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SubjectRe: [PATCH -next] mm/hotplug: silence a lockdep splat with printk()
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On 14.01.20 21:11, Qian Cai wrote:
> Similar to the recent commit [1] merged into the random and -next trees,
> it is not a good idea to call printk() with zone->lock held. The
> standard fix is to use printk_deferred() in those places, but memory
> offline will call dump_page() which need to defer after the lock. While
> at it, remove a similar but unnecessary debug printk() as well.
>
> [1] https://lore.kernel.org/lkml/1573679785-21068-1-git-send-email-cai@lca.pw/
>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> include/linux/page-isolation.h | 2 +-
> mm/memory_hotplug.c | 2 +-
> mm/page_alloc.c | 12 +++++-------
> mm/page_isolation.c | 10 +++++++++-
> 4 files changed, 16 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
> index 148e65a9c606..5d8ba078006f 100644
> --- a/include/linux/page-isolation.h
> +++ b/include/linux/page-isolation.h
> @@ -34,7 +34,7 @@ static inline bool is_migrate_isolate(int migratetype)
> #define REPORT_FAILURE 0x2
>
> bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
> - int flags);
> + int flags, char *dump);
> void set_pageblock_migratetype(struct page *page, int migratetype);
> int move_freepages_block(struct zone *zone, struct page *page,
> int migratetype, int *num_movable);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 7a6de9b0dcab..f10928538fa3 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1149,7 +1149,7 @@ static bool is_pageblock_removable_nolock(unsigned long pfn)
> return false;
>
> return !has_unmovable_pages(zone, page, MIGRATE_MOVABLE,
> - MEMORY_OFFLINE);
> + MEMORY_OFFLINE, NULL);
> }
>
> /* Checks if this range of memory is likely to be hot-removable. */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e56cd1f33242..b6bec3925e80 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8204,7 +8204,7 @@ void *__init alloc_large_system_hash(const char *tablename,
> * race condition. So you can't expect this function should be exact.
> */
> bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
> - int flags)
> + int flags, char *dump)
> {
> unsigned long iter = 0;
> unsigned long pfn = page_to_pfn(page);
> @@ -8305,8 +8305,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int migratetype,
> return false;
> unmovable:
> WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> - if (flags & REPORT_FAILURE)
> - dump_page(pfn_to_page(pfn + iter), reason);
> + if (flags & REPORT_FAILURE) {
> + page = pfn_to_page(pfn + iter);
> + strscpy(dump, reason, 64);
> + }
> return true;
> }
>
> @@ -8711,10 +8713,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
> BUG_ON(!PageBuddy(page));
> order = page_order(page);
> offlined_pages += 1 << order;
> -#ifdef CONFIG_DEBUG_VM
> - pr_info("remove from free list %lx %d %lx\n",
> - pfn, 1 << order, end_pfn);
> -#endif

ack to getting rid of this.

Regarding the other stuff, I remember Michal had an opinion about the
previous approach, so it's best if he comments.

--
Thanks,

David / dhildenb

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