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qemu-kvm/SOURCES/kvm-block-blkio-do-not-use-...

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From b1f0546548e561856252c2bc610a8f4f8fcdf007 Mon Sep 17 00:00:00 2001
From: Stefano Garzarella <sgarzare@redhat.com>
Date: Wed, 26 Jul 2023 09:48:07 +0200
Subject: [PATCH 02/14] block/blkio: do not use open flags in qemu_open()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 194: block/blkio: backport latest fixes for virtio-blk-* drivers
RH-Bugzilla: 2225354 2225439
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Alberto Faria <None>
RH-Commit: [2/6] 1ccd0ef56182bb5e2374c3b5be98ee1ec05066d6 (sgarzarella/qemu-kvm-c-9-s)
qemu_open() in blkio_virtio_blk_common_open() is used to open the
character device (e.g. /dev/vhost-vdpa-0 or /dev/vfio/vfio) or in
the future eventually the unix socket.
In all these cases we cannot open the path in read-only mode,
when the `read-only` option of blockdev is on, because the exchange
of IOCTL commands for example will fail.
In order to open the device read-only, we have to use the `read-only`
property of the libblkio driver as we already do in blkio_file_open().
Fixes: cad2ccc395 ("block/blkio: use qemu_open() to support fd passing for virtio-blk")
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2225439
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20230726074807.14041-1-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit a5942c177b7bcc1357e496b7d68668befcfc2bb9)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
block/blkio.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/block/blkio.c b/block/blkio.c
index 3ea9841bd8..5a82c6cb1a 100644
--- a/block/blkio.c
+++ b/block/blkio.c
@@ -685,15 +685,18 @@ static int blkio_virtio_blk_common_open(BlockDriverState *bs,
* layer through the "/dev/fdset/N" special path.
*/
if (fd_supported) {
- int open_flags;
-
- if (flags & BDRV_O_RDWR) {
- open_flags = O_RDWR;
- } else {
- open_flags = O_RDONLY;
- }
-
- fd = qemu_open(path, open_flags, errp);
+ /*
+ * `path` can contain the path of a character device
+ * (e.g. /dev/vhost-vdpa-0 or /dev/vfio/vfio) or a unix socket.
+ *
+ * So, we should always open it with O_RDWR flag, also if BDRV_O_RDWR
+ * is not set in the open flags, because the exchange of IOCTL commands
+ * for example will fail.
+ *
+ * In order to open the device read-only, we are using the `read-only`
+ * property of the libblkio driver in blkio_file_open().
+ */
+ fd = qemu_open(path, O_RDWR, errp);
if (fd < 0) {
return -EINVAL;
}
--
2.39.3