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invalid opcode: 0000 EIP: zero_user_segments To: Matthew Wilcox Cc: Sebastian Andrzej Siewior , open list , Linux-Next Mailing List , linux-mm , lkft-triage@lists.linaro.org, LTP List , Andrew Morton , torvalds@linuxfoundation.org, Yang Shi , Jan Kara , Michal Hocko , Thomas Gleixner , Mel Gorman , Song Liu , Zi Yan , vtolkm@googlemail.com, Marek Szyprowski , Arnd Bergmann Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 25 Nov 2020 at 06:16, Matthew Wilcox 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