On Tue, 14 Dec 2010 10:24:28 +0300
Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> 2010/12/10 Jeff Layton <jlayton@xxxxxxxxxx>:
> > Currently, when a request is cancelled via signal, we delete the mid
> > immediately. If the request was already transmitted however, the client
> > is still likely to receive a response. When it does, it won't recognize
> > it however and will pop a printk.
> >
> > It's also a little dangerous to just delete the mid entry like this. We
> > may end up reusing that mid. If we do then we could potentially get the
> > response from the first request confused with the later one.
> >
> > Prevent the reuse of mids by marking them as cancelled and keeping them
> > on the pending_mid_q list. If the reply comes in, we'll delete it from
> > the list then. If it never comes, then we'll delete it at reconnect
> > or when cifsd comes down.
> >
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/cifs/cifsglob.h | 2 +-
> > fs/cifs/cifsproto.h | 1 +
> > fs/cifs/connect.c | 44 +++++++++++++++++++++++++++++++++++++-------
> > fs/cifs/transport.c | 30 ++++++++++++++++++++++--------
> > 4 files changed, 61 insertions(+), 16 deletions(-)
> >
> > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> > index cc43ada..fb75f04 100644
> > --- a/fs/cifs/cifsglob.h
> > +++ b/fs/cifs/cifsglob.h
> > @@ -621,7 +621,7 @@ static inline void free_dfs_info_array(struct dfs_info3_param *param,
> > #define MID_REQUEST_SUBMITTED 2
> > #define MID_RESPONSE_RECEIVED 4
> > #define MID_RETRY_NEEDED 8 /* session closed while this request out */
> > -#define MID_NO_RESP_NEEDED 0x10
> > +#define MID_REQUEST_CANCELLED 0x10 /* discard any reply */
> >
> > /* Types of response buffer returned from SendReceive2 */
> > #define CIFS_NO_BUFFER 0 /* Response buffer not returned */
> > diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> > index fe77e69..a8fc606 100644
> > --- a/fs/cifs/cifsproto.h
> > +++ b/fs/cifs/cifsproto.h
> > @@ -61,6 +61,7 @@ extern char *cifs_compose_mount_options(const char *sb_mountdata,
> > const char *fullpath, const struct dfs_info3_param *ref,
> > char **devname);
> > /* extern void renew_parental_timestamps(struct dentry *direntry);*/
> > +extern void DeleteMidQEntry(struct mid_q_entry *midEntry);
> > extern int SendReceive(const unsigned int /* xid */ , struct cifsSesInfo *,
> > struct smb_hdr * /* input */ ,
> > struct smb_hdr * /* out */ ,
> > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> > index 7e20ece..0feb592 100644
> > --- a/fs/cifs/connect.c
> > +++ b/fs/cifs/connect.c
> > @@ -133,7 +133,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
> > {
> > int rc = 0;
> > struct list_head *tmp, *tmp2;
> > - struct list_head retry;
> > + struct list_head retry, dispose;
> > struct cifsSesInfo *ses;
> > struct cifsTconInfo *tcon;
> > struct mid_q_entry *mid_entry;
> > @@ -192,14 +192,23 @@ cifs_reconnect(struct TCP_Server_Info *server)
> > */
> > cFYI(1, "%s: moving mids to retry list", __func__);
> > INIT_LIST_HEAD(&retry);
> > + INIT_LIST_HEAD(&dispose);
> > spin_lock(&GlobalMid_Lock);
> > list_for_each_safe(tmp, tmp2, &server->pending_mid_q) {
> > mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> > if (mid_entry->midState == MID_REQUEST_SUBMITTED)
> > list_move(tmp, &retry);
> > + else if (mid_entry->midState == MID_REQUEST_CANCELLED)
> > + list_move(tmp, &dispose);
> > }
> > spin_unlock(&GlobalMid_Lock);
> >
> > + /* now walk private dispose list and delete entries */
> > + list_for_each_safe(tmp, tmp2, &dispose) {
> > + mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> > + DeleteMidQEntry(mid_entry);
> > + }
> > +
> > while ((server->tcpStatus != CifsExiting) &&
> > (server->tcpStatus != CifsGood)) {
> > try_to_freeze();
> > @@ -219,7 +228,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
> > }
> > }
> >
> > - /* now, issue callback for all mids in flight */
> > + /* issue callback for all mids in flight */
> > list_for_each_safe(tmp, tmp2, &retry) {
> > list_del_init(tmp);
> > mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> > @@ -575,9 +584,13 @@ incomplete_rcv:
> > list_for_each(tmp, &server->pending_mid_q) {
> > mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> >
> > - if ((mid_entry->mid == smb_buffer->Mid) &&
> > - (mid_entry->midState == MID_REQUEST_SUBMITTED) &&
> > - (mid_entry->command == smb_buffer->Command)) {
> > + if (mid_entry->mid != smb_buffer->Mid)
> > + goto next_mid;
> > + if (mid_entry->command != smb_buffer->Command)
> > + goto next_mid;
> > + if (mid_entry->midState == MID_REQUEST_CANCELLED)
> > + break;
