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c04b3d0690
Due to the change about how block layer detects congestion the justification of commit8fd2e0b505
("mm: swap: check if swap backing device is congested or not") doesn't stand anymore, so the commit could be just reverted in order to solve the race reported by commit2efa33fc7f
("mm/shmem: fix shmem_swapin() race with swapoff"). The fix was reverted by the previous patch. Link: https://lkml.kernel.org/r/20210810202936.2672-3-shy828301@gmail.com Signed-off-by: Yang Shi <shy828301@gmail.com> Suggested-by: Hugh Dickins <hughd@google.com> Acked-by: Hugh Dickins <hughd@google.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
913 lines
24 KiB
C
913 lines
24 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/swap_state.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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* Swap reorganised 29.12.95, Stephen Tweedie
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*
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* Rewritten to use page cache, (C) 1998 Stephen Tweedie
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*/
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#include <linux/mm.h>
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#include <linux/gfp.h>
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#include <linux/kernel_stat.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/init.h>
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#include <linux/pagemap.h>
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#include <linux/backing-dev.h>
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#include <linux/blkdev.h>
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#include <linux/pagevec.h>
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#include <linux/migrate.h>
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#include <linux/vmalloc.h>
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#include <linux/swap_slots.h>
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#include <linux/huge_mm.h>
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#include <linux/shmem_fs.h>
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#include "internal.h"
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/*
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* swapper_space is a fiction, retained to simplify the path through
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* vmscan's shrink_page_list.
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*/
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static const struct address_space_operations swap_aops = {
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.writepage = swap_writepage,
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.set_page_dirty = swap_set_page_dirty,
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#ifdef CONFIG_MIGRATION
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.migratepage = migrate_page,
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#endif
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};
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struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
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static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;
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static bool enable_vma_readahead __read_mostly = true;
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#define SWAP_RA_WIN_SHIFT (PAGE_SHIFT / 2)
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#define SWAP_RA_HITS_MASK ((1UL << SWAP_RA_WIN_SHIFT) - 1)
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#define SWAP_RA_HITS_MAX SWAP_RA_HITS_MASK
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#define SWAP_RA_WIN_MASK (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
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#define SWAP_RA_HITS(v) ((v) & SWAP_RA_HITS_MASK)
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#define SWAP_RA_WIN(v) (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
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#define SWAP_RA_ADDR(v) ((v) & PAGE_MASK)
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#define SWAP_RA_VAL(addr, win, hits) \
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(((addr) & PAGE_MASK) | \
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(((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) | \
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((hits) & SWAP_RA_HITS_MASK))
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/* Initial readahead hits is 4 to start up with a small window */
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#define GET_SWAP_RA_VAL(vma) \
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(atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
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#define INC_CACHE_INFO(x) data_race(swap_cache_info.x++)
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#define ADD_CACHE_INFO(x, nr) data_race(swap_cache_info.x += (nr))
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static struct {
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unsigned long add_total;
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unsigned long del_total;
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unsigned long find_success;
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unsigned long find_total;
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} swap_cache_info;
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static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
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void show_swap_cache_info(void)
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{
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printk("%lu pages in swap cache\n", total_swapcache_pages());
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printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
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swap_cache_info.add_total, swap_cache_info.del_total,
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swap_cache_info.find_success, swap_cache_info.find_total);
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printk("Free swap = %ldkB\n",
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get_nr_swap_pages() << (PAGE_SHIFT - 10));
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printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
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}
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void *get_shadow_from_swap_cache(swp_entry_t entry)
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{
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struct address_space *address_space = swap_address_space(entry);
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pgoff_t idx = swp_offset(entry);
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struct page *page;
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page = xa_load(&address_space->i_pages, idx);
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if (xa_is_value(page))
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return page;
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return NULL;
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}
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/*
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* add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
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* but sets SwapCache flag and private instead of mapping and index.
