[PATCH 4.19] x86/mm: add cond_resched() in _set_memory_array() and set_memory_array_wb()

[Yang Wei <albin.yangwei@xxxxxxxxxxxxxxx>]

From: Yang Wei <yang.wei@xxxxxxxxxxxxxxxxx>

We found _set_memory_array() and set_memory_array_wb() takes more than
500ms in kernel space in the following scenario.
So use this patch to trigger schedule for each page, to avoid other
threads getting stuck.

    0xffffffff810a34d2 find_next_iomem_res  ([kernel.kallsyms])
    0xffffffff810a3d40 walk_system_ram_range  ([kernel.kallsyms])
    0xffffffff810772ca pat_pagerange_is_ram  ([kernel.kallsyms])
    0xffffffff8107796f reserve_memtype  ([kernel.kallsyms])
    0xffffffff81075e98 _set_memory_array  ([kernel.kallsyms])
    0xffffffffc0ef6083 nv_alloc_system_pages  [nvidia] ([kernel.kallsyms])

    0xffffffff810a34d2 find_next_iomem_res  ([kernel.kallsyms])
    0xffffffff810a3d40 walk_system_ram_range  ([kernel.kallsyms])
    0xffffffff810772ca pat_pagerange_is_ram  ([kernel.kallsyms])
    0xffffffff8107745a free_memtype.part.7  ([kernel.kallsyms])
    0xffffffff8107606e set_memory_array_wb  ([kernel.kallsyms])
    0xffffffffc0ef6291 nv_free_system_pages  [nvidia]([kernel.kallsyms])

Signed-off-by: Yang Wei <yang.wei@xxxxxxxxxxxxxxxxx>
Tested-by: Yang Wei <yang.wei@xxxxxxxxxxxxxxxxx>
---
 arch/x86/mm/pageattr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 101f3ad..f7c67b8 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1625,6 +1625,7 @@ static int _set_memory_array(unsigned long *addr, int addrinarray,
 					new_type, NULL);
 		if (ret)
 			goto out_free;
+		cond_resched();
 	}
 
 	/* If WC, set to UC- first and then WC */
@@ -1989,6 +1990,7 @@ int set_pages_array_wb(struct page **pages, int addrinarray)
 		start = page_to_pfn(pages[i]) << PAGE_SHIFT;
 		end = start + PAGE_SIZE;
 		free_memtype(start, end);
+		cond_resched();
 	}
 
 	return 0;
-- 
1.8.3.1