[CIFS] Avoid extra large buffer allocation (and memcpy) in cifs_readpages

Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 58 insertions, 35 deletions

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 3565d3bf2e32..1620991cd4d2 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -958,21 +958,19 @@ openRetry:
         return rc;
 }
 
-/* If no buffer passed in, then caller wants to do the copy
-        as in the case of readpages so the SMB buffer must be
-        freed by the caller */
-
 int
 CIFSSMBRead(const int xid, struct cifsTconInfo *tcon,
-            const int netfid, const unsigned int count,
-            const __u64 lseek, unsigned int *nbytes, char **buf)
+            const int netfid, const unsigned int count,
+            const __u64 lseek, unsigned int *nbytes, char **buf,
+            int * pbuf_type)
 {
         int rc = -EACCES;
         READ_REQ *pSMB = NULL;
         READ_RSP *pSMBr = NULL;
         char *pReadData = NULL;
-        int bytes_returned;
         int wct;
+        int resp_buf_type = 0;
+        struct kvec iov[1];
 
         cFYI(1,("Reading %d bytes on fid %d",count,netfid));
         if(tcon->ses->capabilities & CAP_LARGE_FILES)
@@ -981,8 +979,7 @@ CIFSSMBRead(const int xid, struct cifsTconInfo *tcon,
                 wct = 10; /* old style read */
 
         *nbytes = 0;
-        rc = smb_init(SMB_COM_READ_ANDX, wct, tcon, (void **) &pSMB,
-                      (void **) &pSMBr);
+        rc = small_smb_init(SMB_COM_READ_ANDX, wct, tcon, (void **) &pSMB);
         if (rc)
                 return rc;
 
@@ -990,13 +987,13 @@ CIFSSMBRead(const int xid, struct cifsTconInfo *tcon,
         if (tcon->ses->server == NULL)
                 return -ECONNABORTED;
 
-        pSMB->AndXCommand = 0xFF;       /* none */
+        pSMB->AndXCommand = 0xFF;       /* none */
         pSMB->Fid = netfid;
         pSMB->OffsetLow = cpu_to_le32(lseek & 0xFFFFFFFF);
         if(wct == 12)
                 pSMB->OffsetHigh = cpu_to_le32(lseek >> 32);
-        else if((lseek >> 32) > 0) /* can not handle this big offset for old */
-                return -EIO;
+        else if((lseek >> 32) > 0) /* can not handle this big offset for old */
+                return -EIO;
 
         pSMB->Remaining = 0;
         pSMB->MaxCount = cpu_to_le16(count & 0xFFFF);
@@ -1005,14 +1002,18 @@ CIFSSMBRead(const int xid, struct cifsTconInfo *tcon,
                 pSMB->ByteCount = 0;  /* no need to do le conversion since 0 */
         else {
                 /* old style read */
-                struct smb_com_readx_req * pSMBW = 
+                struct smb_com_readx_req * pSMBW =
                         (struct smb_com_readx_req *)pSMB;
-                pSMBW->ByteCount = 0;   
+                pSMBW->ByteCount = 0;
         }
-        
-        rc = SendReceive(xid, tcon->ses, (struct smb_hdr *) pSMB,
-                         (struct smb_hdr *) pSMBr, &bytes_returned, 0);
+
+        iov[0].iov_base = (char *)pSMB;
+        iov[0].iov_len = pSMB->hdr.smb_buf_length + 4;
+        rc = SendReceive2(xid, tcon->ses, iov, 
+                          1 /* num iovecs */,
+                          &resp_buf_type, 0); 
         cifs_stats_inc(&tcon->num_reads);
+        pSMBr = (READ_RSP *)iov[0].iov_base;
         if (rc) {
                 cERROR(1, ("Send error in read = %d", rc));
         } else {
@@ -1022,33 +1023,43 @@ CIFSSMBRead(const int xid, struct cifsTconInfo *tcon,
                 *nbytes = data_length;
 
