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qemu-ga: execute fsfreeze-freeze in reverse order of mounts

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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>
This commit is contained in:
Tomoki Sekiyama 2013-10-01 17:09:53 -04:00 committed by Michael Roth
parent f2c6bcfc2e
commit e5d9adbdab
1 changed files with 2 additions and 2 deletions
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4
qga/commands-posix.c
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@ -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);