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Date:      Tue, 22 Mar 2016 12:59:35 -0400
From:      Nick Evans <nevans@talkpoint.com>
To:        freebsd-questions@freebsd.org
Subject:   Intel 750 Panic Unmounting During TRIM
Message-ID:  <20160322125935.6be25e20@pleiades.nextvenue.com>

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I've got a test system with a 400GB Intel 750 NVME SSD formatted UFS
1mb/4k aligned

http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-750-series.html

I moved a 50 gigabyte directory off the drive so I could try another
drive configuration and while the drive was trimming, I ran umount on
the mounted device. umount sat there without returning to the prompt. On
another terminal, mount showed the drive unmounted, but after a minute
or so in this state with gstat running to show io, the system panicked.

I tried to reproduce this a second time by generating a 100gb file from
/dev/zero. Deleted the file ran umount which hung again. This time
after a while it returned to the prompt stating the device was
busy so I tried to umount again while the drive was still trimming.
After a short while the system panicked. It seems the panic happens
when the TRIM finishes while umount is trying to do its thing. The
system is 10.2-RELEASE-p13, GENERIC kernel, Intel 4790K on a Asus Z97-A
motherboard, 32GB ram. I have a second Intel 750 drive in another PCI
Express slot but it's unused at the moment. 

Below are the dumps recorded after the system booted back up. This is a
test system so I can bring it up and down as needed to test fixes. The
second dump is from my reproduced test:


panic: losing buffer 1
cpuid = 2
KDB: stack backtrace:
#0 0xffffffff80984ef0 at kdb_backtrace+0x60
#1 0xffffffff80948aa6 at vpanic+0x126
#2 0xffffffff80948973 at panic+0x43
#3 0xffffffff809d241b at brelse+0x70b
#4 0xffffffff809e9fa7 at flushbuflist+0x137
#5 0xffffffff809e9c1b at bufobj_invalbuf+0x1cb
#6 0xffffffff808acf29 at g_vfs_close+0x29
#7 0xffffffff80ba3487 at ffs_unmount+0x2a7
#8 0xffffffff809e4dbf at dounmount+0x4ef
#9 0xffffffff809e48c6 at sys_unmount+0x456
#10 0xffffffff80d4b3e7 at amd64_syscall+0x357
#11 0xffffffff80d30acb at Xfast_syscall+0xfb
Uptime: 21m6s
Dumping 1426 out of 32426
MB:..2%..11%..21%..31%..41%..51%..61%..71%..81%..91%

#0  doadump (textdump=<value optimized out>) at pcpu.h:219
219     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) #0  doadump (textdump=<value optimized out>) at pcpu.h:219
#1  0xffffffff80948702 in kern_reboot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:451
#2  0xffffffff80948ae5 in vpanic (fmt=<value optimized out>,
    ap=<value optimized out>) at /usr/src/sys/kern/kern_shutdown.c:758
#3  0xffffffff80948973 in panic (fmt=0x0)
    at /usr/src/sys/kern/kern_shutdown.c:687
#4  0xffffffff809d241b in brelse (bp=<value optimized out>)
    at /usr/src/sys/kern/vfs_bio.c:1768
#5  0xffffffff809e9fa7 in flushbuflist (bufv=<value optimized out>,
    flags=<value optimized out>, bo=0xfffff80014236db8,
    slpflag=<value optimized out>, slptimeo=0)
    at /usr/src/sys/kern/vfs_subr.c:1436
#6  0xffffffff809e9c1b in bufobj_invalbuf (bo=0xfffff80014236db8,
flags=1, slpflag=0, slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1312
#7  0xffffffff808acf29 in g_vfs_close (cp=0xfffff80014126e80)
    at /usr/src/sys/geom/geom_vfs.c:277
#8  0xffffffff80ba3487 in ffs_unmount (mp=0xfffff80014317000,
    mntflags=<value optimized out>)
at /usr/src/sys/ufs/ffs/ffs_vfsops.c:1272 #9  0xffffffff809e4dbf in
dounmount (mp=0xfffff80014317000, flags=134217728,
td=0xfffff800141a4000) at /usr/src/sys/kern/vfs_mount.c:1316 #10
0xffffffff809e48c6 in sys_unmount (td=0xfffff800141a4000,
uap=0xfffffe084caffa40) at /usr/src/sys/kern/vfs_mount.c:1208 #11
0xffffffff80d4b3e7 in amd64_syscall (td=0xfffff800141a4000, traced=0)
at subr_syscall.c:134 #12 0xffffffff80d30acb in Xfast_syscall ()
    at /usr/src/sys/amd64/amd64/exception.S:396
#13 0x000000080089190a in ?? ()
Previous frame inner to this frame (corrupt stack?)
Current language:  auto; currently minimal
(kgdb)



