Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
From:   lipeifeng@oppo.com
To:     akpm@linux-foundation.org, michel@lespinasse.org, hughd@google.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        21cnbao@gmail.com, zhangshiming@oppo.com,
        lipeifeng <lipeifeng@oppo.com>
Subject: [PATCH v2] mm: modify the method to search addr in unmapped_area_topdown
Date:   Wed,  6 Apr 2022 16:13:32 +0800
Message-Id: <20220406081332.347-1-lipeifeng@oppo.com>
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?zozwB6wk7Oxfk7Uk9LwFtivmwifgDQvknqurgTfiYkzC/kxeDJ4f/raBbFK7?=
 =?us-ascii?Q?X/edxPks3zHipfyy+U8y2etlXe+TvGIBLFczj8mDVxNfO7NG7La888vjQP2K?=
 =?us-ascii?Q?XgghtxeiV6E8YrvNrbOfm9aL5TJD13Z6+1fmpIyHQP4ycyih8VnGVJA6v+WL?=
 =?us-ascii?Q?X+OtMueC7ww6C1isHIKQe0RoW/tnY4BMNYPYeUs/lYwHkNkctRugjyFky1fI?=
 =?us-ascii?Q?Wmo2mzWPu3tFDIrZBXXtlOcoYydx90iOzg8OOULqN8EBbgySfFQFhROAm+oU?=
 =?us-ascii?Q?FHpEawr1QfkE2G21LefvmZKxXJI1rV3ev31sdNS0CfAewchw5Du75yMWU65p?=
 =?us-ascii?Q?ztvdCc1yvkkWynbQrrCeAA20jT3ERCNUlRVHIRBPQxUd5BH3UJdERpfkxoZT?=
 =?us-ascii?Q?ZzMkXhJpIWPlB9OpCghrtzkslhGgreU/AMAWH1O5R9WrqwNg/APxjWslIwEw?=
 =?us-ascii?Q?8SdR7iHTyiqAUP4bT9+WeuOl+dRkwk9HZI3vIsvIpo9dci/Pyn+2WI5kqCUg?=
 =?us-ascii?Q?FzhNRpTBKkLQKYdKEqU2Pk5JKx1kTVFask7fx1AcRHMapUvWxtj2ZNONzjUR?=
 =?us-ascii?Q?sQ9+Qg5ha9b5DxySCXxEt6PHKUeR2crrouBGXKfio6oBu73C7OpOK70ijog6?=
 =?us-ascii?Q?jgHI6IkdGMiuDDu6lacsmd6kTNaXESnKOPNJrNtr9JGH4NA8uxTXSTTe0Yky?=
 =?us-ascii?Q?tJn1+WHlsr5vZBPmdOoSDqXMeULrw2TY6GYaGIpP5fGmmmWF91iFPzDRmyiZ?=
 =?us-ascii?Q?JwCLScE8w/34Cw3RA+sH0Wl02SJUQXIuZwRaF5XvPiRE4wnv4trzEH5zpLEJ?=
 =?us-ascii?Q?hsm6RdB2tOuNKcSHPx+QKGL14c0cuwBzf10xlM/F9pQgfASHZBCfqKE2BcXC?=
 =?us-ascii?Q?WH+tFM0RgJs1f5BXR5+hwD5WyBI46SJzKOhLuLEJhyTA/G9vSVWreeRtKBU2?=
 =?us-ascii?Q?yNSBo+sD5AULO04TypvTUWP2pNiWRV9VP65KbsRdH9l4TIio/7rucOzMjyIB?=
 =?us-ascii?Q?gkUDrsMf3Z6A3ElWjRTfrwOitseZ/73E82XkkWDerrntNPoOO5dYrFd9tjJl?=
 =?us-ascii?Q?+0AY56R8tET81ZgE8vuIar1K8dDxyjeVEoUa2KEJ1yV2v/7vrpqcxRmcfOvv?=
 =?us-ascii?Q?9VTkCLA5Hvi3sdgifQ5L1yd59WEHN+18rk2eGknv7e5zj0iOppsWRln4HF3F?=
 =?us-ascii?Q?ovPrteBjL2vJhruNfsIKAi0dKSugVJGWDq/3IPDDTq0HXYO8t5jjNfor8f6m?=
 =?us-ascii?Q?Szb5WMBLJr/0sW7vXkCdIfrKgJUffpO5s13hYaXXbc//Mhg6IQ5LTKxbDgr/?=
 =?us-ascii?Q?7gVmUdwaKWmrW2UitNA06MXE/6Ji1BhRGrPi/CU76gt5Nk0UvjgGm5bPcCDl?=
 =?us-ascii?Q?UvdqofyTZgiMDJ4CW6nQKNbNrFRYU0QhDWajzpO/5QNC8Al0NoeC0WDlUo6A?=
 =?us-ascii?Q?tSmeNqs/1GUKRUyWw5ipdgQr6tmk7tL6P31ZiRmIDkm2384a8/DcCA4/QJOh?=
 =?us-ascii?Q?Ifb/JqXjlzbbQHYACrNa6eZJgKEizGF1zq55B6f1+yFRcc1qzblpIHP7Kzb8?=
 =?us-ascii?Q?9K/ZwnUguY/4OLwumoXH3TX3PRT1bMiSOBu/ukUp3LowKetPzPF+wFH887Sy?=
 =?us-ascii?Q?OKy4DUizmwJopaSRoTOmLBBcPgzjeVJKvetZYKbhgrFBAB2wQtmCCULT8hfs?=
 =?us-ascii?Q?1cSuJdbzqrxm1Nt8YgkGV5mfSE42KFzaISdLpQoLPgvkmJoXG6AZGszxp+Fe?=
 =?us-ascii?Q?fXY2sNVSa6jGknH4iiuANKxAIBMYkr8=3D?=
X-OriginatorOrg: oppo.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 7ad910ec-a448-486d-480b-08da17a59050
X-MS-Exchange-CrossTenant-AuthSource: TY2PR02MB4431.apcprd02.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Apr 2022 08:15:08.7708
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: f1905eb1-c353-41c5-9516-62b4a54b5ee6
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 6jIqgMzJbr3/msZtX1goKfS1jnCNpH9MrDiNlGqJunBjIAX9EorYen4KXv2WeNkVEp3sfR5dh8IP6sqNv+0fuw==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2PR02MB4473
X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE
	autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: lipeifeng <lipeifeng@oppo.com>

