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98f32602d4
My old address will shut down in a few days time: remove it from the tree, and add a tmpfs (shmem filesystem) maintainer entry with the new address. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1230 lines
34 KiB
C
1230 lines
34 KiB
C
/*
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* mm/rmap.c - physical to virtual reverse mappings
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*
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* Copyright 2001, Rik van Riel <riel@conectiva.com.br>
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* Released under the General Public License (GPL).
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*
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* Simple, low overhead reverse mapping scheme.
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* Please try to keep this thing as modular as possible.
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*
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* Provides methods for unmapping each kind of mapped page:
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* the anon methods track anonymous pages, and
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* the file methods track pages belonging to an inode.
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*
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* Original design by Rik van Riel <riel@conectiva.com.br> 2001
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* File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
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* Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
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* Contributions by Hugh Dickins 2003, 2004
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*/
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/*
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* Lock ordering in mm:
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*
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* inode->i_mutex (while writing or truncating, not reading or faulting)
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* inode->i_alloc_sem (vmtruncate_range)
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* mm->mmap_sem
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* page->flags PG_locked (lock_page)
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* mapping->i_mmap_lock
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* anon_vma->lock
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* mm->page_table_lock or pte_lock
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* zone->lru_lock (in mark_page_accessed, isolate_lru_page)
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* swap_lock (in swap_duplicate, swap_info_get)
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* mmlist_lock (in mmput, drain_mmlist and others)
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* mapping->private_lock (in __set_page_dirty_buffers)
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* inode_lock (in set_page_dirty's __mark_inode_dirty)
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* sb_lock (within inode_lock in fs/fs-writeback.c)
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* mapping->tree_lock (widely used, in set_page_dirty,
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* in arch-dependent flush_dcache_mmap_lock,
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* within inode_lock in __sync_single_inode)
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*/
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/rmap.h>
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#include <linux/rcupdate.h>
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#include <linux/module.h>
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#include <linux/memcontrol.h>
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#include <linux/mmu_notifier.h>
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#include <linux/migrate.h>
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#include <asm/tlbflush.h>
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#include "internal.h"
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static struct kmem_cache *anon_vma_cachep;
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static inline struct anon_vma *anon_vma_alloc(void)
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{
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return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
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}
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static inline void anon_vma_free(struct anon_vma *anon_vma)
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{
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kmem_cache_free(anon_vma_cachep, anon_vma);
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}
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/**
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* anon_vma_prepare - attach an anon_vma to a memory region
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* @vma: the memory region in question
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*
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* This makes sure the memory mapping described by 'vma' has
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* an 'anon_vma' attached to it, so that we can associate the
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* anonymous pages mapped into it with that anon_vma.
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*
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* The common case will be that we already have one, but if
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* if not we either need to find an adjacent mapping that we
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* can re-use the anon_vma from (very common when the only
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* reason for splitting a vma has been mprotect()), or we
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* allocate a new one.
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*
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* Anon-vma allocations are very subtle, because we may have
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* optimistically looked up an anon_vma in page_lock_anon_vma()
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* and that may actually touch the spinlock even in the newly
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* allocated vma (it depends on RCU to make sure that the
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* anon_vma isn't actually destroyed).
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*
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* As a result, we need to do proper anon_vma locking even
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* for the new allocation. At the same time, we do not want
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* to do any locking for the common case of already having
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* an anon_vma.
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*
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* This must be called with the mmap_sem held for reading.
