| Message ID | 20200716123810.25292-13-osalvador@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Hwpoison soft-offline rework | expand |
On Thu, Jul 16, 2020 at 02:38:06PM +0200, Oscar Salvador wrote: > This patch changes the way we set and handle in-use poisoned pages. > Until now, poisoned pages were released to the buddy allocator, trusting > that the checks that take place prior to deliver the page to its end > user would act as a safe net and would skip that page. > > This has proved to be wrong, as we got some pfn walkers out there, like > compaction, that all they care is the page to be PageBuddy and be in a > freelist. > Although this might not be the only user, having poisoned pages > in the buddy allocator seems a bad idea as we should only have > free pages that are ready and meant to be used as such. > > Before explaining the taken approach, let us break down the kind > of pages we can soft offline. > > - Anonymous THP (after the split, they end up being 4K pages) > - Hugetlb > - Order-0 pages (that can be either migrated or invalited) > > * Normal pages (order-0 and anon-THP) > > - If they are clean and unmapped page cache pages, we invalidate > then by means of invalidate_inode_page(). > - If they are mapped/dirty, we do the isolate-and-migrate dance. > > Either way, do not call put_page directly from those paths. > Instead, we keep the page and send it to page_set_poison to perform the > right handling. > > Among other things, page_set_poison() sets the HWPoison flag and does the last > put_page. > This call to put_page is mainly to be able to call __page_cache_release, > since this function is not exported. > > Down the chain, we placed a check for HWPoison page in > free_pages_prepare, that just skips any poisoned page, so those pages > do not end up either in a pcplist or in buddy-freelist. > > After that, we set the refcount on the page to 1 and we increment > the poisoned pages counter. > > We could do as we do for free pages: > 1) wait until the page hits buddy's freelists > 2) take it off > 3) flag it > > The problem is that we could race with an allocation, so by the time we > want to take the page off the buddy, the page is already allocated, so we > cannot soft-offline it. > This is not fatal of course, but if it is better if we can close the race > as does not require a lot of code. > > * Hugetlb pages > > - We isolate-and-migrate them > > There is no magic in here, we just isolate and migrate them. > A new set of internal functions have been made to flag a hugetlb page as > poisoned (SetPageHugePoisoned(), PageHugePoisoned(), ClearPageHugePoisoned()) > This allows us to flag the page when we migrate it, back in > move_hugetlb_state(). > > Later on we check whether the page is poisoned in __free_huge_page, > and we bail out in that case before sending the page to e.g: active > free list. > This gives us full control of the page, and we can handle it > page_handle_poison(). > > In other words, we do not allow migrated hugepages to get back to the > freelists. > > Since now the page has no user and has been migrated, we can call > dissolve_free_huge_page, which will end up calling update_and_free_page. > In update_and_free_page(), we check for the page to be poisoned. > If it so, we handle it as we handle gigantic pages, i.e: we break down > the page in order-0 pages and free them one by one. > Doing so, allows us for free_pages_prepare to skip poisoned pages. > > Because of the way we handle now in-use pages, we no longer need the > put-as-isolation-migratetype dance, that was guarding for poisoned pages > to end up in pcplists. I ran Quan Cai's test program (https://github.com/cailca/linux-mm) on a small (4GB memory) VM, and weiredly found that (1) the target hugepages are not always dissolved and (2) dissovled hugetpages are still counted in "HugePages_Total:". See below: $ ./random 1 - start: migrate_huge_offline - use NUMA nodes 0,1. - mmap and free 8388608 bytes hugepages on node 0 - mmap and free 8388608 bytes hugepages on node 1 madvise: Cannot allocate memory $ cat /proc/meminfo MemTotal: 4026772 kB MemFree: 976300 kB MemAvailable: 892840 kB Buffers: 20936 kB Cached: 99768 kB SwapCached: 5904 kB Active: 84332 kB Inactive: 116328 kB Active(anon): 27944 kB Inactive(anon): 68524 kB Active(file): 56388 kB Inactive(file): 47804 kB Unevictable: 7532 kB Mlocked: 0 kB SwapTotal: 2621436 kB SwapFree: 2609844 kB Dirty: 56 kB Writeback: 0 kB AnonPages: 81764 kB Mapped: 54348 kB Shmem: 8948 kB KReclaimable: 22744 kB Slab: 52056 kB SReclaimable: 22744 kB SUnreclaim: 29312 kB KernelStack: 