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c12cd77cb0
linux-stable/mm
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Omar Sandoval c12cd77cb0 mm/vmalloc: fix spinning drain_vmap_work after reading from /proc/vmcore 
Commit 3ee48b6af4 ("mm, x86: Saving vmcore with non-lazy freeing of
vmas") introduced set_iounmap_nonlazy(), which sets vmap_lazy_nr to
lazy_max_pages() + 1, ensuring that any future vunmaps() immediately
purge the vmap areas instead of doing it lazily.

Commit 690467c81b ("mm/vmalloc: Move draining areas out of caller
context") moved the purging from the vunmap() caller to a worker thread.
Unfortunately, set_iounmap_nonlazy() can cause the worker thread to spin
(possibly forever).  For example, consider the following scenario:

 1. Thread reads from /proc/vmcore. This eventually calls
    __copy_oldmem_page() -> set_iounmap_nonlazy(), which sets
    vmap_lazy_nr to lazy_max_pages() + 1.

 2. Then it calls free_vmap_area_noflush() (via iounmap()), which adds 2
    pages (one page plus the guard page) to the purge list and
    vmap_lazy_nr. vmap_lazy_nr is now lazy_max_pages() + 3, so the
    drain_vmap_work is scheduled.

 3. Thread returns from the kernel and is scheduled out.

 4. Worker thread is scheduled in and calls drain_vmap_area_work(). It
    frees the 2 pages on the purge list. vmap_lazy_nr is now
    lazy_max_pages() + 1.

 5. This is still over the threshold, so it tries to purge areas again,
    but doesn't find anything.

 6. Repeat 5.

If the system is running with only one CPU (which is typicial for kdump)
and preemption is disabled, then this will never make forward progress:
there aren't any more pages to purge, so it hangs.  If there is more
than one CPU or preemption is enabled, then the worker thread will spin
forever in the background.  (Note that if there were already pages to be
purged at the time that set_iounmap_nonlazy() was called, this bug is
avoided.)

This can be reproduced with anything that reads from /proc/vmcore
multiple times.  E.g., vmcore-dmesg /proc/vmcore.

It turns out that improvements to vmap() over the years have obsoleted
the need for this "optimization".  I benchmarked `dd if=/proc/vmcore
of=/dev/null` with 4k and 1M read sizes on a system with a 32GB vmcore.
The test was run on 5.17, 5.18-rc1 with a fix that avoided the hang, and
5.18-rc1 with set_iounmap_nonlazy() removed entirely:

    |5.17  |5.18+fix|5.18+removal
  4k|40.86s|  40.09s|      26.73s
  1M|24.47s|  23.98s|      21.84s

The removal was the fastest (by a wide margin with 4k reads).  This
patch removes set_iounmap_nonlazy().