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*/
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int add_to_swap_cache(struct page *page, swp_entry_t entry,
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gfp_t gfp, void **shadowp)
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{
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struct address_space *address_space = swap_address_space(entry);
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pgoff_t idx = swp_offset(entry);
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XA_STATE_ORDER(xas, &address_space->i_pages, idx, compound_order(page));
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unsigned long i, nr = thp_nr_pages(page);
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void *old;
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(PageSwapCache(page), page);
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VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
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page_ref_add(page, nr);
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SetPageSwapCache(page);
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do {
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xas_lock_irq(&xas);
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xas_create_range(&xas);
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if (xas_error(&xas))
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goto unlock;
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for (i = 0; i < nr; i++) {
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VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
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old = xas_load(&xas);
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if (xa_is_value(old)) {
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if (shadowp)
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*shadowp = old;
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}
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set_page_private(page + i, entry.val + i);
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xas_store(&xas, page);
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xas_next(&xas);
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}
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address_space->nrpages += nr;
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__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
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__mod_lruvec_page_state(page, NR_SWAPCACHE, nr);
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ADD_CACHE_INFO(add_total, nr);
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unlock:
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xas_unlock_irq(&xas);
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} while (xas_nomem(&xas, gfp));
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if (!xas_error(&xas))
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return 0;
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ClearPageSwapCache(page);
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page_ref_sub(page, nr);
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return xas_error(&xas);
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}
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/*
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* This must be called only on pages that have
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* been verified to be in the swap cache.
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*/
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void __delete_from_swap_cache(struct page *page,
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swp_entry_t entry, void *shadow)
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{
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struct address_space *address_space = swap_address_space(entry);
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int i, nr = thp_nr_pages(page);
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pgoff_t idx = swp_offset(entry);
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XA_STATE(xas, &address_space->i_pages, idx);
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(!PageSwapCache(page), page);
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VM_BUG_ON_PAGE(PageWriteback(page), page);
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for (i = 0; i < nr; i++) {
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void *entry = xas_store(&xas, shadow);
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VM_BUG_ON_PAGE(entry != page, entry);
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set_page_private(page + i, 0);
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xas_next(&xas);
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}
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ClearPageSwapCache(page);
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address_space->nrpages -= nr;
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__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
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__mod_lruvec_page_state(page, NR_SWAPCACHE, -nr);
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ADD_CACHE_INFO(del_total, nr);
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}
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/**
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* add_to_swap - allocate swap space for a page
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* @page: page we want to move to swap
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*
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* Allocate swap space for the page and add the page to the
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* swap cache. Caller needs to hold the page lock.
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*/
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int add_to_swap(struct page *page)
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{
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swp_entry_t entry;
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int err;
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(!PageUptodate(page), page);
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entry = get_swap_page(page);
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if (!entry.val)
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return 0;
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/*
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* XArray node allocations from PF_MEMALLOC contexts could
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* completely exhaust the page allocator. __GFP_NOMEMALLOC
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* stops emergency reserves from being allocated.
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*
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* TODO: this could cause a theoretical memory reclaim
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* deadlock in the swap out path.
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*/
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/*
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* Add it to the swap cache.
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*/
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err = add_to_swap_cache(page, entry,
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__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN, NULL);
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if (err)
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/*
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* add_to_swap_cache() doesn't return -EEXIST, so we can safely
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* clear SWAP_HAS_CACHE flag.
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*/
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goto fail;
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/*
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* Normally the page will be dirtied in unmap because its pte should be
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* dirty. A special case is MADV_FREE page. The page's pte could have
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* dirty bit cleared but the page's SwapBacked bit is still set because
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* clearing the dirty bit and SwapBacked bit has no lock protected. For
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* such page, unmap will not set dirty bit for it, so page reclaim will
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* not write the page out. This can cause data corruption when the page
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* is swap in later. Always setting the dirty bit for the page solves
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* the problem.
