[rds-devel] [PATCH 4/5] RDS: Copy rds_iovecs into kernel memory instead of rereading from userspace
Andy Grover
andy.grover at oracle.com
Thu Oct 28 18:40:58 PDT 2010
Change rds_rdma_pages to take a passed-in rds_iovec array instead
of doing copy_from_user itself.
Change rds_cmsg_rdma_args to copy rds_iovec array once only. This
eliminates the possibility of userspace changing it after our
sanity checks.
Implement stack-based storage for small numbers of iovecs, based
on net/socket.c, to save an alloc in the extremely common case.
Although this patch reduces iovec copies in cmsg_rdma_args to 1,
we still do another one in rds_rdma_extra_size. Getting rid of
that one will be trickier, so it'll be a separate patch.
Signed-off-by: Andy Grover <andy.grover at oracle.com>
---
net/rds/rdma.c | 104 +++++++++++++++++++++++++++++++++++---------------------
1 files changed, 65 insertions(+), 39 deletions(-)
diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 334acdd..caa4d98 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -479,13 +479,38 @@ void rds_atomic_free_op(struct rm_atomic_op *ao)
/*
- * Count the number of pages needed to describe an incoming iovec.
+ * Count the number of pages needed to describe an incoming iovec array.
*/
-static int rds_rdma_pages(struct rds_rdma_args *args)
+static int rds_rdma_pages(struct rds_iovec iov[], int nr_iovecs)
+{
+ int tot_pages = 0;
+ unsigned int nr_pages;
+ unsigned int i;
+
+ /* figure out the number of pages in the vector */
+ for (i = 0; i < nr_iovecs; i++) {
+ nr_pages = rds_pages_in_vec(&iov[i]);
+ if (nr_pages == 0)
+ return -EINVAL;
+
+ tot_pages += nr_pages;
+
+ /*
+ * nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
+ * so tot_pages cannot overflow without first going negative.
+ */
+ if (tot_pages < 0)
+ return -EINVAL;
+ }
+
+ return tot_pages;
+}
+
+int rds_rdma_extra_size(struct rds_rdma_args *args)
{
struct rds_iovec vec;
struct rds_iovec __user *local_vec;
- unsigned int tot_pages = 0;
+ int tot_pages = 0;
unsigned int nr_pages;
unsigned int i;
@@ -507,16 +532,11 @@ static int rds_rdma_pages(struct rds_rdma_args *args)
* nr_pages for one entry is limited to (UINT_MAX>>PAGE_SHIFT)+1,
* so tot_pages cannot overflow without first going negative.
*/
- if ((int)tot_pages < 0)
+ if (tot_pages < 0)
return -EINVAL;
}
- return tot_pages;
-}
-
-int rds_rdma_extra_size(struct rds_rdma_args *args)
-{
- return rds_rdma_pages(args) * sizeof(struct scatterlist);
+ return tot_pages * sizeof(struct scatterlist);
}
/*
@@ -527,13 +547,12 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
struct cmsghdr *cmsg)
{
struct rds_rdma_args *args;
- struct rds_iovec vec;
struct rm_rdma_op *op = &rm->rdma;
int nr_pages;
unsigned int nr_bytes;
struct page **pages = NULL;
- struct rds_iovec __user *local_vec;
- unsigned int nr;
+ struct rds_iovec iovstack[UIO_FASTIOV], *iovs = iovstack;
+ int iov_size;
unsigned int i, j;
int ret = 0;
@@ -553,7 +572,22 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
goto out;
}
- nr_pages = rds_rdma_pages(args);
+ /* Check whether to allocate the iovec area */
+ iov_size = args->nr_local * sizeof(struct rds_iovec);
+ if (args->nr_local > UIO_FASTIOV) {
+ iovs = sock_kmalloc(rds_rs_to_sk(rs), iov_size, GFP_KERNEL);
+ if (!iovs) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+
+ if (copy_from_user(iovs, (struct rds_iovec __user *)(unsigned long) args->local_vec_addr, iov_size)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ nr_pages = rds_rdma_pages(iovs, args->nr_local);
if (nr_pages < 0) {
ret = -EINVAL;
goto out;
@@ -606,50 +640,40 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
(unsigned long long)args->remote_vec.addr,
op->op_rkey);
- local_vec = (struct rds_iovec __user *)(unsigned long) args->local_vec_addr;
-
for (i = 0; i < args->nr_local; i++) {
- if (copy_from_user(&vec, &local_vec[i],
- sizeof(struct rds_iovec))) {
- ret = -EFAULT;
- goto out;
- }
-
- nr = rds_pages_in_vec(&vec);
- if (nr == 0) {
- ret = -EINVAL;
- goto out;
- }
+ struct rds_iovec *iov = &iovs[i];
+ /* don't need to check, rds_rdma_pages() verified nr will be +nonzero */
+ unsigned int nr = rds_pages_in_vec(iov);
- rs->rs_user_addr = vec.addr;
- rs->rs_user_bytes = vec.bytes;
+ rs->rs_user_addr = iov->addr;
+ rs->rs_user_bytes = iov->bytes;
/* If it's a WRITE operation, we want to pin the pages for reading.
* If it's a READ operation, we need to pin the pages for writing.
*/
- ret = rds_pin_pages(vec.addr, nr, pages, !op->op_write);
+ ret = rds_pin_pages(iov->addr, nr, pages, !op->op_write);
if (ret < 0)
goto out;
- rdsdebug("RDS: nr_bytes %u nr %u vec.bytes %llu vec.addr %llx\n",
- nr_bytes, nr, vec.bytes, vec.addr);
+ rdsdebug("RDS: nr_bytes %u nr %u iov->bytes %llu iov->addr %llx\n",
+ nr_bytes, nr, iov->bytes, iov->addr);
- nr_bytes += vec.bytes;
+ nr_bytes += iov->bytes;
for (j = 0; j < nr; j++) {
- unsigned int offset = vec.addr & ~PAGE_MASK;
+ unsigned int offset = iov->addr & ~PAGE_MASK;
struct scatterlist *sg;
sg = &op->op_sg[op->op_nents + j];
sg_set_page(sg, pages[j],
- min_t(unsigned int, vec.bytes, PAGE_SIZE - offset),
+ min_t(unsigned int, iov->bytes, PAGE_SIZE - offset),
offset);
- rdsdebug("RDS: sg->offset %x sg->len %x vec.addr %llx vec.bytes %llu\n",
- sg->offset, sg->length, vec.addr, vec.bytes);
+ rdsdebug("RDS: sg->offset %x sg->len %x iov->addr %llx iov->bytes %llu\n",
+ sg->offset, sg->length, iov->addr, iov->bytes);
- vec.addr += sg->length;
- vec.bytes -= sg->length;
+ iov->addr += sg->length;
+ iov->bytes -= sg->length;
}
op->op_nents += nr;
@@ -665,6 +689,8 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
op->op_bytes = nr_bytes;
out:
+ if (iovs != iovstack)
+ sock_kfree_s(rds_rs_to_sk(rs), iovs, iov_size);
kfree(pages);
if (ret)
rds_rdma_free_op(op);
--
1.7.1
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