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*/
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int anon_vma_prepare(struct vm_area_struct *vma)
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{
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struct anon_vma *anon_vma = vma->anon_vma;
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might_sleep();
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if (unlikely(!anon_vma)) {
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struct mm_struct *mm = vma->vm_mm;
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struct anon_vma *allocated;
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anon_vma = find_mergeable_anon_vma(vma);
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allocated = NULL;
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if (!anon_vma) {
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anon_vma = anon_vma_alloc();
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if (unlikely(!anon_vma))
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return -ENOMEM;
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allocated = anon_vma;
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}
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spin_lock(&anon_vma->lock);
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/* page_table_lock to protect against threads */
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spin_lock(&mm->page_table_lock);
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if (likely(!vma->anon_vma)) {
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vma->anon_vma = anon_vma;
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list_add_tail(&vma->anon_vma_node, &anon_vma->head);
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allocated = NULL;
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}
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spin_unlock(&mm->page_table_lock);
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spin_unlock(&anon_vma->lock);
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if (unlikely(allocated))
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anon_vma_free(allocated);
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}
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return 0;
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}
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void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
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{
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BUG_ON(vma->anon_vma != next->anon_vma);
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list_del(&next->anon_vma_node);
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}
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void __anon_vma_link(struct vm_area_struct *vma)
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{
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struct anon_vma *anon_vma = vma->anon_vma;
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if (anon_vma)
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list_add_tail(&vma->anon_vma_node, &anon_vma->head);
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}
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void anon_vma_link(struct vm_area_struct *vma)
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{
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struct anon_vma *anon_vma = vma->anon_vma;
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if (anon_vma) {
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spin_lock(&anon_vma->lock);
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list_add_tail(&vma->anon_vma_node, &anon_vma->head);
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spin_unlock(&anon_vma->lock);
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}
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}
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void anon_vma_unlink(struct vm_area_struct *vma)
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{
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struct anon_vma *anon_vma = vma->anon_vma;
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int empty;
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if (!anon_vma)
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return;
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spin_lock(&anon_vma->lock);
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list_del(&vma->anon_vma_node);
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/* We must garbage collect the anon_vma if it's empty */
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empty = list_empty(&anon_vma->head);
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spin_unlock(&anon_vma->lock);
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if (empty)
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anon_vma_free(anon_vma);
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}
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static void anon_vma_ctor(void *data)
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{
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struct anon_vma *anon_vma = data;
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spin_lock_init(&anon_vma->lock);
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INIT_LIST_HEAD(&anon_vma->head);
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}
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void __init anon_vma_init(void)
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{
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anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
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0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
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}
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/*
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* Getting a lock on a stable anon_vma from a page off the LRU is
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* tricky: page_lock_anon_vma rely on RCU to guard against the races.
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*/
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static struct anon_vma *page_lock_anon_vma(struct page *page)
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{
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struct anon_vma *anon_vma;
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unsigned long anon_mapping;
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rcu_read_lock();
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anon_mapping = (unsigned long) page->mapping;
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if (!(anon_mapping & PAGE_MAPPING_ANON))
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goto out;
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if (!page_mapped(page))
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goto out;
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anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
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spin_lock(&anon_vma->lock);
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return anon_vma;
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out:
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rcu_read_unlock();
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return NULL;
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}
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static void page_unlock_anon_vma(struct anon_vma *anon_vma)
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{
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spin_unlock(&anon_vma->lock);
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rcu_read_unlock();
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}
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/*
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* At what user virtual address is page expected in @vma?
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* Returns virtual address or -EFAULT if page's index/offset is not
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* within the range mapped the @vma.
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*/
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static inline unsigned long
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vma_address(struct page *page, struct vm_area_struct *vma)
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{
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pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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unsigned long address;
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address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
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if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
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/* page should be within @vma mapping range */
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return -EFAULT;
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}
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return address;
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}
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/*
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* At what user virtual address is page expected in vma? checking that the
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* page matches the vma: currently only used on anon pages, by unuse_vma;
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*/
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unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
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{
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if (PageAnon(page)) {
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if ((void *)vma->anon_vma !=
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(void *)page->mapping - PAGE_MAPPING_ANON)
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return -EFAULT;
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} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
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if (!vma->vm_file ||
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vma->vm_file->f_mapping != page->mapping)
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return -EFAULT;
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} else
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return -EFAULT;
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return vma_address(page, vma);
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}
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/*
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* Check that @page is mapped at @address into @mm.
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*
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* If @sync is false, page_check_address may perform a racy check to avoid
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* the page table lock when the pte is not present (helpful when reclaiming
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* highly shared pages).
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*
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* On success returns with pte mapped and locked.