The old method will firstly find the space in len(info->length
+ info->align_mask), and get address at the desired alignment.

Sometime, addr  would be failed if there are enough
addr space in kernel by above method, e.g., you can't get a
addr sized in 1Mbytes, align_mask 1Mbytes successfully although
there are still (2M-1)bytes space in kernel.

This patch would fix thr problem above by the new method: find the
space in info->length and judge if at the desired info->align_mask
at the same time.

Do a simple test in TIF_32BIT:
- Try to take addr (size:1M align:2M) until allocation fails;
- Try to take addr (size:1M align:1M) and account how to space can be
alloced successfully.

Before optimization: alloced 0     bytes.
After  optimization: alloced 1.9+G bytes.

Signed-off-by: lipeifeng <lipeifeng@oppo.com>
---
-v2: fix the commit message

 mm/mmap.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index f61a154..30e33d3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2002,13 +2002,14 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
-	unsigned long length, low_limit, high_limit, gap_start, gap_end;
+	unsigned long length, low_limit, high_limit, gap_start, gap_end, gap_end_tmp;
 
 	/* Adjust search length to account for worst case alignment overhead */
 	length = info->length + info->align_mask;
 	if (length < info->length)
 		return -ENOMEM;
 
+	length = info->length;
 	/*
 	 * Adjust search limits by the desired length.
 	 * See implementation comment at top of unmapped_area().
@@ -2024,8 +2025,12 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
 
 	/* Check highest gap, which does not precede any rbtree node */
 	gap_start = mm->highest_vm_end;
-	if (gap_start <= high_limit)
-		goto found_highest;
+	if (gap_start <= high_limit) {
+		gap_end_tmp = gap_end - info->length;
+		gap_end_tmp -= (gap_end_tmp - info->align_offset) & info->align_mask;
+		if (gap_end_tmp >= gap_start)
+			goto found_highest;
+	}
 
 	/* Check if rbtree root looks promising */
 	if (RB_EMPTY_ROOT(&mm->mm_rb))
@@ -2053,8 +2058,13 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
 		if (gap_end < low_limit)
 			return -ENOMEM;
 		if (gap_start <= high_limit &&
-		    gap_end > gap_start && gap_end - gap_start >= length)
-			goto found;
+		    gap_end > gap_start && gap_end - gap_start >= length) {
+			gap_end_tmp = gap_end - info->length;
+			gap_end_tmp -= (gap_end_tmp - info->align_offset) & info->align_mask;
+			if (gap_end_tmp >= gap_start)
+				goto found;
+
+		}
 
 		/* Visit left subtree if it looks promising */
 		if (vma->vm_rb.rb_left) {
-- 
2.7.4