RDS: Explicitly allocate rm in sendmsg()

r_m_copy_from_user used to allocate the rm as well as kernel
buffers for the data, and then copy the data in. Now, sendmsg()
allocates the rm, although the data buffer alloc still happens
in r_m_copy_from_user.

SGs are still allocated with rm, but now r_m_alloc_sgs() is
used to reserve them. This allows multiple SG lists to be
allocated from the one rm -- this is important once we also
want to alloc our rdma sgl from this pool.

Signed-off-by: Andy Grover <andy.grover@oracle.com>

1 files changed, 30 insertions, 21 deletions

diff --git a/net/rds/message.c b/net/rds/message.c
index 4421d16..3498cbcc 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -214,17 +214,22 @@ int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 o
 }
 EXPORT_SYMBOL_GPL(rds_message_add_rdma_dest_extension);
 
-struct rds_message *rds_message_alloc(unsigned int nents, gfp_t gfp)
+/*
+ * Each rds_message is allocated with extra space for the scatterlist entries
+ * rds ops will need. This is to minimize memory allocation count. Then, each rds op
+ * can grab SGs when initializing its part of the rds_message.
+ */
+struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
 {
 	struct rds_message *rm;
 
-	rm = kzalloc(sizeof(struct rds_message) +
-		     (nents * sizeof(struct scatterlist)), gfp);
+	rm = kzalloc(sizeof(struct rds_message) + extra_len, gfp);
 	if (!rm)
 		goto out;
 
-	if (nents)
-		sg_init_table(rm->data.m_sg, nents);
+	rm->m_used_sgs = 0;
+	rm->m_total_sgs = extra_len / sizeof(struct scatterlist);
+
 	atomic_set(&rm->m_refcount, 1);
 	INIT_LIST_HEAD(&rm->m_sock_item);
 	INIT_LIST_HEAD(&rm->m_conn_item);
@@ -234,6 +239,23 @@ out:
 	return rm;
 }
 
+/*
+ * RDS ops use this to grab SG entries from the rm's sg pool.
+ */
+struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents)
+{
+	struct scatterlist *sg_first = (struct scatterlist *) &rm[1];
+	struct scatterlist *sg_ret;
+
+	WARN_ON(rm->m_used_sgs + nents > rm->m_total_sgs);
+
+	sg_ret = &sg_first[rm->m_used_sgs];
+
+	rm->m_used_sgs += nents;
+
+	return sg_ret;
+}
+
 struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len)
 {
 	struct rds_message *rm;
@@ -256,22 +278,15 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in
 	return rm;
 }
 
-struct rds_message *rds_message_copy_from_user(struct iovec *first_iov,
+int rds_message_copy_from_user(struct rds_message *rm, struct iovec *first_iov,
 					       size_t total_len)
 {
 	unsigned long to_copy;
 	unsigned long iov_off;
 	unsigned long sg_off;
-	struct rds_message *rm;
 	struct iovec *iov;
 	struct scatterlist *sg;
-	int ret;
-
-	rm = rds_message_alloc(ceil(total_len, PAGE_SIZE), GFP_KERNEL);
-	if (rm == NULL) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	int ret = 0;
 
 	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
 
@@ -320,14 +335,8 @@ struct rds_message *rds_message_copy_from_user(struct iovec *first_iov,
 			sg++;
 	}
 
-	ret = 0;
 out:
-	if (ret) {
-		if (rm)
-			rds_message_put(rm);
-		rm = ERR_PTR(ret);
-	}
-	return rm;
+	return ret;
 }
 
 int rds_message_inc_copy_to_user(struct rds_incoming *inc,