[PATCH v2 17/20] mm: free_area_init: allow defining max_zone_pfn in descending order

[Guenter Roeck]

On Sun, May 03, 2020 at 10:41:38AM -0700, Guenter Roeck wrote:
> Hi,
> 
> On Wed, Apr 29, 2020 at 03:11:23PM +0300, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt at linux.ibm.com>
> > 
> > Some architectures (e.g. ARC) have the ZONE_HIGHMEM zone below the
> > ZONE_NORMAL. Allowing free_area_init() parse max_zone_pfn array even it is
> > sorted in descending order allows using free_area_init() on such
> > architectures.
> > 
> > Add top -> down traversal of max_zone_pfn array in free_area_init() and use
> > the latter in ARC node/zone initialization.
> > 
> > Signed-off-by: Mike Rapoport <rppt at linux.ibm.com>
> 
> This patch causes my microblazeel qemu boot test in linux-next to fail.
> Reverting it fixes the problem.
> 
The same problem is seen with s390 emulations.

Guenter

> qemu command line:
> 
> qemu-system-microblazeel -M petalogix-ml605 -m 256 \
> 	-kernel arch/microblaze/boot/linux.bin -no-reboot \
> 	-initrd rootfs.cpio \
> 	-append 'panic=-1 slub_debug=FZPUA rdinit=/sbin/init console=ttyS0,115200' \
> 	-monitor none -serial stdio -nographic
> 
> initrd:
> 	https://github.com/groeck/linux-build-test/blob/master/rootfs/microblazeel/rootfs.cpio.gz
> configuration:
> 	https://github.com/groeck/linux-build-test/blob/master/rootfs/microblazeel/qemu_microblazeel_ml605_defconfig
> 
> Bisect log is below.
> 
> Guenter
> 
> ---
> # bad: [fb9d670f57e3f6478602328bbbf71138be06ca4f] Add linux-next specific files for 20200501
> # good: [6a8b55ed4056ea5559ebe4f6a4b247f627870d4c] Linux 5.7-rc3
> git bisect start 'HEAD' 'v5.7-rc3'
> # good: [068b80b68a670f0b17288c8a3d1ee751f35162ab] Merge remote-tracking branch 'drm/drm-next'
> git bisect good 068b80b68a670f0b17288c8a3d1ee751f35162ab
> # good: [46c70fc6a3ac35cd72ddad248dcbe4eee716d2a5] Merge remote-tracking branch 'drivers-x86/for-next'
> git bisect good 46c70fc6a3ac35cd72ddad248dcbe4eee716d2a5
> # good: [f39c4ad479a2f005f972a2b941b40efa6b9c9349] Merge remote-tracking branch 'rpmsg/for-next'
> git bisect good f39c4ad479a2f005f972a2b941b40efa6b9c9349
> # bad: [165d3ee0162fe28efc2c8180176633e33515df15] ipc-convert-ipcs_idr-to-xarray-update
> git bisect bad 165d3ee0162fe28efc2c8180176633e33515df15
> # good: [001f1d211ed2ed0f005838dc4390993930bbbd69] mm: remove early_pfn_in_nid() and CONFIG_NODES_SPAN_OTHER_NODES
> git bisect good 001f1d211ed2ed0f005838dc4390993930bbbd69
> # bad: [aaad7401bd32f10c1d591dd886b3a9b9595c6d77] mm/vmsan: fix some typos in comment
> git bisect bad aaad7401bd32f10c1d591dd886b3a9b9595c6d77
> # bad: [09f9d0ab1fbed85623b283995aa7a7d78daa1611] khugepaged: allow to collapse PTE-mapped compound pages
> git bisect bad 09f9d0ab1fbed85623b283995aa7a7d78daa1611
> # bad: [c942fc8a3e5088407bc32d94f554bab205175f8a] mm/vmstat.c: do not show lowmem reserve protection information of empty zone
> git bisect bad c942fc8a3e5088407bc32d94f554bab205175f8a
> # bad: [b29358d269ace3826d8521bea842fc2984cfc11b] mm/page_alloc.c: rename free_pages_check() to check_free_page()
> git bisect bad b29358d269ace3826d8521bea842fc2984cfc11b
> # bad: [be0fb591a1f1df20a00c8f023f9ca4891f177b0d] mm: simplify find_min_pfn_with_active_regions()
> git bisect bad be0fb591a1f1df20a00c8f023f9ca4891f177b0d
> # bad: [c17422a008d36dcf3e9f51469758c5762716cb0a] mm: rename free_area_init_node() to free_area_init_memoryless_node()
> git bisect bad c17422a008d36dcf3e9f51469758c5762716cb0a
> # bad: [51a2f644fd020d5f090044825c388444d11029d5] mm: free_area_init: allow defining max_zone_pfn in descending order
> git bisect bad 51a2f644fd020d5f090044825c388444d11029d5
> # first bad commit: [51a2f644fd020d5f090044825c388444d11029d5] mm: free_area_init: allow defining max_zone_pfn in descending order