cifs: better instrumentation for coalesce_t2

When coalesce_t2 returns an error, have it throw a cFYI message that
explains the reason. Also rename some variables to clarify what they
represent.

Reported-and-Tested-by: Konstantinos Skarlatos <k.skarlatos@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 50 insertions, 34 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 4666780f315d..5cc15856e4ad 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -225,74 +225,90 @@ static int check2ndT2(struct smb_hdr *pSMB)
 
 static int coalesce_t2(struct smb_hdr *psecond, struct smb_hdr *pTargetSMB)
 {
-        struct smb_t2_rsp *pSMB2 = (struct smb_t2_rsp *)psecond;
+        struct smb_t2_rsp *pSMBs = (struct smb_t2_rsp *)psecond;
         struct smb_t2_rsp *pSMBt  = (struct smb_t2_rsp *)pTargetSMB;
-        char *data_area_of_target;
-        char *data_area_of_buf2;
+        char *data_area_of_tgt;
+        char *data_area_of_src;
         int remaining;
-        unsigned int byte_count, total_in_buf;
-        __u16 total_data_size, total_in_buf2;
+        unsigned int byte_count, total_in_tgt;
+        __u16 tgt_total_cnt, src_total_cnt, total_in_src;
 
-        total_data_size = get_unaligned_le16(&pSMBt->t2_rsp.TotalDataCount);
+        src_total_cnt = get_unaligned_le16(&pSMBs->t2_rsp.TotalDataCount);
+        tgt_total_cnt = get_unaligned_le16(&pSMBt->t2_rsp.TotalDataCount);
 
-        if (total_data_size !=
-            get_unaligned_le16(&pSMB2->t2_rsp.TotalDataCount))
-                cFYI(1, "total data size of primary and secondary t2 differ");
+        if (tgt_total_cnt != src_total_cnt)
+                cFYI(1, "total data count of primary and secondary t2 differ "
+                        "source=%hu target=%hu", src_total_cnt, tgt_total_cnt);
 
-        total_in_buf = get_unaligned_le16(&pSMBt->t2_rsp.DataCount);
+        total_in_tgt = get_unaligned_le16(&pSMBt->t2_rsp.DataCount);
 
-        remaining = total_data_size - total_in_buf;
+        remaining = tgt_total_cnt - total_in_tgt;
 
-        if (remaining < 0)
+        if (remaining < 0) {
+                cFYI(1, "Server sent too much data. tgt_total_cnt=%hu "
+                        "total_in_tgt=%hu", tgt_total_cnt, total_in_tgt);
                 return -EPROTO;
+        }
 
-        if (remaining == 0) /* nothing to do, ignore */
+        if (remaining == 0) {
+                /* nothing to do, ignore */
+                cFYI(1, "no more data remains");
                 return 0;
+        }
 
-        total_in_buf2 = get_unaligned_le16(&pSMB2->t2_rsp.DataCount);
-        if (remaining < total_in_buf2) {
+        total_in_src = get_unaligned_le16(&pSMBs->t2_rsp.DataCount);
+        if (remaining < total_in_src)
                 cFYI(1, "transact2 2nd response contains too much data");
-        }
 
         /* find end of first SMB data area */
-        data_area_of_target = (char *)&pSMBt->hdr.Protocol +
+        data_area_of_tgt = (char *)&pSMBt->hdr.Protocol +
                                 get_unaligned_le16(&pSMBt->t2_rsp.DataOffset);
-        /* validate target area */
 
-        data_area_of_buf2 = (char *)&pSMB2->hdr.Protocol +
-                                get_unaligned_le16(&pSMB2->t2_rsp.DataOffset);
+        /* validate target area */
+        data_area_of_src = (char *)&pSMBs->hdr.Protocol +
+                                get_unaligned_le16(&pSMBs->t2_rsp.DataOffset);
 
-        data_area_of_target += total_in_buf;
+        data_area_of_tgt += total_in_tgt;
 
-        /* copy second buffer into end of first buffer */
-        total_in_buf += total_in_buf2;
+        total_in_tgt += total_in_src;
         /* is the result too big for the field? */
-        if (total_in_buf > USHRT_MAX)
+        if (total_in_tgt > USHRT_MAX) {
+                cFYI(1, "coalesced DataCount too large (%u)", total_in_tgt);
                 return -EPROTO;
-        put_unaligned_le16(total_in_buf, &pSMBt->t2_rsp.DataCount);
+        }
+        put_unaligned_le16(total_in_tgt, &pSMBt->t2_rsp.DataCount);
 
         /* fix up the BCC */
         byte_count = get_bcc(pTargetSMB);
-        byte_count += total_in_buf2;
+        byte_count += total_in_src;
         /* is the result too big for the field? */
-        if (byte_count > USHRT_MAX)
+        if (byte_count > USHRT_MAX) {
+                cFYI(1, "coalesced BCC too large (%u)", byte_count);
                 return -EPROTO;
+        }
         put_bcc(byte_count, pTargetSMB);
 
         byte_count = be32_to_cpu(pTargetSMB->smb_buf_length);
-        byte_count += total_in_buf2;
+        byte_count += total_in_src;
         /* don't allow buffer to overflow */
-        if (byte_count > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4)
+        if (byte_count > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) {
+                cFYI(1, "coalesced BCC exceeds buffer size (%u)", byte_count);
                 return -ENOBUFS;
+        }
         pTargetSMB->smb_buf_length = cpu_to_be32(byte_count);
 
-        memcpy(data_area_of_target, data_area_of_buf2, total_in_buf2);
+        /* copy second buffer into end of first buffer */
+        memcpy(data_area_of_tgt, data_area_of_src, total_in_src);
 
-        if (remaining == total_in_buf2) {
-                cFYI(1, "found the last secondary response");
-                return 0; /* we are done */
-        } else /* more responses to go */
+        if (remaining != total_in_src) {
+                /* more responses to go */
+                cFYI(1, "waiting for more secondary responses");
                 return 1;
+        }
+
+        /* we are done */
+        cFYI(1, "found the last secondary response");
+        return 0;
 }
 
 static void