From 598c0b45b72d7ff313249ea3f9b2713edf6fa818 Mon Sep 17 00:00:00 2001
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Thu, 6 Aug 2015 13:18:17 +0200
Subject: [PATCH 27/28] block/mirror: limit qiov to IOV_MAX elements
Message-id: <1438867097-4840-2-git-send-email-stefanha@redhat.com>
Patchwork-id: 67380
O-Subject: [RHEV-7.2 qemu-kvm-rhev PATCH 1/1] block/mirror: limit qiov to IOV_MAX elements
Bugzilla: 1238585
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
If mirror has more free buffers than IOV_MAX, preadv(2)/pwritev(2)
EINVAL failures may be encountered.
It is possible to trigger this by setting granularity to a low value
like 8192.
This patch stops appending chunks once IOV_MAX is reached.
The spurious EINVAL failure can be reproduced with a qcow2 image file
and the following QMP invocation:
qmp.command('drive-mirror', device='virtio0', target='/tmp/r7.s1',
granularity=8192, sync='full', mode='absolute-paths',
format='raw')
While the guest is running dd if=/dev/zero of=/var/tmp/foo oflag=direct
bs=4k.
Cc: Jeff Cody <jcody@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1435761950-26714-1-git-send-email-stefanha@redhat.com
Signed-off-by: Jeff Cody <jcody@redhat.com>
(cherry picked from commit cae98cb87d269c33d23b2bccd79bb8d99a60d811)
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
block/mirror.c | 4 ++++
trace-events | 1 +
2 files changed, 5 insertions(+)
diff --git a/block/mirror.c b/block/mirror.c
index 775f48e..6f1bc3c 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -248,6 +248,10 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
break;
}
+ if (IOV_MAX < nb_chunks + added_chunks) {
+ trace_mirror_break_iov_max(s, nb_chunks, added_chunks);
+ break;
+ }
/* We have enough free space to copy these sectors. */
bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
diff --git a/trace-events b/trace-events
index 360b0fa..b94bdbf 100644
--- a/trace-events
+++ b/trace-events
@@ -94,6 +94,7 @@ mirror_yield(void *s, int64_t cnt, int buf_free_count, int in_flight) "s %p dirt
mirror_yield_in_flight(void *s, int64_t sector_num, int in_flight) "s %p sector_num %"PRId64" in_flight %d"
mirror_yield_buf_busy(void *s, int nb_chunks, int in_flight) "s %p requested chunks %d in_flight %d"
mirror_break_buf_busy(void *s, int nb_chunks, int in_flight) "s %p requested chunks %d in_flight %d"
+mirror_break_iov_max(void *s, int nb_chunks, int added_chunks) "s %p requested chunks %d added_chunks %d"
# block/backup.c
backup_do_cow_enter(void *job, int64_t start, int64_t sector_num, int nb_sectors) "job %p start %"PRId64" sector_num %"PRId64" nb_sectors %d"
--
1.8.3.1