[openib-general] [PATCH 5/6] [RFC] iser handling of memory for RDMA

[Or Gerlitz]

Christoph Hellwig wrote:
>> +	if (cmd_dir == ISER_DIR_OUT) {
>> +		/* copy the unaligned sg the buffer which is used for RDMA */
>> +		struct scatterlist *p_sg = (struct scatterlist *)p_mem->p_buf;
>> +		int i;
>> +		char *p;
>> +
>> +		for (p = mem, i = 0; i < p_mem->size; i++) {
>> +			memcpy(p,
>> +			       page_address(p_sg[i].page) + p_sg[i].offset,
>> +			       p_sg[i].length);
>> +			p += p_sg[i].length;
> 
> pages you get sent down in a sg list don't have to be kernel mapped,
> you need to use kmap or kmap_atomic to access them.

DONE in r5506, see the patch below

use kmap_atomic instead of page_address in the code copying from/to SG
which is unaligned for rdma

Signed-off-by: Or Gerlitz <ogerlitz at voltaire.com>

Index: iser_memory.c
===================================================================
--- iser_memory.c	(revision 5505)
+++ iser_memory.c	(revision 5506)
@@ -140,12 +140,14 @@ int iser_start_rdma_unaligned_sg(struct
  		/* copy the unaligned sg the buffer which is used for RDMA */
  		struct scatterlist *sg = (struct scatterlist *)data->buf;
  		int i;
-		char *p;
+		char *p, *from;

  		for (p = mem, i = 0; i < data->size; i++) {
+			from = kmap_atomic(sg[i].page, KM_USER0);
  			memcpy(p,
-			       page_address(sg[i].page) + sg[i].offset,
+			       from + sg[i].offset,
  			       sg[i].length);
+			kunmap_atomic(from, KM_USER0);
  			p += sg[i].length;
  		}
  	}
@@ -185,7 +187,7 @@ void iser_finalize_rdma_unaligned_sg(str
  	if (ctask->dir[ISER_DIR_IN]) {
  		char *mem;
  		struct scatterlist *sg;
-		unsigned char *p;
+		unsigned char *p, *to;
  		unsigned int sg_size;
  		int i;

@@ -200,9 +202,11 @@ void iser_finalize_rdma_unaligned_sg(str
  		sg_size = ctask->data[ISER_DIR_IN].size;

  		for (p = mem, i = 0; i < sg_size; i++){
-			memcpy(page_address(sg[i].page) + sg[i].offset,
+			to = kmap_atomic(sg[i].page, KM_SOFTIRQ0);
+			memcpy(to + sg[i].offset,
  			       p,
  			       sg[i].length);
+			kunmap_atomic(to, KM_SOFTIRQ0);
  			p += sg[i].length;
  		}