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*/
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pte_t *page_check_address(struct page *page, struct mm_struct *mm,
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unsigned long address, spinlock_t **ptlp, int sync)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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spinlock_t *ptl;
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pgd = pgd_offset(mm, address);
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if (!pgd_present(*pgd))
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return NULL;
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pud = pud_offset(pgd, address);
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if (!pud_present(*pud))
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return NULL;
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pmd = pmd_offset(pud, address);
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if (!pmd_present(*pmd))
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return NULL;
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pte = pte_offset_map(pmd, address);
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/* Make a quick check before getting the lock */
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if (!sync && !pte_present(*pte)) {
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pte_unmap(pte);
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return NULL;
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}
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ptl = pte_lockptr(mm, pmd);
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spin_lock(ptl);
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if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
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*ptlp = ptl;
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return pte;
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}
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pte_unmap_unlock(pte, ptl);
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return NULL;
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}
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/**
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* page_mapped_in_vma - check whether a page is really mapped in a VMA
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* @page: the page to test
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* @vma: the VMA to test
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*
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* Returns 1 if the page is mapped into the page tables of the VMA, 0
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* if the page is not mapped into the page tables of this VMA. Only
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* valid for normal file or anonymous VMAs.
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*/
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static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
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{
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unsigned long address;
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pte_t *pte;
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spinlock_t *ptl;
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address = vma_address(page, vma);
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if (address == -EFAULT) /* out of vma range */
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return 0;
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pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
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if (!pte) /* the page is not in this mm */
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return 0;
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pte_unmap_unlock(pte, ptl);
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return 1;
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}
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/*
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* Subfunctions of page_referenced: page_referenced_one called
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* repeatedly from either page_referenced_anon or page_referenced_file.
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*/
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static int page_referenced_one(struct page *page,
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struct vm_area_struct *vma, unsigned int *mapcount)
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{
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struct mm_struct *mm = vma->vm_mm;
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unsigned long address;
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pte_t *pte;
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spinlock_t *ptl;
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int referenced = 0;
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address = vma_address(page, vma);
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if (address == -EFAULT)
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goto out;
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pte = page_check_address(page, mm, address, &ptl, 0);
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if (!pte)
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goto out;
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/*
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* Don't want to elevate referenced for mlocked page that gets this far,
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* in order that it progresses to try_to_unmap and is moved to the
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* unevictable list.
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*/
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if (vma->vm_flags & VM_LOCKED) {
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*mapcount = 1; /* break early from loop */
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goto out_unmap;
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}
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if (ptep_clear_flush_young_notify(vma, address, pte)) {
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/*
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* Don't treat a reference through a sequentially read
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* mapping as such. If the page has been used in
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* another mapping, we will catch it; if this other
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* mapping is already gone, the unmap path will have
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* set PG_referenced or activated the page.
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*/
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if (likely(!VM_SequentialReadHint(vma)))
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referenced++;
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}
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/* Pretend the page is referenced if the task has the
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swap token and is in the middle of a page fault. */
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if (mm != current->mm && has_swap_token(mm) &&
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rwsem_is_locked(&mm->mmap_sem))
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referenced++;
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out_unmap:
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(*mapcount)--;
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pte_unmap_unlock(pte, ptl);
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out:
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return referenced;
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}
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static int page_referenced_anon(struct page *page,
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struct mem_cgroup *mem_cont)
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{
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unsigned int mapcount;
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struct anon_vma *anon_vma;
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struct vm_area_struct *vma;
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int referenced = 0;
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anon_vma = page_lock_anon_vma(page);
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if (!anon_vma)
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return referenced;
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mapcount = page_mapcount(page);
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list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
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/*
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* If we are reclaiming on behalf of a cgroup, skip
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* counting on behalf of references from different
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* cgroups
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*/
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if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
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continue;
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referenced += page_referenced_one(page, vma, &mapcount);
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if (!mapcount)
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break;
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}
|
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|
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page_unlock_anon_vma(anon_vma);
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return referenced;
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}
|
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|
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/**
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* page_referenced_file - referenced check for object-based rmap
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* @page: the page we're checking references on.
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* @mem_cont: target memory controller
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*
|
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* For an object-based mapped page, find all the places it is mapped and
|
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* check/clear the referenced flag. This is done by following the page->mapping
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* pointer, then walking the chain of vmas it holds. It returns the number
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* of references it found.