3888 kB PageTables: 2804 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 3260612 kB Committed_AS: 828196 kB VmallocTotal: 34359738367 kB VmallocUsed: 19260 kB VmallocChunk: 0 kB Percpu: 5120 kB HardwareCorrupted: 5368 kB AnonHugePages: 18432 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB FileHugePages: 0 kB FilePmdMapped: 0 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 1342 // still counted as hugetlb pages. HugePages_Free: 0 // all hugepage are still allocated (or leaked?) HugePages_Rsvd: 0 HugePages_Surp: 762 // some are counted in surplus. Hugepagesize: 2048 kB Hugetlb: 2748416 kB DirectMap4k: 112480 kB DirectMap2M: 4081664 kB $ page-types -b hwpoison flags page-count MB symbolic-flags long-symbolic-flags 0x0000000000080008 421 1 ___U_______________X_______________________ uptodate,hwpoison 0x00000000000a8018 1 0 ___UD__________H_G_X_______________________ uptodate,dirty,compound_head,huge,hwpoison 0x00000000000a801c 920 3 __RUD__________H_G_X_______________________ referenced,uptodate,dirty,compound_head,huge,hwpoison total 1342 5 This means that some hugepages are dissolved, but the others not, maybe which is not desirable. I'll dig this more later but just let me share at first. A few minor comment below ... > > Signed-off-by: Oscar Salvador <osalvador@suse.com> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com> > --- > include/linux/page-flags.h | 5 ---- > mm/hugetlb.c | 60 +++++++++++++++++++++++++++++++++----- > mm/memory-failure.c | 53 +++++++++++++-------------------- > mm/migrate.c | 11 ++----- > mm/page_alloc.c | 38 +++++++----------------- > 5 files changed, 86 insertions(+), 81 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 01baf6d426ff..2ac8bfa0cf20 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -426,13 +426,8 @@ PAGEFLAG(HWPoison, hwpoison, PF_ANY) > TESTSCFLAG(HWPoison, hwpoison, PF_ANY) > #define __PG_HWPOISON (1UL << PG_hwpoison) > extern bool take_page_off_buddy(struct page *page); > -extern bool set_hwpoison_free_buddy_page(struct page *page); > #else > PAGEFLAG_FALSE(HWPoison) > -static inline bool set_hwpoison_free_buddy_page(struct page *page) > -{ > - return 0; > -} > #define __PG_HWPOISON 0 > #endif > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 7badb01d15e3..1c6397936512 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -29,6 +29,7 @@ > #include <linux/numa.h> > #include <linux/llist.h> > #include <linux/cma.h> > +#include <linux/migrate.h> > > #include <asm/page.h> > #include <asm/pgalloc.h> > @@ -1209,9 +1210,26 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed) > ((node = hstate_next_node_to_free(hs, mask)) || 1); \ > nr_nodes--) > > -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE > -static void destroy_compound_gigantic_page(struct page *page, > - unsigned int order) > +static inline bool PageHugePoisoned(struct page *page) > +{ > + if (!PageHuge(page)) > + return false; > + > + return (unsigned long)page[3].mapping == -1U; > +} > + > +static inline void SetPageHugePoisoned(struct page *page) > +{ > + page[3].mapping = (void *)-1U; > +} > + > +static inline void ClearPageHugePoisoned(struct page *page) > +{ > + page[3].mapping = NULL; > +} > + > +static void destroy_compound_gigantic_page(struct hstate *h, struct page *page, > + unsigned int order) > { > int i; > int nr_pages = 1 << order; > @@ -1222,14 +1240,19 @@ static void destroy_compound_gigantic_page(struct page *page, > atomic_set(compound_pincount_ptr(page), 0); > > for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) { > + if (!hstate_is_gigantic(h)) > + p->mapping = NULL; > clear_compound_head(p); > set_page_refcounted(p); > } > > + if (PageHugePoisoned(page)) > + ClearPageHugePoisoned(page); > set_compound_order(page, 0); > __ClearPageHead(page); > } > > +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE > static void free_gigantic_page(struct page *page, unsigned int order) > { > /* > @@ -1284,13 +1307,16 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask, > return NULL; > } > static inline void free_gigantic_page(struct page *page, unsigned int order) { } > -static inline void destroy_compound_gigantic_page(struct page *page, > - unsigned int order) { } > +static inline void destroy_compound_gigantic_page(struct hstate *h, > + struct page *page, > + unsigned int order) { } > #endif > > static void update_and_free_page(struct hstate *h, struct page *page) > { > int i; > + bool poisoned = PageHugePoisoned(page); > + unsigned int order = huge_page_order(h); > > if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) > return; > @@ -1313,11 +1339,21 @@ static void update_and_free_page(struct hstate *h, struct page *page) > * we might block in free_gigantic_page(). > */ > spin_unlock(&hugetlb_lock); > - destroy_compound_gigantic_page(page, huge_page_order(h)); > - free_gigantic_page(page, huge_page_order(h)); > + destroy_compound_gigantic_page(h, page, order); > + free_gigantic_page(page, order); > spin_lock(&hugetlb_lock); > } else { > - __free_pages(page, huge_page_order(h)); > + if (unlikely(poisoned)) { > + /* > + * If the hugepage is poisoned, do as we do for > + * gigantic pages and free the pages as order-0. > + * free_pages_prepare will skip over the poisoned ones. > + */ > + destroy_compound_gigantic_page(h, page, order); This function is for gigantic page from its name, so shouldn't be called for non-gigantic huge page. Maybe renaming it and/or introducing some inner function layer to factor out common part would be better. > + free_contig_range(page_to_pfn(page), 1 << order); > + } else { > + __free_pages(page, huge_page_order(h)); > + } > } > } > > @@ -1427,6 +1463,11 @@ static void __free_huge_page(struct page *page) > if (restore_reserve) > h->resv_huge_pages++; > > + if (PageHugePoisoned(page)) { > + spin_unlock(&hugetlb_lock); > + return; > + } > + > if (PageHugeTemporary(page)) { > list_del(&page->lru); > ClearPageHugeTemporary(page); > @@ -5642,6 +5683,9 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason) > hugetlb_cgroup_migrate(oldpage, newpage); > set_page_owner_migrate_reason(newpage, reason); > > + if (reason == MR_MEMORY_FAILURE) > + SetPageHugePoisoned(oldpage); > + > /* > * transfer temporary state of the new huge page. This is > * reverse to other transitions because the newpage is going to > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index caf012d34607..c0ebab4eed4c 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -65,9 +65,17 @@ int sysctl_memory_failure_recovery __read_mostly = 1; > > atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); > > -static void page_handle_poison(struct page *page) > +static void page_handle_poison(struct page *page, bool release, bool set_flag, > + bool huge_flag) > { > - SetPageHWPoison(page); > + if (set_flag) > + SetPageHWPoison(page); > + > + if (huge_flag) > + dissolve_free_huge_page(page); > + else if (release) > + put_page(page); > + Indentation seems to be broken, you can run checkpatch.pl to find details. Thanks, Naoya Horiguchi > page_ref_inc(page); > num_poisoned_pages_inc(); > } > @@ -1717,7 +1725,7 @@ static int get_any_page(struct page *page, unsigned long pfn) > > static int soft_offline_huge_page(struct page *page) > { > - int ret; > + int ret = -EBUSY; > unsigned long pfn = page_to_pfn(page); > struct page *hpage = compound_head(page); > LIST_HEAD(pagelist); > @@ -1757,19 +1765,12 @@ static int soft_offline_huge_page(struct page *page) > ret = -EIO; > } else { > /* > - * We set PG_hwpoison only when the migration source hugepage > - * was successfully dissolved, because otherwise hwpoisoned > - * hugepage remains on free hugepage list, then userspace will > - * find it as SIGBUS by allocation failure. That's not expected > - * in soft-offlining. > + * At this point the page cannot be in-use since we do not > + * let the page to go back to hugetlb freelists. > + * In that case we just need to dissolve it. > + * page_handle_poison will take care of it. > */ > - ret = dissolve_free_huge_page(page); > - if (!ret) { > - if (set_hwpoison_free_buddy_page(page)) > - num_poisoned_pages_inc(); > - else > - ret = -EBUSY; > - } > + page_handle_poison(page, true, true, true); > } > return ret; > } > @@ -1804,10 +1805,8 @@ static int __soft_offline_page(struct page *page) > * would need to fix isolation locking first. > */ > if (ret == 1) { > - put_page(page); > pr_info("soft_offline: %#lx: invalidated\n", pfn); > - SetPageHWPoison(page); > - num_poisoned_pages_inc(); > + page_handle_poison(page, true, true, false); > return 0; > } > > @@ -1838,7 +1837,9 @@ static int __soft_offline_page(struct page *page) > list_add(&page->lru, &pagelist); > ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL, > MIGRATE_SYNC, MR_MEMORY_FAILURE); > - if (ret) { > + if (!ret) { > + page_handle_poison(page, true, true, false); > + } else { > if (!list_empty(&pagelist)) > putback_movable_pages(&pagelist); > > @@ -1857,37 +1858,25 @@ static int __soft_offline_page(struct page *page) > static int soft_offline_in_use_page(struct page *page) > { > int ret; > - int mt; > struct page *hpage = compound_head(page); > > if (!PageHuge(page) && PageTransHuge(hpage)) > if (try_to_split_thp_page(page, "soft offline") < 0) > return -EBUSY; > > - /* > - * Setting MIGRATE_ISOLATE here ensures that the page will be linked > - * to free list immediately (not via pcplist) when released after > - * successful page migration. Otherwise we can't guarantee that the > - * page is really free after put_page() returns, so > - * set_hwpoison_free_buddy_page() highly likely fails. > - */ > - mt = get_pageblock_migratetype(page); > - set_pageblock_migratetype(page, MIGRATE_ISOLATE); > if (PageHuge(page)) > ret = soft_offline_huge_page(page); > else > ret = __soft_offline_page(page); > - set_pageblock_migratetype(page, mt); > return ret; > } > > static int soft_offline_free_page(struct page *page) > { > int rc = -EBUSY; > - int rc = dissolve_free_huge_page(page); > > if (!dissolve_free_huge_page(page) && take_page_off_buddy(page)) { > - page_handle_poison(page); > + page_handle_poison(page, false, true, false); > rc = 0; > } > > diff --git a/mm/migrate.c b/mm/migrate.c > index 75c10d81e833..a68d81d0ae6e 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1222,16 +1222,11 @@ static int unmap_and_move(new_page_t get_new_page, > * we want to retry. > */ > if (rc == MIGRATEPAGE_SUCCESS) { > - put_page(page); > - if (reason == MR_MEMORY_FAILURE) { > + if (reason != MR_MEMORY_FAILURE) > /* > - * Set PG_HWPoison on just freed page > - * intentionally. Although it's rather weird, > - * it's how HWPoison flag works at the moment. > + * We handle poisoned pages in page_handle_poison. > */ > - if (set_hwpoison_free_buddy_page(page)) > - num_poisoned_pages_inc(); > - } > + put_page(page); > } else { > if (rc != -EAGAIN) { > if (likely(!__PageMovable(page))) { > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 4fa0e0887c07..11df51fc2718 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1175,6 +1175,16 @@ static __always_inline bool free_pages_prepare(struct page *page, > > trace_mm_page_free(page, order); > > + if (unlikely(PageHWPoison(page)) && !order) { > + /* > + * Untie memcg state and reset page's owner > + */ > + if (memcg_kmem_enabled() && PageKmemcg(page)) > + __memcg_kmem_uncharge_page(page, order); > + reset_page_owner(page, order); > + return false; > + } > + > /* > * Check tail pages before head page information is cleared to > * avoid checking PageCompound for order-0 pages. > @@ -8844,32 +8854,4 @@ bool take_page_off_buddy(struct page *page) > spin_unlock_irqrestore(&zone->lock, flags); > return ret; > } > - > -/* > - * Set PG_hwpoison flag if a given page is confirmed to be a free page. This > - * test is performed under the zone lock to prevent a race against page > - * allocation. > - */ > -bool set_hwpoison_free_buddy_page(struct page *page) > -{ > - struct zone *zone = page_zone(page); > - unsigned long pfn = page_to_pfn(page); > - unsigned long flags; > - unsigned int order; > - bool hwpoisoned = false; > - > - spin_lock_irqsave(&zone->lock, flags); > - for (order = 0; order < MAX_ORDER; order++) { > - struct page *page_head = page - (pfn & ((1 << order) - 1)); > - > - if (PageBuddy(page_head) && page_order(page_head) >= order) { > - if (!TestSetPageHWPoison(page)) > - hwpoisoned = true; > - break; > - } > - } > - spin_unlock_irqrestore(&zone->lock, flags); > - > - return hwpoisoned; > -} > #endif > -- > 2.26.2 >
On 2020-07-17 08:55, HORIGUCHI NAOYA wrote: > I ran Quan Cai's test program (https://github.com/cailca/linux-mm) on a > small (4GB memory) VM, and weiredly found that (1) the target hugepages > are not always dissolved and (2) dissovled hugetpages are still counted > in "HugePages_Total:". See below: > > $ ./random 1 > - start: migrate_huge_offline > - use NUMA nodes 0,1. > - mmap and free 8388608 bytes hugepages on node 0 > - mmap and free 8388608 bytes hugepages on node 1 > madvise: Cannot allocate memory > > $ cat /proc/meminfo > MemTotal: 4026772 kB > MemFree: 976300 kB > MemAvailable: 892840 kB > Buffers: 20936 kB > Cached: 99768 kB > SwapCached: 5904 kB > Active: 84332 kB > Inactive: 116328 kB > Active(anon): 27944 kB > Inactive(anon): 68524 kB > Active(file): 56388 kB > Inactive(file): 47804 kB > Unevictable: 7532 kB > Mlocked: 0 kB > SwapTotal: 2621436 kB > SwapFree: 2609844 kB > Dirty: 56 kB > Writeback: 0 kB > AnonPages: 81764 kB > Mapped: 54348 kB > Shmem: 8948 kB > KReclaimable: 22744 kB > Slab: 52056 kB > SReclaimable: 22744 kB > SUnreclaim: 29312 kB > KernelStack: 3888 kB > PageTables: 2804 kB > NFS_Unstable: 0 kB > Bounce: 0 kB > WritebackTmp: 0 kB > CommitLimit: 3260612 kB > Committed_AS: 828196 kB > VmallocTotal: 34359738367 kB > VmallocUsed: 19260 kB > VmallocChunk: 0 