Re: panic: vm_object_madvise: page 0xfffffe0413c58630 is fictitious

On Tue, Nov 27, 2012 at 12:26:44PM +0100, Andre Oppermann wrote:
> FreeBSD bbb.ccc 10.0-CURRENT FreeBSD 10.0-CURRENT #0:
> Fri Nov 23 17:00:40 CET 2012
> aaa_at_bbb.ccc:/usr/obj/usr/src/head/sys/GENERIC  amd64
> 
> #0  doadump (textdump=-2014022336) at pcpu.h:229
> #1  0xffffffff8033e2d2 in db_fncall (dummy1=<value optimized out>, 
> dummy2=<value optimized out>,
>      dummy3=<value optimized out>, dummy4=<value optimized out>)
>      at /usr/src/head/sys/ddb/db_command.c:578
> #2  0xffffffff8033e074 in db_command (last_cmdp=<value optimized out>,
>      cmd_table=<value optimized out>, dopager=1) at 
> /usr/src/head/sys/ddb/db_command.c:449
> #3  0xffffffff8033dd62 in db_command_loop () at 
> /usr/src/head/sys/ddb/db_command.c:502
> #4  0xffffffff80340690 in db_trap (type=<value optimized out>, code=0)
>      at /usr/src/head/sys/ddb/db_main.c:231
> #5  0xffffffff808b375e in kdb_trap (type=3, code=0, tf=<value optimized 
> out>)
>      at /usr/src/head/sys/kern/subr_kdb.c:654
> #6  0xffffffff80bfc71a in trap (frame=0xffffff8487f478a0)
>      at /usr/src/head/sys/amd64/amd64/trap.c:579
> #7  0xffffffff80be65b2 in calltrap () at /tmp/exception-3nQ6Cf.s:179
> #8  0xffffffff808b2f5e in kdb_enter (why=0xffffffff80e5e23b "panic", 
> msg=<value optimized out>)
>      at cpufunc.h:63
> #9  0xffffffff8088086f in panic (fmt=<value optimized out>)
>      at /usr/src/head/sys/kern/kern_shutdown.c:628
> #10 0xffffffff80adea4a in vm_object_madvise (object=<value optimized out>,
>      pindex=<value optimized out>, end=8952, advise=<value optimized out>)
>      at /usr/src/head/sys/vm/vm_object.c:1101
> #11 0xffffffff80ad759a in vm_map_madvise (map=0xfffffe0018260188, 
> start=<value optimized out>,
>      end=<value optimized out>, behav=5) at 
> /usr/src/head/sys/vm/vm_map.c:2140
> #12 0xffffffff80adbd8d in sys_madvise (td=<value optimized out>, 
> uap=<value optimized out>)
>      at /usr/src/head/sys/vm/vm_mmap.c:752
> #13 0xffffffff80bfd3a5 in amd64_syscall (td=0xfffffe0018230000, 
> traced=0) at subr_syscall.c:135
> #14 0xffffffff80be689b in Xfast_syscall () at /tmp/exception-3nQ6Cf.s:329
> #15 0x00000000016f3bfa in ?? ()

I think this is an omission in the check for the object types. BTW, this
pattern already repeats in several places, I thought about adding either
new pager method, like boolean_t vm_pager_is_pageable(), or just a flag
fields to the struct vm_pager to classify the vm objects.

I am curious, what was the process which caused the panic ?

diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index e19750c..5b8ed23 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
_at__at_ -1060,7 +1060,10 _at__at_ shadowlookup:
 			    (tobject->flags & OBJ_ONEMAPPING) == 0) {
 				goto unlock_tobject;
 			}
-		} else if (tobject->type == OBJT_PHYS)
+		} else if (tobject->type == OBJT_PHYS ||
+		    tobject->type == OBJT_SG ||
+		    tobject->type == OBJT_MGTDEVICE ||
+		    tobject->type == OBJT_DEVICE)
 			goto unlock_tobject;
 		m = vm_page_lookup(tobject, tpindex);
 		if (m == NULL && advise == MADV_WILLNEED) {