So, since there haven't been any new comments for over a week, I'll be collecting the patchset v2 tomorrow. Regards, -Sergey On Thu, Jan 18, 2018 at 01:22:58AM +0300, Serge Semin <fancer.lancer@xxxxxxxxx> wrote: > Even though it's common to see the architecture code using both > bootmem and memblock early memory allocators, it's not good for > multiple reasons. First of all, it's redundant to have two > early memory allocator while one would be more than enough from > functionality and stability points of view. Secondly, some new > features introduced in the kernel utilize the methods of the most > modern allocator ignoring the older one. It means the architecture > code must keep the both subsystems up synchronized with information > about memory regions and reservations, which leads to the code > complexity increase, that obviously increases bugs probability. > Finally it's better to keep all the architectures code unified for > better readability and code simplification. All these reasons lead > to one conclusion - arch code should use just one memory allocator, > which is supposed to be memblock as the most modern and already > utilized by the most of the kernel platforms. This patchset is > mostly about it. > > One more reason why the MIPS arch code should finally move to > memblock is a BUG somewhere in the initialization process, when > CMA is activated: > > [ 0.248762] BUG: Bad page state in process swapper/0 pfn:01f93 > [ 0.255415] page:8205b0ac count:0 mapcount:-127 mapping: (null) index:0x1 > [ 0.263172] flags: 0x40000000() > [ 0.266723] page dumped because: nonzero mapcount > [ 0.272049] Modules linked in: > [ 0.275511] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.4.88-module #5 > [ 0.282900] Stack : 00000000 00000000 80b6dd6a 0000003a 00000000 00000000 80930000 8092bff4 > 86073a14 80ac88c7 809f21ac 00000000 00000001 80b6998c 00000400 00000000 > 80a00000 801822e8 80b6dd68 00000000 00000002 00000000 809f8024 86077ccc > 80b80000 801e9328 809fcbc0 00000000 00000400 00010000 86077ccc 86073a14 > 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 > ... > [ 0.323148] Call Trace: > [ 0.325935] [<8010e7c4>] show_stack+0x8c/0xa8 > [ 0.330859] [<80404814>] dump_stack+0xd4/0x110 > [ 0.335879] [<801f0bc0>] bad_page+0xfc/0x14c > [ 0.340710] [<801f0e04>] free_pages_prepare+0x1f4/0x330 > [ 0.346632] [<801f36c4>] __free_pages_ok+0x2c/0x104 > [ 0.352154] [<80b23a40>] init_cma_reserved_pageblock+0x5c/0x74 > [ 0.358761] [<80b29390>] cma_init_reserved_areas+0x1b4/0x240 > [ 0.365170] [<8010058c>] do_one_initcall+0xe8/0x27c > [ 0.370697] [<80b14e60>] kernel_init_freeable+0x200/0x2c4 > [ 0.376828] [<808faca4>] kernel_init+0x14/0x104 > [ 0.381939] [<80107598>] ret_from_kernel_thread+0x14/0x1c > > The bugus pfn seems to be the one allocated for bootmem allocator > pages and hasn't been freed before letting the CMA working with its > areas. Anyway the bug is solved by this patchset. > > Another reason why this patchset is useful is that it fixes the fdt > reserved-memory nodes functionality for MIPS. Really it's bug to have > the fdt reserved nodes scanning before the memblock is > fully initialized (calling early_init_fdt_scan_reserved_mem before > bootmem_init is called). Additionally no-map flag of the > reserved-memory node hasn't been taking into account. This patchset > fixes all of these. > > As you probably remember I already did another attempt to merge a > similar functionality into the kernel. This time the patchset got > to be less complex (14 patches vs 21 last time) and fixes the > platform code like SGI IP27 and Loongson3, which due to being > NUMA introduce its own memory initialization process. Although > I have much doubt in SGI IP27 code operability in the first place, > since it got prom_meminit() method of early memory initialization, > which hasn't been called at any other place in the kernel. It must > have been left there unrenamed after arch/mips/mips-boards/generic > code had been discarded. > > Here are the list of folks, who agreed to perform some tests of > the patchset: > Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx> - Octeon2 > Matt Redfearn <matt.redfearn@xxxxxxxx> - Loongson3, etc > Joshua Kinard <kumba@xxxxxxxxxx> - IP27 > Marcin Nowakowski <marcin.nowakowski@xxxxxxxx> > Thanks to you all in regards and for everybody, who will be involved > in reviewing and testing. > > The patchset is applied on top of kernel 4.15-rc8 and can be found > submitted at my repo: > https://github.com/fancer/Linux-kernel-MIPS-memblock-project > > Signed-off-by: Serge Semin <fancer.lancer@xxxxxxxxx> > > Serge Semin (14): > MIPS: memblock: Add RESERVED_NOMAP memory flag > MIPS: memblock: Surely map BSS kernel memory section > MIPS: memblock: Reserve initrd memory in memblock > MIPS: memblock: Discard bootmem initialization > MIPS: memblock: Add reserved memory regions to memblock > MIPS: memblock: Reserve kdump/crash regions in memblock > MIPS: memblock: Mark present sparsemem sections > MIPS: memblock: Simplify DMA contiguous reservation > MIPS: memblock: Allow memblock regions resize > MIPS: memblock: Perform early low memory test > MIPS: memblock: Print out kernel virtual mem layout > MIPS: memblock: Discard bootmem from Loongson3 code > MIPS: memblock: Discard bootmem from SGI IP27 code > MIPS: memblock: Deactivate bootmem allocator > > arch/mips/Kconfig | 2 +- > arch/mips/include/asm/bootinfo.h | 1 + > arch/mips/kernel/prom.c | 8 +- > arch/mips/kernel/setup.c | 218 +++++++++------------ > arch/mips/loongson64/loongson-3/numa.c | 16 +- > arch/mips/mm/init.c | 47 +++++ > arch/mips/sgi-ip27/ip27-memory.c | 9 +- > 7 files changed, 153 insertions(+), 148 deletions(-) > > -- > 2.12.0 >
