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@@ -34,8 +34,6 @@ extern mempool_t *cifs_sm_req_poolp;
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extern mempool_t *cifs_req_poolp;
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extern struct task_struct * oplockThread;
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-static __u16 GlobalMid; /* multiplex id - rotating counter */
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-
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/* The xid serves as a useful identifier for each incoming vfs request,
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in a similar way to the mid which is useful to track each sent smb,
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and CurrentXid can also provide a running counter (although it
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@@ -51,6 +49,8 @@ _GetXid(void)
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GlobalTotalActiveXid++;
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if (GlobalTotalActiveXid > GlobalMaxActiveXid)
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GlobalMaxActiveXid = GlobalTotalActiveXid; /* keep high water mark for number of simultaneous vfs ops in our filesystem */
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+ if(GlobalTotalActiveXid > 65000)
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+ cFYI(1,("warning: more than 65000 requests active"));
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xid = GlobalCurrentXid++;
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spin_unlock(&GlobalMid_Lock);
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return xid;
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@@ -218,6 +218,76 @@ cifs_small_buf_release(void *buf_to_free)
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return;
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}
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+/*
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+ Find a free multiplex id (SMB mid). Otherwise there could be
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+ mid collisions which might cause problems, demultiplexing the
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+ wrong response to this request. Multiplex ids could collide if
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+ one of a series requests takes much longer than the others, or
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+ if a very large number of long lived requests (byte range
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+ locks or FindNotify requests) are pending. No more than
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+ 64K-1 requests can be outstanding at one time. If no
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+ mids are available, return zero. A future optimization
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+ could make the combination of mids and uid the key we use
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+ to demultiplex on (rather than mid alone).
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+ In addition to the above check, the cifs demultiplex
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+ code already used the command code as a secondary
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+ check of the frame and if signing is negotiated the
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+ response would be discarded if the mid were the same
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+ but the signature was wrong. Since the mid is not put in the
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+ pending queue until later (when it is about to be dispatched)
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+ we do have to limit the number of outstanding requests
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+ to somewhat less than 64K-1 although it is hard to imagine
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+ so many threads being in the vfs at one time.
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+*/
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+__u16 GetNextMid(struct TCP_Server_Info *server)
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+{
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+ __u16 mid = 0;
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+ __u16 last_mid;
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+ int collision;
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+
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+ if(server == NULL)
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+ return mid;
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+
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+ spin_lock(&GlobalMid_Lock);
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+ last_mid = server->CurrentMid; /* we do not want to loop forever */
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+ server->CurrentMid++;
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+ /* This nested loop looks more expensive than it is.
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+ In practice the list of pending requests is short,
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+ fewer than 50, and the mids are likely to be unique
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+ on the first pass through the loop unless some request
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+ takes longer than the 64 thousand requests before it
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+ (and it would also have to have been a request that
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+ did not time out) */
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+ while(server->CurrentMid != last_mid) {
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+ struct list_head *tmp;
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+ struct mid_q_entry *mid_entry;
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+
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+ collision = 0;
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+ if(server->CurrentMid == 0)
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+ server->CurrentMid++;
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+
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+ list_for_each(tmp, &server->pending_mid_q) {
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+ mid_entry = list_entry(tmp, struct mid_q_entry, qhead);
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+
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+ if ((mid_entry->mid == server->CurrentMid) &&
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+ (mid_entry->midState == MID_REQUEST_SUBMITTED)) {
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+ /* This mid is in use, try a different one */
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+ collision = 1;
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+ break;
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+ }
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+ }
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+ if(collision == 0) {
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+ mid = server->CurrentMid;
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+ break;
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+ }
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+ server->CurrentMid++;
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+ }
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+ spin_unlock(&GlobalMid_Lock);
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+ return mid;
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+}
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+
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+/* NB: MID can not be set if treeCon not passed in, in that
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+ case it is responsbility of caller to set the mid */
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void
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header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
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const struct cifsTconInfo *treeCon, int word_count
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@@ -233,7 +303,8 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
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(2 * word_count) + sizeof (struct smb_hdr) -
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4 /* RFC 1001 length field does not count */ +
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2 /* for bcc field itself */ ;
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- /* Note that this is the only network field that has to be converted to big endian and it is done just before we send it */
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+ /* Note that this is the only network field that has to be converted
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+ to big endian and it is done just before we send it */
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buffer->Protocol[0] = 0xFF;
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buffer->Protocol[1] = 'S';
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@@ -245,8 +316,6 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
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buffer->Pid = cpu_to_le16((__u16)current->tgid);
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buffer->PidHigh = cpu_to_le16((__u16)(current->tgid >> 16));
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spin_lock(&GlobalMid_Lock);
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- GlobalMid++;
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- buffer->Mid = GlobalMid;
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spin_unlock(&GlobalMid_Lock);
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if (treeCon) {
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buffer->Tid = treeCon->tid;
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@@ -256,8 +325,9 @@ header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
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if (treeCon->ses->capabilities & CAP_STATUS32) {
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buffer->Flags2 |= SMBFLG2_ERR_STATUS;
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}
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-
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- buffer->Uid = treeCon->ses->Suid; /* always in LE format */
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+ /* Uid is not converted */
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+ buffer->Uid = treeCon->ses->Suid;
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+ buffer->Mid = GetNextMid(treeCon->ses->server);
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if(multiuser_mount != 0) {
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/* For the multiuser case, there are few obvious technically */
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/* possible mechanisms to match the local linux user (uid) */
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Steve French