From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49518) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VR7Co-0007Xw-Tl for qemu-devel@nongnu.org; Tue, 01 Oct 2013 17:10:12 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VR7Cj-0007xe-58 for qemu-devel@nongnu.org; Tue, 01 Oct 2013 17:10:06 -0400 Received: from usindpps05.hds.com ([207.126.252.18]:48401) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VR7Ci-0007xP-TP for qemu-devel@nongnu.org; Tue, 01 Oct 2013 17:10:01 -0400 From: Tomoki Sekiyama Date: Tue, 01 Oct 2013 17:09:53 -0400 Message-ID: <20131001210953.23207.28945.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH] qemu-ga: execute fsfreeze-freeze in reverse order of mounts List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: seiji.aguchi@hds.com, mdroth@linux.vnet.ibm.com, lcapitulino@redhat.com Currently, fsfreeze-freeze may cause deadlock if a guest has loopback mounts of image files in its disk; e.g.: # mount | grep ^/ /dev/vda1 / type ext4 (rw,noatime,seclabel,data=ordered) /tmp/disk.img on /mnt type ext4 (rw,relatime,seclabel) To avoid the deadlock, this freeze filesystems in reverse order of mounts. Signed-off-by: Tomoki Sekiyama --- qga/commands-posix.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/qga/commands-posix.c b/qga/commands-posix.c index e199738..f453132 100644 --- a/qga/commands-posix.c +++ b/qga/commands-posix.c @@ -566,7 +566,7 @@ typedef struct FsMount { QTAILQ_ENTRY(FsMount) next; } FsMount; -typedef QTAILQ_HEAD(, FsMount) FsMountList; +typedef QTAILQ_HEAD(FsMountList, FsMount) FsMountList; static void free_fs_mount_list(FsMountList *mounts) { @@ -728,7 +728,7 @@ int64_t qmp_guest_fsfreeze_freeze(Error **err) /* cannot risk guest agent blocking itself on a write in this state */ ga_set_frozen(ga_state); - QTAILQ_FOREACH(mount, &mounts, next) { + QTAILQ_FOREACH_REVERSE(mount, &mounts, FsMountList, next) { fd = qemu_open(mount->dirname, O_RDONLY); if (fd == -1) { error_setg_errno(err, errno, "failed to open %s", mount->dirname);