From e5d9adbdab972a2172815c1174aed3fabcc448f1 Mon Sep 17 00:00:00 2001
From: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Date: Tue, 1 Oct 2013 17:09:53 -0400
Subject: [PATCH] qemu-ga: execute fsfreeze-freeze in reverse order of mounts
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 freezes filesystems in reverse order of mounts.
Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
*fix up commit msg
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
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 e199738c71..f453132b92 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);