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*/
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set_page_dirty(page);
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return 1;
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fail:
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put_swap_page(page, entry);
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return 0;
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}
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/*
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* This must be called only on pages that have
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* been verified to be in the swap cache and locked.
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* It will never put the page into the free list,
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* the caller has a reference on the page.
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*/
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void delete_from_swap_cache(struct page *page)
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{
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swp_entry_t entry = { .val = page_private(page) };
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struct address_space *address_space = swap_address_space(entry);
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xa_lock_irq(&address_space->i_pages);
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__delete_from_swap_cache(page, entry, NULL);
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xa_unlock_irq(&address_space->i_pages);
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put_swap_page(page, entry);
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page_ref_sub(page, thp_nr_pages(page));
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}
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void clear_shadow_from_swap_cache(int type, unsigned long begin,
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unsigned long end)
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{
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unsigned long curr = begin;
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void *old;
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for (;;) {
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swp_entry_t entry = swp_entry(type, curr);
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struct address_space *address_space = swap_address_space(entry);
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XA_STATE(xas, &address_space->i_pages, curr);
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xa_lock_irq(&address_space->i_pages);
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xas_for_each(&xas, old, end) {
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if (!xa_is_value(old))
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continue;
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xas_store(&xas, NULL);
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}
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xa_unlock_irq(&address_space->i_pages);
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/* search the next swapcache until we meet end */
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curr >>= SWAP_ADDRESS_SPACE_SHIFT;
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curr++;
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curr <<= SWAP_ADDRESS_SPACE_SHIFT;
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if (curr > end)
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break;
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}
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}
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/*
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* If we are the only user, then try to free up the swap cache.
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*
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* Its ok to check for PageSwapCache without the page lock
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* here because we are going to recheck again inside
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* try_to_free_swap() _with_ the lock.
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* - Marcelo
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*/
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void free_swap_cache(struct page *page)
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{
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if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
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try_to_free_swap(page);
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unlock_page(page);
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}
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}
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/*
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* Perform a free_page(), also freeing any swap cache associated with
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* this page if it is the last user of the page.
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*/
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void free_page_and_swap_cache(struct page *page)
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{
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free_swap_cache(page);
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if (!is_huge_zero_page(page))
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put_page(page);
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}
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/*
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* Passed an array of pages, drop them all from swapcache and then release
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* them. They are removed from the LRU and freed if this is their last use.
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*/
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void free_pages_and_swap_cache(struct page **pages, int nr)
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{
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struct page **pagep = pages;
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int i;
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lru_add_drain();
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for (i = 0; i < nr; i++)
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free_swap_cache(pagep[i]);
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release_pages(pagep, nr);
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}
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static inline bool swap_use_vma_readahead(void)
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{
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return READ_ONCE(enable_vma_readahead) && !atomic_read(&nr_rotate_swap);
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}
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/*
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* Lookup a swap entry in the swap cache. A found page will be returned
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* unlocked and with its refcount incremented - we rely on the kernel
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* lock getting page table operations atomic even if we drop the page
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* lock before returning.
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*/
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struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
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unsigned long addr)
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{
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struct page *page;
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struct swap_info_struct *si;
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si = get_swap_device(entry);
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if (!si)
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return NULL;
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page = find_get_page(swap_address_space(entry), swp_offset(entry));
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put_swap_device(si);
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INC_CACHE_INFO(find_total);
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if (page) {
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bool vma_ra = swap_use_vma_readahead();
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bool readahead;
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INC_CACHE_INFO(find_success);
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/*
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* At the moment, we don't support PG_readahead for anon THP
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* so let's bail out rather than confusing the readahead stat.
