svn commit: r351472 - head/sys/fs/nullfs
Cy Schubert
Cy.Schubert at cschubert.com
Mon Aug 26 14:11:30 UTC 2019
In message <6C6BF3A4-DC07-4D9A-9A5F-FA075BF535A8 at cschubert.com>, Cy Schubert wr
ites:
> On August 24, 2019 10:13:15 PM PDT, Mateusz Guzik <mjg at FreeBSD.org> wrote:
> >Author: mjg
> >Date: Sun Aug 25 05:13:15 2019
> >New Revision: 351472
> >URL: https://svnweb.freebsd.org/changeset/base/351472
> >
> >Log:
> > nullfs: reduce areas protected by vnode interlock
> >
> >Some places only take the interlock to hold the vnode, which was a
> >requiremnt
> >before they started being manipulated with atomics. Use the newly
> >introduced
> > vholdnz to bump the count.
> >
> > Reviewed by: kib
> > Tested by: pho
> > Sponsored by: The FreeBSD Foundation
> > Differential Revision: https://reviews.freebsd.org/D21358
> >
> >Modified:
> > head/sys/fs/nullfs/null_vnops.c
> >
> >Modified: head/sys/fs/nullfs/null_vnops.c
> >============================================================================
> ==
> >--- head/sys/fs/nullfs/null_vnops.c Sun Aug 25 05:11:43 2019 (r35147
> 1)
> >+++ head/sys/fs/nullfs/null_vnops.c Sun Aug 25 05:13:15 2019 (r35147
> 2)
> >@@ -668,7 +668,7 @@ null_lock(struct vop_lock1_args *ap)
> > * We prevent it from being recycled by holding the vnode
> > * here.
> > */
> >- vholdl(lvp);
> >+ vholdnz(lvp);
> > error = VOP_LOCK(lvp, flags);
> >
> > /*
> >@@ -710,31 +710,16 @@ static int
> > null_unlock(struct vop_unlock_args *ap)
> > {
> > struct vnode *vp = ap->a_vp;
> >- int flags = ap->a_flags;
> >- int mtxlkflag = 0;
> > struct null_node *nn;
> > struct vnode *lvp;
> > int error;
> >
> >- if ((flags & LK_INTERLOCK) != 0)
> >- mtxlkflag = 1;
> >- else if (mtx_owned(VI_MTX(vp)) == 0) {
> >- VI_LOCK(vp);
> >- mtxlkflag = 2;
> >- }
> > nn = VTONULL(vp);
> > if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
> >- VI_LOCK_FLAGS(lvp, MTX_DUPOK);
> >- flags |= LK_INTERLOCK;
> >- vholdl(lvp);
> >- VI_UNLOCK(vp);
> >- error = VOP_UNLOCK(lvp, flags);
> >+ vholdnz(lvp);
> >+ error = VOP_UNLOCK(lvp, 0);
> > vdrop(lvp);
> >- if (mtxlkflag == 0)
> >- VI_LOCK(vp);
> > } else {
> >- if (mtxlkflag == 2)
> >- VI_UNLOCK(vp);
> > error = vop_stdunlock(ap);
> > }
> >
> >@@ -845,10 +830,8 @@ null_getwritemount(struct vop_getwritemount_args
> >*ap)
> > VI_LOCK(vp);
> > xp = VTONULL(vp);
> > if (xp && (lowervp = xp->null_lowervp)) {
> >- VI_LOCK_FLAGS(lowervp, MTX_DUPOK);
> >+ vholdnz(lowervp);
> > VI_UNLOCK(vp);
> >- vholdl(lowervp);
> >- VI_UNLOCK(lowervp);
> > VOP_GETWRITEMOUNT(lowervp, ap->a_mpp);
> > vdrop(lowervp);
> > } else {
>
> Hi mjg@,
>
> This causes trap 12 a few seconds after mountlate during boot. Reverting this
> commit allowed it to boot.
>
> Sorry for no backtrace. I managed to
> revert and test just prior to rushing out to catch the bus, with no time to
> craft a proper email. I'll post the backtrace when I arrive at work.
