[PATCH 5.10 131/161] dma/pool: distinguish between missing and exhausted atomic pools

Greg Kroah-Hartman
2026-02-04T14:49:48Z

From: Sai Sree Kartheek Adivi <s-adivi@ti.com>

[ Upstream commit 56c430c7f06d838fe3b2077dbbc4cc0bf992312b ]

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: 9420139f516d ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/dma/pool.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -271,15 +271,20 @@ struct page *dma_alloc_from_pool(struct
{
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;
}

- WARN(1, "Failed to get suitable pool for %s\n", dev_name(dev));
+ 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;
}