From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Ni Subject: [PATCH] Need update superblock on time when deciding to do reshape Date: Tue, 17 May 2016 16:54:09 +0800 Message-ID: <1463475249-18658-1-git-send-email-xni@redhat.com> Return-path: Sender: linux-raid-owner@vger.kernel.org To: shli@kernel.org Cc: linux-raid@vger.kernel.org, Jes.Sorensen@redhat.com List-Id: linux-raid.ids Hi all If the disks are not enough to have spaces for relocating the data_offset, it needs to run start_reshape and then run mdadm --grow --continue by systemd. But mdadm --grow --continue fails because it checkes that info->reshape_active is 0. The info->reshape_active is set to 1 when the superblock feature_map have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector. Function start_reshape calls raid5_start_reshape which changes mddev->reshape_position to 0. Then in md_check_recovery it updates the superblock to underlying devices. But there is a chance that the superblock haven't written to underlying devices, the mdadm reads the superblock data. So mdadm --grow --continue fails. The steps to reproduce this: mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal mdadm --wait /dev/md0 mdadm /dev/md0 -a /dev/loop3 mdadm --grow --raid-devices 4 /dev/md0 The loop device size is 500MB [root@storageqe-09 ~]# cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0] 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU] [>....................] reshape = 0.0% (1/510976) finish=0.0min speed=255488K/sec bitmap: 1/1 pages [4KB], 65536KB chunk unused devices: So if we update the superblock on time, mdadm can read the right superblock data. Signed-off-by --- drivers/md/md.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/md/md.c b/drivers/md/md.c index 14d3b37..7919606 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char *page, size_t len) else { clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery); err = mddev->pers->start_reshape(mddev); + md_update_sb(mddev, 1); } mddev_unlock(mddev); } -- 2.4.3