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*
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* This function is only called from page_referenced for object-based pages.
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*/
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static int page_referenced_file(struct page *page,
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struct mem_cgroup *mem_cont)
|
|
{
|
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unsigned int mapcount;
|
|
struct address_space *mapping = page->mapping;
|
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pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
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struct vm_area_struct *vma;
|
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struct prio_tree_iter iter;
|
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int referenced = 0;
|
|
|
|
/*
|
|
* The caller's checks on page->mapping and !PageAnon have made
|
|
* sure that this is a file page: the check for page->mapping
|
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* excludes the case just before it gets set on an anon page.
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*/
|
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BUG_ON(PageAnon(page));
|
|
|
|
/*
|
|
* The page lock not only makes sure that page->mapping cannot
|
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* suddenly be NULLified by truncation, it makes sure that the
|
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* structure at mapping cannot be freed and reused yet,
|
|
* so we can safely take mapping->i_mmap_lock.
|
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*/
|
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BUG_ON(!PageLocked(page));
|
|
|
|
spin_lock(&mapping->i_mmap_lock);
|
|
|
|
/*
|
|
* i_mmap_lock does not stabilize mapcount at all, but mapcount
|
|
* is more likely to be accurate if we note it after spinning.
|
|
*/
|
|
mapcount = page_mapcount(page);
|
|
|
|
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
|
|
/*
|
|
* If we are reclaiming on behalf of a cgroup, skip
|
|
* counting on behalf of references from different
|
|
* cgroups
|
|
*/
|
|
if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
|
|
continue;
|
|
referenced += page_referenced_one(page, vma, &mapcount);
|
|
if (!mapcount)
|
|
break;
|
|
}
|
|
|
|
spin_unlock(&mapping->i_mmap_lock);
|
|
return referenced;
|
|
}
|
|
|
|
/**
|
|
* page_referenced - test if the page was referenced
|
|
* @page: the page to test
|
|
* @is_locked: caller holds lock on the page
|
|
* @mem_cont: target memory controller
|
|
*
|
|
* Quick test_and_clear_referenced for all mappings to a page,
|
|
* returns the number of ptes which referenced the page.
|
|
*/
|
|
int page_referenced(struct page *page, int is_locked,
|
|
struct mem_cgroup *mem_cont)
|
|
{
|
|
int referenced = 0;
|
|
|
|
if (TestClearPageReferenced(page))
|
|
referenced++;
|
|
|
|
if (page_mapped(page) && page->mapping) {
|
|
if (PageAnon(page))
|
|
referenced += page_referenced_anon(page, mem_cont);
|
|
else if (is_locked)
|
|
referenced += page_referenced_file(page, mem_cont);
|
|
else if (!trylock_page(page))
|
|
referenced++;
|
|
else {
|
|
if (page->mapping)
|
|
referenced +=
|
|
page_referenced_file(page, mem_cont);
|
|
unlock_page(page);
|
|
}
|
|
}
|
|
|
|
if (page_test_and_clear_young(page))
|
|
referenced++;
|
|
|
|
return referenced;
|
|
}
|
|
|
|
static int page_mkclean_one(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
unsigned long address;
|
|
pte_t *pte;
|
|
spinlock_t *ptl;
|
|
int ret = 0;
|
|
|
|
address = vma_address(page, vma);
|
|
if (address == -EFAULT)
|
|
goto out;
|
|
|
|
pte = page_check_address(page, mm, address, &ptl, 1);
|
|
if (!pte)
|
|
goto out;
|
|
|
|
if (pte_dirty(*pte) || pte_write(*pte)) {
|
|
pte_t entry;
|
|
|
|
flush_cache_page(vma, address, pte_pfn(*pte));
|
|
entry = ptep_clear_flush_notify(vma, address, pte);
|
|
entry = pte_wrprotect(entry);
|
|
entry = pte_mkclean(entry);
|
|
set_pte_at(mm, address, pte, entry);
|
|
ret = 1;
|
|
}
|
|
|
|
pte_unmap_unlock(pte, ptl);
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