Link: https://lkml.kernel.org/r/52f819991051f9b865e9ce25605509bfdbacadcd.1649277321.git.osandov@fb.com
Fixes: 690467c81b  ("mm/vmalloc: Move draining areas out of caller context")
Signed-off-by: Omar Sandoval <osandov@fb.com>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2022-04-15 14:49:56 -07:00
..
damon mm/damon: prevent activated scheme from sleeping by deactivated schemes 2022-04-01 11:46:09 -07:00
kasan kasan: fix hw tags enablement when KUNIT tests are disabled 2022-04-15 14:49:55 -07:00
kfence mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
backing-dev.c remove congestion tracking framework 2022-03-22 15:57:01 -07:00
balloon_compaction.c mm/balloon_compaction: make balloon page compaction callbacks static 2022-03-28 16:52:57 -04:00
bootmem_info.c bootmem: Use page->index instead of page->freelist 2022-01-06 12:27:03 +01:00
cma_debug.c mm/cma: change cma mutex to irq safe spinlock 2021-05-05 11:27:21 -07:00
cma_sysfs.c mm: cma: support sysfs 2021-05-05 11:27:24 -07:00
cma.c mm/cma: provide option to opt out from exposing pages on activation failure 2022-03-22 15:57:09 -07:00
cma.h mm/cma: provide option to opt out from exposing pages on activation failure 2022-03-22 15:57:09 -07:00
compaction.c mm: compaction: fix compiler warning when CONFIG_COMPACTION=n 2022-04-15 14:49:55 -07:00
debug_page_ref.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
debug_vm_pgtable.c mm/debug_vm_pgtable: remove pte entry from the page table 2022-02-04 09:25:04 -08:00
debug.c mm: unexport page_init_poison 2022-03-24 19:06:45 -07:00
dmapool.c mm/dmapool.c: revert "make dma pool to use kmalloc_node" 2022-01-15 16:30:28 +02:00
early_ioremap.c mm/early_ioremap: declare early_memremap_pgprot_adjust() 2022-03-22 15:57:11 -07:00
fadvise.c remove inode_congested() 2022-03-22 15:57:01 -07:00
failslab.c mm/failslab.c: by default, do not fail allocations with direct reclaim only 2019-07-12 11:05:43 -07:00
filemap.c tmpfs: fix regressions from wider use of ZERO_PAGE 2022-04-15 14:49:54 -07:00
folio-compat.c mm/rmap: Convert rmap_walk() to take a folio 2022-03-21 13:01:35 -04:00
frontswap.c frontswap: remove support for multiple ops 2022-01-22 08:33:38 +02:00
gup_test.c selftests/vm: gup_test: test faulting in kernel, and verify pinnable pages 2021-05-05 11:27:26 -07:00
gup_test.h selftests/vm: gup_test: fix test flag 2021-05-05 11:27:26 -07:00
gup.c mm/munlock: add lru_add_drain() to fix memcg_stat_test 2022-04-01 11:46:09 -07:00
highmem.c highmem: fix checks in __kmap_local_sched_{in,out} 2022-04-08 14:20:36 -10:00
hmm.c mm/hmm.c: remove unneeded local variable ret 2022-03-22 15:57:12 -07:00
huge_memory.c mm/huge_memory: Avoid calling pmd_page() on a non-leaf PMD 2022-04-07 09:43:41 -04:00
hugetlb_cgroup.c hugetlb: add hugetlb.*.numa_stat file 2022-01-15 16:30:29 +02:00
hugetlb_vmemmap.c mm: hugetlb: replace hugetlb_free_vmemmap_enabled with a static_key 2022-03-22 15:57:08 -07:00
hugetlb_vmemmap.h mm: hugetlb: introduce nr_free_vmemmap_pages in the struct hstate 2021-06-30 20:47:25 -07:00
hugetlb.c hugetlb: do not demote poisoned hugetlb pages 2022-04-15 14:49:55 -07:00
hwpoison-inject.c mm/hwpoison: avoid the impact of hwpoison_filter() return value on mce handler 2022-03-22 15:57:07 -07:00
init-mm.c kernel/fork: Initialize mm's PASID 2022-02-14 19:51:47 +01:00
internal.h mm/munlock: protect the per-CPU pagevec by a local_lock_t 2022-04-01 11:46:09 -07:00
interval_tree.c mm/interval_tree: add comments to improve code readability 2021-04-30 11:20:38 -07:00
io-mapping.c mm: add a io_mapping_map_user helper 2021-04-30 11:20:39 -07:00
ioremap.c mm: move ioremap_page_range to vmalloc.c 2021-09-08 11:50:24 -07:00
Kconfig mm: generalize ARCH_HAS_FILTER_PGPROT 2022-03-24 19:06:51 -07:00
Kconfig.debug mm: page table check 2022-01-15 16:30:28 +02:00
