The patch titled Subject: mm/page_alloc.c: do not warn allocation failure on zone DMA if no managed pages has been added to the -mm tree. Its filename is mm-page_allocc-do-not-warn-allocation-failure-on-zone-dma-if-no-managed-pages.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-page_allocc-do-not-warn-allocat... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_allocc-do-not-warn-allocat...

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------------------------------------------------------ From: Baoquan He bhe@redhat.com Subject: mm/page_alloc.c: do not warn allocation failure on zone DMA if no managed pages

In kdump kernel of x86_64, page allocation failure is observed:

kworker/u2:2: page allocation failure: order:0, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0 CPU: 0 PID: 55 Comm: kworker/u2:2 Not tainted 5.16.0-rc4+ #5 Hardware name: AMD Dinar/Dinar, BIOS RDN1505B 06/05/2013 Workqueue: events_unbound async_run_entry_fn Call Trace: <TASK> dump_stack_lvl+0x48/0x5e warn_alloc.cold+0x72/0xd6 __alloc_pages_slowpath.constprop.0+0xc69/0xcd0 __alloc_pages+0x1df/0x210 new_slab+0x389/0x4d0 ___slab_alloc+0x58f/0x770 __slab_alloc.constprop.0+0x4a/0x80 kmem_cache_alloc_trace+0x24b/0x2c0 sr_probe+0x1db/0x620 ...... device_add+0x405/0x920 ...... __scsi_add_device+0xe5/0x100 ata_scsi_scan_host+0x97/0x1d0 async_run_entry_fn+0x30/0x130 process_one_work+0x1e8/0x3c0 worker_thread+0x50/0x3b0 ? rescuer_thread+0x350/0x350 kthread+0x16b/0x190 ? set_kthread_struct+0x40/0x40 ret_from_fork+0x22/0x30 </TASK> Mem-Info: ......

The above failure happened when calling kmalloc() to allocate buffer with GFP_DMA. It requests to allocate slab page from DMA zone while no managed pages at all in there.

sr_probe() --> get_capabilities() --> buffer = kmalloc(512, GFP_KERNEL | GFP_DMA);

Because in the current kernel, dma-kmalloc will be created as long as CONFIG_ZONE_DMA is enabled. However, kdump kernel of x86_64 doesn't have managed pages on DMA zone since commit 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified"). The failure can be always reproduced.

For now, let's mute the warning of allocation failure if requesting pages from DMA zone while no managed pages.

Link: https://lkml.kernel.org/r/20211223094435.248523-4-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 Acked-by: John Donnelly john.p.donnelly@oracle.com Reviewed-by: Hyeonggon Yoo 42.hyeyoo@gmail.com Cc: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Borislav Petkov bp@alien8.de Cc: Christoph Hellwig hch@lst.de Cc: David Hildenbrand david@redhat.com Cc: David Laight David.Laight@ACULAB.COM Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: Robin Murphy robin.murphy@arm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_allocc-do-not-warn-allocation-failure-on-zone-dma-if-no-managed-pages +++ a/mm/page_alloc.c @@ -4218,7 +4218,8 @@ void warn_alloc(gfp_t gfp_mask, nodemask va_list args; static DEFINE_RATELIMIT_STATE(nopage_rs, 10*HZ, 1);

- if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs)) + if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) || + (gfp_mask & __GFP_DMA) && !has_managed_dma()) return;

va_start(args, fmt); _

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