static int page_mkclean_file(struct address_space *mapping, struct page *page)
|
|
{
|
|
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
|
|
struct vm_area_struct *vma;
|
|
struct prio_tree_iter iter;
|
|
int ret = 0;
|
|
|
|
BUG_ON(PageAnon(page));
|
|
|
|
spin_lock(&mapping->i_mmap_lock);
|
|
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
|
|
if (vma->vm_flags & VM_SHARED)
|
|
ret += page_mkclean_one(page, vma);
|
|
}
|
|
spin_unlock(&mapping->i_mmap_lock);
|
|
return ret;
|
|
}
|
|
|
|
int page_mkclean(struct page *page)
|
|
{
|
|
int ret = 0;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (page_mapped(page)) {
|
|
struct address_space *mapping = page_mapping(page);
|
|
if (mapping) {
|
|
ret = page_mkclean_file(mapping, page);
|
|
if (page_test_dirty(page)) {
|
|
page_clear_dirty(page);
|
|
ret = 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_mkclean);
|
|
|
|
/**
|
|
* __page_set_anon_rmap - setup new anonymous rmap
|
|
* @page: the page to add the mapping to
|
|
* @vma: the vm area in which the mapping is added
|
|
* @address: the user virtual address mapped
|
|
*/
|
|
static void __page_set_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
|
|
BUG_ON(!anon_vma);
|
|
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
|
|
page->mapping = (struct address_space *) anon_vma;
|
|
|
|
page->index = linear_page_index(vma, address);
|
|
|
|
/*
|
|
* nr_mapped state can be updated without turning off
|
|
* interrupts because it is not modified via interrupt.
|
|
*/
|
|
__inc_zone_page_state(page, NR_ANON_PAGES);
|
|
}
|
|
|
|
/**
|
|
* __page_check_anon_rmap - sanity check anonymous rmap addition
|
|
* @page: the page to add the mapping to
|
|
* @vma: the vm area in which the mapping is added
|
|
* @address: the user virtual address mapped
|
|
*/
|
|
static void __page_check_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
#ifdef CONFIG_DEBUG_VM
|
|
/*
|
|
* The page's anon-rmap details (mapping and index) are guaranteed to
|
|
* be set up correctly at this point.
|
|
*
|
|
* We have exclusion against page_add_anon_rmap because the caller
|
|
* always holds the page locked, except if called from page_dup_rmap,
|
|
* in which case the page is already known to be setup.
|
|
*
|
|
* We have exclusion against page_add_new_anon_rmap because those pages
|
|
* are initially only visible via the pagetables, and the pte is locked
|
|
* over the call to page_add_new_anon_rmap.
|
|
*/
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
|
|
BUG_ON(page->mapping != (struct address_space *)anon_vma);
|
|
BUG_ON(page->index != linear_page_index(vma, address));
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* page_add_anon_rmap - add pte mapping to an anonymous page
|
|
* @page: the page to add the mapping to
|
|
* @vma: the vm area in which the mapping is added
|
|
* @address: the user virtual address mapped
|
|
*
|
|
* The caller needs to hold the pte lock and the page must be locked.
|
|
*/
|
|
void page_add_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
VM_BUG_ON(!PageLocked(page));
|
|
VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
|
|
if (atomic_inc_and_test(&page->_mapcount))
|
|
__page_set_anon_rmap(page, vma, address);
|
|
else
|
|
__page_check_anon_rmap(page, vma, address);
|
|
}
|
|
|
|
/**
|
|
* page_add_new_anon_rmap - add pte mapping to a new anonymous page
|
|
* @page: the page to add the mapping to
|
|
* @vma: the vm area in which the mapping is added
|
|
* @address: the user virtual address mapped
|
|
*
|
|
* Same as page_add_anon_rmap but must only be called on *new* pages.
|
|
* This means the inc-and-test can be bypassed.
|
|
* Page does not have to be locked.
|
|
*/
|
|
void page_add_new_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
|
|
SetPageSwapBacked(page);
|
|
atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
|
|
__page_set_anon_rmap(page, vma, address);
|
|
if (page_evictable(page, vma))
|
|
lru_cache_add_lru(page, LRU_ACTIVE_ANON);
|
|
else
|
|
add_page_to_unevictable_list(page);
|
|
}
|
|
|
|
/**
|
|
* page_add_file_rmap - add pte mapping to a file page
|
|
* @page: the page to add the mapping to
|
|
*
|
|
* The caller needs to hold the pte lock.
