Re: main [and, likely, stable/14]: do not set vfs.zfs.bclone_enabled=1 with that zpool feature enabled because it still leads to panics

From: Mark Millard <>
Date: Thu, 07 Sep 2023 23:32:34 UTC
On Sep 7, 2023, at 13:07, Alexander Motin <> wrote:

> Thanks, Mark.
> On 07.09.2023 15:40, Mark Millard wrote:
>> On Sep 7, 2023, at 11:48, Glen Barber <> wrote:
>>> On Thu, Sep 07, 2023 at 11:17:22AM -0700, Mark Millard wrote:
>>>> When I next have time, should I retry based on a more recent
>>>> vintage of main that includes 969071be938c ?
>>> Yes, please, if you can.
>> As stands, I rebooted that machine into my normal
>> enviroment, so the after-crash-with-dump-info
>> context is preserved. I'll presume lack of a need
>> to preserve that context unless I hear otherwise.
>> (But I'll work on this until later today.)
>> Even my normal environment predates the commit in
>> question by a few commits. So I'll end up doing a
>> more general round of updates overall.
>> Someone can let me know if there is a preference
>> for debug over non-debug for the next test run.
> It is not unknown when some bugs disappear once debugging is enabled due to different execution timings, but generally debug may to detect the problem closer to its origin instead of looking on random consequences. I am only starting to look on this report (unless Pawel or somebody beat me on it), and don't have additional requests yet, but if you can repeat the same with debug kernel (in-base ZFS's ZFS_DEBUG setting follows kernel's INVARIANTS), it may give us some additional information.

So I did a zpool import, rewinding to the checkpoint.
(This depends on the questionable zfs doing fully as
desired for this. Notably the normal environment has
vfs.zfs.bclone_enabled=0 , including when it was
doing this activity.) My normal environment reported
no problems.

Note: the earlier snapshot from my first setup was
still in place since it was made just before the
original checkpoint used above.

However, the rewind did remove the /var/crash/
material that had been added.

I did the appropriate zfs mount.

I installed a debug kernel and world to the import. Again,
no problems reported.

I did the appropriate zfs umount.

I did the appropriate zpool export.

I rebooted with the test media.

# sysctl vfs.zfs.bclone_enabled
vfs.zfs.bclone_enabled: 1

# zpool trim -w zamd64

# zpool checkpoint zamd64

# uname -apKU
FreeBSD amd64-ZFS 15.0-CURRENT FreeBSD 15.0-CURRENT amd64 1500000 #74 main-n265188-117c54a78ccd-dirty: Tue Sep  5 21:29:53 PDT 2023     root@amd64-ZFS:/usr/obj/BUILDs/main-amd64-dbg-clang/usr/main-src/amd64.amd64/sys/GENERIC-DBG amd64 amd64 1500000 1500000

(So, before the 969071be938c vintage, same sources as for
my last run but a debug build.)

# poudriere bulk -jmain-amd64-bulk_a -a
. . .
[00:03:23] Building 34214 packages using up to 32 builders
[00:03:23] Hit CTRL+t at any time to see build progress and stats
[00:03:23] [01] [00:00:00] Builder starting
[00:04:19] [01] [00:00:56] Builder started
[00:04:20] [01] [00:00:01] Building ports-mgmt/pkg | pkg-1.20.6
[00:05:33] [01] [00:01:14] Finished ports-mgmt/pkg | pkg-1.20.6: Success
[00:05:53] [01] [00:00:00] Building print/indexinfo | indexinfo-0.3.1
[00:05:53] [02] [00:00:00] Builder starting
. . .
[00:05:54] [32] [00:00:00] Builder starting
[00:06:11] [01] [00:00:18] Finished print/indexinfo | indexinfo-0.3.1: Success
[00:06:12] [01] [00:00:00] Building devel/gettext-runtime | gettext-runtime-0.22_1
[00:08:24] [01] [00:02:12] Finished devel/gettext-runtime | gettext-runtime-0.22_1: Success
[00:08:31] [01] [00:00:00] Building devel/libtextstyle | libtextstyle-0.22
[00:10:06] [05] [00:04:13] Builder started
[00:10:06] [05] [00:00:00] Building devel/autoconf-switch | autoconf-switch-20220527
[00:10:06] [31] [00:04:12] Builder started
[00:10:06] [31] [00:00:00] Building devel/libatomic_ops | libatomic_ops-7.8.0
. . .

Crashed again, with 158 *.pkg files in .building/All/ after

The crash is similar to the non-debug one. No extra output
from the debug build.

