From mboxrd@z Thu Jan 1 00:00:00 1970 From: bingjingc Subject: [PATCH] mdadm: prevent out-of-date reshaping devices from force assemble Date: Tue, 06 Feb 2018 17:09:47 +0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: Jes.Sorensen@gmail.com Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids With "--force", we can assemble the array even if some superblocks appear out-of-date. But their data layout is regarded to make sense. In reshape cases, if two devices claims different reshape progresses, we cannot forcely assemble them back to array. Kernel will treat only one of them as reshape progress. However, their data is still laid on different layouts. It may lead to disaster if reshape goes on. Reproducible Steps: mdadm -C /dev/md0 --assume-clean -l5 -n3 /dev/loop[012] mdadm -a /dev/md0 /dev/loop3 mdadm -G /dev/md0 -n4 mdadm -f /dev/md0 /dev/loop0 # after a period mdadm -S /dev/md0 # after another period mdadm -E /dev/loop[01] # make sure that they claims different ones mdadm -Af -R /dev/md0 /dev/loop[023] # give no enough devices for force_array() to pick non-fresh devices cat /sys/block/md0/md/reshape_position # You can see that Kernel resume reshape the from any progress of them. Note: The unit of mdadm -E is KB, but reshape_position's is sector. In order to prevent disaster, we add logics to prevent devices with different reshape progress from being added into the array. Reported-by: Allen Peng Reviewed-by: Alex Wu Signed-off-by: BingJing Chang --- Assemble.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/Assemble.c b/Assemble.c index 9e19246..9f33c61 100644 --- a/Assemble.c +++ b/Assemble.c @@ -846,7 +846,19 @@ static int force_array(struct mdinfo *content, /* OK */; else continue; - } + } else if (devices[j].i.reshape_active != + content->reshape_active || + (devices[j].i.reshape_active && + devices[j].i.reshape_progress != + content->reshape_progress)) + /* Here, it may be a source of data. If two + * devices claim different progresses, it + * means that reshape boundaries differ for + * their own devices. Kernel will only treat + * the first one as reshape progress and + * go on. It may cause disaster, so avoid it. + */ + continue; if (chosen_drive < 0 || devices[j].i.events > devices[chosen_drive].i.events) @@ -908,7 +920,13 @@ static int force_array(struct mdinfo *content, if (j >= 0 && !devices[j].uptodate && devices[j].i.recovery_start == MaxSector && - devices[j].i.events == current_events) { + devices[j].i.events == current_events && + ((!devices[j].i.reshape_active && + !content->reshape_active) || + (devices[j].i.reshape_active == + content->reshape_active && + devices[j].i.reshape_progress == + content->reshape_progress))) { chosen_drive = j; goto add_another; } -- 2.7.4