Re: [PATCH v11 0/6] Use pageblock_order for cma and alloc_contig_range alignment.
From: Qian Cai
Date: Tue Apr 26 2022 - 16:19:12 EST
On Mon, Apr 25, 2022 at 10:31:12AM -0400, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
>
> Hi David,
>
> This patchset tries to remove the MAX_ORDER-1 alignment requirement for CMA
> and alloc_contig_range(). It prepares for my upcoming changes to make
> MAX_ORDER adjustable at boot time[1]. It is on top of mmotm-2022-04-20-17-12.
>
> Changelog
> ===
> V11
> ---
> 1. Moved start_isolate_page_range()/undo_isolate_page_range() alignment
> change to a separate patch after the unmovable page check change and
> alloc_contig_range() change to avoid some unwanted memory
> hotplug/hotremove failures.
> 2. Cleaned up has_unmovable_pages() in Patch 2.
>
> V10
> ---
> 1. Reverted back to the original outer_start, outer_end range for
> test_pages_isolated() and isolate_freepages_range() in Patch 3,
> otherwise isolation will fail if start in alloc_contig_range() is in
> the middle of a free page.
>
> V9
> ---
> 1. Limited has_unmovable_pages() check within a pageblock.
> 2. Added a check to ensure page isolation is done within a single zone
> in isolate_single_pageblock().
> 3. Fixed an off-by-one bug in isolate_single_pageblock().
> 4. Fixed a NULL-deferencing bug when the pages before to-be-isolated pageblock
> is not online in isolate_single_pageblock().
>
> V8
> ---
> 1. Cleaned up has_unmovable_pages() to remove page argument.
>
> V7
> ---
> 1. Added page validity check in isolate_single_pageblock() to avoid out
> of zone pages.
> 2. Fixed a bug in split_free_page() to split and free pages in correct
> page order.
>
> V6
> ---
> 1. Resolved compilation error/warning reported by kernel test robot.
> 2. Tried to solve the coding concerns from Christophe Leroy.
> 3. Shortened lengthy lines (pointed out by Christoph Hellwig).
>
> V5
> ---
> 1. Moved isolation address alignment handling in start_isolate_page_range().
> 2. Rewrote and simplified how alloc_contig_range() works at pageblock
> granularity (Patch 3). Only two pageblock migratetypes need to be saved and
> restored. start_isolate_page_range() might need to migrate pages in this
> version, but it prevents the caller from worrying about
> max(MAX_ORDER_NR_PAEGS, pageblock_nr_pages) alignment after the page range
> is isolated.
>
> V4
> ---
> 1. Dropped two irrelevant patches on non-lru compound page handling, as
> it is not supported upstream.
> 2. Renamed migratetype_has_fallback() to migratetype_is_mergeable().
> 3. Always check whether two pageblocks can be merged in
> __free_one_page() when order is >= pageblock_order, as the case (not
> mergeable pageblocks are isolated, CMA, and HIGHATOMIC) becomes more common.
> 3. Moving has_unmovable_pages() is now a separate patch.
> 4. Removed MAX_ORDER-1 alignment requirement in the comment in virtio_mem code.
>
> Description
> ===
>
> The MAX_ORDER - 1 alignment requirement comes from that alloc_contig_range()
> isolates pageblocks to remove free memory from buddy allocator but isolating
> only a subset of pageblocks within a page spanning across multiple pageblocks
> causes free page accounting issues. Isolated page might not be put into the
> right free list, since the code assumes the migratetype of the first pageblock
> as the whole free page migratetype. This is based on the discussion at [2].
>
> To remove the requirement, this patchset:
> 1. isolates pages at pageblock granularity instead of
> max(MAX_ORDER_NR_PAEGS, pageblock_nr_pages);
> 2. splits free pages across the specified range or migrates in-use pages
> across the specified range then splits the freed page to avoid free page
> accounting issues (it happens when multiple pageblocks within a single page
> have different migratetypes);
> 3. only checks unmovable pages within the range instead of MAX_ORDER - 1 aligned
> range during isolation to avoid alloc_contig_range() failure when pageblocks
> within a MAX_ORDER - 1 aligned range are allocated separately.
> 4. returns pages not in the range as it did before.
>
> One optimization might come later:
> 1. make MIGRATE_ISOLATE a separate bit to be able to restore the original
> migratetypes when isolation fails in the middle of the range.
>
> Feel free to give comments and suggestions. Thanks.
>
> [1] https://lore.kernel.org/linux-mm/20210805190253.2795604-1-zi.yan@xxxxxxxx/
> [2] https://lore.kernel.org/linux-mm/d19fb078-cb9b-f60f-e310-fdeea1b947d2@xxxxxxxxxx/
>
> Zi Yan (6):
> mm: page_isolation: move has_unmovable_pages() to mm/page_isolation.c
> mm: page_isolation: check specified range for unmovable pages
> mm: make alloc_contig_range work at pageblock granularity
> mm: page_isolation: enable arbitrary range page isolation.
> mm: cma: use pageblock_order as the single alignment
> drivers: virtio_mem: use pageblock size as the minimum virtio_mem
> size.
>
> drivers/virtio/virtio_mem.c | 6 +-
> include/linux/cma.h | 4 +-
> include/linux/mmzone.h | 5 +-
> include/linux/page-isolation.h | 6 +-
> mm/internal.h | 6 +
> mm/memory_hotplug.c | 3 +-
> mm/page_alloc.c | 191 +++++-------------
> mm/page_isolation.c | 345 +++++++++++++++++++++++++++++++--
> 8 files changed, 392 insertions(+), 174 deletions(-)
Reverting this series fixed a deadlock during memory offline/online
tests and then a crash.
