From 82d4a912b8b197d9d2f56ffc54ca89c535a0f47c Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Wed, 3 Apr 2019 18:43:30 +0200
Subject: [PATCH 153/163] block/file-posix: do not fail on unlock bytes

RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <20190403184330.1210-2-mreitz@redhat.com>
Patchwork-id: 85432
O-Subject: [RHV-7.7 qemu-kvm-rhev PATCH 1/1] block/file-posix: do not fail on unlock bytes
Bugzilla: 1603104
RH-Acked-by: John Snow <jsnow@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@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: Miroslav Rezanina <mrezanin@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 0cf7261..518f16b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -795,6 +795,18 @@ 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