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*/
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if (unlikely(PageTransCompound(page)))
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return page;
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readahead = TestClearPageReadahead(page);
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if (vma && vma_ra) {
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unsigned long ra_val;
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int win, hits;
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ra_val = GET_SWAP_RA_VAL(vma);
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win = SWAP_RA_WIN(ra_val);
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hits = SWAP_RA_HITS(ra_val);
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if (readahead)
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hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
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atomic_long_set(&vma->swap_readahead_info,
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SWAP_RA_VAL(addr, win, hits));
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}
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if (readahead) {
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count_vm_event(SWAP_RA_HIT);
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if (!vma || !vma_ra)
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atomic_inc(&swapin_readahead_hits);
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}
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}
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return page;
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}
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/**
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* find_get_incore_page - Find and get a page from the page or swap caches.
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* @mapping: The address_space to search.
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* @index: The page cache index.
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*
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* This differs from find_get_page() in that it will also look for the
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* page in the swap cache.
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*
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* Return: The found page or %NULL.
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*/
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struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
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{
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swp_entry_t swp;
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struct swap_info_struct *si;
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struct page *page = pagecache_get_page(mapping, index,
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FGP_ENTRY | FGP_HEAD, 0);
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if (!page)
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return page;
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if (!xa_is_value(page))
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return find_subpage(page, index);
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if (!shmem_mapping(mapping))
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return NULL;
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swp = radix_to_swp_entry(page);
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/* Prevent swapoff from happening to us */
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si = get_swap_device(swp);
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if (!si)
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return NULL;
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page = find_get_page(swap_address_space(swp), swp_offset(swp));
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put_swap_device(si);
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return page;
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}
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|
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struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
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struct vm_area_struct *vma, unsigned long addr,
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bool *new_page_allocated)
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{
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struct swap_info_struct *si;
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struct page *page;
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void *shadow = NULL;
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*new_page_allocated = false;
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|
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for (;;) {
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int err;
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/*
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* First check the swap cache. Since this is normally
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* called after lookup_swap_cache() failed, re-calling
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* that would confuse statistics.
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*/
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si = get_swap_device(entry);
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if (!si)
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return NULL;
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page = find_get_page(swap_address_space(entry),
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swp_offset(entry));
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put_swap_device(si);
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if (page)
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return page;
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|
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/*
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* Just skip read ahead for unused swap slot.
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* During swap_off when swap_slot_cache is disabled,
|
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* we have to handle the race between putting
|
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* swap entry in swap cache and marking swap slot
|
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* as SWAP_HAS_CACHE. That's done in later part of code or
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* else swap_off will be aborted if we return NULL.
|
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*/
|
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if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
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return NULL;
|
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|
|
/*
|
|
* Get a new page to read into from swap. Allocate it now,
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* before marking swap_map SWAP_HAS_CACHE, when -EEXIST will
|
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* cause any racers to loop around until we add it to cache.
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*/
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page = alloc_page_vma(gfp_mask, vma, addr);
|
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if (!page)
|
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return NULL;
|
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|
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/*
|
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* Swap entry may have been freed since our caller observed it.
|
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*/
|
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err = swapcache_prepare(entry);
|
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if (!err)
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break;
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|
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put_page(page);
|
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if (err != -EEXIST)
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|
return NULL;
|
|
|
|
/*
|
|
* We might race against __delete_from_swap_cache(), and
|
|
* stumble across a swap_map entry whose SWAP_HAS_CACHE
|
|
* has not yet been cleared. Or race against another
|
|
* __read_swap_cache_async(), which has set SWAP_HAS_CACHE
|
|
* in swap_map, but not yet added its page to swap cache.
|
|
*/
|
|
cond_resched();
|
|
}
|
|
|
|
/*
|
|
* The swap entry is ours to swap in. Prepare the new page.