kB > Percpu: 5120 kB > HardwareCorrupted: 5368 kB > AnonHugePages: 18432 kB > ShmemHugePages: 0 kB > ShmemPmdMapped: 0 kB > FileHugePages: 0 kB > FilePmdMapped: 0 kB > CmaTotal: 0 kB > CmaFree: 0 kB > HugePages_Total: 1342 // still counted as hugetlb pages. > HugePages_Free: 0 // all hugepage are still allocated > (or leaked?) > HugePages_Rsvd: 0 > HugePages_Surp: 762 // some are counted in surplus. > Hugepagesize: 2048 kB > Hugetlb: 2748416 kB > DirectMap4k: 112480 kB > DirectMap2M: 4081664 kB > > > $ page-types -b hwpoison > flags page-count MB symbolic-flags > long-symbolic-flags > 0x0000000000080008 421 1 > ___U_______________X_______________________ uptodate,hwpoison > 0x00000000000a8018 1 0 > ___UD__________H_G_X_______________________ > uptodate,dirty,compound_head,huge,hwpoison > 0x00000000000a801c 920 3 > __RUD__________H_G_X_______________________ > referenced,uptodate,dirty,compound_head,huge,hwpoison > total 1342 5 > > This means that some hugepages are dissolved, but the others not, > maybe which is not desirable. > I'll dig this more later but just let me share at first. > > A few minor comment below ... Uhm, weird. I will be taking a look today. Thanks
On 2020-07-20 10:27, osalvador@suse.de wrote: > On 2020-07-17 08:55, HORIGUCHI NAOYA wrote: >> I ran Quan Cai's test program (https://github.com/cailca/linux-mm) on >> a >> small (4GB memory) VM, and weiredly found that (1) the target >> hugepages >> are not always dissolved and (2) dissovled hugetpages are still >> counted >> in "HugePages_Total:". See below: >> >> $ ./random 1 >> - start: migrate_huge_offline >> - use NUMA nodes 0,1. >> - mmap and free 8388608 bytes hugepages on node 0 >> - mmap and free 8388608 bytes hugepages on node 1 >> madvise: Cannot allocate memory >> >> $ cat /proc/meminfo >> MemTotal: 4026772 kB >> MemFree: 976300 kB >> MemAvailable: 892840 kB >> Buffers: 20936 kB >> Cached: 99768 kB >> SwapCached: 5904 kB >> Active: 84332 kB >> Inactive: 116328 kB >> Active(anon): 27944 kB >> Inactive(anon): 68524 kB >> Active(file): 56388 kB >> Inactive(file): 47804 kB >> Unevictable: 7532 kB >> Mlocked: 0 kB >> SwapTotal: 2621436 kB >> SwapFree: 2609844 kB >> Dirty: 56 kB >> Writeback: 0 kB >> AnonPages: 81764 kB >> Mapped: 54348 kB >> Shmem: 8948 kB >> KReclaimable: 22744 kB >> Slab: 52056 kB >> SReclaimable: 22744 kB >> SUnreclaim: 29312 kB >> KernelStack: 3888 kB >> PageTables: 2804 kB >> NFS_Unstable: 0 kB >> Bounce: 0 kB >> WritebackTmp: 0 kB >> CommitLimit: 3260612 kB >> Committed_AS: 828196 kB >> VmallocTotal: 34359738367 kB >> VmallocUsed: 19260 kB >> VmallocChunk: 0 kB >> Percpu: 5120 kB >> HardwareCorrupted: 5368 kB >> AnonHugePages: 18432 kB >> ShmemHugePages: 0 kB >> ShmemPmdMapped: 0 kB >> FileHugePages: 0 kB >> FilePmdMapped: 0 kB >> CmaTotal: 0 kB >> CmaFree: 0 kB >> HugePages_Total: 1342 // still counted as hugetlb pages. >> HugePages_Free: 0 // all hugepage are still allocated >> (or leaked?) >> HugePages_Rsvd: 0 >> HugePages_Surp: 762 // some are counted in surplus. >> Hugepagesize: 2048 kB >> Hugetlb: 2748416 kB >> DirectMap4k: 112480 kB >> DirectMap2M: 4081664 kB >> >> >> $ page-types -b hwpoison >> flags page-count MB symbolic-flags >> long-symbolic-flags >> 0x0000000000080008 421 1 >> ___U_______________X_______________________ uptodate,hwpoison >> 0x00000000000a8018 1 0 >> ___UD__________H_G_X_______________________ >> uptodate,dirty,compound_head,huge,hwpoison >> 0x00000000000a801c 920 3 >> __RUD__________H_G_X_______________________ >> referenced,uptodate,dirty,compound_head,huge,hwpoison >> total 1342 5 >> >> This means that some hugepages are dissolved, but the others not, >> maybe which is not desirable. >> I'll dig this more later but just let me share at first. >> >> A few minor comment below ... > > > Uhm, weird. > > I will be taking a look today. After some digging up I __think__ I found the problem. I will try to fix it up and I will be running tests. I might reach out to you once I am done because I remember you had a test-suite that worked quite well, so you can give it a spin there. Thanks
On Wed, Jul 22, 2020 at 10:08:59AM +0200, osalvador@suse.de wrote: > On 2020-07-20 10:27, osalvador@suse.de wrote: > > > This means that some hugepages are dissolved, but the others not, > > > maybe which is not desirable. > > > I'll dig this more later but just let me share at first. > > > > > > A few minor comment below ... > > > > > > Uhm, weird. > > > > I will be taking a look today. > > After some digging up I __think__ I found the problem. > I will try to fix it up and I will be running tests. I found the problem. I re-ran the tests again with small and large memory and the stats look correct this time. After some more testing, I also fixed a list corruption that was happening due to the same problem. I am creating a git branch so you can re-run your tests on it as well.
