kernel/linux.git/mm/page_isolation.c, branch v5.16

mm/page_isolation: guard against possible putback unisolated page

2021-11-06T20:30:40+00:00

Isolating a free page in an isolated pageblock is expected to always work as watermarks don't apply here. But if __isolate_free_page() failed, due to condition changes, the page will be left on the free list. And the page will be put back to free list again via __putback_isolated_page(). This may trigger VM_BUG_ON_PAGE() on page->flags checking in __free_one_page() if PageReported is set. Or we will corrupt the free list because list_add() will be called for pages already on another list. Add a VM_WARN_ON() to complain about this change. Link: https://lkml.kernel.org/r/20210914114508.23725-1-linmiaohe@huawei.com Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") Signed-off-by: Miaohe Lin Reviewed-by: David Hildenbrand Acked-by: Vlastimil Babka Cc: John Hubbard Cc: Joonsoo Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_isolation: fix potential missing call to unset_migratetype_isolate()

2021-11-06T20:30:40+00:00

In start_isolate_page_range() undo path, pfn_to_online_page() just checks the first pfn in a pageblock while __first_valid_page() will traverse the pageblock until the first online pfn is found. So we may miss the call to unset_migratetype_isolate() in undo path and pages will remain isolated unexpectedly. Fix this by calling undo_isolate_page_range() and this will also help to simplify the code further. Note we shouldn't ever trigger it because MAX_ORDER-1 aligned pfn ranges shouldn't contain memory holes now. Link: https://lkml.kernel.org/r/20210914114348.15569-1-linmiaohe@huawei.com Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages") Signed-off-by: Miaohe Lin Reviewed-by: David Hildenbrand Cc: Michal Hocko Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2021-09-08T19:55:35+00:00

Merge more updates from Andrew Morton: "147 patches, based on 7d2a07b769330c34b4deabeed939325c77a7ec2f. Subsystems affected by this patch series: mm (memory-hotplug, rmap, ioremap, highmem, cleanups, secretmem, kfence, damon, and vmscan), alpha, percpu, procfs, misc, core-kernel, MAINTAINERS, lib, checkpatch, epoll, init, nilfs2, coredump, fork, pids, criu, kconfig, selftests, ipc, and scripts" * emailed patches from Andrew Morton : (94 commits) scripts: check_extable: fix typo in user error message mm/workingset: correct kernel-doc notations ipc: replace costly bailout check in sysvipc_find_ipc() selftests/memfd: remove unused variable Kconfig.debug: drop selecting non-existing HARDLOCKUP_DETECTOR_ARCH configs: remove the obsolete CONFIG_INPUT_POLLDEV prctl: allow to setup brk for et_dyn executables pid: cleanup the stale comment mentioning pidmap_init(). kernel/fork.c: unexport get_{mm,task}_exe_file coredump: fix memleak in dump_vma_snapshot() fs/coredump.c: log if a core dump is aborted due to changed file permissions nilfs2: use refcount_dec_and_lock() to fix potential UAF nilfs2: fix memory leak in nilfs_sysfs_delete_snapshot_group nilfs2: fix memory leak in nilfs_sysfs_create_snapshot_group nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group nilfs2: fix memory leak in nilfs_sysfs_create_##name##_group nilfs2: fix NULL pointer in nilfs_##name##_attr_release nilfs2: fix memory leak in nilfs_sysfs_create_device_group trap: cleanup trap_init() init: move usermodehelper_enable() to populate_rootfs() ...

mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE

2021-09-08T18:50:22+00:00

Patch series "mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE". After recent updates to freeing unused parts of the memory map, no architecture can have holes in the memory map within a pageblock. This makes pfn_valid_within() check and CONFIG_HOLES_IN_ZONE configuration option redundant. The first patch removes them both in a mechanical way and the second patch simplifies memory_hotplug::test_pages_in_a_zone() that had pfn_valid_within() surrounded by more logic than simple if. This patch (of 2): After recent changes in freeing of the unused parts of the memory map and rework of pfn_valid() in arm and arm64 there are no architectures that can have holes in the memory map within a pageblock and so nothing can enable CONFIG_HOLES_IN_ZONE which guards non trivial implementation of pfn_valid_within(). With that, pfn_valid_within() is always hardwired to 1 and can be completely removed. Remove calls to pfn_valid_within() and CONFIG_HOLES_IN_ZONE. Link: https://lkml.kernel.org/r/20210713080035.7464-1-rppt@kernel.org Link: https://lkml.kernel.org/r/20210713080035.7464-2-rppt@kernel.org Signed-off-by: Mike Rapoport Acked-by: David Hildenbrand Cc: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_isolation: tracing: trace all test_pages_isolated failures

2021-09-03T16:58:15+00:00

Some test_pages_isolated failure conditions don't include trace points. For debugging issues caused by "pinned" pages, make sure to trace all calls whether they succeed or fail. In this case, a failure case did not result in a trace point. So add the missing failure case in test_pages_isolated traces. Link: https://lkml.kernel.org/r/20210823202823.13765-1-george_davis@mentor.com Signed-off-by: George G. Davis Cc: Eugeniu Rosca Cc: David Hildenbrand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/page_isolation: do not isolate the max order page

2020-12-15T20:13:45+00:00

A max order page has no buddy page and never merges to another order. So isolating and then freeing it is pointless. Link: https://lkml.kernel.org/r/20201202122114.75316-1-songmuchun@bytedance.com Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") Signed-off-by: Muchun Song Reviewed-by: Andrew Morton Acked-by: Vlastimil Babka Reviewed-by: David Hildenbrand Reviewed-by: Oscar Salvador Cc: Joonsoo Kim Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, page_alloc: disable pcplists during memory offline