> > + if (mid_entry->midState == MID_REQUEST_SUBMITTED) {
> > if (check2ndT2(smb_buffer,server->maxBuf) > 0) {
> > /* We have a multipart transact2 resp */
> > isMultiRsp = true;
> > @@ -623,11 +636,16 @@ multi_t2_fnd:
> > server->lstrp = jiffies;
> > break;
> > }
> > +next_mid:
> > mid_entry = NULL;
> > }
> > spin_unlock(&GlobalMid_Lock);
> >
> > if (mid_entry != NULL) {
> > + if (mid_entry->midState == MID_REQUEST_CANCELLED) {
> > + DeleteMidQEntry(mid_entry);
> > + continue;
> > + }
> > mid_entry->callback(mid_entry);
> > /* Was previous buf put in mpx struct for multi-rsp? */
> > if (!isMultiRsp) {
> > @@ -704,6 +722,9 @@ multi_t2_fnd:
> > }
> > spin_unlock(&cifs_tcp_ses_lock);
> > } else {
> > + struct mid_q_entry *tmp_mid;
> > + struct list_head dispose;
> > +
> > /* although we can not zero the server struct pointer yet,
> > since there are active requests which may depnd on them,
> > mark the corresponding SMB sessions as exiting too */
> > @@ -713,17 +734,26 @@ multi_t2_fnd:
> > ses->status = CifsExiting;
> > }
> >
> > + INIT_LIST_HEAD(&dispose);
> > spin_lock(&GlobalMid_Lock);
> > - list_for_each(tmp, &server->pending_mid_q) {
> > - mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
> > + list_for_each_entry_safe(mid_entry, tmp_mid,
> > + &server->pending_mid_q, qhead) {
> > if (mid_entry->midState == MID_REQUEST_SUBMITTED) {
> > cFYI(1, "Clearing Mid 0x%x - issuing callback",
> > mid_entry->mid);
> > mid_entry->callback(mid_entry);
> > + } else if (mid_entry->midState == MID_REQUEST_CANCELLED) {
> > + cFYI(1, "Clearing Mid 0x%x - Cancelled",
> > + mid_entry->mid);
> > + list_move(&mid_entry->qhead, &dispose);
>
> Why do we need another list here? It seems to me that we can simply
> delete cancelled mid.
>
Nope, we can't. DeleteMidQEntry will try to take the GlobalMid_Lock on
its own, so you can't call it there without deadlocking. You also can't
drop the spinlock and then call DeleteMidQEntry since that might mean
that the list will change in the middle of walking it. We could add a
"DeleteMidQEntry_locked", but dealing with locked and non-locked
variants gets messy.
Moving it to a private dispose list and then walking that list outside
of the lock takes care of those problems. I added the "retry" list in
this function for similar reasons.
> > }
> > }
> > spin_unlock(&GlobalMid_Lock);
> > spin_unlock(&cifs_tcp_ses_lock);
> > +
> > + /* now delete all of the cancelled mids */
> > + list_for_each_entry_safe(mid_entry, tmp_mid, &dispose, qhead)
> > + DeleteMidQEntry(mid_entry);
> > /* 1/8th of sec is more than enough time for them to exit */
> > msleep(125);
> > }
> > diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> > index 79647db..97a1170 100644
> > --- a/fs/cifs/transport.c
> > +++ b/fs/cifs/transport.c
> > @@ -81,7 +81,7 @@ AllocMidQEntry(const struct smb_hdr *smb_buffer, struct TCP_Server_Info *server)
> > return temp;
> > }
> >
> > -static void
> > +void
> > DeleteMidQEntry(struct mid_q_entry *midEntry)
> > {
> > #ifdef CONFIG_CIFS_STATS2
> > @@ -480,8 +480,13 @@ SendReceive2(const unsigned int xid, struct cifsSesInfo *ses,
> > goto out;
> >
> > rc = wait_for_response(ses->server, midQ);
> > - if (rc != 0)
> > - goto out;
> > + if (rc != 0) {
> > + /* no longer considered to be "in-flight" */
> > + midQ->midState = MID_REQUEST_CANCELLED;
> > + atomic_dec(&ses->server->inFlight);
> > + wake_up(&ses->server->request_q);
> > + return rc;
> > + }
> >
> > rc = handle_mid_result(midQ, ses->server);
> > if (rc != 0)
> > @@ -623,8 +628,13 @@ SendReceive(const unsigned int xid, struct cifsSesInfo *ses,
> > goto out;
> >
> > rc = wait_for_response(ses->server, midQ);
> > - if (rc != 0)
> > - goto out;
> > + if (rc != 0) {
> > + /* no longer considered to be "in-flight" */
> > + midQ->midState = MID_REQUEST_CANCELLED;
> > + atomic_dec(&ses->server->inFlight);
> > + wake_up(&ses->server->request_q);
> > + return rc;
> > + }
> >
> > rc = handle_mid_result(midQ, ses->server);
> > if (rc != 0)
> > @@ -842,10 +852,14 @@ SendReceiveBlockingLock(const unsigned int xid, struct cifsTconInfo *tcon,
> > }
> > }
> >
> > - if (wait_for_response(ses->server, midQ) == 0) {
> > - /* We got the response - restart system call. */
> > - rstart = 1;
> > + rc = wait_for_response(ses->server, midQ);
> > + if (rc) {
> > + midQ->midState = MID_REQUEST_CANCELLED;
> > + return rc;
> > }
> > +
> > + /* We got the response - restart system call. */
> > + rstart = 1;
> > }
> >
> > rc = handle_mid_result(midQ, ses->server);
> > --
> > 1.7.3.2
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
>
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
