[RFC PATCH v2 4/5] dma/pool: create dma atomic pool only if dma zone has mamaged pages

[Baoquan He]

Currently three dma atomic pools are initialized as long as the relevant
kernel codes are built in. While in kdump kernel of x86_64, this is not
right when trying to create atomic_pool_dma, because there's no managed
pages in DMA zone. In the case, DMA zone only has low 1M memory presented
and locked down by memblock allocator. So no pages are added into buddy
of DMA zone. Please check commit f1d4d47c5851 ("x86/setup: Always reserve
the first 1M of RAM").

Then in kdump kernel of x86_64, it always prints below failure message:

 DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
 swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-0.rc5.20210611git929d931f2b40.42.fc35.x86_64 #1
 Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.12.0 06/04/2018
 Call Trace:
  dump_stack+0x7f/0xa1
  warn_alloc.cold+0x72/0xd6
  ? _raw_spin_unlock_irq+0x24/0x40
  ? __alloc_pages_direct_compact+0x90/0x1b0
  __alloc_pages_slowpath.constprop.0+0xf29/0xf50
  ? __cond_resched+0x16/0x50
  ? prepare_alloc_pages.constprop.0+0x19d/0x1b0
  __alloc_pages+0x24d/0x2c0
  ? __dma_atomic_pool_init+0x93/0x93
  alloc_page_interleave+0x13/0xb0
  atomic_pool_expand+0x118/0x210
  ? __dma_atomic_pool_init+0x93/0x93
  __dma_atomic_pool_init+0x45/0x93
  dma_atomic_pool_init+0xdb/0x176
  do_one_initcall+0x67/0x320
  ? rcu_read_lock_sched_held+0x3f/0x80
  kernel_init_freeable+0x290/0x2dc
  ? rest_init+0x24f/0x24f
  kernel_init+0xa/0x111
  ret_from_fork+0x22/0x30
 Mem-Info:
 ......
 DMA: failed to allocate 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation
 DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations

Here, let's check if DMA zone has managed pages, then create atomic_pool_dma
if yes. Otherwise just skip it.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx
---
 kernel/dma/pool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 5a85804b5beb..00df3edd6c5d 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -206,7 +206,7 @@ static int __init dma_atomic_pool_init(void)
 						    GFP_KERNEL);
 	if (!atomic_pool_kernel)
 		ret = -ENOMEM;
-	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
+	if (has_managed_dma()) {
 		atomic_pool_dma = __dma_atomic_pool_init(atomic_pool_size,
 						GFP_KERNEL | GFP_DMA);
 		if (!atomic_pool_dma)
@@ -229,7 +229,7 @@ static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t gfp)
 	if (prev == NULL) {
 		if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32))
 			return atomic_pool_dma32;
-		if (IS_ENABLED(CONFIG_ZONE_DMA) && (gfp & GFP_DMA))
+		if (atomic_pool_dma && (gfp & GFP_DMA))
 			return atomic_pool_dma;
 		return atomic_pool_kernel;
 	}
-- 
2.17.2