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Re: [Qemu-devel] [PATCH] qemu-ga: execute fsfreeze-freeze in reverse ord
From: |
Michael Roth |
Subject: |
Re: [Qemu-devel] [PATCH] qemu-ga: execute fsfreeze-freeze in reverse order of mounts |
Date: |
Tue, 08 Oct 2013 15:49:07 -0500 |
User-agent: |
alot/0.3.4 |
Quoting Tomoki Sekiyama (2013-10-01 16:09:53)
> 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 <address@hidden>
Thanks, applied to qga tree:
https://github.com/mdroth/qemu/commits/qga
> ---
> 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);