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

[john.p.donnelly@oracle.com]

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@vger.kernel.org
> Signed-off-by: Baoquan He <bhe@redhat.com>

  Acked-by: John Donnelly <john.p.donnelly@oracle.com>
  Tested-by:  John Donnelly <john.p.donnelly@oracle.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>
> ---
>   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,