Hi mjg@,
The gory details below. Don't be fooled by the panic when yppasswd is started. I was able to reproduce this panic in single user by simply mounting and using a nullfs.
kernel trap 12 with interrupts disabled
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0xc
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xffffffff806f0633
stack pointer = 0x28:0xfffffe004b3fa7c0
frame pointer = 0x28:0xfffffe004b3fa7e0
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = resume, IOPL = 0
current process = 26 (syncer)
trap number = 12
panic: page fault
cpuid = 0
time = 1566821203
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe004b3fa470
vpanic() at vpanic+0x19d/frame 0xfffffe004b3fa4c0
panic() at panic+0x43/frame 0xfffffe004b3fa520
trap_fatal() at trap_fatal+0x39c/frame 0xfffffe004b3fa580
trap_pfault() at trap_pfault+0x49/frame 0xfffffe004b3fa5e0
trap() at trap+0x29d/frame 0xfffffe004b3fa6f0
calltrap() at calltrap+0x8/frame 0xfffffe004b3fa6f0
--- trap 0xc, rip = 0xffffffff806f0633, rsp = 0xfffffe004b3fa7c0, rbp = 0xfffffe004b3fa7e0 ---
propagate_priority() at propagate_priority+0x153/frame 0xfffffe004b3fa7e0
turnstile_wait() at turnstile_wait+0x32b/frame 0xfffffe004b3fa830
__mtx_lock_sleep() at __mtx_lock_sleep+0x191/frame 0xfffffe004b3fa8c0
mnt_vnode_next_active() at mnt_vnode_next_active+0x2cb/frame 0xfffffe004b3fa920
vfs_msync() at vfs_msync+0x266/frame 0xfffffe004b3fa980
sync_fsync() at sync_fsync+0xe6/frame 0xfffffe004b3fa9c0
VOP_FSYNC_APV() at VOP_FSYNC_APV+0x56/frame 0xfffffe004b3fa9e0
sched_sync() at sched_sync+0x379/frame 0xfffffe004b3faa70
fork_exit() at fork_exit+0x83/frame 0xfffffe004b3faab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe004b3faab0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
Uptime: 3m25s
Dumping 921 out of 7974 MB:..2%..11%..21%..32%..42%..51%..61%..72%..82%..91%
__curthread () at /opt/src/svn-current/sys/amd64/include/pcpu.h:246
246 __asm("movq %%gs:%P1,%0" : "=r" (td) : "n" (OFFSETOF_CURTHREAD));
(kgdb) #0 __curthread () at /opt/src/svn-current/sys/amd64/include/pcpu.h:246
#1 doadump (textdump=1) at /opt/src/svn-current/sys/kern/kern_shutdown.c:392
#2 0xffffffff8068aead in kern_reboot (howto=260)
at /opt/src/svn-current/sys/kern/kern_shutdown.c:479
#3 0xffffffff8068b369 in vpanic (fmt=<optimized out>, ap=<optimized out>)
at /opt/src/svn-current/sys/kern/kern_shutdown.c:905
#4 0xffffffff8068b163 in panic (fmt=<unavailable>)
at /opt/src/svn-current/sys/kern/kern_shutdown.c:832
#5 0xffffffff80a11c2c in trap_fatal (frame=0xfffffe004b3fa700, eva=12)
at /opt/src/svn-current/sys/amd64/amd64/trap.c:943
#6 0xffffffff80a11c79 in trap_pfault (frame=0xfffffe004b3fa700, usermode=0)
at /opt/src/svn-current/sys/amd64/amd64/trap.c:767
#7 0xffffffff80a1126d in trap (frame=0xfffffe004b3fa700)
at /opt/src/svn-current/sys/amd64/amd64/trap.c:443
#8 <signal handler called>
#9 propagate_priority (td=0xfffff8003e43b000)
at /opt/src/svn-current/sys/kern/subr_turnstile.c:279
#10 0xffffffff806f13db in turnstile_wait (ts=0xfffff8000258a780,
owner=<optimized out>, queue=-512)
at /opt/src/svn-current/sys/kern/subr_turnstile.c:785
#11 0xffffffff80669271 in __mtx_lock_sleep (c=0xfffff80132e4ebf0,
