Commit 56c430c7 authored Jan 28, 2026 by Sai Sree Kartheek Adivi Committed by Marek Szyprowski Jan 29, 2026

dma/pool: distinguish between missing and exhausted atomic pools



Currently, dma_alloc_from_pool() unconditionally warns and dumps a stack
trace when an allocation fails, with the message "Failed to get suitable
pool".

This conflates two distinct failure modes:
1. Configuration error: No atomic pool is available for the requested
   DMA mask (a fundamental system setup issue)
2. Resource Exhaustion: A suitable pool exists but is currently full (a
   recoverable runtime state)

This lack of distinction prevents drivers from using __GFP_NOWARN to
suppress error messages during temporary pressure spikes, such as when
awaiting synchronous reclaim of descriptors.

Refactor the error handling to distinguish these cases:
- If no suitable pool is found, keep the unconditional WARN regarding
  the missing pool.
- If a pool was found but is exhausted, respect __GFP_NOWARN and update
  the warning message to explicitly state "DMA pool exhausted".

Fixes: 9420139f ("dma-pool: fix coherent pool allocations for IOMMU mappings")
Signed-off-by: Sai Sree Kartheek Adivi <s-adivi@ti.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260128133554.3056582-1-s-adivi@ti.com

parent 0fd17e59

kernel/dma/pool.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -277,14 +277,19 @@ struct page dma_alloc_from_pool(struct device dev, size_t size,
		{
		struct gen_pool *pool = NULL;
		struct page *page;
		bool pool_found = false;

		while ((pool = dma_guess_pool(pool, gfp))) {
		pool_found = true;
		page = __dma_alloc_from_pool(dev, size, pool, cpu_addr,
		phys_addr_ok);
		if (page)
		return page;
		}

		if (pool_found)
		WARN(!(gfp & __GFP_NOWARN), "DMA pool exhausted for %s\n", dev_name(dev));
		else
		WARN(1, "Failed to get suitable pool for %s\n", dev_name(dev));
		return NULL;
		}