From: John Snow <jsnow@redhat.com>
To: qemu-block@nongnu.org
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, dgilbert@redhat.com,
stefanha@redhat.com, pbonzini@redhat.com, pjp@redhat.com,
John Snow <jsnow@redhat.com>
Subject: [Qemu-devel] [PATCH 0/4] IDE: Do not flush empty drives
Date: Tue, 8 Aug 2017 13:57:07 -0400 [thread overview]
Message-ID: <20170808175711.12203-1-jsnow@redhat.com> (raw)
Patches one and two here are a 2.10 bandaid that avoids a crash.
Patches three and four are a more comprehensive fix as written by
Kevin in another discussion and are being posted here for the sake
of a discussion.
Patch three as written causes hangs in iotests 20, 39, 97, 98, 129,
153, 176, and 185. 124 actually segfaults.
For the purposes of 2.10, we'll likely just want patches 1 and 2
for now.
The problem in a nutshell: incrementing the in-flight counter of the
BDS from the BB layer assumes that every BB always has a BDS. That's
not true; and some devices like IDE have not in the past checked to
see if a given blk_ operation WOULD fail.
This culminates in a new regression where issuing a cache flush to a
CDROM (which is, for some reason, specification valid) will crash QEMU
due to a null dereference when attempting to atomically increment that
backend's in-flight counter.
John Snow (1):
IDE: Do not flush empty CDROM drives
Kevin Wolf (3):
IDE: test flush on empty CDROM
block-backend: shift in-flight counter to BB from BDS
block-backend: test flush op on empty backend
block.c | 2 +-
block/block-backend.c | 40 +++++++++++++++++++++++++-----
hw/ide/core.c | 11 +++++---
tests/Makefile.include | 2 ++
tests/ide-test.c | 19 ++++++++++++++
tests/test-block-backend.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 125 insertions(+), 11 deletions(-)
create mode 100644 tests/test-block-backend.c
--
2.9.4
next reply other threads:[~2017-08-08 17:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-08 17:57 John Snow [this message]
2017-08-08 17:57 ` [Qemu-devel] [PATCH 1/4] IDE: Do not flush empty CDROM drives John Snow
2017-08-08 19:19 ` Eric Blake
2017-08-09 9:34 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-08-08 17:57 ` [Qemu-devel] [PATCH 2/4] IDE: test flush on empty CDROM John Snow
2017-08-08 19:20 ` Eric Blake
2017-08-08 19:32 ` John Snow
2017-08-09 9:35 ` [Qemu-devel] [Qemu-block] " Stefan Hajnoczi
2017-08-08 17:57 ` [Qemu-devel] [PATCH 3/4] block-backend: shift in-flight counter to BB from BDS John Snow
2017-08-08 18:34 ` Paolo Bonzini
2017-08-08 18:48 ` John Snow
2017-08-09 16:01 ` Kevin Wolf
2017-08-08 17:57 ` [Qemu-devel] [PATCH 4/4] block-backend: test flush op on empty backend John Snow
2017-08-09 16:02 ` Kevin Wolf
2017-08-09 15:53 ` [Qemu-devel] [Qemu-block] [PATCH 0/4] IDE: Do not flush empty drives Stefan Hajnoczi
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