Hi, I have a hypothesis of what happened. My swap volume is also on LVM, and thus also eventually backed by bcache. Hibernation and resume work fine. But when the hibernation image is read during resume, the contents of the cache device change because with bcache reading is no longer a read-only operation. When the hibernation image is loaded, the kernel looses track of these changes so that what's on the cache disk no longer matches the structures in the kernel. Therefore, on the first boot after the successful resume, havoc ensures.
I needed the system running again, so I've now detached the backing volumes, re-initialized the cache volume and re-attached the backing volumes. Unfortunately there was too much filesystem damage, so I restored everything from backup. Is there a way to prevent this from happening? Could eg the kernel detect that the swap devices is (indirectly) on bcache and refuse to hibernate? Or is there a way to do a "true" read-only mount of a bcache volume so that one can safely resume from it? Best, -Nikolaus -- GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.« On Tue, 3 Apr 2018, at 23:38, Jens Axboe wrote: > CC'ing Mike > > On 4/3/18 1:01 PM, Nikolaus Rath wrote: > > [ Re-send to both linux-block and linux-bcache ] > > > > Hi, > > > > A few days ago, my system refused to boot because it couldn't find the root > > filesystem anymore. The root filesystem is ext4 on LVM on dm-crypt on > > bcache, using kernel 4.9.92 (from Debian stretch). Booting from a recovery > > medium with Kernel 4.16, I got: > > > > [ 84.551715] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 84.553188] bcache: register_bcache() error /dev/sdc2: device already > > registered > > [ 84.616438] bcache: error on 1330b5f6-0c13-43ec-b925-2ee2734b135f: > > [ 84.616440] bad btree header at bucket 85065, block 0, 0 keys > > [ 84.616442] , disabling caching > > [ 84.616445] bcache: register_cache() registered cache device sdb2 > > [ 84.616597] bcache: cache_set_free() Cache set > > 1330b5f6-0c13-43ec-b925-2ee2734b135f unregistered > > [ 85.375933] sdb: sdb1 sdb2 sdb4 < sdb5 > > > [ 85.416610] bcache: error on 1330b5f6-0c13-43ec-b925-2ee2734b135f: > > [ 85.416612] bad btree header at bucket 85065, block 0, 0 keys > > [ 85.416614] , disabling caching > > [ 85.416618] bcache: register_cache() registered cache device sdb2 > > [ 85.416624] bcache: register_bcache() error /dev/sdc2: device already > > registered > > [ 85.416626] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 85.416796] bcache: cache_set_free() Cache set > > 1330b5f6-0c13-43ec-b925-2ee2734b135f unregistered > > [ 85.488246] bcache: error on 1330b5f6-0c13-43ec-b925-2ee2734b135f: > > [ 85.488249] bad btree header at bucket 85065, block 0, 0 keys > > [ 85.488251] , disabling caching > > [ 85.488254] bcache: register_cache() registered cache device sdb2 > > [ 85.488429] bcache: cache_set_free() Cache set > > 1330b5f6-0c13-43ec-b925-2ee2734b135f unregistered > > [ 85.560003] bcache: error on 1330b5f6-0c13-43ec-b925-2ee2734b135f: > > [ 85.560006] bad btree header at bucket 85065, block 0, 0 keys > > [ 85.560008] , disabling caching > > [ 85.560013] bcache: register_cache() registered cache device sdb2 > > [ 85.560017] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 85.560217] bcache: cache_set_free() Cache set > > 1330b5f6-0c13-43ec-b925-2ee2734b135f unregistered > > [ 85.571950] bcache: register_bcache() error /dev/sdc2: device already > > registered > > [ 85.580628] bcache: register_bcache() error /dev/sdc2: device already > > registered > > [ 85.761969] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 85.792749] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 85.952931] bcache: register_bcache() error /dev/sda4: device already > > registered > > [ 85.955640] bcache: register_bcache() error /dev/sda4: device already > > registered > > [...] > > > > These are the first messages that mention bcache. Note that the first > > message is that the device is already registered - is that normal? > > > > smartctl does not report any errors on backing or caching disks, and the > > system was shutdown cleanly. > > > > The only possibly related thing that comes to mind is that a few days ago I > > hibernated and resumed the system (this is something I normally don't do). > > Resume worked fine as far as I could tell though, and there have been no > > unclean shutdowns. > > > > Is there a way to narrow down what may have caused this corruption? > > > > And, is there a way to gracefully recover from this situation without > > wiping everything? Since the message mentions only problems with one block, > > can I maybe tell bcache to just ignore/drop this specific block? > > > > Thanks! > > -Nikolaus > > -- > > GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F > > > > »Time flies like an arrow, fruit flies like a Banana.« > > > > > -- > Jens Axboe >