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 01baf6d426ff..2ac8bfa0cf20 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -426,13 +426,8 @@ PAGEFLAG(HWPoison, hwpoison, PF_ANY) TESTSCFLAG(HWPoison, hwpoison, PF_ANY) #define __PG_HWPOISON (1UL << PG_hwpoison) extern bool take_page_off_buddy(struct page *page); -extern bool set_hwpoison_free_buddy_page(struct page *page); #else PAGEFLAG_FALSE(HWPoison) -static inline bool set_hwpoison_free_buddy_page(struct page *page) -{ - return 0; -} #define __PG_HWPOISON 0 #endif diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7badb01d15e3..1c6397936512 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -29,6 +29,7 @@ #include <linux/numa.h> #include <linux/llist.h> #include <linux/cma.h> +#include <linux/migrate.h> #include <asm/page.h> #include <asm/pgalloc.h> @@ -1209,9 +1210,26 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed) ((node = hstate_next_node_to_free(hs, mask)) || 1); \ nr_nodes--) -#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE -static void destroy_compound_gigantic_page(struct page *page, - unsigned int order) +static inline bool PageHugePoisoned(struct page *page) +{ + if (!PageHuge(page)) + return false; + + return (unsigned long)page[3].mapping == -1U; +} + +static inline void SetPageHugePoisoned(struct page *page) +{ + page[3].mapping = (void *)-1U; +} + +static inline void ClearPageHugePoisoned(struct page *page) +{ + page[3].mapping = NULL; +} + +static void destroy_compound_gigantic_page(struct hstate *h, struct page *page, + unsigned int order) { int i; int nr_pages = 1 << order; @@ -1222,14 +1240,19 @@ static void destroy_compound_gigantic_page(struct page *page, atomic_set(compound_pincount_ptr(page), 0); for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) { + if (!hstate_is_gigantic(h)) + p->mapping = NULL; clear_compound_head(p); set_page_refcounted(p); } + if (PageHugePoisoned(page)) + ClearPageHugePoisoned(page); set_compound_order(page, 0); __ClearPageHead(page); } +#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE static void free_gigantic_page(struct page *page, unsigned int order) { /* @@ -1284,13 +1307,16 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask, return NULL; } static inline void free_gigantic_page(struct page *page, unsigned int order) { } -static inline void destroy_compound_gigantic_page(struct page *page, - unsigned int order) { } +static inline void destroy_compound_gigantic_page(struct hstate *h, + struct page *page, + unsigned int order) { } #endif static void update_and_free_page(struct hstate *h, struct page *page) { int i; + bool poisoned = PageHugePoisoned(page); + unsigned int order = huge_page_order(h); if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) return; @@ -1313,11 +1339,21 @@ static void update_and_free_page(struct hstate *h, struct page *page) * we might block in free_gigantic_page(). */ spin_unlock(&hugetlb_lock); - destroy_compound_gigantic_page(page, huge_page_order(h)); - free_gigantic_page(page, huge_page_order(h)); + destroy_compound_gigantic_page(h, page, order); + free_gigantic_page(page, order); spin_lock(&hugetlb_lock); } else { - __free_pages(page, huge_page_order(h)); + if (unlikely(poisoned)) { + /* + * If the hugepage is poisoned, do as we do for + * gigantic pages and free the pages as order-0. + * free_pages_prepare will skip over the poisoned ones. + */ + destroy_compound_gigantic_page(h, page, order); + free_contig_range(page_to_pfn(page), 1 << order); + } else { + __free_pages(page, huge_page_order(h)); + } } } @@ -1427,6 +1463,11 @@ static void __free_huge_page(struct page *page) if (restore_reserve) h->resv_huge_pages++; + if (PageHugePoisoned(page)) { + spin_unlock(&hugetlb_lock); + return; + } + if (PageHugeTemporary(page)) { list_del(&page->lru); ClearPageHugeTemporary(page); @@ -5642,6 +5683,9 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason) hugetlb_cgroup_migrate(oldpage, newpage); set_page_owner_migrate_reason(newpage, reason); + if (reason == MR_MEMORY_FAILURE) + SetPageHugePoisoned(oldpage); + /* * transfer temporary state of the new huge page. This is * reverse to other transitions because the newpage is going to diff --git a/mm/memory-failure.c b/mm/memory-failure.c index caf012d34607..c0ebab4eed4c 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -65,9 +65,17 @@ int sysctl_memory_failure_recovery __read_mostly = 1; atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); -static void page_handle_poison(struct page *page) +static void page_handle_poison(struct page *page, bool release, bool set_flag, + bool huge_flag) { - SetPageHWPoison(page); + if (set_flag) + SetPageHWPoison(page); + + if (huge_flag) + dissolve_free_huge_page(page); + else if (release) + put_page(page); + page_ref_inc(page); num_poisoned_pages_inc(); } @@ -1717,7 +1725,7 @@ static int get_any_page(struct page *page, unsigned long pfn) static int soft_offline_huge_page(struct page *page) { - int ret; + int ret = -EBUSY; unsigned long pfn = page_to_pfn(page); struct page *hpage = compound_head(page); LIST_HEAD(pagelist); @@ -1757,19 +1765,12 @@ static int soft_offline_huge_page(struct page *page) ret = -EIO; } else { /* - * We set PG_hwpoison only when the migration source hugepage - * was successfully dissolved, because otherwise hwpoisoned - * hugepage remains on free hugepage list, then userspace will - * find it as SIGBUS by allocation failure. That's not expected - * in soft-offlining. + * At this point the page cannot be in-use since we do not + * let the page to go back to hugetlb freelists. + * In that case we just need to dissolve it. + * page_handle_poison will take care of it. */ - ret = dissolve_free_huge_page(page); - if (!ret) { - if (set_hwpoison_free_buddy_page(page)) - num_poisoned_pages_inc(); - else - ret = -EBUSY; - } + page_handle_poison(page, true, true, true); } return ret; } @@ -1804,10 +1805,8 @@ static int __soft_offline_page(struct page *page) * would need to fix isolation locking first. */ if (ret == 1) { - put_page(page); pr_info("soft_offline: %#lx: invalidated\n", pfn); - SetPageHWPoison(page); - num_poisoned_pages_inc(); + page_handle_poison(page, true, true, false); return 0; } @@ -1838,7 +1837,9 @@ static int __soft_offline_page(struct page *page) list_add(&page->lru, &pagelist); ret = migrate_pages(&pagelist, new_page, NULL, MPOL_MF_MOVE_ALL, MIGRATE_SYNC, MR_MEMORY_FAILURE); - if (ret) { + if (!ret) { + page_handle_poison(page, true, true, false); + } else { if (!list_empty(&pagelist)) putback_movable_pages(&pagelist); @@ -1857,37 +1858,25 @@ static int __soft_offline_page(struct page *page) static int soft_offline_in_use_page(struct page *page) { int ret; - int mt; struct page *hpage = compound_head(page); if (!PageHuge(page) && PageTransHuge(hpage)) if (try_to_split_thp_page(page, "soft offline") < 0) return -EBUSY; - /* - * Setting MIGRATE_ISOLATE here ensures that the page will be linked - * to free list immediately (not via pcplist) when released after - * successful page migration. Otherwise we can't guarantee that the - * page is really free after put_page() returns, so - * set_hwpoison_free_buddy_page() highly likely fails. - */ - mt = get_pageblock_migratetype(page); - set_pageblock_migratetype(page, MIGRATE_ISOLATE); if (PageHuge(page)) ret = soft_offline_huge_page(page); else ret = __soft_offline_page(page); - set_pageblock_migratetype(page, mt); return ret; } static int soft_offline_free_page(struct page *page) { int rc = -EBUSY; - int rc = dissolve_free_huge_page(page); if (!dissolve_free_huge_page(page) && take_page_off_buddy(page)) { - page_handle_poison(page); + page_handle_poison(page, false, true, false); rc = 0; } diff --git a/mm/migrate.c b/mm/migrate.c index 75c10d81e833..a68d81d0ae6e 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1222,16 +1222,11 @@ static int unmap_and_move(new_page_t get_new_page, * we want to retry. */ if (rc == MIGRATEPAGE_SUCCESS) { - put_page(page); - if (reason == MR_MEMORY_FAILURE) { + if (reason != MR_MEMORY_FAILURE) /* - * Set PG_HWPoison on just freed page - * intentionally. Although it's rather weird, - * it's how HWPoison flag works at the moment. + * We handle poisoned pages in page_handle_poison. */ - if (set_hwpoison_free_buddy_page(page)) - num_poisoned_pages_inc(); - } + put_page(page); } else { if (rc != -EAGAIN) { if (likely(!