From mboxrd@z Thu Jan 1 00:00:00 1970 From: Francis Moreau Subject: Re: /sys/block/md126 still exists even after stopping the array Date: Fri, 26 Sep 2014 14:21:04 +0200 Message-ID: <54255A30.9010406@gmail.com> References: <53A99B76.3020603@gmail.com> <20140625110348.48ab2d7a@notabene.brown> <54243ED7.6090904@gmail.com> <20140926103348.5f5ea568@notabene.brown> <54253E9F.4070505@gmail.com> <20140926204445.1ec830b9@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140926204445.1ec830b9@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid , sebastian.riemer@profitbricks.com List-Id: linux-raid.ids On 09/26/2014 12:44 PM, NeilBrown wrote: > On Fri, 26 Sep 2014 12:23:27 +0200 Francis Moreau > wrote: > >> Hello Neil, >> >> On 09/26/2014 02:33 AM, NeilBrown wrote: >>> On Thu, 25 Sep 2014 18:12:07 +0200 Francis Moreau >>> 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. Here's the patch: diff --git a/drivers/md/md.c b/drivers/md/md.c index 73aedcb..08ead8d 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6703,6 +6703,8 @@ static int md_open(struct block_device *bdev, fmode_t mode) struct mddev *mddev = mddev_find(bdev->bd_dev); int err; + printk("md_open(): opened by %s\n", current->comm); + if (!mddev) return -ENODEV; @@ -6735,6 +6737,8 @@ static void md_release(struct gendisk *disk, fmode_t mode) { struct mddev *mddev = disk->private_data; + printk("md_release(): released by %s\n", current->comm); + BUG_ON(!mddev); atomic_dec(&mddev->openers); mddev_put(mddev); > > 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. > Here's the new trace, this time md_release() was called, so I probably did something wrong the first time, sorry for that. [ 1.470744] md_open(): md127 opened by mdadm [388] [ 1.485437] md_release(): md127 released by mdadm [388] [ 1.486888] md_open(): md126 opened by mdadm [381] [ 1.487468] md_release(): md126 released by mdadm [381] [ 1.488646] md_open(): md125 opened by mdadm [383] [ 1.489074] md_release(): md125 released by mdadm [383] [ 1.490555] md_open(): md127 opened by mdadm [385] [ 1.512556] md_release(): md127 released by mdadm [385] [ 1.512582] md_open(): md127 opened by mdadm [385] [ 1.512682] md_open(): md126 opened by mdadm [384] [ 1.553414] md_release(): md126 released by mdadm [384] [ 1.553442] md_open(): md126 opened by mdadm [384] [ 1.553549] md_open(): md125 opened by mdadm [382] [ 1.573263] md_release(): md125 released by mdadm [382] [ 1.573288] md_open(): md125 opened by mdadm [382] [ 1.601034] md_open(): md125 opened by mdadm [459] [ 1.601041] md_release(): md125 released by mdadm [459] [ 1.601065] md_open(): md126 opened by mdadm [459] [ 1.601067] md_release(): md126 released by mdadm [459] [ 1.601090] md_open(): md127 opened by mdadm [459] [ 1.601092] md_release(): md127 released by mdadm [459] [ 1.601130] md_open(): md127 opened by mdadm [459] [ 1.601220] md_release(): md127 released by mdadm [459] [ 1.601633] md_open(): md126 opened by mdadm [459] [ 1.601661] md_release(): md126 released by mdadm [459] [ 1.601673] md_open(): md125 opened by mdadm [459] [ 1.601695] md_release(): md125 released by mdadm [459] [ 1.606127] md_open(): md125 opened by mdadm [454] [ 1.608682] md_open(): md126 opened by mdadm [453] [ 1.609514] md_open(): md127 opened by mdadm [448] [ 1.622512] md_release(): md126 released by mdadm [453] [ 1.623028] md_release(): md127 released by mdadm [448] [ 1.625288] md_open(): md126 opened