INFO: task kmemleak:1027 blocked for more than 120 seconds.
Not tainted 5.18.0-rc4-next-20220426-dirty #27
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kmemleak state:D stack:27744 pid: 1027 ppid: 2 flags:0x00000008
Call trace:
__switch_to
__schedule
schedule
percpu_rwsem_wait
__percpu_down_read
percpu_down_read.constprop.0
get_online_mems
kmemleak_scan
kmemleak_scan_thread
kthread
ret_from_fork
Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/11:
#0: ffffc1e2cefc17f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp
1 lock held by rcu_tasks_rude_/12:
#0: ffffc1e2cefc1a90 (rcu_tasks_rude.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp
1 lock held by rcu_tasks_trace/13:
#0: ffffc1e2cefc1db0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp
1 lock held by khungtaskd/824:
#0: ffffc1e2cefc2820 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks
2 locks held by kmemleak/1027:
#0: ffffc1e2cf1aa628 (scan_mutex){+.+.}-{3:3}, at: kmemleak_scan_thread
#1: ffffc1e2cf14e690 (mem_hotplug_lock){++++}-{0:0}, at: get_online_mems
2 locks held by cppc_fie/1805:
1 lock held by in:imklog/2822:
8 locks held by tee/3334:
#0: ffff0816d65c9438 (sb_writers#6){.+.+}-{0:0}, at: vfs_write
#1: ffff40025438be88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter
#2: ffff4000c8261eb0 (kn->active#298){.+.+}-{0:0}, at: kernfs_fop_write_iter
#3: ffffc1e2d0013f68 (device_hotplug_lock){+.+.}-{3:3}, at: online_store
#4: ffff0800cd8bb998 (&dev->mutex){....}-{3:3}, at: device_offline
#5: ffffc1e2ceed3750 (cpu_hotplug_lock){++++}-{0:0}, at: cpus_read_lock
#6: ffffc1e2cf14e690 (mem_hotplug_lock){++++}-{0:0}, at: offline_pages
#7: ffffc1e2cf13bf68 (pcp_batch_high_lock){+.+.}-{3:3}, at: zone_pcp_disable
__zone_set_pageset_high_and_batch at mm/page_alloc.c:7005
(inlined by) zone_pcp_disable at mm/page_alloc.c:9286
Later, running some kernel compilation workloads could trigger a crash.
Unable to handle kernel paging request at virtual address fffffbfffe000030
KASAN: maybe wild-memory-access in range [0x0003dffff0000180-0x0003dffff0000187]
Mem abort info:
ESR = 0x96000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000817545fd000
[fffffbfffe000030] pgd=00000817581e9003, p4d=00000817581e9003, pud=00000817581ea003, pmd=0000000000000000
Internal error: Oops: 96000006 [#1] PREEMPT SMP
Modules linked in: bridge stp llc cdc_ether usbnet ipmi_devintf ipmi_msghandler cppc_cpufreq fuse ip_tables x_tables ipv6 btrfs blake2b_generic libcrc32c xor xor_neon raid6_pq zstd_compress dm_mod nouveau drm_ttm_helper ttm crct10dif_ce mlx5_core drm_display_helper drm_kms_helper nvme mpt3sas xhci_pci nvme_core drm raid_class xhci_pci_renesas
CPU: 147 PID: 3334 Comm: tee Not tainted 5.18.0-rc4-next-20220426-dirty #27
pstate: 10400009 (nzcV daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : isolate_single_pageblock
lr : isolate_single_pageblock
sp : ffff80003e767500
x29: ffff80003e767500 x28: 0000000000000000 x27: ffff783c59963b1f
x26: dfff800000000000 x25: ffffc1e2ccb1d000 x24: ffffc1e2ccb1d8f8
x23: 00000000803bfe00 x22: ffffc1e2cee39098 x21: 0000000000000020
x20: 00000000803c0000 x19: fffffbfffe000000 x18: ffffc1e2cee37d1c
x17: 0000000000000000 x16: 1fffe8004a86f14c x15: 1fffe806c89e154a
x14: 1fffe8004a86f11c x13: 0000000000000004 x12: ffff783c5c455e6d
x11: 1ffff83c5c455e6c x10: ffff783c5c455e6c x9 : dfff800000000000
x8 : ffffc1e2e22af363 x7 : 0000000000000001 x6 : 0000000000000003
x5 : ffffc1e2e22af360 x4 : ffff783c5c455e6c x3 : ffff700007cece90
x2 : 0000000000000003 x1 : 0000000000000000 x0 : fffffbfffe000030
Call trace:
Call trace:
isolate_single_pageblock
PageBuddy at ./include/linux/page-flags.h:969 (discriminator 3)
(inlined by) isolate_single_pageblock at mm/page_isolation.c:414 (discriminator 3)
start_isolate_page_range
offline_pages
memory_subsys_offline
device_offline
online_store
dev_attr_store
sysfs_kf_write
kernfs_fop_write_iter
new_sync_write
vfs_write
ksys_write
__arm64_sys_write
invoke_syscall
el0_svc_common.constprop.0
do_el0_svc
el0_svc
el0t_64_sync_handler
el0t_64_sync
Code: 38fa6821 7100003f 7a411041 54000dca (b9403260)
---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
Kernel Offset: 0x41e2c0720000 from 0xffff800008000000
PHYS_OFFSET: 0x80000000
CPU features: 0x000,0021700d,19801c82
Memory Limit: none