The patch titled Subject: dma/pool: create dma atomic pool only if dma zone has managed pages has been added to the -mm tree. Its filename is dma-pool-create-dma-atomic-pool-only-if-dma-zone-has-managed-pages.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/dma-pool-create-dma-atomic-pool-on... and later at https://ozlabs.org/~akpm/mmotm/broken-out/dma-pool-create-dma-atomic-pool-on...

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------------------------------------------------------ From: Baoquan He bhe@redhat.com Subject: dma/pool: create dma atomic pool only if dma zone has managed pages

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.

Link: https://lkml.kernel.org/r/20211223094435.248523-3-bhe@redhat.com Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified") Signed-off-by: Baoquan He bhe@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: John Donnelly john.p.donnelly@oracle.com Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: Robin Murphy robin.murphy@arm.com Cc: Borislav Petkov bp@alien8.de Cc: Christoph Lameter cl@linux.com Cc: David Hildenbrand david@redhat.com Cc: David Laight David.Laight@ACULAB.COM Cc: David Rientjes rientjes@google.com Cc: Hyeonggon Yoo 42.hyeyoo@gmail.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Pekka Enberg penberg@kernel.org Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

kernel/dma/pool.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/dma/pool.c~dma-pool-create-dma-atomic-pool-only-if-dma-zone-has-managed-pages +++ a/kernel/dma/pool.c @@ -203,7 +203,7 @@ static int __init dma_atomic_pool_init(v 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) @@ -226,7 +226,7 @@ static inline struct gen_pool *dma_guess 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; } _

Patches currently in -mm which might be from bhe@redhat.com are

mm_zone-add-function-to-check-if-managed-dma-zone-exists.patch dma-pool-create-dma-atomic-pool-only-if-dma-zone-has-managed-pages.patch mm-page_allocc-do-not-warn-allocation-failure-on-zone-dma-if-no-managed-pages.patch