khugepaged.c mm/khugepaged: remove reuse_swap_page() usage 2022-03-24 19:06:51 -07:00
kmemleak.c mm/kmemleak: reset tag when compare object pointer 2022-04-01 11:46:09 -07:00
ksm.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
list_lru.c mm/list_lru.c: revert "mm/list_lru: optimize memcg_reparent_list_lru_node()" 2022-04-08 14:20:36 -10:00
maccess.c asm-generic updates for 5.18 2022-03-23 18:03:08 -07:00
madvise.c Revert "mm: madvise: skip unmapped vma holes passed to process_madvise" 2022-04-01 11:46:09 -07:00
Makefile mm: move the migrate_vma_* device migration code into its own file 2022-03-03 12:47:33 -05:00
mapping_dirty_helpers.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
memblock.c memblock: test suite and a small cleanup 2022-03-27 13:36:06 -07:00
memcontrol.c ptrace: Cleanups for v5.18 2022-03-28 17:29:53 -07:00
memfd.c memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-05 11:08:32 -08:00
memory_hotplug.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
memory-failure.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
memory.c mm,hwpoison: unmap poisoned page before invalidation 2022-04-01 11:46:09 -07:00
mempolicy.c Merge branch 'akpm' (patches from Andrew) 2022-04-08 14:31:41 -10:00
mempool.c mm: remove spurious blkdev.h includes 2021-10-18 06:17:01 -06:00
memremap.c mm: delete __ClearPageWaiters() 2022-03-24 19:06:45 -07:00
memtest.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
migrate_device.c mm/migrate: Convert remove_migration_ptes() to folios 2022-03-21 13:01:35 -04:00
migrate.c mm: migrate: use thp_order instead of HPAGE_PMD_ORDER for new page allocation. 2022-04-08 14:20:36 -10:00
mincore.c inode: make init and permission helpers idmapped mount aware 2021-01-24 14:27:16 +01:00
mlock.c mm/munlock: protect the per-CPU pagevec by a local_lock_t 2022-04-01 11:46:09 -07:00
mm_init.c include/linux/page-flags-layout.h: cleanups 2021-04-30 11:20:42 -07:00
mmap_lock.c mm: mmap_lock: fix disabling preemption directly 2021-07-23 17:43:28 -07:00
mmap.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
mmu_gather.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
mmu_notifier.c mm/mmu_notifiers: ensure range_end() is paired with range_start() 2021-03-25 09:22:55 -07:00
mmzone.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
mprotect.c memory tiering: skip to scan fast memory 2022-03-22 15:57:09 -07:00
mremap.c mmmremap.c: avoid pointless invalidate_range_start/end on mremap(old_size=0) 2022-04-08 14:20:36 -10:00
msync.c mm/msync: exit early when the flags is an MS_ASYNC and start < vm_start 2021-04-30 11:20:37 -07:00
nommu.c Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
oom_kill.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
page_alloc.c mm, page_alloc: fix build_zonerefs_node() 2022-04-15 14:49:55 -07:00
page_counter.c mm/page_counter: remove an incorrect call to propagate_protected_usage() 2022-01-15 16:30:27 +02:00
page_ext.c mm: make some vars and functions static or __init 2022-01-15 16:30:31 +02:00
page_idle.c mm/rmap: Constify the rmap_walk_control argument 2022-03-21 13:01:35 -04:00
page_io.c mm: fix unexpected zeroed page mapping with zram swap 2022-04-15 14:49:55 -07:00
page_isolation.c Revert "mm/page_isolation: unset migratetype directly for non Buddy page" 2022-02-04 09:25:04 -08:00
page_owner.c mm/page_owner.c: record tgid 2022-03-24 19:06:44 -07:00
page_poison.c mm: page_poison: print page info when corruption is caught 2021-04-30 11:20:36 -07:00
page_reporting.c mm/page_reporting: allow driver to specify reporting order 2021-06-29 10:53:47 -07:00
page_reporting.h mm/page_reporting: export reporting order as module parameter 2021-06-29 10:53:47 -07:00
page_table_check.c mm/page_table_check.c: use strtobool for param parsing 2022-03-22 15:57:11 -07:00
page_vma_mapped.c mm/rmap: Fix handling of hugetlbfs pages in page_vma_mapped_walk 2022-04-07 10:11:20 -04:00
