CIFS: Expand CurrentMid field

While in CIFS/SMB we have 16 bit mid, in SMB2 it is 64 bit.
Convert the existing field to 64 bit and mask off higher bits
for CIFS/SMB.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>

3 files changed, 48 insertions, 40 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index a40339826178..b213458b852a 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -282,7 +282,7 @@ struct TCP_Server_Info {
                                    vcnumbers */
         int capabilities; /* allow selective disabling of caps by smb sess */
         int timeAdj;  /* Adjust for difference in server time zone in sec */
-        __u16 CurrentMid;         /* multiplex id - rotating counter */
+        __u64 CurrentMid;         /* multiplex id - rotating counter */
         char cryptkey[CIFS_CRYPTO_KEY_SIZE]; /* used by ntlm, ntlmv2 etc */
         /* 16th byte of RFC1001 workstation name is always null */
         char workstation_RFC1001_name[RFC1001_NAME_LEN_WITH_NULL];
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 05f0a2e7e14a..95ee5a64e0b0 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -115,7 +115,7 @@ extern int small_smb_init_no_tc(const int smb_cmd, const int wct,
                                 void **request_buf);
 extern int CIFS_SessSetup(unsigned int xid, struct cifs_ses *ses,
                              const struct nls_table *nls_cp);
-extern __u16 GetNextMid(struct TCP_Server_Info *server);
+extern __u64 GetNextMid(struct TCP_Server_Info *server);
 extern struct timespec cifs_NTtimeToUnix(__le64 utc_nanoseconds_since_1601);
 extern u64 cifs_UnixTimeToNT(struct timespec);
 extern struct timespec cnvrtDosUnixTm(__le16 le_date, __le16 le_time,
diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index dc61dff2c42a..d2ccce89062f 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -213,54 +213,61 @@ cifs_small_buf_release(void *buf_to_free)
 }
 
 /*
-        Find a free multiplex id (SMB mid). Otherwise there could be
-        mid collisions which might cause problems, demultiplexing the
-        wrong response to this request. Multiplex ids could collide if
-        one of a series requests takes much longer than the others, or
-        if a very large number of long lived requests (byte range
-        locks or FindNotify requests) are pending.  No more than
-        64K-1 requests can be outstanding at one time.  If no
-        mids are available, return zero.  A future optimization
-        could make the combination of mids and uid the key we use
-        to demultiplex on (rather than mid alone).
-        In addition to the above check, the cifs demultiplex
-        code already used the command code as a secondary
-        check of the frame and if signing is negotiated the
-        response would be discarded if the mid were the same
-        but the signature was wrong.  Since the mid is not put in the
-        pending queue until later (when it is about to be dispatched)
-        we do have to limit the number of outstanding requests
-        to somewhat less than 64K-1 although it is hard to imagine
-        so many threads being in the vfs at one time.
-*/
-__u16 GetNextMid(struct TCP_Server_Info *server)
+ * Find a free multiplex id (SMB mid). Otherwise there could be
+ * mid collisions which might cause problems, demultiplexing the
+ * wrong response to this request. Multiplex ids could collide if
+ * one of a series requests takes much longer than the others, or
+ * if a very large number of long lived requests (byte range
+ * locks or FindNotify requests) are pending. No more than
+ * 64K-1 requests can be outstanding at one time. If no
+ * mids are available, return zero. A future optimization
+ * could make the combination of mids and uid the key we use
+ * to demultiplex on (rather than mid alone).
+ * In addition to the above check, the cifs demultiplex
+ * code already used the command code as a secondary
+ * check of the frame and if signing is negotiated the
+ * response would be discarded if the mid were the same
+ * but the signature was wrong. Since the mid is not put in the
+ * pending queue until later (when it is about to be dispatched)
+ * we do have to limit the number of outstanding requests
+ * to somewhat less than 64K-1 although it is hard to imagine
+ * so many threads being in the vfs at one time.
+ */
+__u64 GetNextMid(struct TCP_Server_Info *server)
 {
-        __u16 mid = 0;
-        __u16 last_mid;
+        __u64 mid = 0;
+        __u16 last_mid, cur_mid;
         bool collision;
 
         spin_lock(&GlobalMid_Lock);
-        last_mid = server->CurrentMid; /* we do not want to loop forever */
-        server->CurrentMid++;
-        /* This nested loop looks more expensive than it is.
-        In practice the list of pending requests is short,
-        fewer than 50, and the mids are likely to be unique
-        on the first pass through the loop unless some request
-        takes longer than the 64 thousand requests before it
-        (and it would also have to have been a request that
-         did not time out) */
-        while (server->CurrentMid != last_mid) {
+
+        /* mid is 16 bit only for CIFS/SMB */
+        cur_mid = (__u16)((server->CurrentMid) & 0xffff);
+        /* we do not want to loop forever */
+        last_mid = cur_mid;
+        cur_mid++;
+
+        /*
+         * This nested loop looks more expensive than it is.
+         * In practice the list of pending requests is short,
+         * fewer than 50, and the mids are likely to be unique
+         * on the first pass through the loop unless some request
+         * takes longer than the 64 thousand requests before it
+         * (and it would also have to have been a request that
+         * did not time out).
+         */
+        while (cur_mid != last_mid) {
                 struct mid_q_entry *mid_entry;
                 unsigned int num_mids;
 
                 collision = false;
-                if (server->CurrentMid == 0)
-                        server->CurrentMid++;
+                if (cur_mid == 0)
+                        cur_mid++;
 
                 num_mids = 0;
                 list_for_each_entry(mid_entry, &server->pending_mid_q, qhead) {
                         ++num_mids;
-                        if (mid_entry->mid == server->CurrentMid &&
+                        if (mid_entry->mid == cur_mid &&
                             mid_entry->midState == MID_REQUEST_SUBMITTED) {
                                 /* This mid is in use, try a different one */
                                 collision = true;
@@ -282,10 +289,11 @@ __u16 GetNextMid(struct TCP_Server_Info *server)
                         server->tcpStatus = CifsNeedReconnect;
 
                 if (!collision) {
-                        mid = server->CurrentMid;
+                        mid = (__u64)cur_mid;
+                        server->CurrentMid = mid;
                         break;
                 }
-                server->CurrentMid++;
+                cur_mid++;
         }
         spin_unlock(&GlobalMid_Lock);
         return mid;