For reference:

Unread portion of the kernel message buffer:
panic: Solaris(panic): zfs: accessing past end of object 422/10b1c02 (size=2560 access=2560+2560)
cpuid = 15
time = 1694127988
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe02e783b5a0
vpanic() at vpanic+0x132/frame 0xfffffe02e783b6d0
panic() at panic+0x43/frame 0xfffffe02e783b730
vcmn_err() at vcmn_err+0xeb/frame 0xfffffe02e783b860
zfs_panic_recover() at zfs_panic_recover+0x59/frame 0xfffffe02e783b8c0
dmu_buf_hold_array_by_dnode() at dmu_buf_hold_array_by_dnode+0xb8/frame 0xfffffe02e783b970
dmu_brt_clone() at dmu_brt_clone+0x61/frame 0xfffffe02e783b9f0
zfs_clone_range() at zfs_clone_range+0xaa3/frame 0xfffffe02e783bbc0
zfs_freebsd_copy_file_range() at zfs_freebsd_copy_file_range+0x18a/frame 0xfffffe02e783bc40
vn_copy_file_range() at vn_copy_file_range+0x114/frame 0xfffffe02e783bce0
kern_copy_file_range() at kern_copy_file_range+0x36c/frame 0xfffffe02e783bdb0
sys_copy_file_range() at sys_copy_file_range+0x78/frame 0xfffffe02e783be00
amd64_syscall() at amd64_syscall+0x14f/frame 0xfffffe02e783bf30
fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe02e783bf30
--- syscall (569, FreeBSD ELF64, copy_file_range), rip = 0xa8a8d32b55a, rsp = 0xa8a8c8fa158, rbp = 0xa8a8c8fa5f0 ---
KDB: enter: panic

__curthread () at /usr/main-src/sys/amd64/include/pcpu_aux.h:57
57              __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (offsetof(struct pcpu,
(kgdb) #0  __curthread () at /usr/main-src/sys/amd64/include/pcpu_aux.h:57
#1  doadump (textdump=textdump@entry=0)
    at /usr/main-src/sys/kern/kern_shutdown.c:405
#2  0xffffffff804a505a in db_dump (dummy=<optimized out>, 
    dummy2=<optimized out>, dummy3=<optimized out>, dummy4=<optimized out>)
    at /usr/main-src/sys/ddb/db_command.c:591
#3  0xffffffff804a4e5d in db_command (last_cmdp=<optimized out>, 
    cmd_table=<optimized out>, dopager=true)
    at /usr/main-src/sys/ddb/db_command.c:504
#4  0xffffffff804a4b1d in db_command_loop ()
    at /usr/main-src/sys/ddb/db_command.c:551
#5  0xffffffff804a81f6 in db_trap (type=<optimized out>, code=<optimized out>)
    at /usr/main-src/sys/ddb/db_main.c:268
#6  0xffffffff80bb0793 in kdb_trap (type=type@entry=3, code=code@entry=0, 
    tf=tf@entry=0xfffffe02e783b4e0) at /usr/main-src/sys/kern/subr_kdb.c:790
#7  0xffffffff810623c9 in trap (frame=0xfffffe02e783b4e0)
    at /usr/main-src/sys/amd64/amd64/trap.c:608
#8  <signal handler called>
#9  kdb_enter (why=<optimized out>, msg=<optimized out>)
    at /usr/main-src/sys/kern/subr_kdb.c:556
#10 0xffffffff80b61b33 in vpanic (fmt=0xffffffff82c3914f "%s%s", 
    at /usr/main-src/sys/kern/kern_shutdown.c:958
#11 0xffffffff80b61913 in panic (
    fmt=0xffffffff82369800 <cnputs_mtx> "W\346\025\201\377\377\377\377")
    at /usr/main-src/sys/kern/kern_shutdown.c:894
#12 0xffffffff8299464b in vcmn_err (ce=<optimized out>, 
    fmt=0xffffffff82c6f791 "zfs: accessing past end of object %llx/%llx (size=%u access=%llu+%llu)", adx=0xfffffe02e783b8a0)
    at /usr/main-src/sys/contrib/openzfs/module/os/freebsd/spl/spl_cmn_err.c:60
#13 0xffffffff82ab1ab9 in zfs_panic_recover (
    fmt=0x12 <error: Cannot access memory at address 0x12>)
    at /usr/main-src/sys/contrib/openzfs/module/zfs/spa_misc.c:1594
#14 0xffffffff82a10138 in dmu_buf_hold_array_by_dnode (dn=0xfffff80b9edd67f0, 
    offset=offset@entry=2560, length=length@entry=2560, read=read@entry=0, 
    tag=0xffffffff82c1c507, numbufsp=numbufsp@entry=0xfffffe02e783b9bc, 
    dbpp=0xfffffe02e783b9c0, flags=0)
    at /usr/main-src/sys/contrib/openzfs/module/zfs/dmu.c:543
#15 0xffffffff82a13c91 in dmu_buf_hold_array (os=<optimized out>, 
    object=<optimized out>, read=0, numbufsp=0xfffffe02e783b9bc, 
    dbpp=0xfffffe02e783b9c0, offset=<optimized out>, length=<optimized out>, 
    tag=<optimized out>)
    at /usr/main-src/sys/contrib/openzfs/module/zfs/dmu.c:654
#16 dmu_brt_clone (os=os@entry=0xfffff8011e989800, object=<optimized out>, 
    offset=offset@entry=2560, length=length@entry=2560, 
    tx=tx@entry=0xfffff81b68d0bb00, bps=bps@entry=0xfffffe04bcc60000, nbps=1, 
    replay=0) at /usr/main-src/sys/contrib/openzfs/module/zfs/dmu.c:2301
#17 0xffffffff82b7e393 in zfs_clone_range (inzp=0xfffff805a65f7000, 
    inoffp=0xfffff805c5e13548, outzp=0xfffff809d42c2cb0, 
    outoffp=0xfffff80134c184f8, lenp=lenp@entry=0xfffffe02e783bc00, 
    at /usr/main-src/sys/contrib/openzfs/module/zfs/zfs_vnops.c:1302
#18 0xffffffff829b77ca in zfs_freebsd_copy_file_range (ap=0xfffffe02e783bc58)
    at /usr/main-src/sys/contrib/openzfs/module/os/freebsd/zfs/zfs_vnops_os.c:6294
#19 0xffffffff80c74694 in VOP_COPY_FILE_RANGE (invp=<optimized out>, 
    inoffp=<optimized out>, outvp=0xffffffff81183b4f, 
    outvp@entry=0xfffffe02e783bce0, outoffp=0xffffffff812265a2, lenp=0x0, 
    lenp@entry=0xfffffe02e783bc70, flags=0, incred=0xfffff8041841f700, 
    outcred=0x0, fsizetd=0xfffffe021b5f4740) at ./vnode_if.h:2385
#20 vn_copy_file_range (invp=invp@entry=0xfffff80435eef8c0, 
    inoffp=inoffp@entry=0xfffff805c5e13548, outvp=0xffffffff81183b4f, 
    outvp@entry=0xfffff80ce8c8ee00, outoffp=0xffffffff812265a2, lenp=0x0, 
    lenp@entry=0xfffffe02e783bd40, flags=flags@entry=0, 
    incred=0xfffff8041841f700, outcred=0xfffff8041841f700, 
    fsize_td=0xfffffe021b5f4740) at /usr/main-src/sys/kern/vfs_vnops.c:3085
#21 0xffffffff80c6f22c in kern_copy_file_range (
    td=td@entry=0xfffffe021b5f4740, infd=<optimized out>, 
    inoffp=0xfffff805c5e13548, inoffp@entry=0x0, outfd=<optimized out>, 
    outoffp=0xffffffff812265a2, outoffp@entry=0x0, len=9223372036854775807, 
    flags=0) at /usr/main-src/sys/kern/vfs_syscalls.c:4971
#22 0xffffffff80c6f338 in sys_copy_file_range (td=0xfffffe021b5f4740, 
    uap=0xfffffe021b5f4b40) at /usr/main-src/sys/kern/vfs_syscalls.c:5009
#23 0xffffffff8106323f in syscallenter (td=0xfffffe021b5f4740)
    at /usr/main-src/sys/amd64/amd64/../../kern/subr_syscall.c:187
#24 amd64_syscall (td=0xfffffe021b5f4740, traced=0)
    at /usr/main-src/sys/amd64/amd64/trap.c:1197
#25 <signal handler called>
#26 0x00000a8a8d32b55a in ?? ()
Backtrace stopped: Cannot access memory at address 0xa8a8c8fa158

