From 59807685a7e77e8c8fe5925613968841538d53d7 Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Wed, 6 Sep 2017 16:22:34 -0700 Subject: [PATCH] mm, THP, swap: support splitting THP for THP swap out After adding swapping out support for THP (Transparent Huge Page), it is possible that a THP in swap cache (partly swapped out) need to be split. To split such a THP, the swap cluster backing the THP need to be split too, that is, the CLUSTER_FLAG_HUGE flag need to be cleared for the swap cluster. The patch implemented this. And because the THP swap writing needs the THP keeps as huge page during writing. The PageWriteback flag is checked before splitting. Link: http://lkml.kernel.org/r/20170724051840.2309-8-ying.huang@intel.com Signed-off-by: "Huang, Ying" Cc: Johannes Weiner Cc: Minchan Kim Cc: Hugh Dickins Cc: Shaohua Li Cc: Rik van Riel Cc: Andrea Arcangeli Cc: "Kirill A . Shutemov" Cc: Dan Williams Cc: Jens Axboe Cc: Michal Hocko Cc: Ross Zwisler [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 9 +++++++++ mm/huge_memory.c | 10 +++++++++- mm/swapfile.c | 15 +++++++++++++++ 3 files changed, 33 insertions(+), 1 deletion(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 7176ba780e83..461cf107ad52 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -527,6 +527,15 @@ static inline swp_entry_t get_swap_page(struct page *page) #endif /* CONFIG_SWAP */ +#ifdef CONFIG_THP_SWAP +extern int split_swap_cluster(swp_entry_t entry); +#else +static inline int split_swap_cluster(swp_entry_t entry) +{ + return 0; +} +#endif + #ifdef CONFIG_MEMCG static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 02dfe635c9fe..772048c233d1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2481,6 +2481,9 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageCompound(page), page); + if (PageWriteback(page)) + return -EBUSY; + if (PageAnon(head)) { /* * The caller does not necessarily hold an mmap_sem that would @@ -2558,7 +2561,12 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) __dec_node_page_state(page, NR_SHMEM_THPS); spin_unlock(&pgdata->split_queue_lock); __split_huge_page(page, list, flags); - ret = 0; + if (PageSwapCache(head)) { + swp_entry_t entry = { .val = page_private(head) }; + + ret = split_swap_cluster(entry); + } else + ret = 0; } else { if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { pr_alert("total_mapcount: %u, page_count(): %u\n", diff --git a/mm/swapfile.c b/mm/swapfile.c index 267b1fe41844..42eff9e4e972 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1216,6 +1216,21 @@ static void swapcache_free_cluster(swp_entry_t entry) } } } + +int split_swap_cluster(swp_entry_t entry) +{ + struct swap_info_struct *si; + struct swap_cluster_info *ci; + unsigned long offset = swp_offset(entry); + + si = _swap_info_get(entry); + if (!si) + return -EBUSY; + ci = lock_cluster(si, offset); + cluster_clear_huge(ci); + unlock_cluster(ci); + return 0; +} #else static inline void swapcache_free_cluster(swp_entry_t entry) { -- 2.30.2