|
|
*/
|
|
void page_add_file_rmap(struct page *page)
|
|
{
|
|
if (atomic_inc_and_test(&page->_mapcount))
|
|
__inc_zone_page_state(page, NR_FILE_MAPPED);
|
|
}
|
|
|
|
#ifdef CONFIG_DEBUG_VM
|
|
/**
|
|
* page_dup_rmap - duplicate pte mapping to a page
|
|
* @page: the page to add the mapping to
|
|
* @vma: the vm area being duplicated
|
|
* @address: the user virtual address mapped
|
|
*
|
|
* For copy_page_range only: minimal extract from page_add_file_rmap /
|
|
* page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's
|
|
* quicker.
|
|
*
|
|
* The caller needs to hold the pte lock.
|
|
*/
|
|
void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
if (PageAnon(page))
|
|
__page_check_anon_rmap(page, vma, address);
|
|
atomic_inc(&page->_mapcount);
|
|
}
|
|
#endif
|
|
|
|
/**
|
|
* page_remove_rmap - take down pte mapping from a page
|
|
* @page: page to remove mapping from
|
|
*
|
|
* The caller needs to hold the pte lock.
|
|
*/
|
|
void page_remove_rmap(struct page *page)
|
|
{
|
|
if (atomic_add_negative(-1, &page->_mapcount)) {
|
|
/*
|
|
* Now that the last pte has gone, s390 must transfer dirty
|
|
* flag from storage key to struct page. We can usually skip
|
|
* this if the page is anon, so about to be freed; but perhaps
|
|
* not if it's in swapcache - there might be another pte slot
|
|
* containing the swap entry, but page not yet written to swap.
|
|
*/
|
|
if ((!PageAnon(page) || PageSwapCache(page)) &&
|
|
page_test_dirty(page)) {
|
|
page_clear_dirty(page);
|
|
set_page_dirty(page);
|
|
}
|
|
if (PageAnon(page))
|
|
mem_cgroup_uncharge_page(page);
|
|
__dec_zone_page_state(page,
|
|
PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
|
|
/*
|
|
* It would be tidy to reset the PageAnon mapping here,
|
|
* but that might overwrite a racing page_add_anon_rmap
|
|
* which increments mapcount after us but sets mapping
|
|
* before us: so leave the reset to free_hot_cold_page,
|
|
* and remember that it's only reliable while mapped.
|
|
* Leaving it set also helps swapoff to reinstate ptes
|
|
* faster for those pages still in swapcache.
|
|
*/
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Subfunctions of try_to_unmap: try_to_unmap_one called
|
|
* repeatedly from either try_to_unmap_anon or try_to_unmap_file.
|
|
*/
|
|
static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
|
|
int migration)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
unsigned long address;
|
|
pte_t *pte;
|
|
pte_t pteval;
|
|
spinlock_t *ptl;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
address = vma_address(page, vma);
|
|
if (address == -EFAULT)
|
|
goto out;
|
|
|
|
pte = page_check_address(page, mm, address, &ptl, 0);
|
|
if (!pte)
|
|
goto out;
|
|
|
|
/*
|
|
* If the page is mlock()d, we cannot swap it out.
|
|
* If it's recently referenced (perhaps page_referenced
|
|
* skipped over this mm) then we should reactivate it.
|
|
*/
|
|
if (!migration) {
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
ret = SWAP_MLOCK;
|
|
goto out_unmap;
|
|
}
|
|
if (ptep_clear_flush_young_notify(vma, address, pte)) {
|
|
ret = SWAP_FAIL;
|
|
goto out_unmap;
|
|
}
|
|
}
|
|
|
|
/* Nuke the page table entry. */
|
|
flush_cache_page(vma, address, page_to_pfn(page));
|
|
pteval = ptep_clear_flush_notify(vma, address, pte);
|
|
|
|
/* Move the dirty bit to the physical page now the pte is gone. */
|
|
if (pte_dirty(pteval))
|
|
set_page_dirty(page);
|
|
|
|
/* Update high watermark before we lower rss */
|
|
update_hiwater_rss(mm);
|
|
|
|
if (PageAnon(page)) {
|
|
swp_entry_t entry = { .val = page_private(page) };
|
|
|
|
if (PageSwapCache(page)) {
|
|
/*
|
|
* Store the swap location in the pte.
