iommu/io-pgtable-armv7s: Fix kmem_cache_alloc() flags

Whilst the default SLUB allocator happily just merges the original allocation flags from kmem_cache_create() with those passed through kmem_cache_alloc(), there is a code path in the SLAB allocator which will aggressively BUG_ON() if the cache was created with SLAB_CACHE_DMA but GFP_DMA is not specified for an allocation:

kernel BUG at mm/slab.c:2536!

  Internal error: Oops - BUG: 0 [#1] SMP ARM
  Modules linked in:[    1.299311] Modules linked in:

  CPU: 1 PID: 1 Comm: swapper/0 Not tainted
  4.5.0-rc6-koelsch-05892-ge7e45ad53ab6795e #2270
  Hardware name: Generic R8A7791 (Flattened Device Tree)
  task: ef422040 ti: ef442000 task.ti: ef442000
  PC is at cache_alloc_refill+0x2a0/0x530
  LR is at _raw_spin_unlock+0x8/0xc

...
[<c02c6928>] (cache_alloc_refill) from [<c02c6630>] (kmem_cache_alloc+0x7c/0xd4) [<c02c6630>] (kmem_cache_alloc) from [<c04444bc>] (__arm_v7s_alloc_table+0x5c/0x278)
[<c04444bc>] (__arm_v7s_alloc_table) from [<c0444e1c>] (__arm_v7s_map.constprop.6+0x68/0x25c)
[<c0444e1c>] (__arm_v7s_map.constprop.6) from [<c0445044>] (arm_v7s_map+0x34/0xa4)
[<c0445044>] (arm_v7s_map) from [<c0c18ee4>] (arm_v7s_do_selftests+0x140/0x418) [<c0c18ee4>] (arm_v7s_do_selftests) from [<c0201760>] (do_one_initcall+0x100/0x1b4)
[<c0201760>] (do_one_initcall) from [<c0c00d4c>] (kernel_init_freeable+0x120/0x1e8)
[<c0c00d4c>] (kernel_init_freeable) from [<c067a364>] (kernel_init+0x8/0xec) [<c067a364>] (kernel_init) from [<c0206b68>] (ret_from_fork+0x14/0x2c)

  Code: 1a000003 e7f001f2 e3130001 0a000000 (e7f001f2)
  ---[ end trace 190f6f6b84352efd ]---

Keep the peace by adding GFP_DMA when allocating a table.

---

v2: Add the backtrace to the commit log, add Will's ack.

 drivers/iommu/io-pgtable-arm-v7s.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 9fcceb1..9488e3c 100644
@@ -192,7 +192,7 @@ static void *__arm_v7s_alloc_table(int lvl, gfp_t gfp,
 	if (lvl == 1)
 		table = (void *)__get_dma_pages(__GFP_ZERO, get_order(size));
 	else if (lvl == 2)
-		table = kmem_cache_zalloc(data->l2_tables, gfp);
+		table = kmem_cache_zalloc(data->l2_tables, gfp | GFP_DMA);
 	if (table && !selftest_running) {
 		dma = dma_map_single(dev, table, size, DMA_TO_DEVICE);
 		if (dma_mapping_error(dev, dma))

2.7.2.333.g70bd996.dirty

Thanks, this makes the test succeed:

arm-v7s io-pgtable: self test ok

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Applied, thanks.