|
|
*/
|
|
|
|
__SetPageLocked(page);
|
|
__SetPageSwapBacked(page);
|
|
|
|
if (mem_cgroup_swapin_charge_page(page, NULL, gfp_mask, entry))
|
|
goto fail_unlock;
|
|
|
|
/* May fail (-ENOMEM) if XArray node allocation failed. */
|
|
if (add_to_swap_cache(page, entry, gfp_mask & GFP_RECLAIM_MASK, &shadow))
|
|
goto fail_unlock;
|
|
|
|
mem_cgroup_swapin_uncharge_swap(entry);
|
|
|
|
if (shadow)
|
|
workingset_refault(page, shadow);
|
|
|
|
/* Caller will initiate read into locked page */
|
|
lru_cache_add(page);
|
|
*new_page_allocated = true;
|
|
return page;
|
|
|
|
fail_unlock:
|
|
put_swap_page(page, entry);
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Locate a page of swap in physical memory, reserving swap cache space
|
|
* and reading the disk if it is not already cached.
|
|
* A failure return means that either the page allocation failed or that
|
|
* the swap entry is no longer in use.
|
|
*/
|
|
struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
|
|
struct vm_area_struct *vma, unsigned long addr, bool do_poll)
|
|
{
|
|
bool page_was_allocated;
|
|
struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
|
|
vma, addr, &page_was_allocated);
|
|
|
|
if (page_was_allocated)
|
|
swap_readpage(retpage, do_poll);
|
|
|
|
return retpage;
|
|
}
|
|
|
|
static unsigned int __swapin_nr_pages(unsigned long prev_offset,
|
|
unsigned long offset,
|
|
int hits,
|
|
int max_pages,
|
|
int prev_win)
|
|
{
|
|
unsigned int pages, last_ra;
|
|
|
|
/*
|
|
* This heuristic has been found to work well on both sequential and
|
|
* random loads, swapping to hard disk or to SSD: please don't ask
|
|
* what the "+ 2" means, it just happens to work well, that's all.
|
|
*/
|
|
pages = hits + 2;
|
|
if (pages == 2) {
|
|
/*
|
|
* We can have no readahead hits to judge by: but must not get
|
|
* stuck here forever, so check for an adjacent offset instead
|
|
* (and don't even bother to check whether swap type is same).
|
|
*/
|
|
if (offset != prev_offset + 1 && offset != prev_offset - 1)
|
|
pages = 1;
|
|
} else {
|
|
unsigned int roundup = 4;
|
|
while (roundup < pages)
|
|
roundup <<= 1;
|
|
pages = roundup;
|
|
}
|
|
|
|
if (pages > max_pages)
|
|
pages = max_pages;
|
|
|
|
/* Don't shrink readahead too fast */
|
|
last_ra = prev_win / 2;
|
|
if (pages < last_ra)
|
|
pages = last_ra;
|
|
|
|
return pages;
|
|
}
|
|
|
|
static unsigned long swapin_nr_pages(unsigned long offset)
|
|
{
|
|
static unsigned long prev_offset;
|
|
unsigned int hits, pages, max_pages;
|
|
static atomic_t last_readahead_pages;
|
|
|
|
max_pages = 1 << READ_ONCE(page_cluster);
|
|
if (max_pages <= 1)
|
|
return 1;
|
|
|
|
hits = atomic_xchg(&swapin_readahead_hits, 0);
|
|
pages = __swapin_nr_pages(READ_ONCE(prev_offset), offset, hits,
|
|
max_pages,
|
|
atomic_read(&last_readahead_pages));
|
|
if (!hits)
|
|
WRITE_ONCE(prev_offset, offset);
|
|
atomic_set(&last_readahead_pages, pages);
|
|
|
|
return pages;
|
|
}
|
|
|
|
/**
|
|
* swap_cluster_readahead - swap in pages in hope we need them soon
|
|
* @entry: swap entry of this memory
|
|
* @gfp_mask: memory allocation flags
|
|
* @vmf: fault information
|
|
*
|
|
* Returns the struct page for entry and addr, after queueing swapin.
