[linux-cifs-client] [PATCH 5/5] cifs: cancel oplock release callbacks during reconnect

[Shirish Pargaonkar]

On Fri, Aug 28, 2009 at 2:26 PM, Jeff Layton<jlayton at redhat.com> wrote:
> On Fri, 28 Aug 2009 14:14:43 -0500
> Shirish Pargaonkar <shirishpargaonkar at gmail.com> wrote:
>
>> On Tue, Aug 18, 2009 at 1:07 PM, Jeff Layton<jlayton at redhat.com> wrote:
>> > cifs_oplock_thread has a check for pTcon->needs_reconnect and will skip
>> > the CIFSSMBLock call if it's set.
>> >
>> > Problem: what if the tcon has this set and then gets reconnected before
>> > the call goes out on the wire? The oplock release isn't needed and could
>> > be a bad thing at that point if the filehandle was reclaimed.
>> >
>> > Cancel oplock release calls during a reconnect event.
>> >
>> > Signed-off-by: Jeff Layton <jlayton at redhat.com>
>> > ---
>> >  fs/cifs/cifsfs.c   |    2 +-
>> >  fs/cifs/cifsglob.h |    1 +
>> >  fs/cifs/connect.c  |    9 +++++++++
>> >  fs/cifs/misc.c     |    1 +
>> >  4 files changed, 12 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
>> > index 647c5bc..92e06c1 100644
>> > --- a/fs/cifs/cifsfs.c
>> > +++ b/fs/cifs/cifsfs.c
>> > @@ -1024,7 +1024,7 @@ static int cifs_oplock_thread(void *dummyarg)
>> >                         * to server still is disconnected since oplock
>> >                         * already released by the server in that case
>> >                         */
>> > -                       if (!tcon->need_reconnect) {
>> > +                       if (!oplock->cancel) {
>> >                                rc = CIFSSMBLock(0, tcon, oplock->netfid,
>> >                                                0 /* len */ , 0 /* offset */, 0,
>> >                                                0, LOCKING_ANDX_OPLOCK_RELEASE,
>> > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
>> > index 363dbcf..676c107 100644
>> > --- a/fs/cifs/cifsglob.h
>> > +++ b/fs/cifs/cifsglob.h
>> > @@ -448,6 +448,7 @@ struct oplock_q_entry {
>> >        struct inode *pinode;
>> >        struct cifsTconInfo *tcon;
>> >        __u16 netfid;
>> > +       bool cancel;
>> >  };
>> >
>> >  /* for pending dnotify requests */
>> > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
>> > index f49304d..b7b67e9 100644
>> > --- a/fs/cifs/connect.c
>> > +++ b/fs/cifs/connect.c
>> > @@ -121,6 +121,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
>> >        struct cifsSesInfo *ses;
>> >        struct cifsTconInfo *tcon;
>> >        struct mid_q_entry *mid_entry;
>> > +       struct oplock_q_entry *oplock;
>> >
>> >        spin_lock(&GlobalMid_Lock);
>> >        if (server->tcpStatus == CifsExiting) {
>> > @@ -137,6 +138,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
>> >
>> >        /* before reconnecting the tcp session, mark the smb session (uid)
>> >                and the tid bad so they are not used until reconnected */
>> > +       spin_lock(&cifs_oplock_lock);
>> >        read_lock(&cifs_tcp_ses_lock);
>> >        list_for_each(tmp, &server->smb_ses_list) {
>> >                ses = list_entry(tmp, struct cifsSesInfo, smb_ses_list);
>> > @@ -145,9 +147,16 @@ cifs_reconnect(struct TCP_Server_Info *server)
>> >                list_for_each(tmp2, &ses->tcon_list) {
>> >                        tcon = list_entry(tmp2, struct cifsTconInfo, tcon_list);
>> >                        tcon->need_reconnect = true;
>> > +                       list_for_each_entry(oplock, &cifs_oplock_list, qhead) {
>> > +                               if (oplock->tcon == tcon)
>> > +                                       oplock->cancel = true;
>> > +                       }
>> >                }
>> > +
>> >        }
>> >        read_unlock(&cifs_tcp_ses_lock);
>> > +       spin_unlock(&cifs_oplock_lock);
>> > +
>> >        /* do not want to be sending data on a socket we are freeing */
>> >        mutex_lock(&server->srv_mutex);
>> >        if (server->ssocket) {
>> > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
>> > index 3bf3a52..4a2d297 100644
>> > --- a/fs/cifs/misc.c
>> > +++ b/fs/cifs/misc.c
>> > @@ -612,6 +612,7 @@ is_valid_oplock_break(struct smb_hdr *buf, struct TCP_Server_Info *srv,
>> >                                oplock->tcon = tcon;
>> >                                oplock->pinode = inode;
>> >                                oplock->netfid = netfile->netfid;
>> > +                               oplock->cancel = false;
>> >                                spin_lock(&cifs_oplock_lock);
>> >                                list_add_tail(&oplock->qhead,
>> >                                              &cifs_oplock_list);
>> > --
>> > 1.6.0.6
>> >
>> > _______________________________________________
>> > linux-cifs-client mailing list
>> > linux-cifs-client at lists.samba.org
>> > https://lists.samba.org/mailman/listinfo/linux-cifs-client
>> >
>>
>>
>> Acked-by: Shirish Pargaonkar <shiishpargaonkar at yahoo.com>
>>
>> with a question, does what you say about pTcon->needs_reconnect  apply
>> to oplock->cancel also?
>
> I don't think so. oplock->cancel doesn't get cleared on a reconnect.
>
> ...or did I misunderstand the question?
>
> Thanks,
> --
> Jeff Layton <jlayton at redhat.com>
>

Jeff, I was thinking, if oplock->cancel is false but before call is
sent out, reconnect happens
and it is not necessary to send the call (oplock->cancel is true) and
yet it could get sent,
similar to what can happen in case of tcon->need_reconnect?