Re: [PATCH v7 1/6] userfaultfd: add minor fault registration mode

[Peter Xu <peterx@redhat.com>]

On Thu, Feb 18, 2021 at 04:48:19PM -0800, Axel Rasmussen wrote:

[...]

> @@ -1290,14 +1299,20 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
>  	ret = -EINVAL;
>  	if (!uffdio_register.mode)
>  		goto out;
> -	if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
> -				     UFFDIO_REGISTER_MODE_WP))
> +	if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES)
>  		goto out;
>  	vm_flags = 0;
>  	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
>  		vm_flags |= VM_UFFD_MISSING;
>  	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)
>  		vm_flags |= VM_UFFD_WP;
> +	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
> +		/* VM_UFFD_MINOR == VM_NONE if this arch doesn't support it. */

How about check CONFIG_HAVE_ARCH_USERFAULTFD_MINOR below directly instead of
commenting?

> +		ret = -EINVAL;

Should be able to drop this line too since ret is -EINVAL already?

> +		if (!VM_UFFD_MINOR)
> +			goto out;
> +		vm_flags |= VM_UFFD_MINOR;
> +	}

[...]

> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
> index 67018d367b9f..a743a0f9ebde 100644
> --- a/include/trace/events/mmflags.h
> +++ b/include/trace/events/mmflags.h
> @@ -137,6 +137,12 @@ IF_HAVE_PG_ARCH_2(PG_arch_2,		"arch_2"	)
>  #define IF_HAVE_VM_SOFTDIRTY(flag,name)
>  #endif
>  
> +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> +# define IF_HAVE_UFFD_MINOR(flag, name) {flag, name},
> +#else
> +# define IF_HAVE_UFFD_MINOR(flag, name)
> +#endif
> +
>  #define __def_vmaflag_names						\
>  	{VM_READ,			"read"		},		\
>  	{VM_WRITE,			"write"		},		\
> @@ -148,6 +154,7 @@ IF_HAVE_PG_ARCH_2(PG_arch_2,		"arch_2"	)
>  	{VM_MAYSHARE,			"mayshare"	},		\
>  	{VM_GROWSDOWN,			"growsdown"	},		\
>  	{VM_UFFD_MISSING,		"uffd_missing"	},		\
> +IF_HAVE_UFFD_MINOR(VM_UFFD_MINOR,	"uffd_minor"	)		\
>  	{VM_PFNMAP,			"pfnmap"	},		\
>  	{VM_DENYWRITE,			"denywrite"	},		\
>  	{VM_UFFD_WP,			"uffd_wp"	},		\
> @@ -169,7 +176,7 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY,	"softdirty"	)		\
>  	{VM_MIXEDMAP,			"mixedmap"	},		\
>  	{VM_HUGEPAGE,			"hugepage"	},		\
>  	{VM_NOHUGEPAGE,			"nohugepage"	},		\
> -	{VM_MERGEABLE,			"mergeable"	}		\
> +	{VM_MERGEABLE,			"mergeable"	}

This change seems irrelevant.

If you agree with above comments, please feel free to add:

Reviewed-by: Peter Xu <peterx@redhat.com>

Thanks,

-- 
Peter Xu