page-writeback.c mm: warn on deleting redirtied only if accounted 2022-03-24 19:06:51 -07:00
pagewalk.c mm: pagewalk: fix walk for hugepage tables 2021-06-29 10:53:49 -07:00
percpu-internal.h mm: memcg/percpu: account extra objcg space to memory cgroups 2022-01-15 16:30:31 +02:00
percpu-km.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu-stats.c mm: use vmalloc_array and vcalloc for array allocations 2022-03-08 09:30:46 -05:00
percpu-vm.c percpu: flush tlb in pcpu_reclaim_populated() 2021-07-04 18:30:17 +00:00
percpu.c bitmap patches for 5.17-rc1 2022-01-23 06:20:44 +02:00
pgalloc-track.h mm: fix typos in comments 2021-05-07 00:26:35 -07:00
pgtable-generic.c mm: move tlb_flush_pending inline helpers to mm_inline.h 2022-01-15 16:30:27 +02:00
process_vm_access.c mm/process_vm_access.c: remove duplicate include 2021-05-05 11:27:27 -07:00
ptdump.c mm: sparsemem: use page table lock to protect kernel pmd operations 2022-03-22 15:57:08 -07:00
readahead.c readahead: Update comments 2022-04-01 14:40:42 -04:00
rmap.c mm/munlock: protect the per-CPU pagevec by a local_lock_t 2022-04-01 11:46:09 -07:00
rodata_test.c mm/rodata_test.c: fix missing function declaration 2020-08-21 09:52:53 -07:00
secretmem.c mm/secretmem: fix panic when growing a memfd_secret 2022-04-15 14:49:54 -07:00
shmem.c tmpfs: fix regressions from wider use of ZERO_PAGE 2022-04-15 14:49:54 -07:00
shuffle.c mm: eliminate "expecting prototype" kernel-doc warnings 2021-04-16 16:10:36 -07:00
shuffle.h mm/shuffle: fix section mismatch warning 2021-05-22 15:09:07 -10:00
slab_common.c mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
slab.c mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
slab.h mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
slob.c mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
slub.c mm, kfence: support kmem_dump_obj() for KFENCE objects 2022-04-15 14:49:55 -07:00
sparse-vmemmap.c mm: sparsemem: move vmemmap related to HugeTLB to CONFIG_HUGETLB_PAGE_FREE_VMEMMAP 2022-03-22 15:57:08 -07:00
sparse.c mm/sparse: make mminit_validate_memmodel_limits() static 2022-03-22 15:57:05 -07:00
swap_cgroup.c mm: use vmalloc_array and vcalloc for array allocations 2022-03-08 09:30:46 -05:00
swap_slots.c treewide: Add missing includes masked by cgroup -> bpf dependency 2021-12-03 10:58:13 -08:00
swap_state.c Filesystem folio changes for 5.18 2022-03-22 18:26:56 -07:00
swap.c mm/munlock: protect the per-CPU pagevec by a local_lock_t 2022-04-01 11:46:09 -07:00
swapfile.c mm/swapfile: remove stale reuse_swap_page() 2022-03-24 19:06:51 -07:00
truncate.c Filesystem folio changes for 5.18 2022-03-22 18:26:56 -07:00
usercopy.c Merge branch 'akpm' (patches from Andrew) 2022-03-22 16:11:53 -07:00
userfaultfd.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
util.c ARM: 2022-03-24 11:58:57 -07:00
vmacache.c kernel: better document the use_mm/unuse_mm API contract 2020-06-10 19:14:18 -07:00
vmalloc.c mm/vmalloc: fix spinning drain_vmap_work after reading from /proc/vmcore 2022-04-15 14:49:56 -07:00
vmpressure.c mm/vmpressure: fix data-race with memcg->socket_pressure 2021-11-06 13:30:40 -07:00
vmscan.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
vmstat.c mm: only re-generate demotion targets when a numa node changes its N_CPU state 2022-03-22 15:57:11 -07:00
workingset.c Folio changes for 5.18 2022-03-22 17:03:12 -07:00
z3fold.c mm/z3fold: add kerneldoc fields for z3fold_pool 2021-07-01 11:06:03 -07:00
zbud.c mm/zbud: add kerneldoc fields for zbud_pool 2021-07-01 11:06:03 -07:00
zpool.c zpool: remove the list of pools_head 2022-01-15 16:30:31 +02:00
zsmalloc.c zsmalloc: replace get_cpu_var with local_lock 2022-01-22 08:33:37 +02:00
zswap.c mm/zswap.c: allow handling just same-value filled pages 2022-03-22 15:57:11 -07:00