From cfeed8ffe55b37fa10286aaaa1369da00cb88440 Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 21 Aug 2023 18:08:46 +0200 Subject: mm/swap: stop using page->private on tail pages for THP_SWAP Patch series "mm/swap: stop using page->private on tail pages for THP_SWAP + cleanups". This series stops using page->private on tail pages for THP_SWAP, replaces folio->private by folio->swap for swapcache folios, and starts using "new_folio" for tail pages that we are splitting to remove the usage of page->private for swapcache handling completely. This patch (of 4): Let's stop using page->private on tail pages, making it possible to just unconditionally reuse that field in the tail pages of large folios. The remaining usage of the private field for THP_SWAP is in the THP splitting code (mm/huge_memory.c), that we'll handle separately later. Update the THP_SWAP documentation and sanity checks in mm_types.h and __split_huge_page_tail(). [david@redhat.com: stop using page->private on tail pages for THP_SWAP] Link: https://lkml.kernel.org/r/6f0a82a3-6948-20d9-580b-be1dbf415701@redhat.com Link: https://lkml.kernel.org/r/20230821160849.531668-1-david@redhat.com Link: https://lkml.kernel.org/r/20230821160849.531668-2-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Catalin Marinas [arm64] Reviewed-by: Yosry Ahmed Cc: Dan Streetman Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Seth Jennings Cc: Vitaly Wool Cc: Will Deacon Signed-off-by: Andrew Morton --- mm/huge_memory.c | 15 ++++++--------- mm/memory.c | 2 +- mm/rmap.c | 2 +- mm/swap_state.c | 5 +++-- mm/swapfile.c | 4 ++-- 5 files changed, 13 insertions(+), 15 deletions(-) (limited to 'mm') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index cb4432792b88..a28e9fe16585 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2446,18 +2446,15 @@ static void __split_huge_page_tail(struct page *head, int tail, page_tail->index = head->index + tail; /* - * page->private should not be set in tail pages with the exception - * of swap cache pages that store the swp_entry_t in tail pages. - * Fix up and warn once if private is unexpectedly set. - * - * What of 32-bit systems, on which folio->_pincount overlays - * head[1].private? No problem: THP_SWAP is not enabled on 32-bit, and - * pincount must be 0 for folio_ref_freeze() to have succeeded. + * page->private should not be set in tail pages. Fix up and warn once + * if private is unexpectedly set. */ - if (!folio_test_swapcache(page_folio(head))) { - VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail); + if (unlikely(page_tail->private)) { + VM_WARN_ON_ONCE_PAGE(true, page_tail); page_tail->private = 0; } + if (PageSwapCache(head)) + set_page_private(page_tail, (unsigned long)head->private + tail); /* Page flags must be visible before we make the page non-compound. */ smp_wmb(); diff --git a/mm/memory.c b/mm/memory.c index 9d7fb721a680..d104a38e8545 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3879,7 +3879,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) * changed. */ if (unlikely(!folio_test_swapcache(folio) || - page_private(page) != entry.val)) + page_swap_entry(page).val != entry.val)) goto out_page; /* diff --git a/mm/rmap.c b/mm/rmap.c index 1f04debdc87a..ec7f8e6c9e48 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1647,7 +1647,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, */ dec_mm_counter(mm, mm_counter(&folio->page)); } else if (folio_test_anon(folio)) { - swp_entry_t entry = { .val = page_private(subpage) }; + swp_entry_t entry = page_swap_entry(subpage); pte_t swp_pte; /* * Store the swap location in the pte. diff --git a/mm/swap_state.c b/mm/swap_state.c index 01f15139b7d9..2f2417810052 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -100,6 +100,7 @@ int add_to_swap_cache(struct folio *folio, swp_entry_t entry, folio_ref_add(folio, nr); folio_set_swapcache(folio); + folio_set_swap_entry(folio, entry); do { xas_lock_irq(&xas); @@ -113,7 +114,6 @@ int add_to_swap_cache(struct folio *folio, swp_entry_t entry, if (shadowp) *shadowp = old; } - set_page_private(folio_page(folio, i), entry.val + i); xas_store(&xas, folio); xas_next(&xas); } @@ -154,9 +154,10 @@ void __delete_from_swap_cache(struct folio *folio, for (i = 0; i < nr; i++) { void *entry = xas_store(&xas, shadow); VM_BUG_ON_PAGE(entry != folio, entry); - set_page_private(folio_page(folio, i), 0); xas_next(&xas); } + entry.val = 0; + folio_set_swap_entry(folio, entry); folio_clear_swapcache(folio); address_space->nrpages -= nr; __node_stat_mod_folio(folio, NR_FILE_PAGES, -nr); diff --git a/mm/swapfile.c b/mm/swapfile.c index d46933adf789..bd9d904671b9 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3369,7 +3369,7 @@ struct swap_info_struct *swp_swap_info(swp_entry_t entry) struct swap_info_struct *page_swap_info(struct page *page) { - swp_entry_t entry = { .val = page_private(page) }; + swp_entry_t entry = page_swap_entry(page); return swp_swap_info(entry); } @@ -3384,7 +3384,7 @@ EXPORT_SYMBOL_GPL(swapcache_mapping); pgoff_t __page_file_index(struct page *page) { - swp_entry_t swap = { .val = page_private(page) }; + swp_entry_t swap = page_swap_entry(page); return swp_offset(swap); } EXPORT_SYMBOL_GPL(__page_file_index); -- cgit v1.2.3