[PATCH v4 13/13] mm/debug_vm_pgtable: Avoid none pte in pte_clear_test

[Guenter Roeck]

On Wed, Sep 02, 2020 at 05:12:22PM +0530, Aneesh Kumar K.V wrote:
> pte_clear_tests operate on an existing pte entry. Make sure that
> is not a none pte entry.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>

This patch causes all riscv64 images to crash. Reverting it
as well as the follow-up patch fixes the problem, but there are
still several warning messages starting with
	BUG kmem_cache (Not tainted): Freechain corrupt
I did not try to track down this other problem.

A detailed crash log is at
	https://kerneltests.org/builders/qemu-riscv64-next/builds/523/steps/qemubuildcommand/logs/stdio

Bisect log is attached.

Guenter

---
# bad: [d67bc7812221606e1886620a357b13f906814af7] Add linux-next specific files for 20201009
# good: [549738f15da0e5a00275977623be199fbbf7df50] Linux 5.9-rc8
git bisect start 'HEAD' 'v5.9-rc8'
# good: [b71be15b496cc71a3434a198fc1a1b9e08af6c57] Merge remote-tracking branch 'bpf-next/master' into master
git bisect good b71be15b496cc71a3434a198fc1a1b9e08af6c57
# good: [3542e5a87341bdca83e3d7f061b0f4e0f4c23f73] Merge remote-tracking branch 'spi/for-next' into master
git bisect good 3542e5a87341bdca83e3d7f061b0f4e0f4c23f73
# good: [65f9c957115c749ba79fb469083caf14101a93bb] Merge remote-tracking branch 'char-misc/char-misc-next' into master
git bisect good 65f9c957115c749ba79fb469083caf14101a93bb
# good: [aadfe5ecb55641d5994a5f3b27f074beead8f49b] Merge remote-tracking branch 'scsi-mkp/for-next' into master
git bisect good aadfe5ecb55641d5994a5f3b27f074beead8f49b
# good: [060196553d119d5c252f09ed5b0316929cc25983] Merge remote-tracking branch 'memblock/for-next' into master
git bisect good 060196553d119d5c252f09ed5b0316929cc25983
# bad: [d2340d89ffa6d2643f0689600dbf0969d86fdd3c] x86/setup: simplify initrd relocation and reservation
git bisect bad d2340d89ffa6d2643f0689600dbf0969d86fdd3c
# bad: [4b23734f5ba1a0487b2b569a9e64e4e5360009c1] mm/swapfile.c: remove unnecessary goto out in _swap_info_get()
git bisect bad 4b23734f5ba1a0487b2b569a9e64e4e5360009c1
# good: [b30f5277e97be65a99ca5af3d4337cb9acbf8fa7] device-dax: introduce 'struct dev_dax' typed-driver operations
git bisect good b30f5277e97be65a99ca5af3d4337cb9acbf8fa7
# good: [8c2075296dbbbce685fa14bbf46d29fba54f8a62] mm/debug_vm_pgtable: drop hugetlb_advanced_tests()
git bisect good 8c2075296dbbbce685fa14bbf46d29fba54f8a62
# bad: [52ce97889b3c85826995d22a690cd1430c14f316] mm/filemap: fix filemap_map_pages for THP
git bisect bad 52ce97889b3c85826995d22a690cd1430c14f316
# bad: [1ddc0b707be99faece6cdd77f34544f408c6617d] proc: optimise smaps for shmem entries
git bisect bad 1ddc0b707be99faece6cdd77f34544f408c6617d
# bad: [5d685be3785638202430b6baa2ecde482b52c41e] mm: factor find_get_incore_page out of mincore_page
git bisect bad 5d685be3785638202430b6baa2ecde482b52c41e
# bad: [0797f84d689b9f1e7256d954280b28bfeaf5b1fc] mm/debug_vm_pgtable: avoid doing memory allocation with pgtable_t mapped.
git bisect bad 0797f84d689b9f1e7256d954280b28bfeaf5b1fc
# bad: [4f9a78e6bcd60a25b187adc1526ab3815fc40dae] mm/debug_vm_pgtable: avoid none pte in pte_clear_test
git bisect bad 4f9a78e6bcd60a25b187adc1526ab3815fc40dae
# first bad commit: [4f9a78e6bcd60a25b187adc1526ab3815fc40dae] mm/debug_vm_pgtable: avoid none pte in pte_clear_test