Re: ZFS crash -- zvol_geom_bio_getattr called when volmode=dev

On 10/9/20 6:22 PM, Alan Somers wrote:
> This sounds like it might be a regression introduced by the OpenZFS merge.
> Have you compared vdev_geom.c in OpenZFS vs the old version?
> -Alan


I don't think vdev_geom.c is involved, we're taking a wrong path in 
zvol_os.c because
it seems the volume is created using the default volmode and later 
changed to volmode=dev.

> On Fri, Oct 9, 2020 at 3:48 PM Eric van Gyzen <eric_at_vangyzen.net> wrote:
>
>> On 10/9/20 4:39 PM, Eric van Gyzen wrote:
>>> Does this look familiar?  I'm creating a zvol with volmode=dev, but some
>>> geom code paths were taken.  If this looks new, I'll provide more
>> details.
>>
>> primarycache=none also seems to be a factor.  I can easily repro with:
>>
>> zfs create -s -V 10G -o primarycache=none -o volmode=dev .../testvol


I don't think primarycache is a factor, I can easily repro with 
primarycache left at the default.
The volmode property is being set asynchronously and losing the race 
with the initial creation of
the minors. When volmode is changed the minor is supposed to be 
destroyed and then recreated
in the correct mode, but that does not seem to be working correctly. 
Setting vfs.zfs.debug=1 you
can see in dmesg the zvol is created once in volmode=geom and then a 
second attempt to create
the zvol fails, because zvol_free did not occur.

zvol_create_minor_impl:1250[1]: Creating ZVOL p0/testvol...
name=p0/testvol error=0 volmode=1
zvol_create_minor_impl:1372[1]: ZVOL p0/testvol created.
zvol_create_minor_impl:1250[1]: Creating ZVOL p0/testvol...

So something is preventing zv_free from being called by 
zvol_remove_minors_impl.

-Ryan


>>
>>> 13.0-CURRENT r366500+84ccaf49083c-c272054 GENERIC
>>>
>>> #8  <signal handler called>
>>> #9  zvol_geom_bio_getattr (bp=0xfffff80376132900)
>>>       at /usr/src/sys/contrib/openzfs/module/os/freebsd/zfs/zvol_os.c:545
>>> #10 zvol_geom_bio_start (bp=0xfffff80376132900)
>>>       at /usr/src/sys/contrib/openzfs/module/os/freebsd/zfs/zvol_os.c:519
>>> #11 0xffffffff80b1c684 in g_io_schedule_down (tp=<optimized out>)
>>>       at /usr/src/sys/geom/geom_io.c:848
>>> #12 0xffffffff80b1cfcc in g_down_procbody (arg=<optimized out>)
>>>       at /usr/src/sys/geom/geom_kern.c:111
>>>
>>> (kgdb) f 9
>>> #9  zvol_geom_bio_getattr (bp=0xfffff80376132900)
>>>       at /usr/src/sys/contrib/openzfs/module/os/freebsd/zfs/zvol_os.c:545
>>> 545        spa_t *spa = dmu_objset_spa(zv->zv_objset);
>>>
>>> (kgdb) l
>>> 540        zvol_state_t *zv;
>>> 541
>>> 542        zv = bp->bio_to->private;
>>> 543        ASSERT(zv != NULL);
>>> 544
>>> 545        spa_t *spa = dmu_objset_spa(zv->zv_objset);
>>> 546        uint64_t refd, avail, usedobjs, availobjs;
>>> 547
>>> 548        if (g_handleattr_int(bp, "GEOM::candelete", 1))
>>> 549            return (0);
>>>
>>> (kgdb) p zv
>>> $1 = (zvol_state_t *) 0x0
>>>
>>> (kgdb) p *bp
>>> $3 = {
>>>     bio_cmd = 4,
>>>     bio_flags = 0,
>>>     bio_cflags = 0,
>>>     bio_pflags = 0,
>>>     bio_dev = 0x0,
>>>     bio_disk = 0x0,
>>>     bio_offset = 0,
>>>     bio_bcount = 0,
>>>     bio_data = 0xfffff801fa687c00 "",
>>>     bio_ma = 0x0,
>>>     bio_ma_offset = 0,
>>>     bio_ma_n = 0,
>>>     bio_error = 0,
>>>     bio_resid = 0,
>>>     bio_done = 0x0,
>>>     bio_driver1 = 0x0,
>>>     bio_driver2 = 0x0,
>>>     bio_caller1 = 0x0,
>>>     bio_caller2 = 0x0,
>>>     bio_queue = {
>>>       tqe_next = 0xffffffffffffffff,
>>>       tqe_prev = 0xffffffffffffffff
>>>     },
>>>     bio_attribute = 0xffffffff81223c03 "GEOM::physpath",
>>>     bio_zone = {
>>>       zone_cmd = 0 '\000',
>>>       zone_params = {
>>>         disk_params = {
>>>           zone_mode = 0,
>>>           flags = 0,
>>>           optimal_seq_zones = 0,
>>>           optimal_nonseq_zones = 0,
>>>           max_seq_zones = 0
>>>         },
>>>         rwp = {
>>>           id = 0,
>>>           flags = 0 '\000'
>>>         },
>>>         report = {
>>>           starting_id = 0,
>>>           rep_options = 0 '\000',
>>>           header = {
>>>             same = 0 '\000',
>>>             maximum_lba = 0,
>>>             reserved = '\000' <repeats 63 times>
>>>           },
>>>           entries_allocated = 0,
>>>           entries_filled = 0,
>>>           entries_available = 0,
>>>           entries = 0x0
>>>         }
>>>       }
>>>     },
>>>     bio_from = 0xfffff80006b92880,
>>>     bio_to = 0xfffff80006972500,
>>>     bio_length = 1024,
>>>     bio_completed = 0,
>>>     bio_children = 0,
>>>     bio_inbed = 0,
>>>     bio_parent = 0x0,
>>>     bio_t0 = {
>>>       sec = 50,
>>>       frac = 10248368299661698441
>>>     },
>>>     bio_task = 0x0,
>>>     bio_task_arg = 0x0,
>>>     bio_spare1 = 0x0,
>>>     bio_spare2 = 0x0,
>>>     bio_track_bp = 0x0,
>>>     bio_pblkno = 0
>>> }
>>>
>>> (kgdb) p *bp->bio_to
>>> $4 = {
>>>     name = 0xfffff80006972598 "zvol/disco_fast/vm/onefs1-1/disk7",
>>>     provider = {
>>>       le_next = 0x0,
>>>       le_prev = 0xfffff80006972428
>>>     },
>>>     geom = 0xfffff80006972400,
>>>     consumers = {
>>>       lh_first = 0xfffff80006b92880
>>>     },
>>>     acr = 1,
>>>     acw = 0,
>>>     ace = 0,
>>>     error = 0,
>>>     orphan = {
>>>       tqe_next = 0x0,
>>>       tqe_prev = 0x0
>>>     },
>>>     mediasize = 5368709120,
>>>     sectorsize = 512,
>>>     stripesize = 8192,
>>>     stripeoffset = 0,
>>>     stat = 0xfffff80006d3d120,
>>>     spare1 = 0,
>>>     spare2 = 0,
>>>     flags = 48,
>>>     aliases = {
>>>       lh_first = 0x0
>>>     },
>>>     private = 0x0,
>>>     index = 0
>>> }
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