From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34313) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e1unn-0002Fv-V7 for qemu-devel@nongnu.org; Tue, 10 Oct 2017 09:42:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e1unk-0006Xu-0i for qemu-devel@nongnu.org; Tue, 10 Oct 2017 09:42:32 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:37197 helo=relay.sw.ru) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e1unj-0006XH-LY for qemu-devel@nongnu.org; Tue, 10 Oct 2017 09:42:27 -0400 From: Vladimir Sementsov-Ogievskiy Date: Tue, 10 Oct 2017 16:42:05 +0300 Message-Id: <20171010134205.6120-1-vsementsov@virtuozzo.com> Subject: [Qemu-devel] [PATCH RFC] file-posix: make lock_fd read-only List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: mreitz@redhat.com, kwolf@redhat.com, den@openvz.org, vsementsov@virtuozzo.com, berrange@redhat.com, eblake@redhat.com We do not reopen lock_fd on bdrv_reopen which leads to problems on reopen image RO. So, lets make lock_fd be always RO. This is correct, because qemu_lock_fd always called with exclusive=false on lock_fd. Signed-off-by: Vladimir Sementsov-Ogievskiy --- Hi all! We've faced the following problem with our shared-storage migration scheme. We make an external snapshot and need base image to be reopened RO. However, bdrv_reopen reopens only .fd of BDRVRawState but not .lock_fd. So, .lock_fd is left opened RW and this breaks the whole thing. The simple fix is here: let's just open lock_fd as RO always. This looks fine for current code, as we never try to set write locks (qemu_lock_fd always called with exclusive=false). However it will not work if we are going to use write locks. block/file-posix.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index 36ee89e940..5c52df9174 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -514,7 +514,8 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, s->lock_fd = -1; if (s->use_lock) { - fd = qemu_open(filename, s->open_flags); + /* open it read-only, as we do not reopen it on bdrv_reopen */ + fd = qemu_open(filename, (s->open_flags & ~BDRV_O_RDWR)); if (fd < 0) { ret = -errno; error_setg_errno(errp, errno, "Could not open '%s' for locking", -- 2.11.1