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 <kw...@redhat.com>
---
block/file-posix.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/block/file-posix.c b/block/file-posix.c
index 2da3a76355..eead3f2df3 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -527,6 +527,19 @@ static int raw_open_common(BlockDriverState *bs, QDict
*options,
s->fd = -1;
fd = qemu_open(filename, s->open_flags, 0644);
+
+ if (fd < 0 && (errno == EACCES || errno == EROFS)) {
+ /* Try to degrade to read-only, but if it doesn't work, still use the
+ * normal error message. */
+ ret = bdrv_apply_auto_read_only(bs, NULL, NULL);
+ if (ret == 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);
+ }
+ }
+
if (fd < 0) {
ret = -errno;
error_setg_errno(errp, errno, "Could not open '%s'", filename);
--
2.19.1
