# git rev-parse -q --verify ba25b5ebe96a63940a12d9f8d73edebfcaad470c^{commit}
ba25b5ebe96a63940a12d9f8d73edebfcaad470c
already have revision, skipping fetch
# git checkout -q -f -B kisskb ba25b5ebe96a63940a12d9f8d73edebfcaad470c
# git clean -qxdf
# < git log -1
# commit ba25b5ebe96a63940a12d9f8d73edebfcaad470c
# Author: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
# Date:   Fri Mar 13 15:18:42 2020 +0530
# 
#     powerpc/hash64/devmap: Use H_PAGE_THP_HUGE when setting up huge devmap PTE entries
#     
#     H_PAGE_THP_HUGE is used to differentiate between a THP hugepage and
#     hugetlb hugepage entries. The difference is WRT how we handle hash
#     fault on these address. THP address enables MPSS in segments. We want
#     to manage devmap hugepage entries similar to THP pt entries. Hence use
#     H_PAGE_THP_HUGE for devmap huge PTE entries.
#     
#     With current code while handling hash PTE fault, we do set is_thp =
#     true when finding devmap PTE huge PTE entries.
#     
#     Current code also does the below sequence we setting up huge devmap
#     entries.
#     
#             entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
#             if (pfn_t_devmap(pfn))
#                     entry = pmd_mkdevmap(entry);
#     
#     In that case we would find both H_PAGE_THP_HUGE and PAGE_DEVMAP set
#     for huge devmap PTE entries. This results in false positive error like
#     below.
#     
#       kernel BUG at /home/kvaneesh/src/linux/mm/memory.c:4321!
#       Oops: Exception in kernel mode, sig: 5 [#1]
#       LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
#       Modules linked in:
#       CPU: 56 PID: 67996 Comm: t_mmap_dio Not tainted 5.6.0-rc4-59640-g371c804dedbc #128
#       ....
#       NIP [c00000000044c9e4] __follow_pte_pmd+0x264/0x900
#       LR [c0000000005d45f8] dax_writeback_one+0x1a8/0x740
#       Call Trace:
#         str_spec.74809+0x22ffb4/0x2d116c (unreliable)
#         dax_writeback_one+0x1a8/0x740
#         dax_writeback_mapping_range+0x26c/0x700
#         ext4_dax_writepages+0x150/0x5a0
#         do_writepages+0x68/0x180
#         __filemap_fdatawrite_range+0x138/0x180
#         file_write_and_wait_range+0xa4/0x110
#         ext4_sync_file+0x370/0x6e0
#         vfs_fsync_range+0x70/0xf0
#         sys_msync+0x220/0x2e0
#         system_call+0x5c/0x68
#     
#     This is because our pmd_trans_huge check doesn't exclude _PAGE_DEVMAP.
#     
#     To make this all consistent, update pmd_mkdevmap to set
#     H_PAGE_THP_HUGE and pmd_trans_huge check now excludes _PAGE_DEVMAP
#     correctly.
#     
#     Fixes: ebd31197931d ("powerpc/mm: Add devmap support for ppc64")
#     Cc: stable@vger.kernel.org # v4.13+
#     Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20200313094842.351830-1-aneesh.kumar@linux.ibm.com
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 ba25b5ebe96a63940a12d9f8d73edebfcaad470c
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  chrp32_defconfig
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-next_chrp32_defconfig_powerpc-gcc5
# Build took: 0:00:50.590184