Subject: [PATCH] mm/debug_vm_pgtable: Avoid doing memory allocation with pgtable_t mapped.

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Sun, 13 Sep 2020 16:33:27 +0530

With highmem, pte_alloc_map() keep the level4 page table mapped using
kmap_atomic(). Avoid doing new memory allocation with page table
mapped like above.

[    9.409233] BUG: sleeping function called from invalid context at mm/page_alloc.c:4822
[    9.410557] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper
[    9.411932] no locks held by swapper/1.
[    9.412595] CPU: 0 PID: 1 Comm: swapper Not tainted 5.9.0-rc3-00323-gc50eb1ed654b5 #2
[    9.413824] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
[    9.415207] Call Trace:
[    9.415651]  ? ___might_sleep.cold+0xa7/0xcc
[    9.416367]  ? __alloc_pages_nodemask+0x14c/0x5b0
[    9.417055]  ? swap_migration_tests+0x50/0x293
[    9.417704]  ? debug_vm_pgtable+0x4bc/0x708
[    9.418287]  ? swap_migration_tests+0x293/0x293
[    9.418911]  ? do_one_initcall+0x82/0x3cb
[    9.419465]  ? parse_args+0x1bd/0x280
[    9.419983]  ? rcu_read_lock_sched_held+0x36/0x60
[    9.420673]  ? trace_initcall_level+0x1f/0xf3
[    9.421279]  ? trace_initcall_level+0xbd/0xf3
[    9.421881]  ? do_basic_setup+0x9d/0xdd
[    9.422410]  ? do_basic_setup+0xc3/0xdd
[    9.422938]  ? kernel_init_freeable+0x72/0xa3
[    9.423539]  ? rest_init+0x134/0x134
[    9.424055]  ? kernel_init+0x5/0x12c
[    9.424574]  ? ret_from_fork+0x19/0x30

Reported-by: kernel test robot <[email-masked]>
Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 mm/debug_vm_pgtable.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index d12bde82ae95..612c665a1136 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -994,7 +994,13 @@ static int __init debug_vm_pgtable(void)
 	p4dp = p4d_alloc(mm, pgdp, vaddr);
 	pudp = pud_alloc(mm, p4dp, vaddr);
 	pmdp = pmd_alloc(mm, pudp, vaddr);
-	ptep = pte_alloc_map(mm, pmdp, vaddr);
+	/*
+	 * Allocate pgtable_t
+	 */
+	if (pte_alloc(mm, pmdp)) {
+		pr_err("pgtable allocation failed\n");
+		return 1;
+	}
 
 	/*
 	 * Save all the page table page addresses as the page table
@@ -1048,8 +1054,7 @@ static int __init debug_vm_pgtable(void)
 	 * proper page table lock.
 	 */
 
-	ptl = pte_lockptr(mm, pmdp);
-	spin_lock(ptl);
+	ptep = pte_offset_map_lock(mm, pmdp, vaddr, &ptl);
 	pte_clear_tests(mm, ptep, pte_aligned, vaddr, prot);
 	pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
 	pte_unmap_unlock(ptep, ptl);
-- 
2.26.2