| Message ID | 20131001210953.23207.28945.stgit@localhost.localdomain |
|---|---|
| State | New |
| Headers | show |
On 10/01/2013 03:09 PM, Tomoki Sekiyama wrote: > 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. s/freeze/freezes/ > > Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com> > --- > qga/commands-posix.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) Thaw already worked in the forward direction; with your patch, this means thaw undoes the actions by freeze in the opposite order (last frozen is first thawed), which is also a good thing. Reviewed-by: Eric Blake <eblake@redhat.com>
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 <tomoki.sekiyama@hds.com> 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);
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);
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 <tomoki.sekiyama@hds.com> --- qga/commands-posix.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)