|
|
*
|
|
* Primitive swap readahead code. We simply read an aligned block of
|
|
* (1 << page_cluster) entries in the swap area. This method is chosen
|
|
* because it doesn't cost us any seek time. We also make sure to queue
|
|
* the 'original' request together with the readahead ones...
|
|
*
|
|
* This has been extended to use the NUMA policies from the mm triggering
|
|
* the readahead.
|
|
*
|
|
* Caller must hold read mmap_lock if vmf->vma is not NULL.
|
|
*/
|
|
struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
|
|
struct vm_fault *vmf)
|
|
{
|
|
struct page *page;
|
|
unsigned long entry_offset = swp_offset(entry);
|
|
unsigned long offset = entry_offset;
|
|
unsigned long start_offset, end_offset;
|
|
unsigned long mask;
|
|
struct swap_info_struct *si = swp_swap_info(entry);
|
|
struct blk_plug plug;
|
|
bool do_poll = true, page_allocated;
|
|
struct vm_area_struct *vma = vmf->vma;
|
|
unsigned long addr = vmf->address;
|
|
|
|
mask = swapin_nr_pages(offset) - 1;
|
|
if (!mask)
|
|
goto skip;
|
|
|
|
do_poll = false;
|
|
/* Read a page_cluster sized and aligned cluster around offset. */
|
|
start_offset = offset & ~mask;
|
|
end_offset = offset | mask;
|
|
if (!start_offset) /* First page is swap header. */
|
|
start_offset++;
|
|
if (end_offset >= si->max)
|
|
end_offset = si->max - 1;
|
|
|
|
blk_start_plug(&plug);
|
|
for (offset = start_offset; offset <= end_offset ; offset++) {
|
|
/* Ok, do the async read-ahead now */
|
|
page = __read_swap_cache_async(
|
|
swp_entry(swp_type(entry), offset),
|
|
gfp_mask, vma, addr, &page_allocated);
|
|
if (!page)
|
|
continue;
|
|
if (page_allocated) {
|
|
swap_readpage(page, false);
|
|
if (offset != entry_offset) {
|
|
SetPageReadahead(page);
|
|
count_vm_event(SWAP_RA);
|
|
}
|
|
}
|
|
put_page(page);
|
|
}
|
|
blk_finish_plug(&plug);
|
|
|
|
lru_add_drain(); /* Push any new pages onto the LRU now */
|
|
skip:
|
|
return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
|
|
}
|
|
|
|
int init_swap_address_space(unsigned int type, unsigned long nr_pages)
|
|
{
|
|
struct address_space *spaces, *space;
|
|
unsigned int i, nr;
|
|
|
|
nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
|
|
spaces = kvcalloc(nr, sizeof(struct address_space), GFP_KERNEL);
|
|
if (!spaces)
|
|
return -ENOMEM;
|
|
for (i = 0; i < nr; i++) {
|
|
space = spaces + i;
|
|
xa_init_flags(&space->i_pages, XA_FLAGS_LOCK_IRQ);
|
|
atomic_set(&space->i_mmap_writable, 0);
|
|
space->a_ops = &swap_aops;
|
|
/* swap cache doesn't use writeback related tags */
|
|
mapping_set_no_writeback_tags(space);
|
|
}
|
|
nr_swapper_spaces[type] = nr;
|
|
swapper_spaces[type] = spaces;
|
|
|
|
return 0;
|
|
}
|
|
|
|
void exit_swap_address_space(unsigned int type)
|
|
{
|
|
int i;
|
|
struct address_space *spaces = swapper_spaces[type];
