Hello,
2017-03-30 23:46 GMT+08:00 Greg Kurz <gr...@kaod.org>:
> On Thu, 30 Mar 2017 08:25:25 -0500
> Eric Blake <ebl...@redhat.com> wrote:
>
> > On 03/30/2017 07:27 AM, Li Qiang wrote:
> > > The guest can leave the pdu->s->migration_blocker exists by attach
> >
> > s/exists/in place/
> > s/attach/attaching/
> >
>
Eric,
Thanks for pointing my mistakes!
> > > but not remove a fid. Then if we hot unplug the 9pfs device, the
> >
>
> In theory you're right, but the current 9p client in linux won't let you
> hot
> unplug the device unless you unmount the 9p share first, hence freeing the
> blocker.
>
>
I think we should consider every possible situation.
> > s/remove/removing/
> >
> > > v9fs_reset() just free the fids, but not free the migration_blocker.
> > > This will leak a memory leak. This patch avoid this.
>
> I had a similar issue sitting my TODO list for quite a time: the blocker
> survives a system_reset. It doesn't cause a memory leak but it prevents
> migration until the guest mounts/unmounts the 9p share again.
>
> This boils down to virtfs_reset() calling free_fid() instead of put_fid()
> IIRC.
>
> >
> > s/leak a/cause a/
> > s/avoid/avoids/
> >
> > >
> > > Signed-off-by: Li Qiang <liqiang...@360.cn>
> > > ---
> > > hw/9pfs/9p.c | 6 ++++++
> > > 1 file changed, 6 insertions(+)
> >
> > Probably worth including in 2.9 as a bug fix.
> >
> > Reviewed-by: Eric Blake <ebl...@redhat.com>
> >
> > >
> > > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> > > index 48babce..b55c02d 100644
> > > --- a/hw/9pfs/9p.c
> > > +++ b/hw/9pfs/9p.c
> > > @@ -548,6 +548,12 @@ static void coroutine_fn virtfs_reset(V9fsPDU
> *pdu)
> > > free_fid(pdu, fidp);
> > > }
> > > }
> > > +
> > > + if (pdu->s->migration_blocker) {
> > > + migrate_del_blocker(pdu->s->migration_blocker);
> > > + error_free(pdu->s->migration_blocker);
> > > + pdu->s->migration_blocker = NULL;
> > > + }
>
> I'd prefer to drain all PDUs in virtfs_reset() and have the loop above
> to call put_fid() instead of free_fid(). If this isn't doable for 2.9,
> I'll apply this patch with a comment.
>
>
Yes, I have considered to use put_fid() to fix this. But I'm not sure the
'fidp->ref' is at most 1 in virtfs_reset() function(I think it is).
IIUC I think omit the 'else' branch, and call put_fid() directly like this.
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 48babce..ae97e79 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -544,9 +544,8 @@ static void coroutine_fn virtfs_reset(V9fsPDU *pdu)
if (fidp->ref) {
fidp->clunked = 1;
- } else {
- free_fid(pdu, fidp);
}
+ put_fid(pdu, fidp);
}
}
If you agree, I will send a formal patch.
> > > }
> > >
> > > #define P9_QID_TYPE_DIR 0x80
> > >
> >
>
>
