Received-SPF: pass (google.com: domain of linux-kernel+bounces-34446-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Date: Mon, 22 Jan 2024 19:18:30 -0500
From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Yajun Deng <yajun.deng@linux.dev>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/mmap: introduce vma_range_init()
Message-ID: <20240123001830.glqdmrv2qc56zfpc@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Yajun Deng <yajun.deng@linux.dev>, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
References: <20240111021526.3461825-1-yajun.deng@linux.dev>
 <20240122220031.pwiravglee7o7k34@revolver>
 <20240122154031.b710f834b14d9027176f439a@linux-foundation.org>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240122154031.b710f834b14d9027176f439a@linux-foundation.org>
User-Agent: NeoMutt/20220429
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: 
	=?us-ascii?Q?EkBZuwfsmxnQd42EgKEhS+B2Lz/ylRgFn659ToDjSqAXRAop8inmGh9itLNi?=
 =?us-ascii?Q?r90N/n4i4CcwXjz/tinhBWzzoQc+hIak6or18yrgALh2qqdC9khde2LDEJeT?=
 =?us-ascii?Q?AkhxvMomwCm3Ri9biqhhPBYWdwpkVY7DZm0NfWKUf4FTeHiTnuNhhI9w0gTr?=
 =?us-ascii?Q?bjCrPTmF1DArovodgD9QQJffbQ7HUgHHUgn8/Y3PTEJWul8Vl9gIZIPSKLft?=
 =?us-ascii?Q?NFIDuBJEQmJEtU7qHKbg1e0FlKlAi19I5+7AxzUYLWMdb57UGWOP9odyePtL?=
 =?us-ascii?Q?4QAv7HmgsROIInG/ffA8WlfipaPYVvo4et0wxyMFS0TEOiHj91rM9wbY+zXY?=
 =?us-ascii?Q?HNJSmof2gUAxMfYS0M7Ot6uu7EbAk1pUvCLfDrb6YRUYXtxTqD9jl+09MhK0?=
 =?us-ascii?Q?NPBEGyHFL36TAf0xViaNCywEZkd035LBcXEgg51U07VaDezLvTWQr6BCzTC+?=
 =?us-ascii?Q?3pMYvuvlBorT1D++Piq4vOazwy/DwzS5EaTN3hd14iuHrgdhqHyPxzUboi2g?=
 =?us-ascii?Q?1Ynt1/GLDthVwIQ9vWGQlf+stAMi2kYfttAs34+ekc9ggjt4DfWZWRoI/5SI?=
 =?us-ascii?Q?kQ8AuBMRCV6+IuRRrzSdKC5ipCt0NRZuiMcXKcl5U1PdSY05CoQSScwKnOpC?=
 =?us-ascii?Q?+XPoPXbGtktWL3rrIBV26lTdPv7vNktMzC/jOpLkl7VN6vItu46tutUovWlg?=
 =?us-ascii?Q?kjSJN+sS62lRXv3wfPwSOpFqjgieMdAR79gFt4KmrtL+yHcOVGSIHahKm3QS?=
 =?us-ascii?Q?M8PEWyBqV3zxxmcygvG99x+t4/KqmuoJGOQIUfj2n3GEff/HMMI+GLIchdOU?=
 =?us-ascii?Q?RCTNA3Zj2CQjNJVtLrYG9nkJd7v0m7+cB787b8fhhwPYizMmzVBP5qqZFtPz?=
 =?us-ascii?Q?4sXW7Khrw7g8JfmJYRkRscVo7Q+r8oTk7e+w44+gu53WjiLC/zdjJPOw07Dw?=
 =?us-ascii?Q?n5NBQj4cEzXtCTG8SOG6Xu16JZHXhjHUanfHXpkPds1MhOSUDXN6Ml7hYlYQ?=
 =?us-ascii?Q?FmIj7onafo2XSPpRfxpsPmQFONVJmd+qfsgynAZLylgBueB8XAMdNr/u6/vp?=
 =?us-ascii?Q?z2FIgQ9UvweMCX7QTmXqnZpk/hQQZeq7b1oEwOFAIezdgGZM9rB/drIDpRzm?=
 =?us-ascii?Q?n91Oz19tv6kSOoxU9tA41p6XGF0NKZHRSQiNVI6zdUctMTCOvjUMnd4rvtQ2?=
 =?us-ascii?Q?5OMMWumwdnG4dv1enX/uEWkX6EWZzN+RbnZHH3j+fgFKDh0a21tFBO8NSOCB?=
 =?us-ascii?Q?cnrQaXWmOEgDLmxlxgzdcrzI7WW7CqCPDd08GVbdfazdf2h6vT7BaFkEN14b?=
 =?us-ascii?Q?Ww5DSRFldX8kVQLhXFepzT405MnzJhDwDT406qaURPCIT7ZLDZwBkvsXERu1?=
 =?us-ascii?Q?VwjBhaHywbDdlhWqp57X9r08BPkSLSc311hqTqCu6hC6UNlWzHqk4+n67+wq?=
 =?us-ascii?Q?4Tfw10e068npZ0FfCTL/4B2rLPPJg4XLpYFJ0TwxnGLCMpHjkxeSwXcQmDIg?=
 =?us-ascii?Q?mFqyfHPnYuOf9ppBPHxnumhjdJLoI5XKKpVWw94Xze9++9QCSppW6d8aCVEQ?=
 =?us-ascii?Q?0V/uQpbNnuiZMx/I0Xx96qEyubZxH816cID1RoQf?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 
	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
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 2e0ce681-6d04-4775-7358-08dc1ba8d4fc
X-MS-Exchange-CrossTenant-AuthSource: DS0PR10MB7933.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jan 2024 00:18:32.2759
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: TvzPUY0fT6MUUOjLpeLbu80GKa2p6c7rX3mQugYOggaifuOqHkG0l5Z1xtpwdMCFxtUNbSoU9GA64XlywtfpDg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR10MB6226
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26
 definitions=2024-01-22_12,2024-01-22_01,2023-05-22_02
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxlogscore=999
 spamscore=0 mlxscore=0 adultscore=0 bulkscore=0 phishscore=0
 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2311290000 definitions=main-2401230001
X-Proofpoint-ORIG-GUID: Q1DlWZK-eAowavQ8lECKuoAAAP5-ShOX
X-Proofpoint-GUID: Q1DlWZK-eAowavQ8lECKuoAAAP5-ShOX

