mm, THP, swap: support splitting THP for THP swap out (59807685) · Commits · 戴 / test

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" <ying.huang@intel.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Michal Hocko <mhocko@kernel.org> Cc: Ross Zwisler <ross.zwisler@intel.com> [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma <vishal.l.verma@intel.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/swap.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -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)
		{

mm/huge_memory.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -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
		@@ -2558,6 +2561,11 @@ 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);
		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) {

mm/swapfile.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -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)
		{

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