On 09/26/2014 12:44 PM, NeilBrown wrote:
> On Fri, 26 Sep 2014 12:23:27 +0200 Francis Moreau <francis.moro@xxxxxxxxx>
> wrote:
>
>> Hello Neil,
>>
>> On 09/26/2014 02:33 AM, NeilBrown wrote:
>>> On Thu, 25 Sep 2014 18:12:07 +0200 Francis Moreau <francis.moro@xxxxxxxxx>
>>> wrote:
>> [...]
>>>> I tried to find out what could have opened the md device by using fuser,
>>>> but fuser reports no users.
>>>
>>> It is probably a transient open/close.
>>>
>>
>> If it's open/close wouldn't the 'close' part make the device disapear ?
>
> No. It's ... complicated.
>
>>
>>>>
>>>> I took a look to the udev rules which are the one shipped by mdadm 3.3.2
>>>> but nothing keep the device opened during the remove event.
>>>>
>>>> Could you give me some hints here to debug this ?
>>>
>>> Modify md_open in drivers/md/md.c to add
>>> printk("Opened by %s\n", current->comm);
>>>
>>> and build a new kernel. That will tell you the name of the process which
>>> opened the device.
>>>
>>
>> I did that I also added a trace in md_release() but strangely no trace
>> were outputed from there.
>
> Without seeing your patch I can't guess what it happening, but I am *certain*
> that md_release() would get called providing md_open didn't return an error.
>
> It might be helpful to print out the pid and the md device number too
> task_tgid_vnr(current)
> will give you the pid.
> mdname(mddev)
> give the name of the device.
>
> Probably there is a 'change' event happening just before the 'remove' event,
> and udev runs "mdadm" on the 'change' event, and that ends up happening after
> the device has been removed.
>
> Is this really a problem? Can't you just ignore it and pretend it isn't
> there?
>
> NeilBrown
>
>>
>> Here's the details of what I did:
>>
>> --- %< ---
>> [root@localhost ~]# cat /proc/mdstat
>> Personalities : [raid1]
>> md125 : active raid1 vdc1[1] vdb1[0]
>> 65472 blocks super 1.0 [2/2] [UU]
>>
>> md126 : active raid1 vdc2[1] vdb2[0]
>> 209536 blocks super 1.2 [2/2] [UU]
>>
>> md127 : active raid1 vdb3[0] vdc3[1]
>> 1819584 blocks super 1.2 [2/2] [UU]
>>
>> unused devices: <none>
>>
>> [root@localhost ~]# mdadm --stop --scan
>>
>> [root@localhost ~]# dmesg | grep md_
>> [ 1.474207] md_open(): opened by mdadm
>> [ 1.475316] md_open(): opened by mdadm
>> [ 1.492880] md_open(): opened by mdadm
>> [ 1.493201] md_open(): opened by mdadm
>> [ 1.494690] md_open(): opened by mdadm
>> [ 1.499369] md_open(): opened by mdadm
>> [ 1.533566] md_open(): opened by mdadm
>> [ 1.533697] md_open(): opened by mdadm
>> [ 1.554419] md_open(): opened by mdadm
>> [ 1.574451] md_open(): opened by mdadm
>> [ 1.574666] md_open(): opened by mdadm
>> [ 1.574877] md_open(): opened by mdadm
>> [ 1.576822] md_open(): opened by systemd-udevd
>> [ 1.576895] md_open(): opened by systemd-udevd
>> [ 1.577029] md_open(): opened by systemd-udevd
>> [ 1.581850] md_open(): opened by mdadm
>> [ 1.584054] md_open(): opened by systemd-udevd
>> [ 1.584770] md_open(): opened by mdadm
>> [ 1.585175] md_open(): opened by mdadm
>> [ 1.586328] md_open(): opened by systemd-udevd
>> [ 1.586933] md_open(): opened by systemd-udevd
>> [ 1.651265] md_open(): opened by mdadm
>> [ 1.651320] md_open(): opened by mdadm
>> [ 1.651364] md_open(): opened by mdadm
>> [ 1.651437] md_open(): opened by mdadm
>> [ 1.652376] md_open(): opened by mdadm
>> [ 1.652452] md_open(): opened by mdadm
>> [ 33.486704] md_open(): opened by mdadm
>> [ 33.489259] md_open(): opened by mdadm
>> [ 33.491000] md_open(): opened by mdadm
>> [ 33.491767] md_open(): opened by systemd-udevd
>> [ 33.692255] md_open(): opened by mdadm
>> [ 33.692288] md_open(): opened by mdadm
>> [ 33.692606] md_open(): opened by mdadm
>> [ 33.692858] md_open(): opened by mdadm
>> [ 33.692942] md_open(): opened by mdadm
>> [ 33.693237] md_open(): opened by mdadm
>> [ 33.694254] md_open(): opened by mdadm
>> [ 33.694275] md_open(): opened by mdadm
>> [ 33.694373] md_open(): opened by mdadm
>> [ 33.695558] md_open(): opened by mdadm
