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: 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

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index c5da29ad010c4db6a14879e39ab6fbb2e5cc539c..2b2fbb7092429abdb686978f40b415119a3de1f5 100644 (file)
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -277,15 +277,20 @@ 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;
        }
 
-       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;
 }