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Date: Tue, 18 Dec 2018 21:56:49 +0100
From: Christoph Hellwig <hch@....de>
To: Stephen Warren <swarren@...dotorg.org>
Cc: Tariq Toukan <tariqt@...lanox.com>, xavier.huwei@...wei.com,
netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
Doug Ledford <dledford@...hat.com>,
Jason Gunthorpe <jgg@...lanox.com>,
Christoph Hellwig <hch@....de>,
Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCH V2] net/mlx4: Get rid of page operation after
dma_alloc_coherent
This goes in the right direction, but I think we need to stop
abusing the scatterlist for the coherent mapping entirely. Something
like the patch below (based on yours):
diff --git a/drivers/net/ethernet/mellanox/mlx4/icm.c b/drivers/net/ethernet/mellanox/mlx4/icm.c
index 4b4351141b94..717ee2fad707 100644
--- a/drivers/net/ethernet/mellanox/mlx4/icm.c
+++ b/drivers/net/ethernet/mellanox/mlx4/icm.c
@@ -57,12 +57,12 @@ static void mlx4_free_icm_pages(struct mlx4_dev *dev, struct mlx4_icm_chunk *chu
int i;
if (chunk->nsg > 0)
- pci_unmap_sg(dev->persist->pdev, chunk->mem, chunk->npages,
+ pci_unmap_sg(dev->persist->pdev, chunk->sg, chunk->npages,
PCI_DMA_BIDIRECTIONAL);
for (i = 0; i < chunk->npages; ++i)
- __free_pages(sg_page(&chunk->mem[i]),
- get_order(chunk->mem[i].length));
+ __free_pages(sg_page(&chunk->sg[i]),
+ get_order(chunk->sg[i].length));
}
static void mlx4_free_icm_coherent(struct mlx4_dev *dev, struct mlx4_icm_chunk *chunk)
@@ -71,9 +71,9 @@ 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])),
- sg_dma_address(&chunk->mem[i]));
+ chunk->buf[i].size,
+ chunk->buf[i].addr,
+ chunk->buf[i].dma_addr);
}
void mlx4_free_icm(struct mlx4_dev *dev, struct mlx4_icm *icm, int coherent)
@@ -111,22 +111,21 @@ static int mlx4_alloc_icm_pages(struct scatterlist *mem, int order,
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_buf *buf,
+ int order, gfp_t gfp_mask)
{
- void *buf = dma_alloc_coherent(dev, PAGE_SIZE << order,
- &sg_dma_address(mem), gfp_mask);
- if (!buf)
+ buf->addr = dma_alloc_coherent(dev, PAGE_SIZE << order,
+ &buf->dma_addr, gfp_mask);
+ if (!buf->addr)
return -ENOMEM;
- if (offset_in_page(buf)) {
- dma_free_coherent(dev, PAGE_SIZE << order,
- buf, sg_dma_address(mem));
+ if (offset_in_page(buf->addr)) {
+ dma_free_coherent(dev, PAGE_SIZE << order, buf->addr,
+ buf->dma_addr);
return -ENOMEM;
}
- sg_set_buf(mem, buf, PAGE_SIZE << order);
- sg_dma_len(mem) = PAGE_SIZE << order;
+ buf->size = PAGE_SIZE << order;
return 0;
}
@@ -159,21 +158,20 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
while (npages > 0) {
if (!chunk) {
- chunk = kmalloc_node(sizeof(*chunk),
+ chunk = kzalloc_node(sizeof(*chunk),
gfp_mask & ~(__GFP_HIGHMEM |
__GFP_NOWARN),
dev->numa_node);
if (!chunk) {
- chunk = kmalloc(sizeof(*chunk),
+ chunk = kzalloc(sizeof(*chunk),
gfp_mask & ~(__GFP_HIGHMEM |
__GFP_NOWARN));
if (!chunk)
goto fail;
}
- sg_init_table(chunk->mem, MLX4_ICM_CHUNK_LEN);
- chunk->npages = 0;
- chunk->nsg = 0;
+ if (!coherent)
+ sg_init_table(chunk->sg, MLX4_ICM_CHUNK_LEN);
list_add_tail(&chunk->list, &icm->chunk_list);
}
@@ -186,10 +184,10 @@ 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],
+ &chunk->buf[chunk->npages],
cur_order, mask);
