From 8aff951dc5acb2965131e43e10b1cd9fce17992e Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 10 Jan 2019 12:44:36 +0000
Subject: [PATCH 06/14] file-posix: Support auto-read-only option

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <20190110124442.30132-7-kwolf@redhat.com>
Patchwork-id: 83955
O-Subject: [RHEL-8.0 qemu-kvm PATCH 06/12] file-posix: Support auto-read-only option
Bugzilla: 1644996
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Eric Blake <eblake@redhat.com>

If read-only=off, but auto-read-only=on is given, open the file
read-write if we have the permissions, but instead of erroring out for
read-only files, just degrade to read-only.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 64107dc044a54ebe46348ac0fe87584be2eb3e81)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 block/file-posix.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index c12cdb7..7e6869d 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -517,9 +517,22 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
 
     s->fd = -1;
     fd = qemu_open(filename, s->open_flags, 0644);
-    if (fd < 0) {
-        ret = -errno;
-        error_setg_errno(errp, errno, "Could not open '%s'", filename);
+    ret = fd < 0 ? -errno : 0;
+
+    if (ret == -EACCES || ret == -EROFS) {
+        /* Try to degrade to read-only, but if it doesn't work, still use the
+         * normal error message. */
+        if (bdrv_apply_auto_read_only(bs, NULL, NULL) == 0) {
+            bdrv_flags &= ~BDRV_O_RDWR;
+            raw_parse_flags(bdrv_flags, &s->open_flags);
+            assert(!(s->open_flags & O_CREAT));
+            fd = qemu_open(filename, s->open_flags);
+            ret = fd < 0 ? -errno : 0;
+        }
+    }
+
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Could not open '%s'", filename);
         if (ret == -EROFS) {
             ret = -EACCES;
         }
-- 
1.8.3.1