                 /*check that DataLength would not go beyond end of SMB */
-                if ((data_length > CIFSMaxBufSize) 
+                if ((data_length > CIFSMaxBufSize)
                                 || (data_length > count)) {
                         cFYI(1,("bad length %d for count %d",data_length,count));
                         rc = -EIO;
                         *nbytes = 0;
                 } else {
-                        pReadData =
-                            (char *) (&pSMBr->hdr.Protocol) +
+                        pReadData = (char *) (&pSMBr->hdr.Protocol) +
                             le16_to_cpu(pSMBr->DataOffset);
-/*                      if(rc = copy_to_user(buf, pReadData, data_length)) {
-                                cERROR(1,("Faulting on read rc = %d",rc));
-                                rc = -EFAULT;
-                        }*/ /* can not use copy_to_user when using page cache*/
+/*                      if(rc = copy_to_user(buf, pReadData, data_length)) {
+                                cERROR(1,("Faulting on read rc = %d",rc));
+                                rc = -EFAULT;
+                        }*/ /* can not use copy_to_user when using page cache*/
                         if(*buf)
-                            memcpy(*buf,pReadData,data_length);
+                                memcpy(*buf,pReadData,data_length);
                 }
         }
-        if(*buf)
-                cifs_buf_release(pSMB);
-        else
-                *buf = (char *)pSMB;
 
-        /* Note: On -EAGAIN error only caller can retry on handle based calls 
+        cifs_small_buf_release(pSMB);
+        if(*buf) {
+                if(resp_buf_type == CIFS_SMALL_BUFFER)
+                        cifs_small_buf_release(iov[0].iov_base);
+                else if(resp_buf_type == CIFS_LARGE_BUFFER)
+                        cifs_buf_release(iov[0].iov_base);
+        } else /* return buffer to caller to free */ /* BB FIXME how do we tell caller if it is not a large buffer */ {
+                *buf = iov[0].iov_base;
+                if(resp_buf_type == CIFS_SMALL_BUFFER)
+                        *pbuf_type = CIFS_SMALL_BUFFER;
+                else if(resp_buf_type == CIFS_LARGE_BUFFER)
+                        *pbuf_type = CIFS_LARGE_BUFFER;
+        }
+
+        /* Note: On -EAGAIN error only caller can retry on handle based calls
                 since file handle passed in no longer valid */
         return rc;
 }
 
+
 int
 CIFSSMBWrite(const int xid, struct cifsTconInfo *tcon,
              const int netfid, const unsigned int count,
@@ -1163,10 +1174,10 @@ CIFSSMBWrite2(const int xid, struct cifsTconInfo *tcon,
 {
         int rc = -EACCES;
         WRITE_REQ *pSMB = NULL;
-        int bytes_returned, wct;
+        int wct;
         int smb_hdr_len;
+        int resp_buf_type = 0;
 
-        /* BB removeme BB */
         cFYI(1,("write2 at %lld %d bytes", (long long)offset, count));
 
         if(tcon->ses->capabilities & CAP_LARGE_FILES)
@@ -1209,22 +1220,34 @@ CIFSSMBWrite2(const int xid, struct cifsTconInfo *tcon,
                 pSMBW->ByteCount = cpu_to_le16(count + 5);
         }
         iov[0].iov_base = pSMB;
-        iov[0].iov_len = smb_hdr_len + 4;
+        if(wct == 14)
+                iov[0].iov_len = smb_hdr_len + 4;
+        else /* wct == 12 pad bigger by four bytes */
+                iov[0].iov_len = smb_hdr_len + 8;
+        
 
-        rc = SendReceive2(xid, tcon->ses, iov, n_vec + 1, &bytes_returned,
+        rc = SendReceive2(xid, tcon->ses, iov, n_vec + 1, &resp_buf_type,
                           long_op);
         cifs_stats_inc(&tcon->num_writes);
         if (rc) {
                 cFYI(1, ("Send error Write2 = %d", rc));
                 *nbytes = 0;
+        } else if(resp_buf_type == 0) {
+                /* presumably this can not happen, but best to be safe */
+                rc = -EIO;
+                *nbytes = 0;
         } else {
-                WRITE_RSP * pSMBr = (WRITE_RSP *)pSMB;
+                WRITE_RSP * pSMBr = (WRITE_RSP *)iov[0].iov_base;
                 *nbytes = le16_to_cpu(pSMBr->CountHigh);
                 *nbytes = (*nbytes) << 16;
                 *nbytes += le16_to_cpu(pSMBr->Count);
         } 
 
         cifs_small_buf_release(pSMB);
+        if(resp_buf_type == CIFS_SMALL_BUFFER)
+                cifs_small_buf_release(iov[0].iov_base);
+        else if(resp_buf_type == CIFS_LARGE_BUFFER)
+                cifs_buf_release(iov[0].iov_base);
 
         /* Note: On -EAGAIN error only caller can retry on handle based calls 
                 since file handle passed in no longer valid */