Re: [Qemu-devel] [BUG] qemu-ga: failed to fsfreeze-thaw on RHEL 5.8 Guest

["MATSUDA, Daiki" <matsudadik@intellilink.co.jp>]

I researched the source of the bug.

qemu-ga calls guest_fsfreeze_build_mount_list from
qemp_guest_fsreeze_thaw in qga/commands-posix.c. And it tries to read
/etc/mtab (= MOUNTED) to get mounted filesystems. But when they are
frozen, getmntent(fp) is not finished in the situation /etc/mtab in
frozen filesystem.

I suggest to read the list from not frozen filesystem file or on-memory
data, e.g. /proc/mounts.

Regards
MATSUDA Daiki

--- qga/commands-posix.c.orig   2012-05-28 08:10:47.842332018 +0900
+++ qga/commands-posix.c        2012-05-28 08:11:01.598340937 +0900
@@ -347,7 +347,7 @@ static int guest_fsfreeze_build_mount_li
 {
     struct mntent *ment;
     GuestFsfreezeMount *mount;
-    char const *mtab = MOUNTED;
+    char const *mtab = "/proc/mounts";
     FILE *fp;

     fp = setmntent(mtab, "r");

> I encountered the serious bug on QEMU Guest Agent.
> 
> environment
> Guest OS : RHEL 5.8 / 5.7 (i686)
> Guest Agent Version : qemu-1.1.0rc2 and rc3
> 
> I am trying to take snapshot via virsh snapshot-create-as command. And
> to freeze guest's filesystem and take snapshot is succeed. But after
> sending the thaw command to Guest, time error occurs on libvirt qemu
> agent because of not catch Guest's answer.
> In addition, its situation is worst because the Guest Filesystem is kept
> as frozen.
> 
> The problem does not occur on RHEL 6.2 Guest OS and in about qemu-1.0 it
> does not occur.
> 
> Regards
> MATSUDA Daiki
> 
> 
> 
>