by systemd-udevd [363] [ 1.625391] md_release(): md125 released by mdadm [454] [ 1.625619] md_open(): md127 opened by systemd-udevd [368] [ 1.625737] md_open(): md125 opened by systemd-udevd [366] [ 1.637137] md_release(): md125 released by systemd-udevd [366] [ 1.643982] md_open(): md125 opened by mdadm [476] [ 1.644071] md_release(): md127 released by systemd-udevd [368] [ 1.647787] md_release(): md125 released by mdadm [382] [ 1.648171] md_release(): md126 released by systemd-udevd [363] [ 1.651629] md_open(): md126 opened by mdadm [479] [ 1.656666] md_open(): md127 opened by mdadm [480] [ 1.657771] md_release(): md125 released by mdadm [476] [ 1.659312] md_open(): md125 opened by systemd-udevd [365] [ 1.663193] md_release(): md127 released by mdadm [385] [ 1.673669] md_release(): md125 released by systemd-udevd [365] [ 1.685527] md_release(): md127 released by mdadm [480] [ 1.685599] md_release(): md126 released by mdadm [479] [ 1.686058] md_open(): md126 opened by systemd-udevd [366] [ 1.686282] md_release(): md126 released by systemd-udevd [366] [ 1.691024] md_open(): md127 opened by systemd-udevd [363] [ 1.695415] md_release(): md126 released by mdadm [384] [ 1.707163] md_release(): md127 released by systemd-udevd [363] >>> mdadm --stop --scan <<< [ 89.975162] md_open(): md125 opened by mdadm [930] [ 89.975305] md_release(): md125 released by mdadm [930] [ 89.977434] md_open(): md125 opened by mdadm [932] [ 89.978813] md_open(): md125 opened by mdadm [930] [ 89.979365] md_release(): md125 released by mdadm [932] [ 89.979693] md_open(): md125 opened by systemd-udevd [931] [ 89.985790] md_release(): md125 released by systemd-udevd [931] [ 90.179911] md_release(): md125 released by mdadm [930] [ 90.180168] md_open(): md127 opened by mdadm [459] [ 90.180187] md_release(): md127 released by mdadm [459] [ 90.180199] md_open(): md126 opened by mdadm [459] [ 90.180205] md_release(): md126 released by mdadm [459] [ 90.180556] md_open(): md126 opened by mdadm [930] [ 90.180653] md_release(): md126 released by mdadm [930] [ 90.180690] md_open(): md126 opened by mdadm [930] [ 90.180758] md_open(): mdX opened by mdadm [459] [ 90.180995] md_open(): md125 opened by mdadm [459] [ 90.181056] md_release(): md125 released by mdadm [459] [ 90.182717] md_open(): md127 opened by mdadm [459] [ 90.182725] md_release(): md127 released by mdadm [459] [ 90.182732] md_open(): md126 opened by mdadm [459] [ 90.182761] md_release(): md126 released by mdadm [459] [ 90.182770] md_open(): md125 opened by mdadm [459] [ 90.182775] md_release(): md125 released by mdadm [459] [ 90.182940] md_release(): md126 released by mdadm [930] [ 90.183167] md_open(): md127 opened by mdadm [930] [ 90.183257] md_release(): md127 released by mdadm [930] [ 90.183288] md_open(): md127 opened by mdadm [930] [ 90.183461] md_open(): md127 opened by mdadm [459] [ 90.183488] md_release(): md127 released by mdadm [459] [ 90.183499] md_open(): md125 opened by mdadm [459] [ 90.183505] md_release(): md125 released by mdadm [459] [ 90.183686] md_release(): md127 released by mdadm [930] > 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? Well, if you list the block devices that the kernel detected in order to operate on them, it could. I don't know exactly what would be the result to use it but it could confuse some tools. Is there a way to check that the 'ghost' device has been removed by poking sysfs ? Thanks