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qemu-kvm/SOURCES/kvm-block-blkio-use-qemu_op...

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From fd57241cf0f8c2906fa56118f8da1e65a5b1e4d8 Mon Sep 17 00:00:00 2001
From: Stefano Garzarella <sgarzare@redhat.com>
Date: Tue, 30 May 2023 09:19:40 +0200
Subject: [PATCH 3/5] block/blkio: use qemu_open() to support fd passing for
virtio-blk
RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 169: block/blkio: support fd passing for virtio-blk-vhost-vdpa driver
RH-Bugzilla: 2180076
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Commit: [1/2] 9ff1a1510500db101648341207a36318a0c41c5a (sgarzarella/qemu-kvm-c-9-s)
Some virtio-blk drivers (e.g. virtio-blk-vhost-vdpa) supports the fd
passing. Let's expose this to the user, so the management layer
can pass the file descriptor of an already opened path.
If the libblkio virtio-blk driver supports fd passing, let's always
use qemu_open() to open the `path`, so we can handle fd passing
from the management layer through the "/dev/fdset/N" special path.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20230530071941.8954-2-sgarzare@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit cad2ccc395c7113fb30bc9390774b67b34f06c68)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
block/blkio.c | 53 ++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 44 insertions(+), 9 deletions(-)
diff --git a/block/blkio.c b/block/blkio.c
index 0cdc99a729..6a6f20f923 100644
--- a/block/blkio.c
+++ b/block/blkio.c
@@ -672,25 +672,60 @@ static int blkio_virtio_blk_common_open(BlockDriverState *bs,
{
const char *path = qdict_get_try_str(options, "path");
BDRVBlkioState *s = bs->opaque;
- int ret;
+ bool fd_supported = false;
+ int fd, ret;
if (!path) {
error_setg(errp, "missing 'path' option");
return -EINVAL;
}
- ret = blkio_set_str(s->blkio, "path", path);
- qdict_del(options, "path");
- if (ret < 0) {
- error_setg_errno(errp, -ret, "failed to set path: %s",
- blkio_get_error_msg());
- return ret;
- }
-
if (!(flags & BDRV_O_NOCACHE)) {
error_setg(errp, "cache.direct=off is not supported");
return -EINVAL;
}
+
+ if (blkio_get_int(s->blkio, "fd", &fd) == 0) {
+ fd_supported = true;
+ }
+
+ /*
+ * If the libblkio driver supports fd passing, let's always use qemu_open()
+ * to open the `path`, so we can handle fd passing from the management
+ * 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);
+ if (fd < 0) {
+ return -EINVAL;
+ }
+
+ ret = blkio_set_int(s->blkio, "fd", fd);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set fd: %s",
+ blkio_get_error_msg());
+ qemu_close(fd);
+ return ret;
+ }
+ } else {
+ ret = blkio_set_str(s->blkio, "path", path);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set path: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+ }
+
+ qdict_del(options, "path");
+
return 0;
}
--
2.39.3