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From: Kevin Wolf <kwolf@redhat.com>
To: qemu-block@nongnu.org
Date: Mon, 5 Nov 2018 17:37:32 +0100
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Subject: [Qemu-devel] [PULL 24/36] file-posix: Support auto-read-only option
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If read-only=3Doff, but auto-read-only=3Don 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>
---
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 2da3a76355..0c1b81ce4b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -527,9 +527,22 @@ static int raw_open_common(BlockDriverState *bs, QDict=
*options,
=20
s->fd =3D -1;
fd =3D qemu_open(filename, s->open_flags, 0644);
- if (fd < 0) {
- ret =3D -errno;
- error_setg_errno(errp, errno, "Could not open '%s'", filename);
+ ret =3D fd < 0 ? -errno : 0;
+
+ if (ret =3D=3D -EACCES || ret =3D=3D -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) =3D=3D 0) {
+ bdrv_flags &=3D ~BDRV_O_RDWR;
+ raw_parse_flags(bdrv_flags, &s->open_flags);
+ assert(!(s->open_flags & O_CREAT));
+ fd =3D qemu_open(filename, s->open_flags);
+ ret =3D fd < 0 ? -errno : 0;
+ }
+ }
+
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Could not open '%s'", filename);
if (ret =3D=3D -EROFS) {
ret =3D -EACCES;
}
--=20
2.19.1