Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone

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On 12/13/21 6:27 AM, Baoquan He wrote:
Dma-kmalloc will be created as long as CONFIG_ZONE_DMA is enabled.
However, it will fail if DMA zone has no managed pages. The failure
can be seen in kdump kernel of x86_64 as below:

  CPU: 0 PID: 65 Comm: kworker/u2:1 Not tainted 5.14.0-rc2+ #9
  Hardware name: Intel Corporation SandyBridge Platform/To be filled by O.E.M., BIOS RMLSDP.86I.R2.28.D690.1306271008 06/27/2013
  Workqueue: events_unbound async_run_entry_fn
  Call Trace:
   dump_stack_lvl+0x57/0x72
   warn_alloc.cold+0x72/0xd6
   __alloc_pages_slowpath.constprop.0+0xf56/0xf70
   __alloc_pages+0x23b/0x2b0
   allocate_slab+0x406/0x630
   ___slab_alloc+0x4b1/0x7e0
   ? sr_probe+0x200/0x600
   ? lock_acquire+0xc4/0x2e0
   ? fs_reclaim_acquire+0x4d/0xe0
   ? lock_is_held_type+0xa7/0x120
   ? sr_probe+0x200/0x600
   ? __slab_alloc+0x67/0x90
   __slab_alloc+0x67/0x90
   ? sr_probe+0x200/0x600
   ? sr_probe+0x200/0x600
   kmem_cache_alloc_trace+0x259/0x270
   sr_probe+0x200/0x600
   ......
   bus_probe_device+0x9f/0xb0
   device_add+0x3d2/0x970
   ......
   __scsi_add_device+0xea/0x100
   ata_scsi_scan_host+0x97/0x1d0
   async_run_entry_fn+0x30/0x130
   process_one_work+0x2b0/0x5c0
   worker_thread+0x55/0x3c0
   ? process_one_work+0x5c0/0x5c0
   kthread+0x149/0x170
   ? set_kthread_struct+0x40/0x40
   ret_from_fork+0x22/0x30
  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 in there.
  sr_probe()
  --> get_capabilities()
      --> buffer = kmalloc(512, GFP_KERNEL | GFP_DMA);

The DMA zone should be checked if it has managed pages, then try to create
dma-kmalloc.

Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>

 Acked-by: John Donnelly <john.p.donnelly@xxxxxxxxxx>
 Tested-by:  John Donnelly <john.p.donnelly@xxxxxxxxxx>

Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
---
  mm/slab_common.c | 9 +++++++++
  1 file changed, 9 insertions(+)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index e5d080a93009..ae4ef0f8903a 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -878,6 +878,9 @@ void __init create_kmalloc_caches(slab_flags_t flags)
  {
  	int i;
  	enum kmalloc_cache_type type;
+#ifdef CONFIG_ZONE_DMA
+	bool managed_dma;
+#endif
/*
  	 * Including KMALLOC_CGROUP if CONFIG_MEMCG_KMEM defined
@@ -905,10 +908,16 @@ void __init create_kmalloc_caches(slab_flags_t flags)
  	slab_state = UP;
#ifdef CONFIG_ZONE_DMA
+	managed_dma = has_managed_dma();
+
  	for (i = 0; i <= KMALLOC_SHIFT_HIGH; i++) {
  		struct kmem_cache *s = kmalloc_caches[KMALLOC_NORMAL][i];
if (s) {
+			if (!managed_dma) {
+				kmalloc_caches[KMALLOC_DMA][i] = kmalloc_caches[KMALLOC_NORMAL][i];
+				continue;
+			}
  			kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
  				kmalloc_info[i].name[KMALLOC_DMA],
  				kmalloc_info[i].size,





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