[PATCH 3/6] dma-direct: simplify the use atomic pool logic in dma_direct_alloc

Christoph Hellwig
2023-10-09T07:41:45Z

The logic in dma_direct_alloc when to use the atomic pool vs remapping
grew a bit unreadable. Consolidate it into a single check, and clean
up the set_uncached vs remap logic a bit as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
kernel/dma/direct.c | 25 ++++++++++---------------
1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index ec410af1d8a14e..1327d04fa32a25 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -234,27 +234,22 @@ void *dma_direct_alloc(struct device *dev, size_t size,
dma_handle);

/*
- * Otherwise remap if the architecture is asking for it. But
- * given that remapping memory is a blocking operation we'll
- * instead have to dip into the atomic pools.
+ * Otherwise we require the architecture to either be able to
+ * mark arbitrary parts of the kernel direct mapping uncached,
+ * or remapped it uncached.
*/
+ set_uncached = IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED);
remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
- if (remap) {
- if (dma_direct_use_pool(dev, gfp))
- return dma_direct_alloc_from_pool(dev, size,
- dma_handle, gfp);
- } else {
- if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
- return NULL;
- set_uncached = true;
- }
+ if (!set_uncached && !remap)
+ return NULL;
}

/*
- * Decrypting memory may block, so allocate the memory from the atomic
- * pools if we can't block.
+ * Remapping or decrypting memory may block, allocate the memory from
+ * the atomic pools instead if we aren't allowed block.
*/
- if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
+ if ((remap || force_dma_unencrypted(dev)) &&
+ dma_direct_use_pool(dev, gfp))
return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);

/* we always manually zero the memory once we are done */
--
2.39.2