From 87240c5fcfb3e3ba68c5c87d2175f2dd98921a7e Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Wed, 3 Apr 2019 17:13:15 +0100
Subject: [PATCH 08/11] block/file-posix: do not fail on unlock bytes

RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <20190403171315.20841-9-mreitz@redhat.com>
Patchwork-id: 85406
O-Subject: [RHEL-8.1 qemu-kvm PATCH 8/8] block/file-posix: do not fail on unlock bytes
Bugzilla: 1694148
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

bdrv_replace_child() calls bdrv_check_perm() with error_abort on
loosening permissions. However file-locking operations may fail even
in this case, for example on NFS. And this leads to Qemu crash.

Let's avoid such errors. Note, that we ignore such things anyway on
permission update commit and abort.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 696aaaed579ac5bf5fa336216909b46d3d8f07a8)
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 block/file-posix.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/block/file-posix.c b/block/file-posix.c
index deecf58..5fb5a9a 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -800,6 +800,18 @@ static int raw_handle_perm_lock(BlockDriverState *bs,
 
     switch (op) {
     case RAW_PL_PREPARE:
+        if ((s->perm | new_perm) == s->perm &&
+            (s->shared_perm & new_shared) == s->shared_perm)
+        {
+            /*
+             * We are going to unlock bytes, it should not fail. If it fail due
+             * to some fs-dependent permission-unrelated reasons (which occurs
+             * sometimes on NFS and leads to abort in bdrv_replace_child) we
+             * can't prevent such errors by any check here. And we ignore them
+             * anyway in ABORT and COMMIT.
+             */
+            return 0;
+        }
         ret = raw_apply_lock_bytes(s, s->fd, s->perm | new_perm,
                                    ~s->shared_perm | ~new_shared,
                                    false, errp);
-- 
1.8.3.1