|
|
|
|
for (i = 0; i < nr_swapper_spaces[type]; i++)
|
|
VM_WARN_ON_ONCE(!mapping_empty(&spaces[i]));
|
|
kvfree(spaces);
|
|
nr_swapper_spaces[type] = 0;
|
|
swapper_spaces[type] = NULL;
|
|
}
|
|
|
|
static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
|
|
unsigned long faddr,
|
|
unsigned long lpfn,
|
|
unsigned long rpfn,
|
|
unsigned long *start,
|
|
unsigned long *end)
|
|
{
|
|
*start = max3(lpfn, PFN_DOWN(vma->vm_start),
|
|
PFN_DOWN(faddr & PMD_MASK));
|
|
*end = min3(rpfn, PFN_DOWN(vma->vm_end),
|
|
PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
|
|
}
|
|
|
|
static void swap_ra_info(struct vm_fault *vmf,
|
|
struct vma_swap_readahead *ra_info)
|
|
{
|
|
struct vm_area_struct *vma = vmf->vma;
|
|
unsigned long ra_val;
|
|
unsigned long faddr, pfn, fpfn;
|
|
unsigned long start, end;
|
|
pte_t *pte, *orig_pte;
|
|
unsigned int max_win, hits, prev_win, win, left;
|
|
#ifndef CONFIG_64BIT
|
|
pte_t *tpte;
|
|
#endif
|
|
|
|
max_win = 1 << min_t(unsigned int, READ_ONCE(page_cluster),
|
|
SWAP_RA_ORDER_CEILING);
|
|
if (max_win == 1) {
|
|
ra_info->win = 1;
|
|
return;
|
|
}
|
|
|
|
faddr = vmf->address;
|
|
orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
|
|
|
|
fpfn = PFN_DOWN(faddr);
|
|
ra_val = GET_SWAP_RA_VAL(vma);
|
|
pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
|
|
prev_win = SWAP_RA_WIN(ra_val);
|
|
hits = SWAP_RA_HITS(ra_val);
|
|
ra_info->win = win = __swapin_nr_pages(pfn, fpfn, hits,
|
|
max_win, prev_win);
|
|
atomic_long_set(&vma->swap_readahead_info,
|
|
SWAP_RA_VAL(faddr, win, 0));
|
|
|
|
if (win == 1) {
|
|
pte_unmap(orig_pte);
|
|
return;
|
|
}
|
|
|
|
/* Copy the PTEs because the page table may be unmapped */
|
|
if (fpfn == pfn + 1)
|
|
swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
|
|
else if (pfn == fpfn + 1)
|
|
swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
|
|
&start, &end);
|
|
else {
|
|
left = (win - 1) / 2;
|
|
swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
|
|
&start, &end);
|
|
}
|
|
ra_info->nr_pte = end - start;
|
|
ra_info->offset = fpfn - start;
|
|
pte -= ra_info->offset;
|
|
#ifdef CONFIG_64BIT
|
|
ra_info->ptes = pte;
|
|
#else
|
|
tpte = ra_info->ptes;
|
|
for (pfn = start; pfn != end; pfn++)
|
|
*tpte++ = *pte++;
|
|
#endif
|
|
pte_unmap(orig_pte);
|
|
}
|
|
|
|
/**
|
|
* swap_vma_readahead - swap in pages in hope we need them soon
|
|
* @fentry: swap entry of this memory
|
|
* @gfp_mask: memory allocation flags
|
|
* @vmf: fault information
|
|
*
|
|
* Returns the struct page for entry and addr, after queueing swapin.
|
|
*
|
|
* Primitive swap readahead code. We simply read in a few pages whose
|
|
* virtual addresses are around the fault address in the same vma.
|
|
*
|
|
* Caller must hold read mmap_lock if vmf->vma is not NULL.
