and hlist_unhashed */
> +	spinlock_t lock;
> +};
> +
>  /*
>   * This function can't run concurrently against mmu_notifier_register
>   * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
> -- 
> 2.23.0
>