On Wed, 25 Nov 2020 at 06:16, Matthew Wilcox <willy@xxxxxxxxxxxxx> 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@xxxxxxxxxx> - Naresh