2020-12-15T20:13:43+00:00

Memory offlining relies on page isolation to guarantee a forward progress because pages cannot be reused while they are isolated. But the page isolation itself doesn't prevent from races while freed pages are stored on pcp lists and thus can be reused. This can be worked around by repeated draining of pcplists, as done by commit 968318261221 ("mm/memory_hotplug: drain per-cpu pages again during memory offline"). David and Michal would prefer that this race was closed in a way that callers of page isolation who need stronger guarantees don't need to repeatedly drain. David suggested disabling pcplists usage completely during page isolation, instead of repeatedly draining them. To achieve this without adding special cases in alloc/free fastpath, we can use the same approach as boot pagesets - when pcp->high is 0, any pcplist addition will be immediately flushed. The race can thus be closed by setting pcp->high to 0 and draining pcplists once, before calling start_isolate_page_range(). The draining will serialize after processes that already disabled interrupts and read the old value of pcp->high in free_unref_page_commit(), and processes that have not yet disabled interrupts, will observe pcp->high == 0 when they are rescheduled, and skip pcplists. This guarantees no stray pages on pcplists in zones where isolation happens. This patch thus adds zone_pcp_disable() and zone_pcp_enable() functions that page isolation users can call before start_isolate_page_range() and after unisolating (or offlining) the isolated pages. Also, drain_all_pages() is optimized to only execute on cpus where pcplists are not empty. The check can however race with a free to pcplist that has not yet increased the pcp->count from 0 to 1. Thus make the drain optionally skip the racy check and drain on all cpus, and use this option in zone_pcp_disable(). As we have to avoid external updates to high and batch while pcplists are disabled, we take pcp_batch_high_lock in zone_pcp_disable() and release it in zone_pcp_enable(). This also synchronizes multiple users of zone_pcp_disable()/enable(). Currently the only user of this functionality is offline_pages(). [vbabka@suse.cz: add comment, per David] Link: https://lkml.kernel.org/r/527480ef-ed72-e1c1-52a0-1c5b0113df45@suse.cz Link: https://lkml.kernel.org/r/20201111092812.11329-8-vbabka@suse.cz Signed-off-by: Vlastimil Babka Suggested-by: David Hildenbrand Suggested-by: Michal Hocko Reviewed-by: Oscar Salvador Reviewed-by: David Hildenbrand Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, page_alloc: move draining pcplists to page isolation users

2020-12-15T20:13:43+00:00

Currently, pcplists are drained during set_migratetype_isolate() which means once per pageblock processed start_isolate_page_range(). This is somewhat wasteful. Moreover, the callers might need different guarantees, and the draining is currently prone to races and does not guarantee that no page from isolated pageblock will end up on the pcplist after the drain. Better guarantees are added by later patches and require explicit actions by page isolation users that need them. Thus it makes sense to move the current imperfect draining to the callers also as a preparation step. Link: https://lkml.kernel.org/r/20201111092812.11329-7-vbabka@suse.cz Suggested-by: David Hildenbrand Suggested-by: Pavel Tatashin Signed-off-by: Vlastimil Babka Reviewed-by: David Hildenbrand Reviewed-by: Oscar Salvador Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: rename page_order() to buddy_order()

2020-10-16T18:11:19+00:00

The current page_order() can only be called on pages in the buddy allocator. For compound pages, you have to use compound_order(). This is confusing and led to a bug, so rename page_order() to buddy_order(). Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton Link: https://lkml.kernel.org/r/20201001152259.14932-2-willy@infradead.org Signed-off-by: Linus Torvalds

mm/page_alloc: move pages to tail in move_to_free_list()

2020-10-16T18:11:18+00:00

Whenever we move pages between freelists via move_to_free_list()/ move_freepages_block(), we don't actually touch the pages: 1. Page isolation doesn't actually touch the pages, it simply isolates pageblocks and moves all free pages to the MIGRATE_ISOLATE freelist. When undoing isolation, we move the pages back to the target list. 2. Page stealing (steal_suitable_fallback()) moves free pages directly between lists without touching them. 3. reserve_highatomic_pageblock()/unreserve_highatomic_pageblock() moves free pages directly between freelists without touching them. We already place pages to the tail of the freelists when undoing isolation via __putback_isolated_page(), let's do it in any case (e.g., if order <= pageblock_order) and document the behavior. To simplify, let's move the pages to the tail for all move_to_free_list()/move_freepages_block() users. In 2., the target list is empty, so there should be no change. In 3., we might observe a change, however, highatomic is more concerned about allocations succeeding than cache hotness - if we ever realize this change degrades a workload, we can special-case this instance and add a proper comment. This change results in all pages getting onlined via online_pages() to be placed to the tail of the freelist. Signed-off-by: David Hildenbrand Signed-off-by: Andrew Morton Reviewed-by: Oscar Salvador Reviewed-by: Wei Yang Acked-by: Pankaj Gupta Acked-by: Michal Hocko Cc: Alexander Duyck Cc: Mel Gorman Cc: Dave Hansen Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Scott Cheloha Cc: Michael Ellerman Cc: Haiyang Zhang Cc: "K. Y. Srinivasan" Cc: Matthew Wilcox Cc: Michal Hocko Cc: Stephen Hemminger Cc: Wei Liu Link: https://lkml.kernel.org/r/20201005121534.15649-4-david@redhat.com Signed-off-by: Linus Torvalds