* Andrew Morton <akpm@linux-foundation.org> [240122 18:40]:
> On Mon, 22 Jan 2024 17:00:31 -0500 "Liam R. Howlett" <Liam.Howlett@Oracle.com> wrote:
> 
> > * Yajun Deng <yajun.deng@linux.dev> [240110 21:15]:
> > > There is a lot of code needs to set the range of vma, introduce
> > > vma_range_init() to initialize the range of vma.
> > > 
> > > Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
> > > ---
> > >  include/linux/mm.h |  9 +++++++++
> > >  mm/mmap.c          | 29 +++++++----------------------
> > >  2 files changed, 16 insertions(+), 22 deletions(-)
> > 
> > This isn't a whole lot of code, are there others?  We're losing code
> > clarity in favour of saving 6 lines?
> > 
> 
> Oh.  I thought it was a nice cleanup which made things more clear.

I'm not totally against it; that's why I suggested the changes below. I
think a name change would go a long way for clarity. It's not as much as
I though it would be though.

> 
> > > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > > index f5a97dec5169..abb4534be3cc 100644
> > > --- a/include/linux/mm.h
> > > +++ b/include/linux/mm.h
> > > @@ -3516,6 +3516,15 @@ static inline bool range_in_vma(struct vm_area_struct *vma,
> > >  	return (vma && vma->vm_start <= start && end <= vma->vm_end);
> > >  }
> > >  
> > > +static inline void vma_range_init(struct vm_area_struct *vma,
> > 
> > Any reason this can't be in mm/internal.h ?
> 
> That would be good.

One other thing, do we trust this to be inlined correctly by the
compiler or should this be __always_inline?  I'd expect it to be okay as
it is, but I've been proven wrong in a perf trace before..

> 
> > vma_range_set(), vma_set_range(), or just vma_range() might be a better
> > name?  My thinking is that some of these are actually modifying the vma
> > and not just initializing it, right?
> 
> I'd vote for vma_set_range().
> 

Using vma_set_range() leaves vma_range() or vma_size(), which could be
added for the calculations of vma->vm_end - vma->vm_start.  Davidlohr
suggested such a beast a few years ago, but that one would need to live
in the include/linux/mm.h as it occurs a lot more.

$ git grep "vma->vm_end - vma->vm_start" | wc -l
198

. for just those named vma.