Hi, Andrew, On Mon, 2022-04-25 at 12:10 -0700, Andrew Morton wrote: > 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 > > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > The -mm tree is included into linux-next and is updated > there every 3-4 working days > > ------------------------------------------------------ > From: Miaohe Lin <linmiaohe@xxxxxxxxxx> > 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@xxxxxxxxxx > Link: https://lkml.kernel.org/r/20220425132723.34824-2-linmiaohe@xxxxxxxxxx > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> > Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Cc: Huang Ying <ying.huang@xxxxxxxxx> > Cc: David Howells <dhowells@xxxxxxxxxx> > Cc: Christoph Lameter <cl@xxxxxxxxx> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> I think that there is still a remaining issue to be addressed for this patch as in the following threads, https://lore.kernel.org/linux-mm/8735ju7as9.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/lkml/34f3aff7-0111-a8d6-a559-92bf6d0bd62a@xxxxxxxxxx/ Best Regards, Huang, Ying > --- > > 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@xxxxxxxxxx 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 >