|
|
* See handle_pte_fault() ...
|
|
*/
|
|
swap_duplicate(entry);
|
|
if (list_empty(&mm->mmlist)) {
|
|
spin_lock(&mmlist_lock);
|
|
if (list_empty(&mm->mmlist))
|
|
list_add(&mm->mmlist, &init_mm.mmlist);
|
|
spin_unlock(&mmlist_lock);
|
|
}
|
|
dec_mm_counter(mm, anon_rss);
|
|
} else if (PAGE_MIGRATION) {
|
|
/*
|
|
* Store the pfn of the page in a special migration
|
|
* pte. do_swap_page() will wait until the migration
|
|
* pte is removed and then restart fault handling.
|
|
*/
|
|
BUG_ON(!migration);
|
|
entry = make_migration_entry(page, pte_write(pteval));
|
|
}
|
|
set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
|
|
BUG_ON(pte_file(*pte));
|
|
} else if (PAGE_MIGRATION && migration) {
|
|
/* Establish migration entry for a file page */
|
|
swp_entry_t entry;
|
|
entry = make_migration_entry(page, pte_write(pteval));
|
|
set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
|
|
} else
|
|
dec_mm_counter(mm, file_rss);
|
|
|
|
|
|
page_remove_rmap(page);
|
|
page_cache_release(page);
|
|
|
|
out_unmap:
|
|
pte_unmap_unlock(pte, ptl);
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* objrmap doesn't work for nonlinear VMAs because the assumption that
|
|
* offset-into-file correlates with offset-into-virtual-addresses does not hold.
|
|
* Consequently, given a particular page and its ->index, we cannot locate the
|
|
* ptes which are mapping that page without an exhaustive linear search.
|
|
*
|
|
* So what this code does is a mini "virtual scan" of each nonlinear VMA which
|
|
* maps the file to which the target page belongs. The ->vm_private_data field
|
|
* holds the current cursor into that scan. Successive searches will circulate
|
|
* around the vma's virtual address space.
|
|
*
|
|
* So as more replacement pressure is applied to the pages in a nonlinear VMA,
|
|
* more scanning pressure is placed against them as well. Eventually pages
|
|
* will become fully unmapped and are eligible for eviction.
|
|
*
|
|
* For very sparsely populated VMAs this is a little inefficient - chances are
|
|
* there there won't be many ptes located within the scan cluster. In this case
|
|
* maybe we could scan further - to the end of the pte page, perhaps.
|
|
*
|
|
* Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can
|
|
* acquire it without blocking. If vma locked, mlock the pages in the cluster,
|
|
* rather than unmapping them. If we encounter the "check_page" that vmscan is
|
|
* trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
|
|
*/
|
|
#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
|
|
#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
|
|
|
|
static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
|
|
struct vm_area_struct *vma, struct page *check_page)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
pgd_t *pgd;
|
|
pud_t *pud;
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
pte_t pteval;
|
|
spinlock_t *ptl;
|
|
struct page *page;
|
|
unsigned long address;
|
|
unsigned long end;
|
|
int ret = SWAP_AGAIN;
|
|
int locked_vma = 0;
|
|
|
|
address = (vma->vm_start + cursor) & CLUSTER_MASK;
|
|
end = address + CLUSTER_SIZE;
|
|
if (address < vma->vm_start)
|
|
address = vma->vm_start;
|
|
if (end > vma->vm_end)
|
|
end = vma->vm_end;
|
|
|
|
pgd = pgd_offset(mm, address);
|
|
if (!pgd_present(*pgd))
|
|
return ret;
|
|
|
|
pud = pud_offset(pgd, address);
|
|
if (!pud_present(*pud))
|
|
return ret;
|
|
|
|
pmd = pmd_offset(pud, address);
|
|
if (!pmd_present(*pmd))
|
|
return ret;
|
|
|
|
/*
|
|
* MLOCK_PAGES => feature is configured.
