+ mm-migration-reduce-the-rcu-lock-duration.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/migration: reduce the rcu lock duration
has been added to the -mm tree.  Its filename is
     mm-migration-reduce-the-rcu-lock-duration.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-migration-reduce-the-rcu-lock-duration.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-migration-reduce-the-rcu-lock-duration.patch

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------------------------------------------------------
From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/migration: reduce the rcu lock duration

Patch series "A few cleanup and fixup patches for migration", v2.

This series contains a few patches to remove unneeded lock page and
PageMovable check, reduce the rcu lock duration.  Also we fix potential
pte_unmap on an not mapped pte.  More details can be found in the
respective changelogs.


This patch (of 4):

rcu_read_lock is required by grabbing the task refcount but it's not
needed for ptrace_may_access.  So we could release the rcu lock after task
refcount is successfully grabbed to reduce the rcu holding time.

Link: https://lkml.kernel.org/r/20220425132723.34824-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220425132723.34824-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Huang Ying <ying.huang@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/migrate.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/migrate.c~mm-migration-reduce-the-rcu-lock-duration
+++ a/mm/migrate.c
@@ -1902,17 +1902,16 @@ static struct mm_struct *find_mm_struct(
 		return ERR_PTR(-ESRCH);
 	}
 	get_task_struct(task);
+	rcu_read_unlock();
 
 	/*
 	 * Check if this process has the right to modify the specified
 	 * process. Use the regular "ptrace_may_access()" checks.
 	 */
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
-		rcu_read_unlock();
 		mm = ERR_PTR(-EPERM);
 		goto out;
 	}
-	rcu_read_unlock();
 
 	mm = ERR_PTR(security_task_movememory(task));
 	if (IS_ERR(mm))
_

Patches currently in -mm which might be from linmiaohe@huawei.com are

mm-shmem-make-shmem_init-return-void.patch
mm-memcg-remove-unneeded-nr_scanned.patch
mm-mmapc-use-helper-mlock_future_check.patch
mm-mremap-use-helper-mlock_future_check.patch
mm-mremap-avoid-unneeded-do_munmap-call.patch
mm-memory-failurec-minor-cleanup-for-hwpoisonhandlable.patch
mm-memory-failurec-dissolve-truncated-hugetlb-page.patch
mm-vmscan-remove-obsolete-comment-in-get_scan_count.patch
mm-vmscan-fix-comment-for-current_may_throttle.patch
mm-vmscan-fix-comment-for-isolate_lru_pages.patch
mm-z3fold-declare-z3fold_mount-with-__init.patch
mm-z3fold-remove-obsolete-comment-in-z3fold_alloc.patch
mm-z3fold-minor-clean-up-for-z3fold_free.patch
mm-z3fold-remove-unneeded-page_mapcount_reset-and-clearpageprivate.patch
mm-z3fold-remove-confusing-local-variable-l-reassignment.patch
mm-z3fold-move-decrement-of-pool-pages_nr-into-__release_z3fold_page.patch
mm-z3fold-remove-redundant-list_del_init-of-zhdr-buddy-in-z3fold_free.patch
mm-z3fold-remove-unneeded-page_headless-check-in-free_handle.patch
mm-compaction-use-helper-isolation_suitable.patch
drivers-base-nodec-fix-compaction-sysfs-file-leak.patch
mm-mempolicy-clean-up-the-code-logic-in-queue_pages_pte_range.patch
mm-migration-remove-unneeded-local-variable-mapping_locked.patch
mm-migration-remove-unneeded-local-variable-page_lru.patch
mm-migration-use-helper-function-vma_lookup-in-add_page_for_migration.patch
mm-migration-use-helper-macro-min-in-do_pages_stat.patch
mm-migration-avoid-unneeded-nodemask_t-initialization.patch
mm-migration-remove-some-duplicated-codes-in-migrate_pages.patch
mm-migration-fix-potential-page-refcounts-leak-in-migrate_pages.patch
mm-migration-fix-potential-invalid-node-access-for-reclaim-based-migration.patch
mm-migration-fix-possible-do_pages_stat_array-racing-with-memory-offline.patch
mm-madvise-fix-potential-pte_unmap_unlock-pte-error.patch
mm-madvise-free-hwpoison-and-swapin-error-entry-in-madvise_free_pte_range.patch
mm-compaction-remove-unneeded-return-value-of-kcompactd_run.patch
mm-compaction-remove-unneeded-pfn-update.patch
mm-compaction-remove-unneeded-assignment-to-isolate_start_pfn.patch
mm-compaction-clean-up-comment-for-sched-contention.patch
mm-compaction-clean-up-comment-about-suitable-migration-target-recheck.patch
mm-compaction-use-compact_cluster_max-in-compactionc.patch
mm-compaction-use-helper-compound_nr-in-isolate_migratepages_block.patch
mm-compaction-clean-up-comment-about-async-compaction-in-isolate_migratepages.patch
mm-compaction-avoid-possible-null-pointer-dereference-in-kcompactd_cpu_online.patch
mm-compaction-make-compaction_zonelist_suitable-return-false-when-compact_success.patch
mm-compaction-simplify-the-code-in-__compact_finished.patch
mm-compaction-make-sure-highest-is-above-the-min_pfn.patch
mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
mm-swapfile-fix-lost-swap-bits-in-unuse_pte.patch
mm-migration-reduce-the-rcu-lock-duration.patch
mm-migration-remove-unneeded-lock-page-and-pagemovable-check.patch
mm-migration-return-errno-when-isolate_huge_page-failed.patch
mm-migration-fix-potential-pte_unmap-on-an-not-mapped-pte.patch