v=<optimized out>) at /opt/src/svn-current/sys/kern/kern_mutex.c:654
#12 0xffffffff80767b1b in mnt_vnode_next_active_relock (
mvp=0xfffff80002449800, mp=0xfffff80132d1e000, vp=0xfffff80132e4eb40)
at /opt/src/svn-current/sys/kern/vfs_subr.c:5590
#13 mnt_vnode_next_active (mvp=<optimized out>, mp=0xfffff80132d1e000)
at /opt/src/svn-current/sys/kern/vfs_subr.c:5649
#14 0xffffffff80766206 in __mnt_vnode_next_active (mvp=0xfffff80002449800,
mp=<optimized out>) at /opt/src/svn-current/sys/kern/vfs_subr.c:5682
#15 vfs_msync (mp=0xfffff80132d1e000, flags=2)
at /opt/src/svn-current/sys/kern/vfs_subr.c:4238
#16 0xffffffff8076b4a6 in sync_fsync (ap=<optimized out>)
at /opt/src/svn-current/sys/kern/vfs_subr.c:4468
#17 0xffffffff80a7be46 in VOP_FSYNC_APV (
vop=0xffffffff80cb4120 <sync_vnodeops>, a=0xfffffe004b3faa08)
at vnode_if.c:1312
#18 0xffffffff80769319 in VOP_FSYNC (vp=<optimized out>, waitfor=3,
td=0xfffff800061dc5a0) at ./vnode_if.h:549
#19 sync_vnode (bo=<optimized out>, td=0xfffff800061dc5a0,
slp=<optimized out>) at /opt/src/svn-current/sys/kern/vfs_subr.c:2316
#20 sched_sync () at /opt/src/svn-current/sys/kern/vfs_subr.c:2418
#21 0xffffffff80647e33 in fork_exit (callout=0xffffffff80768fa0 <sched_sync>,
arg=0x0, frame=0xfffffe004b3faac0)
at /opt/src/svn-current/sys/kern/kern_fork.c:1045
#22 <signal handler called>
dmesg output:
Updating motd:.
Mounting late filesystems:.
Starting nscd.
Security policy loaded: MAC/ntpd (mac_ntpd)
Starting ntpd.
Starting yppasswdd.
kernel trap 12 with interrupts disabled
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address = 0xc
fault code = supervisor read data, page not present
instruction pointer = 0x20:0xffffffff806f0633
stack pointer = 0x28:0xfffffe004b7fa7c0
frame pointer = 0x28:0xfffffe004b7fa7e0
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = resume, IOPL = 0
current process = 26 (syncer)
trap number = 12
panic: page fault
cpuid = 0
time = 1566820700
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe004b7fa470
vpanic() at vpanic+0x19d/frame 0xfffffe004b7fa4c0
panic() at panic+0x43/frame 0xfffffe004b7fa520
trap_fatal() at trap_fatal+0x39c/frame 0xfffffe004b7fa580
trap_pfault() at trap_pfault+0x49/frame 0xfffffe004b7fa5e0
trap() at trap+0x29d/frame 0xfffffe004b7fa6f0
calltrap() at calltrap+0x8/frame 0xfffffe004b7fa6f0
--- trap 0xc, rip = 0xffffffff806f0633, rsp = 0xfffffe004b7fa7c0, rbp = 0xfffffe004b7fa7e0 ---
propagate_priority() at propagate_priority+0x153/frame 0xfffffe004b7fa7e0
turnstile_wait() at turnstile_wait+0x32b/frame 0xfffffe004b7fa830
__mtx_lock_sleep() at __mtx_lock_sleep+0x191/frame 0xfffffe004b7fa8c0
mnt_vnode_next_active() at mnt_vnode_next_active+0x2cb/frame 0xfffffe004b7fa920
vfs_msync() at vfs_msync+0x266/frame 0xfffffe004b7fa980
sync_fsync() at sync_fsync+0xe6/frame 0xfffffe004b7fa9c0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
Uptime: 1m38s
Dumping 810 out of 7974 MB:..2%..12%..22%..32%..42%..52%..62%..72%..81%..91%---<<BOOT>>---
--
Cheers,
Cy Schubert <Cy.Schubert at cschubert.com>
FreeBSD UNIX: <cy at FreeBSD.org> Web: http://www.FreeBSD.org
The need of the many outweighs the greed of the few.
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