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Tue, 2 Feb 2021 13:54:01 +0000 Received: from DB7PR04MB4666.eurprd04.prod.outlook.com ([fe80::dd78:1e78:3ad2:9d7e]) by DB7PR04MB4666.eurprd04.prod.outlook.com ([fe80::dd78:1e78:3ad2:9d7e%6]) with mapi id 15.20.3805.024; Tue, 2 Feb 2021 13:54:01 +0000 From: Zhao Heming To: linux-raid@vger.kernel.org, jes@trained-monkey.org Cc: Zhao Heming , xni@redhat.com, lidong.zhong@suse.com Subject: [PATCH] super1.c: avoid useless sync when bitmap switches from clustered to none Date: Tue, 2 Feb 2021 21:53:41 +0800 Message-Id: <1612274021-21899-1-git-send-email-heming.zhao@suse.com> X-Mailer: git-send-email 1.8.3.1 Content-Type: text/plain X-Originating-IP: [123.123.133.229] X-ClientProxiedBy: HK0PR03CA0098.apcprd03.prod.outlook.com (2603:1096:203:b0::14) To DB7PR04MB4666.eurprd04.prod.outlook.com (2603:10a6:5:2b::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from c73.home (123.123.133.229) by HK0PR03CA0098.apcprd03.prod.outlook.com (2603:1096:203:b0::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3805.16 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: =?us-ascii?Q?A7+dzpUUCz4OPDquWlC+TyT5sHPk/PbZX4yrEuEuIrs7Sd2KczA4ZAar5Snb?= =?us-ascii?Q?saWjdXn7TIQaRO3i3m7QGUJTFJjG5aIuFyguPyaGolXA0toYRI9J84qv2+yz?= =?us-ascii?Q?yKkPI8KBf0Piy1qqxxuojZy08Ggp5wxAMKY6g0F1unj+kYdqXi3QqfjHUbqF?= =?us-ascii?Q?PVk9ZOwiW2l3gsmT5jVvLGqYtplgcNbJXzgrDT7grohpdk9tI4l9VXNpMokb?= =?us-ascii?Q?Gn7qIo4TQ647T5FA8yn8nSlXDLNqZ/V36j4dKVLxdfHspXWInp6jlE/iZk3Z?= =?us-ascii?Q?510+8R2gF7p7e+c2CBWNv3BEUhEbFGvIZAb6fD9eloOAWRLPAhVUz1iDmp75?= =?us-ascii?Q?LsDKTXWAVSiY9qstO1JBGDCF7CNYZDji0Nnh4Am7i7cb8x8E+YonX5ynqMwV?= =?us-ascii?Q?W7IwxtcI3sXHVjY9+6/bbEeRG039kLmspDsl0WtV3sNZLnRAwDuzmXkroFDG?= =?us-ascii?Q?dVITU0PkAT//pH47dA0URCQ8Wy9Bf4U9kdMkHIJv+1cwdj4qnPQaBBRH8SHp?= =?us-ascii?Q?4TlEx6Rj4cPEgEon+iyQHRt9ETzQJtctHDqXqHSVFOj5e1BmAXBtuAr/NRfB?= =?us-ascii?Q?ShBoC+qM2NkwvLGb7qTEqqcB0Q5HpEXa3KG3cTNjRbEcppCy80hUgA2CBmu5?= =?us-ascii?Q?jMLRgGXViQ4g+zheUXjbDMtJWYXQU2zw/gxKaOp/Qk6e5YnyEzYUIEEllqFV?= =?us-ascii?Q?YAG8wqjQrVRm8v4djUC3auzPDkbTrwGwIuqkC6G2IshQKayshYklEBcr5oXj?= =?us-ascii?Q?0sSlUio9Btf6R+z6GxVOZJC/23E0mRe7qw13SqjkDTfu+VyHV9EhQD7bJKCo?= =?us-ascii?Q?SqrWDbKQMqN9jsW6tH1dom0Qq7zd4pgaIVPNBzr2zVzNGYwcjKNkRzaNvUUp?= =?us-ascii?Q?cJVruPsfpPIPaiZFN4h6CjK53/S5UnJjvoZ47O9Zuu1LY69KlX4g0nKLlbCE?= =?us-ascii?Q?PXyO2pw8WJ5I3Ff+JBVeTpnEPRr42VuXtQ4uneuaDmh9eJyI8hm1SjGEOnRj?= =?us-ascii?Q?atY1SevXookLhJkyhhLw5aepRYYbTa2awpiZazA5OH2mllvx8Msv0nigjLDg?= =?us-ascii?Q?P9BaB9Ro?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9a058be9-408b-4dc5-3369-08d8c781fecd X-MS-Exchange-CrossTenant-AuthSource: DB7PR04MB4666.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Feb 2021 13:54:01.6312 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: TSzUWKUN1GJ/0S5awamZuvVSTtzv3X9Jllb/acpIbc9wyl6OflciuPaXKcvM1PqQjTJ0fRbWe3JudwUoSzCwxg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR04MB6908 Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org With kernel commit 480523feae58 ("md: only call set_in_sync() when it is expected to succeed."), mddev->in_sync in clustered array is always zero. It makes metadata resync_offset to always zero. When assembling a clusterd array with "-U no-bitmap" option, kernel md layer "mddev->resync_offset == 0" and "mddev->bitmap == NULL" will trigger raid1 do sync on every bitmap chunk. the sync action is useless, we should avoid it. Related kernel flow: ``` md_do_sync mddev->pers->sync_request raid1_sync_request md_bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) __bitmap_start_sync(bitmap, offset,&blocks1, degraded) if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */ *blocks = 1024; return 1; /* always resync if no bitmap */ } ``` Reprodusible steps: ``` mdadm -C /dev/md0 -b clustered -e 1.2 -n 2 -l mirror /dev/sd{a,b} mdadm -Ss (in another shell, executing: watch -n 1 'cat /proc/mdstat') mdadm -A -U no-bitmap /dev/md0 /dev/sd{a,b} ``` Signed-off-by: Zhao Heming --- super1.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/super1.c b/super1.c index 19fe6f5..92047d5 100644 --- a/super1.c +++ b/super1.c @@ -1318,6 +1318,8 @@ static int update_super1(struct supertype *st, struct mdinfo *info, memcpy(bms->uuid, sb->set_uuid, 16); } else if (strcmp(update, "no-bitmap") == 0) { sb->feature_map &= ~__cpu_to_le32(MD_FEATURE_BITMAP_OFFSET); + if (bms->version == BITMAP_MAJOR_CLUSTERED) + sb->resync_offset = MaxSector; } else if (strcmp(update, "bbl") == 0) { /* only possible if there is room after the bitmap, or if * there is no bitmap -- 2.30.0