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Date: Fri, 14 Dec 2018 16:32:54 -0700
From: Stephen Warren <swarren@...dotorg.org>
To: Tariq Toukan <tariqt@...lanox.com>, Wei@...dotorg.org,
Hu@...dotorg.org, "\\ (Xavier\\)" <xavier.huwei@...wei.com>
Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
Doug Ledford <dledford@...hat.com>,
Jason Gunthorpe <jgg@...lanox.com>,
Stephen Warren <swarren@...dia.com>
Subject: [RFC PATCH] net/mlx4: Get rid of page operation after dma_alloc_coherent
From: Stephen Warren <swarren@...dia.com>
This is a port of commit 378efe798ecf ("RDMA/hns: Get rid of page
operation after dma_alloc_coherent") to the mlx4 driver. That change was
described as:
> In general, dma_alloc_coherent() returns a CPU virtual address and
> a DMA address, and we have no guarantee that the underlying memory
> even has an associated struct page at all.
>
> This patch gets rid of the page operation after dma_alloc_coherent,
> and records the VA returned form dma_alloc_coherent in the struct
> of hem in hns RoCE driver.
Differences in this port relative to the hns patch:
1) The hns patch only needed to fix a dma_alloc_coherent path, but this
patch also needs to fix an alloc_pages path. This appears to be simple
except for the next point.
2) The hns patch converted a bunch of code to consistently use
sg_dma_len(mem) rather than a mix of that and mem->length However, it
seems that sg_dma_len(mem) can be modified or zeroed at runtime, and so
using it when calling e.g. __free_pages is problematic. I suspect the
same issue affects mlx4_table_find() somehow too, and similarly I expect
the hns driver has an issue in this area. Instead, this patch converts
everything to use mem->length instead. I'd like some feedback on this
issue.
Signed-off-by: Stephen Warren <swarren@...dia.com>
---
Note: I've tested this patch in downstream 4.9 and 4.14 based kernels,
but can't test it in mainline (at least ibping works) since my system
isn't supported their yet. I have compile-tested it in mainline at
least, for ARM64.
drivers/net/ethernet/mellanox/mlx4/icm.c | 51 ++++++++++++++----------
drivers/net/ethernet/mellanox/mlx4/icm.h | 1 +
2 files changed, 30 insertions(+), 22 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/icm.c b/drivers/net/ethernet/mellanox/mlx4/icm.c
index 4b4351141b94..b14207cef69e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/icm.c
+++ b/drivers/net/ethernet/mellanox/mlx4/icm.c
@@ -72,7 +72,7 @@ static void mlx4_free_icm_coherent(struct mlx4_dev *dev, struct mlx4_icm_chunk *
for (i = 0; i < chunk->npages; ++i)
dma_free_coherent(&dev->persist->pdev->dev,
chunk->mem[i].length,
- lowmem_page_address(sg_page(&chunk->mem[i])),
+ chunk->buf[i],
sg_dma_address(&chunk->mem[i]));
}
@@ -95,9 +95,11 @@ void mlx4_free_icm(struct mlx4_dev *dev, struct mlx4_icm *icm, int coherent)
kfree(icm);
}
-static int mlx4_alloc_icm_pages(struct scatterlist *mem, int order,
+static int mlx4_alloc_icm_pages(struct mlx4_icm_chunk *chunk, int order,
gfp_t gfp_mask, int node)
{
+ struct scatterlist *mem = &chunk->mem[chunk->npages];
+ void **buf = &chunk->buf[chunk->npages];
struct page *page;
page = alloc_pages_node(node, gfp_mask, order);
@@ -108,25 +110,30 @@ static int mlx4_alloc_icm_pages(struct scatterlist *mem, int order,
}
sg_set_page(mem, page, PAGE_SIZE << order, 0);
