unimore/kernel-hacking-2024-linux-steffo
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dma-direct: optimize page freeing when it is not addressable

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When the CMA allocation succeeds but isn't addressable, its buffer has
already been released and the page is set to NULL.  So later when the
normal page allocation succeeds but isn't addressable, __free_pages()
can be used to free that normal page rather than using
dma_free_contiguous that does extra checks that are not needed.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Chen Yu 2024-08-31 19:01:19 +08:00 committed by Christoph Hellwig
parent de6c85bf91
commit f689a3ab7b
1 changed files with 1 additions and 1 deletions
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2
kernel/dma/direct.c
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@ -140,7 +140,7 @@ static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
if (!page) if (!page)
page = alloc_pages_node(node, gfp, get_order(size)); page = alloc_pages_node(node, gfp, get_order(size));
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
dma_free_contiguous(dev, page, size); __free_pages(page, get_order(size));
page = NULL; page = NULL;
if (IS_ENABLED(CONFIG_ZONE_DMA32) && if (IS_ENABLED(CONFIG_ZONE_DMA32) &&