panic: losing buffer 1
cpuid = 3
KDB: stack backtrace:
#0 0xffffffff80984ef0 at kdb_backtrace+0x60
#1 0xffffffff80948aa6 at vpanic+0x126
#2 0xffffffff80948973 at panic+0x43
#3 0xffffffff809d241b at brelse+0x70b
#4 0xffffffff809e9fa7 at flushbuflist+0x137
#5 0xffffffff809e9c1b at bufobj_invalbuf+0x1cb
#6 0xffffffff808acf29 at g_vfs_close+0x29
#7 0xffffffff80ba3487 at ffs_unmount+0x2a7
#8 0xffffffff809e4dbf at dounmount+0x4ef
#9 0xffffffff809e48c6 at sys_unmount+0x456
#10 0xffffffff80d4b3e7 at amd64_syscall+0x357
#11 0xffffffff80d30acb at Xfast_syscall+0xfb
Uptime: 1h29m40s
Dumping 2342 out of 32426 MB:..1%..11%..21%..31%..41%..51%..61%..71%..81%..91%

#0  doadump (textdump=<value optimized out>) at pcpu.h:219
219     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) #0  doadump (textdump=<value optimized out>) at pcpu.h:219
#1  0xffffffff80948702 in kern_reboot (howto=260)
    at /usr/src/sys/kern/kern_shutdown.c:451
#2  0xffffffff80948ae5 in vpanic (fmt=<value optimized out>,
    ap=<value optimized out>) at /usr/src/sys/kern/kern_shutdown.c:758
#3  0xffffffff80948973 in panic (fmt=0x0)
    at /usr/src/sys/kern/kern_shutdown.c:687
#4  0xffffffff809d241b in brelse (bp=<value optimized out>)
    at /usr/src/sys/kern/vfs_bio.c:1768
#5  0xffffffff809e9fa7 in flushbuflist (bufv=<value optimized out>,
    flags=<value optimized out>, bo=0xfffff8001428fa08,
    slpflag=<value optimized out>, slptimeo=0)
    at /usr/src/sys/kern/vfs_subr.c:1436
#6  0xffffffff809e9c1b in bufobj_invalbuf (bo=0xfffff8001428fa08, flags=1,
    slpflag=0, slptimeo=0) at /usr/src/sys/kern/vfs_subr.c:1312
#7  0xffffffff808acf29 in g_vfs_close (cp=0xfffff80014033700)
    at /usr/src/sys/geom/geom_vfs.c:277
#8  0xffffffff80ba3487 in ffs_unmount (mp=0xfffff800142b0000,
    mntflags=<value optimized out>) at /usr/src/sys/ufs/ffs/ffs_vfsops.c:1272
#9  0xffffffff809e4dbf in dounmount (mp=0xfffff800142b0000, flags=134217728,
    td=0xfffff8001434c000) at /usr/src/sys/kern/vfs_mount.c:1316
#10 0xffffffff809e48c6 in sys_unmount (td=0xfffff8001434c000,
    uap=0xfffffe084cb0aa40) at /usr/src/sys/kern/vfs_mount.c:1208
#11 0xffffffff80d4b3e7 in amd64_syscall (td=0xfffff8001434c000, traced=0)
    at subr_syscall.c:134
#12 0xffffffff80d30acb in Xfast_syscall ()
    at /usr/src/sys/amd64/amd64/exception.S:396
#13 0x000000080089190a in ?? ()
Previous frame inner to this frame (corrupt stack?)
Current language:  auto; currently minimal
(kgdb)



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