>> Looking at "git: 969071be938c - main", the relevant
>> part seems to be just (white space possibly not
>> preserved accurately):
>> diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
>> index 9fb5aee6a023..4e4161ef1a7f 100644
>> --- a/sys/kern/vfs_vnops.c
>> +++ b/sys/kern/vfs_vnops.c
>> @@ -3076,12 +3076,14 @@ vn_copy_file_range(struct vnode *invp, off_t *inoffp, struct vnode *outvp,
>>   goto out;
>>     /*
>> - * If the two vnode are for the same file system, call
>> + * If the two vnodes are for the same file system type, call
>>   * VOP_COPY_FILE_RANGE(), otherwise call vn_generic_copy_file_range()
>> - * which can handle copies across multiple file systems.
>> + * which can handle copies across multiple file system types.
>>   */
>>   *lenp = len;
>> - if (invp->v_mount == outvp->v_mount)
>> + if (invp->v_mount == outvp->v_mount ||
>> +    strcmp(invp->v_mount->mnt_vfc->vfc_name,
>> +    outvp->v_mount->mnt_vfc->vfc_name) == 0)
>>   error = VOP_COPY_FILE_RANGE(invp, inoffp, outvp, outoffp,
>>      lenp, flags, incred, outcred, fsize_td);
>>   else
>> That looks to call VOP_COPY_FILE_RANGE in more contexts and
>> vn_generic_copy_file_range in fewer.
>> The backtrace I reported involves: VOP_COPY_FILE_RANGE
>> So it appears this change is unlikely to invalidate my
>> test result,  although failure might happen sooner if
>> more VOP_COPY_FILE_RANGE calls happen with the newer code.
> Your logic is likely right, but if you have block cloning requests both within and between datasets, this patch may change the pattern.  Though it is obviously not a fix for the issue.  I responded to the commit email only because it makes no difference while vfs.zfs.bclone_enabled is 0.
>> That in turns means that someone may come up with some
>> other change for me to test by the time I get around to
>> setting up another test. Let me know if so.
> -- 
> Alexander Motin

Mark Millard
marklmi at