Re: git: 112c453ba910 - stable/15 - geom(9): struct bio KBI fix

On 22 Dec 2025, at 1:38, Ka Ho Ng wrote:
> The branch stable/15 has been updated by khng:
>
> URL: 
> https://cgit.FreeBSD.org/src/commit/?id=112c453ba91012f19ed140c56a3ac8fc929ddabb
>
> commit 112c453ba91012f19ed140c56a3ac8fc929ddabb
> Author:     Ka Ho Ng <khng@FreeBSD.org>
> AuthorDate: 2025-12-21 22:45:03 +0000
> Commit:     Ka Ho Ng <khng@FreeBSD.org>
> CommitDate: 2025-12-22 00:37:40 +0000
>
>     geom(9): struct bio KBI fix
>
>     The struct bio was changed after cb85c2e2e995 on the branch. To 
> fix
>     this, move BIO_ERROR flag to another value, and now 
> BIO_ERROR_COMPAT
>     occupies 0x1 instead. Also, introduce b_error_compat field at the 
> place
>     where the old bio_error was.
>
>     This allows non-CAM(9) disk drivers and software volume manager 
> modules
>     compiled against 15.0-RELEASE kernel to work on 15-STABLE kernel 
> again.
>
>     Reviewed by:    kib
>     Differential Revision:  https://reviews.freebsd.org/D54327
>
>     Approved by:    re (cperciva)

I’m seeing panics on boot now:

	vtnet0: Ethernet address: 58:9c:fc:0c:60:85
	vtnet0: netmap queues/slots: TX 1/1024, RX 1panic: Memory modified 
after free 0xfffff800038b51a8 (424, g_bio) + 0 = deadc0dedeacc0de

	cpuid = 6
	time = 1
	KDB: stack backtrace:
	db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 
0xfffffe008d5679a0
	vpanic() at vpanic+0x136/frame 0xfffffe008d567ad0
	panic() at panic+0x43/frame 0xfffffe008d567b30
	trash_ctor() at trash_ctor+0x74/frame 0xfffffe008d567b40
	item_ctor() at item_ctor+0x59/frame 0xfffffe008d567b90
	g_clone_bio() at g_clone_bio+0x1d/frame 0xfffffe008d567bb0
	g_part_start() at g_part_start+0x96/frame 0xfffffe008d567c40
	g_io_request() at g_io_request+0x2ca/frame 0xfffffe008d567c70
	g_read_data() at g_read_data+0x95/frame 0xfffffe008d567cb0
	g_raid_md_taste_intel() at g_raid_md_taste_intel+0x1d8/frame 
0xfffffe008d567e50
	g_raid_taste() at g_raid_taste+0x18e/frame 0xfffffe008d567ea0
	g_new_provider_event() at g_new_provider_event+0xaa/frame 
0xfffffe008d567ec0
	g_run_events() at g_run_events+0x104/frame 0xfffffe008d567ef0
	fork_exit() at fork_exit+0x82/frame 0xfffffe008d567f30
	fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe008d567f30
	--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
	KDB: enter: panic
	[ thread pid 13 tid 100069 ]
	Stopped at      kdb_enter+0x33: movq    $0,0x121aa92(%rip)
	db>

With this commit (and the follow-up “geom(9): unset the 
BIO_ERROR_COMPAT flag correctly”) reverted the VM boots again.

Best regards,
Kristof