OpenZFS 8373 - TXG_WAIT in ZIL commit path

[dinatale2]

Authored by: Andriy Gapon avg@FreeBSD.org
Reviewed by: Prakash Surya prakash.surya@delphix.com
Reviewed by: Matthew Ahrens mahrens@delphix.com
Approved by: Dan McDonald danmcd@joyent.com
Ported-by: Giuseppe Di Natale dinatale2@llnl.gov

OpenZFS-issue: https://www.illumos.org/issues/8373
OpenZFS-commit: openzfs/openzfs@7f04961

[Nasf-Fan]

Hit some failure in the following test:
http://build.zfsonlinux.org/builders/CentOS%206.7%20x86_64%20%28TEST%29/builds/6535
http://build.zfsonlinux.org/builders/CentOS%206.7%20x86_64%20%28TEST%29/builds/6535/steps/shell_5/logs/stdio

Program terminated with signal 6, Aborted.
#0 0x00007fc7bdd25495 in raise () from /lib64/libc.so.6
*

• Backtrace

#0 0x00007fc7bdd25495 in raise () from /lib64/libc.so.6
#1 0x00007fc7bdd26c75 in abort () from /lib64/libc.so.6
#2 0x00007fc7bf726303 in libspl_assertf (file=0x7fc7bf7a1cd7 "../../module/zfs/zil.c", func=0x7fc7bf7a2cb0 "zil_lwb_write_start", line=1026, format=) at ../../lib/libspl/include/assert.h:55
#3 0x00007fc7bf728e18 in zil_lwb_write_start (zilog=0x1afb250, lwb=0x7fc794030f20) at ../../module/zfs/zil.c:1026
#4 0x00007fc7bf7294f8 in zil_commit_writer (zilog=0x1afb250, foid=) at ../../module/zfs/zil.c:1620
#5 zil_commit (zilog=0x1afb250, foid=) at ../../module/zfs/zil.c:1706
#6 0x0000000000408757 in ztest_zil_commit (zd=0x1267890, id=) at ztest.c:2573
#7 0x0000000000408abd in ztest_execute (arg=0x1) at ztest.c:6131
#8 ztest_thread (arg=0x1) at ztest.c:6178
#9 0x00007fc7bf610400 in zk_thread_helper (arg=0x1a43470) at kernel.c:140
#10 0x00007fc7be08eaa1 in start_thread () from /lib64/libpthread.so.0
#11 0x00007fc7bdddbbcd in clone () from /lib64/libc.so.6