+ *buf = lowmem_page_address(page);
return 0;
}
-static int mlx4_alloc_icm_coherent(struct device *dev, struct scatterlist *mem,
- int order, gfp_t gfp_mask)
+static int mlx4_alloc_icm_coherent(struct device *dev,
+ struct mlx4_icm_chunk *chunk, int order,
+ gfp_t gfp_mask)
{
- void *buf = dma_alloc_coherent(dev, PAGE_SIZE << order,
- &sg_dma_address(mem), gfp_mask);
- if (!buf)
+ struct scatterlist *mem = &chunk->mem[chunk->npages];
+ void **buf = &chunk->buf[chunk->npages];
+
+ *buf = dma_alloc_coherent(dev, PAGE_SIZE << order,
+ &sg_dma_address(mem), gfp_mask);
+ if (!*buf)
return -ENOMEM;
- if (offset_in_page(buf)) {
+ if (offset_in_page(*buf)) {
dma_free_coherent(dev, PAGE_SIZE << order,
- buf, sg_dma_address(mem));
+ *buf, sg_dma_address(mem));
return -ENOMEM;
}
- sg_set_buf(mem, buf, PAGE_SIZE << order);
sg_dma_len(mem) = PAGE_SIZE << order;
+ mem->length = PAGE_SIZE << order;
return 0;
}
@@ -174,6 +181,7 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
sg_init_table(chunk->mem, MLX4_ICM_CHUNK_LEN);
chunk->npages = 0;
chunk->nsg = 0;
+ memset(chunk->buf, 0, sizeof(chunk->buf));
list_add_tail(&chunk->list, &icm->chunk_list);
}
@@ -186,11 +194,9 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
if (coherent)
ret = mlx4_alloc_icm_coherent(&dev->persist->pdev->dev,
- &chunk->mem[chunk->npages],
- cur_order, mask);
+ chunk, cur_order, mask);
else
- ret = mlx4_alloc_icm_pages(&chunk->mem[chunk->npages],
- cur_order, mask,
+ ret = mlx4_alloc_icm_pages(chunk, cur_order, mask,
dev->numa_node);
if (ret) {
@@ -316,11 +322,11 @@ void mlx4_table_put(struct mlx4_dev *dev, struct mlx4_icm_table *table, u32 obj)
void *mlx4_table_find(struct mlx4_icm_table *table, u32 obj,
dma_addr_t *dma_handle)
{
- int offset, dma_offset, i;
+ int offset, dma_offset, i, length;
u64 idx;
struct mlx4_icm_chunk *chunk;
struct mlx4_icm *icm;
- struct page *page = NULL;
+ void *addr = NULL;
if (!table->lowmem)
return NULL;
@@ -336,28 +342,29 @@ void *mlx4_table_find(struct mlx4_icm_table *table, u32 obj,
list_for_each_entry(chunk, &icm->chunk_list, list) {
for (i = 0; i < chunk->npages; ++i) {
+ length = chunk->mem[i].length;
if (dma_handle && dma_offset >= 0) {
- if (sg_dma_len(&chunk->mem[i]) > dma_offset)
+ if (length > dma_offset)
*dma_handle = sg_dma_address(&chunk->mem[i]) +
dma_offset;
- dma_offset -= sg_dma_len(&chunk->mem[i]);
+ dma_offset -= length;
}
/*
* DMA mapping can merge pages but not split them,
* so if we found the page, dma_handle has already
* been assigned to.
*/
- if (chunk->mem[i].length > offset) {
- page = sg_page(&chunk->mem[i]);
+ if (length > offset) {
+ addr = chunk->buf[i] + offset;
goto out;
}
- offset -= chunk->mem[i].length;
+ offset -= length;
}
}
out:
mutex_unlock(&table->mutex);
- return page ? lowmem_page_address(page) + offset : NULL;
+ return addr;
}
int mlx4_table_get_range(struct mlx4_dev *dev, struct mlx4_icm_table *table,
diff --git a/drivers/net/ethernet/mellanox/mlx4/icm.h b/drivers/net/ethernet/mellanox/mlx4/icm.h
index c9169a490557..a565188dc391 100644
--- a/drivers/net/ethernet/mellanox/mlx4/icm.h
+++ b/drivers/net/ethernet/mellanox/mlx4/icm.h
@@ -52,6 +52,7 @@ struct mlx4_icm_chunk {
int npages;
int nsg;
struct scatterlist mem[MLX4_ICM_CHUNK_LEN];
+ void *buf[MLX4_ICM_CHUNK_LEN];
};
struct mlx4_icm {
--
2.19.2
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