>> [ 33.695679] md_open(): opened by mdadm
>> [ 33.695855] md_open(): opened by mdadm
>> [ 33.695894] md_open(): opened by mdadm
>>
>> [root@localhost ~]# ls /dev/md125
>> /dev/md125
>>
>> [root@localhost ~]# fuser /dev/md125
>>
>> [root@localhost ~]# ps aux | grep "mdadm\|systemd-udevd"
>> root 366 0.0 0.1 38172 1696 ? Ss 06:04 0:00
>> /usr/lib/systemd/systemd-udevd
>> root 465 0.0 0.0 4964 924 ? Ss 06:04 0:00
>> /sbin/mdadm --monitor --scan --daemonise --syslog
>> --pid-file=/run/mdadm/mdadm.pid
>>
>> [root@localhost ~]# ls -l /proc/366/fd/
>> total 0
>> lrwx------ 1 root root 64 Sep 26 06:04 0 -> /dev/null
>> lrwx------ 1 root root 64 Sep 26 06:04 1 -> /dev/null
>> lrwx------ 1 root root 64 Sep 26 06:04 10 -> socket:[8665]
>> lr-x------ 1 root root 64 Sep 26 06:04 11 -> /etc/udev/hwdb.bin
>> lrwx------ 1 root root 64 Sep 26 06:04 12 -> anon_inode:[eventpoll]
>> lrwx------ 1 root root 64 Sep 26 06:04 2 -> /dev/null
>> lrwx------ 1 root root 64 Sep 26 06:04 3 -> socket:[8144]
>> lrwx------ 1 root root 64 Sep 26 06:04 4 -> socket:[8103]
>> lrwx------ 1 root root 64 Sep 26 06:04 5 -> socket:[8660]
>> lrwx------ 1 root root 64 Sep 26 06:04 6 -> /run/udev/queue.bin
>> lr-x------ 1 root root 64 Sep 26 06:04 7 -> anon_inode:inotify
>> lrwx------ 1 root root 64 Sep 26 06:04 8 -> anon_inode:[signalfd]
>> lrwx------ 1 root root 64 Sep 26 06:04 9 -> socket:[8664]
>>
>> [root@localhost ~]# ls -l /proc/465/fd/
>> total 0
>> lrwx------ 1 root root 64 Sep 26 06:04 0 -> /dev/null
>> lrwx------ 1 root root 64 Sep 26 06:04 1 -> /dev/null
>> lrwx------ 1 root root 64 Sep 26 06:04 2 -> /dev/null
>> lr-x------ 1 root root 64 Sep 26 06:06 4 -> /proc/mdstat
>> lrwx------ 1 root root 64 Sep 26 06:06 5 -> socket:[10038]
>>
>> [root@localhost ~]# cat /proc/mdstat
>> Personalities : [raid1]
>> unused devices: <none>
>>
>> [root@localhost ~]# ls /sys/block/md125/md/
>> array_size array_state bitmap/ chunk_size component_size layout
>> level max_read_errors metadata_version new_dev raid_disks
>> reshape_direction reshape_position resync_start safe_mode_delay
>>
>> --- >% ---
>>
>> So in my understanding, only mdadm and udevd are opening the MD devices
>> and mdamd was the last to open the device. For some unknown reasons,
>> md_release() is never called.
>>
>> This happens with:
>>
>> - kernel 3.14.19
>> - mdadm 3.3.2
>> - systemd 208
>>
>> Can you see something wrong here ?
>>
>> Thanks.
>> --
Hi,
I have also been debugging this issue and I came up with this
fix/workaround. It works for me. Can you take a look a this?
Thanks,
Artur
>From c547e39789cde93d4a7ea1d3f845d61b82e4f0ed Mon Sep 17 00:00:00 2001
From: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
Date: Fri, 26 Sep 2014 12:20:46 +0200
Subject: [PATCH] md: avoid creating new devices for stopped arrays in
md_open()
When an array is about to be destroyed, set mddev->gendisk->private_data
to NULL as it is no longer needed and check it in md_open(). If
bdev->bd_disk->private_data is NULL, then this indicates that the array
is stopped and return -ENODEV.
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
---
drivers/md/md.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1294238..7109d48 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -449,6 +449,7 @@ static void mddev_put(struct mddev *mddev)
bs = mddev->bio_set;
mddev->bio_set = NULL;
if (mddev->gendisk) {
+ mddev->gendisk->private_data = NULL;
/* We did a probe so need to clean up. Call
* queue_work inside the spinlock so that
* flush_workqueue() after mddev_find will
@@ -6693,9 +6694,14 @@ static int md_open(struct block_device *bdev, fmode_t mode)
* Succeed if we can lock the mddev, which confirms that
* it isn't being stopped right now.
*/
- struct mddev *mddev = mddev_find(bdev->bd_dev);
+ struct mddev *mddev;
int err;
+ if (!bdev->bd_disk->private_data)
+ return -ENODEV;
+
+ mddev = mddev_find(bdev->bd_dev);
+
if (!mddev)
return -ENODEV;
--
1.8.4.5
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