__PageMovable(page))) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4fa0e0887c07..11df51fc2718 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1175,6 +1175,16 @@ static __always_inline bool free_pages_prepare(struct page *page, trace_mm_page_free(page, order); + if (unlikely(PageHWPoison(page)) && !order) { + /* + * Untie memcg state and reset page's owner + */ + if (memcg_kmem_enabled() && PageKmemcg(page)) + __memcg_kmem_uncharge_page(page, order); + reset_page_owner(page, order); + return false; + } + /* * Check tail pages before head page information is cleared to * avoid checking PageCompound for order-0 pages. @@ -8844,32 +8854,4 @@ bool take_page_off_buddy(struct page *page) spin_unlock_irqrestore(&zone->lock, flags); return ret; } - -/* - * Set PG_hwpoison flag if a given page is confirmed to be a free page. This - * test is performed under the zone lock to prevent a race against page - * allocation. - */ -bool set_hwpoison_free_buddy_page(struct page *page) -{ - struct zone *zone = page_zone(page); - unsigned long pfn = page_to_pfn(page); - unsigned long flags; - unsigned int order; - bool hwpoisoned = false; - - spin_lock_irqsave(&zone->lock, flags); - for (order = 0; order < MAX_ORDER; order++) { - struct page *page_head = page - (pfn & ((1 << order) - 1)); - - if (PageBuddy(page_head) && page_order(page_head) >= order) { - if (!TestSetPageHWPoison(page)) - hwpoisoned = true; - break; - } - } - spin_unlock_irqrestore(&zone->lock, flags); - - return hwpoisoned; -} #endif
This patch changes the way we set and handle in-use poisoned pages. Until now, poisoned pages were released to the buddy allocator, trusting that the checks that take place prior to deliver the page to its end user would act as a safe net and would skip that page. This has proved to be wrong, as we got some pfn walkers out there, like compaction, that all they care is the page to be PageBuddy and be in a freelist. Although this might not be the only user, having poisoned pages in the buddy allocator seems a bad idea as we should only have free pages that are ready and meant to be used as such. Before explaining the taken approach, let us break down the kind of pages we can soft offline. - Anonymous THP (after the split, they end up being 4K pages) - Hugetlb - Order-0 pages (that can be either migrated or invalited) * Normal pages (order-0 and anon-THP) - If they are clean and unmapped page cache pages, we invalidate then by means of invalidate_inode_page(). - If they are mapped/dirty, we do the isolate-and-migrate dance. Either way, do not call put_page directly from those paths. Instead, we keep the page and send it to page_set_poison to perform the right handling. Among other things, page_set_poison() sets the HWPoison flag and does the last put_page. This call to put_page is mainly to be able to call __page_cache_release, since this function is not exported. Down the chain, we placed a check for HWPoison page in free_pages_prepare, that just skips any poisoned page, so those pages do not end up either in a pcplist or in buddy-freelist. After that, we set the refcount on the page to 1 and we increment the poisoned pages counter. We could do as we do for free pages: 1) wait until the page hits buddy's freelists 2) take it off 3) flag it The problem is that we could race with an allocation, so by the time we want to take the page off the buddy, the page is already allocated, so we cannot soft-offline it. This is not fatal of course, but if it is better if we can close the race as does not require a lot of code. * Hugetlb pages - We isolate-and-migrate them There is no magic in here, we just isolate and migrate them. A new set of internal functions have been made to flag a hugetlb page as poisoned (SetPageHugePoisoned(), PageHugePoisoned(), ClearPageHugePoisoned()) This allows us to flag the page when we migrate it, back in move_hugetlb_state(). Later on we check whether the page is poisoned in __free_huge_page, and we bail out in that case before sending the page to e.g: active free list. This gives us full control of the page, and we can handle it page_handle_poison(). In other words, we do not allow migrated hugepages to get back to the freelists. Since now the page has no user and has been migrated, we can call dissolve_free_huge_page, which will end up calling update_and_free_page. In update_and_free_page(), we check for the page to be poisoned. If it so, we handle it as we handle gigantic pages, i.e: we break down the page in order-0 pages and free them one by one. Doing so, allows us for free_pages_prepare to skip poisoned pages. Because of the way we handle now in-use pages, we no longer need the put-as-isolation-migratetype dance, that was guarding for poisoned pages to end up in pcplists. Signed-off-by: Oscar Salvador <osalvador@suse.com> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com> --- include/linux/page-flags.h | 5 ---- mm/hugetlb.c | 60 +++++++++++++++++++++++++++++++++----- mm/memory-failure.c | 53 +++++++++++++-------------------- mm/migrate.c | 11 ++----- mm/page_alloc.c | 38 +++++++----------------- 5 files changed, 86 insertions(+), 81 deletions(-)