On Wed, 25 Nov 2020 at 06:16, Matthew Wilcox willy@infradead.org wrote:
On Tue, Nov 24, 2020 at 06:16:28PM +0100, Sebastian Andrzej Siewior wrote:
On 2020-11-24 18:52:44 [+0530], Naresh Kamboju wrote:
While running LTP test case access01 the following kernel BUG noticed on linux next 20201124 tag kernel on i386.
git short log:
git log --oneline next-20201120..next-20201124 -- mm/highmem.c d9927d46febf Merge branch 'akpm-current/current' 72d22a0d0e86 mm: support THPs in zero_user_segments 2a656cad337e mm/highmem: Take kmap_high_get() properly into account
Please find these easy steps to reproduce the kernel build and boot.
This BUG_ON() is in zero_user_segments() which ash been added in commit 72d22a0d0e86 mm: support THPs in zero_user_segments
[ 50.852189] kernel BUG at mm/highmem.c:417!
I managed to capture one invocation with: zero_user_segments(0xd4367a90, 0x1000, 0x1000, 0x0, 0x50) page_compound() -> 1 page_size() -> 4096
Thanks for debugging this! I didn't realise start1 was allowed to be less than start2. Try this ... (systemd is sabotaging my efforts to test an i386 kernel)
This patch tested on i386, x86_64 and arm and the reported problem got fixed. Tested-by: Naresh Kamboju naresh.kamboju@linaro.org
- Naresh