|
|
*
|
|
*/
|
|
static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
|
|
struct vm_fault *vmf)
|
|
{
|
|
struct blk_plug plug;
|
|
struct vm_area_struct *vma = vmf->vma;
|
|
struct page *page;
|
|
pte_t *pte, pentry;
|
|
swp_entry_t entry;
|
|
unsigned int i;
|
|
bool page_allocated;
|
|
struct vma_swap_readahead ra_info = {
|
|
.win = 1,
|
|
};
|
|
|
|
swap_ra_info(vmf, &ra_info);
|
|
if (ra_info.win == 1)
|
|
goto skip;
|
|
|
|
blk_start_plug(&plug);
|
|
for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte;
|
|
i++, pte++) {
|
|
pentry = *pte;
|
|
if (pte_none(pentry))
|
|
continue;
|
|
if (pte_present(pentry))
|
|
continue;
|
|
entry = pte_to_swp_entry(pentry);
|
|
if (unlikely(non_swap_entry(entry)))
|
|
continue;
|
|
page = __read_swap_cache_async(entry, gfp_mask, vma,
|
|
vmf->address, &page_allocated);
|
|
if (!page)
|
|
continue;
|
|
if (page_allocated) {
|
|
swap_readpage(page, false);
|
|
if (i != ra_info.offset) {
|
|
SetPageReadahead(page);
|
|
count_vm_event(SWAP_RA);
|
|
}
|
|
}
|
|
put_page(page);
|
|
}
|
|
blk_finish_plug(&plug);
|
|
lru_add_drain();
|
|
skip:
|
|
return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
|
|
ra_info.win == 1);
|
|
}
|
|
|
|
/**
|
|
* swapin_readahead - swap in pages in hope we need them soon
|
|
* @entry: swap entry of this memory
|
|
* @gfp_mask: memory allocation flags
|
|
* @vmf: fault information
|
|
*
|
|
* Returns the struct page for entry and addr, after queueing swapin.
|
|
*
|
|
* It's a main entry function for swap readahead. By the configuration,
|
|
* it will read ahead blocks by cluster-based(ie, physical disk based)
|
|
* or vma-based(ie, virtual address based on faulty address) readahead.
|
|
*/
|
|
struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
|
|
struct vm_fault *vmf)
|
|
{
|
|
return swap_use_vma_readahead() ?
|
|
swap_vma_readahead(entry, gfp_mask, vmf) :
|
|
swap_cluster_readahead(entry, gfp_mask, vmf);
|
|
}
|
|
|
|
#ifdef CONFIG_SYSFS
|
|
static ssize_t vma_ra_enabled_show(struct kobject *kobj,
|
|
struct kobj_attribute *attr, char *buf)
|
|
{
|
|
return sysfs_emit(buf, "%s\n",
|
|
enable_vma_readahead ? "true" : "false");
|
|
}
|
|
static ssize_t vma_ra_enabled_store(struct kobject *kobj,
|
|
struct kobj_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
|
|
enable_vma_readahead = true;
|
|
else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
|
|
enable_vma_readahead = false;
|
|
else
|
|
return -EINVAL;
|
|
|
|
return count;
|
|
}
|
|
static struct kobj_attribute vma_ra_enabled_attr =
|
|
__ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
|
|
vma_ra_enabled_store);
|
|
|
|
static struct attribute *swap_attrs[] = {
|
|
&vma_ra_enabled_attr.attr,
|
|
NULL,
|
|
};
|
|
|
|
static const struct attribute_group swap_attr_group = {
|
|
.attrs = swap_attrs,
|
|
};
|
|
|
|
static int __init swap_init_sysfs(void)
|
|
{
|
|
int err;
|
|
struct kobject *swap_kobj;
|
|
|
|
swap_kobj = kobject_create_and_add("swap", mm_kobj);
|
|
if (!swap_kobj) {
|
|
pr_err("failed to create swap kobject\n");
|
|
return -ENOMEM;
|
|
}
|
|
err = sysfs_create_group(swap_kobj, &swap_attr_group);
|
|
if (err) {
|
|
pr_err("failed to register swap group\n");
|
|
goto delete_obj;
|
|
}
|
|
return 0;
|
|
|
|
delete_obj:
|
|
kobject_put(swap_kobj);
|
|
return err;
|
|
}
|
|
subsys_initcall(swap_init_sysfs);
|
|
#endif
|