else
- ret = mlx4_alloc_icm_pages(&chunk->mem[chunk->npages],
+ ret = mlx4_alloc_icm_pages(&chunk->sg[chunk->npages],
cur_order, mask,
dev->numa_node);
@@ -205,7 +203,7 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
if (coherent)
++chunk->nsg;
else if (chunk->npages == MLX4_ICM_CHUNK_LEN) {
- chunk->nsg = pci_map_sg(dev->persist->pdev, chunk->mem,
+ chunk->nsg = pci_map_sg(dev->persist->pdev, chunk->sg,
chunk->npages,
PCI_DMA_BIDIRECTIONAL);
@@ -220,7 +218,7 @@ struct mlx4_icm *mlx4_alloc_icm(struct mlx4_dev *dev, int npages,
}
if (!coherent && chunk) {
- chunk->nsg = pci_map_sg(dev->persist->pdev, chunk->mem,
+ chunk->nsg = pci_map_sg(dev->persist->pdev, chunk->sg,
chunk->npages,
PCI_DMA_BIDIRECTIONAL);
@@ -320,7 +318,7 @@ void *mlx4_table_find(struct mlx4_icm_table *table, u32 obj,
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 +334,48 @@ 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) {
+ dma_addr_t dma_addr;
+ size_t len;
+
+ if (table->coherent) {
+ len = chunk->buf[i].size;
+ dma_addr = chunk->buf[i].dma_addr;
+ addr = chunk->buf[i].addr;
+ } else {
+ len = sg_dma_len(&chunk->sg[i]);
+ dma_addr = sg_dma_address(&chunk->sg[i]);
+
+ /*
+ * XXX: we should never do this for highmem
+ * allocation. This function either needs
+ * to be split, or the kernel virtual address
+ * return needs to be made optional.
+ */
+ addr = lowmem_page_address(
+ sg_page(&chunk->sg[i]));
+ }
+
if (dma_handle && dma_offset >= 0) {
- if (sg_dma_len(&chunk->mem[i]) > dma_offset)
- *dma_handle = sg_dma_address(&chunk->mem[i]) +
- dma_offset;
- dma_offset -= sg_dma_len(&chunk->mem[i]);
+ if (len > dma_offset)
+ *dma_handle = dma_addr + dma_offset;
+ dma_offset -= len;
}
+
/*
* 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 (len > offset)
goto out;
- }
- offset -= chunk->mem[i].length;
+ offset -= len;
}
}
+ addr = NULL;
out:
mutex_unlock(&table->mutex);
- return page ? lowmem_page_address(page) + offset : NULL;
+ return addr ? addr + offset : NULL;
}
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..5ccf08ac47a3 100644
--- a/drivers/net/ethernet/mellanox/mlx4/icm.h
+++ b/drivers/net/ethernet/mellanox/mlx4/icm.h
@@ -47,11 +47,20 @@ enum {
MLX4_ICM_PAGE_SIZE = 1 << MLX4_ICM_PAGE_SHIFT,
};
+struct mlx4_icm_buf {
+ void *addr;
+ size_t size;
+ dma_addr_t dma_addr;
+};
+
struct mlx4_icm_chunk {
struct list_head list;
int npages;
int nsg;
- struct scatterlist mem[MLX4_ICM_CHUNK_LEN];
+ union {
+ struct scatterlist sg[MLX4_ICM_CHUNK_LEN];
+ struct mlx4_icm_buf buf[MLX4_ICM_CHUNK_LEN];
+ };
};
struct mlx4_icm {
@@ -112,14 +121,16 @@ static inline void mlx4_icm_next(struct mlx4_icm_iter *iter)
}
}
+/* Note: won't work on coherent tables */
static inline dma_addr_t mlx4_icm_addr(struct mlx4_icm_iter *iter)
{
- return sg_dma_address(&iter->chunk->mem[iter->page_idx]);
+ return sg_dma_address(&iter->chunk->sg[iter->page_idx]);
}
+/* Note: won't work on coherent tables */
static inline unsigned long mlx4_icm_size(struct mlx4_icm_iter *iter)
{
- return sg_dma_len(&iter->chunk->mem[iter->page_idx]);
+ return sg_dma_len(&iter->chunk->sg[iter->page_idx]);
}
int mlx4_MAP_ICM_AUX(struct mlx4_dev *dev, struct mlx4_icm *icm);
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