Re: [PATCH v5 08/10] mmap locking API: add MMAP_LOCK_INITIALIZER

From: Vlastimil Babka <vbabka@suse.cz>
To: Michel Lespinasse <walken@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-mm <linux-mm@kvack.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Laurent Dufour <ldufour@linux.ibm.com>,
	Matthew Wilcox <willy@infradead.org>,
	Liam Howlett <Liam.Howlett@oracle.com>,
	Jerome Glisse <jglisse@redhat.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	David Rientjes <rientjes@google.com>,
	Hugh Dickins <hughd@google.com>, Ying Han <yinghan@google.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Daniel Jordan <daniel.m.jordan@oracle.com>
Subject: Re: [PATCH v5 08/10] mmap locking API: add MMAP_LOCK_INITIALIZER
Date: Mon, 18 May 2020 12:45:06 +0200	[thread overview]
Message-ID: <90cfe0e5-2ec9-3a10-0ce6-245bb456a120@suse.cz> (raw)
In-Reply-To: <20200422001422.232330-9-walken@google.com>

On 4/22/20 2:14 AM, Michel Lespinasse wrote:
> Define a new initializer for the mmap locking api.
> Initially this just evaluates to __RWSEM_INITIALIZER as the API
> is defined as wrappers around rwsem.
> 
> Signed-off-by: Michel Lespinasse <walken@google.com>

Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Nit below.

> ---
>  arch/x86/kernel/tboot.c    | 2 +-
>  drivers/firmware/efi/efi.c | 2 +-
>  include/linux/mmap_lock.h  | 3 +++
>  mm/init-mm.c               | 2 +-
>  4 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
> index b89f6ac6a0c0..885058325c20 100644
> --- a/arch/x86/kernel/tboot.c
> +++ b/arch/x86/kernel/tboot.c
> @@ -90,7 +90,7 @@ static struct mm_struct tboot_mm = {
>  	.pgd            = swapper_pg_dir,
>  	.mm_users       = ATOMIC_INIT(2),
>  	.mm_count       = ATOMIC_INIT(1),
> -	.mmap_sem       = __RWSEM_INITIALIZER(init_mm.mmap_sem),
> +	MMAP_LOCK_INITIALIZER(init_mm)
>  	.page_table_lock =  __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
>  	.mmlist         = LIST_HEAD_INIT(init_mm.mmlist),
>  };
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 911a2bd0f6b7..916313ec8acb 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -54,7 +54,7 @@ struct mm_struct efi_mm = {
>  	.mm_rb			= RB_ROOT,
>  	.mm_users		= ATOMIC_INIT(2),
>  	.mm_count		= ATOMIC_INIT(1),
> -	.mmap_sem		= __RWSEM_INITIALIZER(efi_mm.mmap_sem),
> +	MMAP_LOCK_INITIALIZER(efi_mm)
>  	.page_table_lock	= __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
>  	.mmlist			= LIST_HEAD_INIT(efi_mm.mmlist),
>  	.cpu_bitmap		= { [BITS_TO_LONGS(NR_CPUS)] = 0},
> diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h
> index d1826ce42f00..9e104835a0d1 100644
> --- a/include/linux/mmap_lock.h
> +++ b/include/linux/mmap_lock.h
> @@ -1,6 +1,9 @@
>  #ifndef _LINUX_MMAP_LOCK_H
>  #define _LINUX_MMAP_LOCK_H
>  
> +#define MMAP_LOCK_INITIALIZER(name) \
> +	.mmap_sem = __RWSEM_INITIALIZER(name.mmap_sem),

"(name).mmap_sem" is safer in a macro?

> +
>  static inline void mmap_init_lock(struct mm_struct *mm)
>  {
>  	init_rwsem(&mm->mmap_sem);
> diff --git a/mm/init-mm.c b/mm/init-mm.c
> index 19603302a77f..fe9c03d8e07b 100644
> --- a/mm/init-mm.c
> +++ b/mm/init-mm.c
> @@ -31,7 +31,7 @@ struct mm_struct init_mm = {
>  	.pgd		= swapper_pg_dir,
>  	.mm_users	= ATOMIC_INIT(2),
>  	.mm_count	= ATOMIC_INIT(1),
> -	.mmap_sem	= __RWSEM_INITIALIZER(init_mm.mmap_sem),
> +	MMAP_LOCK_INITIALIZER(init_mm)
>  	.page_table_lock =  __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
>  	.arg_lock	=  __SPIN_LOCK_UNLOCKED(init_mm.arg_lock),
>  	.mmlist		= LIST_HEAD_INIT(init_mm.mmlist),
> 