|
|
* if we can acquire the mmap_sem for read, and vma is VM_LOCKED,
|
|
* keep the sem while scanning the cluster for mlocking pages.
|
|
*/
|
|
if (MLOCK_PAGES && down_read_trylock(&vma->vm_mm->mmap_sem)) {
|
|
locked_vma = (vma->vm_flags & VM_LOCKED);
|
|
if (!locked_vma)
|
|
up_read(&vma->vm_mm->mmap_sem); /* don't need it */
|
|
}
|
|
|
|
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
|
|
|
|
/* Update high watermark before we lower rss */
|
|
update_hiwater_rss(mm);
|
|
|
|
for (; address < end; pte++, address += PAGE_SIZE) {
|
|
if (!pte_present(*pte))
|
|
continue;
|
|
page = vm_normal_page(vma, address, *pte);
|
|
BUG_ON(!page || PageAnon(page));
|
|
|
|
if (locked_vma) {
|
|
mlock_vma_page(page); /* no-op if already mlocked */
|
|
if (page == check_page)
|
|
ret = SWAP_MLOCK;
|
|
continue; /* don't unmap */
|
|
}
|
|
|
|
if (ptep_clear_flush_young_notify(vma, address, pte))
|
|
continue;
|
|
|
|
/* Nuke the page table entry. */
|
|
flush_cache_page(vma, address, pte_pfn(*pte));
|
|
pteval = ptep_clear_flush_notify(vma, address, pte);
|
|
|
|
/* If nonlinear, store the file page offset in the pte. */
|
|
if (page->index != linear_page_index(vma, address))
|
|
set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
|
|
|
|
/* Move the dirty bit to the physical page now the pte is gone. */
|
|
if (pte_dirty(pteval))
|
|
set_page_dirty(page);
|
|
|
|
page_remove_rmap(page);
|
|
page_cache_release(page);
|
|
dec_mm_counter(mm, file_rss);
|
|
(*mapcount)--;
|
|
}
|
|
pte_unmap_unlock(pte - 1, ptl);
|
|
if (locked_vma)
|
|
up_read(&vma->vm_mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* common handling for pages mapped in VM_LOCKED vmas
|
|
*/
|
|
static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
int mlocked = 0;
|
|
|
|
if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
mlock_vma_page(page);
|
|
mlocked++; /* really mlocked the page */
|
|
}
|
|
up_read(&vma->vm_mm->mmap_sem);
|
|
}
|
|
return mlocked;
|
|
}
|
|
|
|
/**
|
|
* try_to_unmap_anon - unmap or unlock anonymous page using the object-based
|
|
* rmap method
|
|
* @page: the page to unmap/unlock
|
|
* @unlock: request for unlock rather than unmap [unlikely]
|
|
* @migration: unmapping for migration - ignored if @unlock
|
|
*
|
|
* Find all the mappings of a page using the mapping pointer and the vma chains
|
|
* contained in the anon_vma struct it points to.
|
|
*
|
|
* This function is only called from try_to_unmap/try_to_munlock for
|
|
* anonymous pages.
|
|
* When called from try_to_munlock(), the mmap_sem of the mm containing the vma
|
|
* where the page was found will be held for write. So, we won't recheck
|
|
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
|
|
* 'LOCKED.
|
|
*/
|
|
static int try_to_unmap_anon(struct page *page, int unlock, int migration)
|
|
{
|
|
struct anon_vma *anon_vma;
|
|
struct vm_area_struct *vma;
|
|
unsigned int mlocked = 0;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
if (MLOCK_PAGES && unlikely(unlock))
|
|
ret = SWAP_SUCCESS; /* default for try_to_munlock() */
|
|
|
|
anon_vma = page_lock_anon_vma(page);
|
|
if (!anon_vma)
|
|
return ret;
|
|
|
|
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
|
|
if (MLOCK_PAGES && unlikely(unlock)) {
|
|
if (!((vma->vm_flags & VM_LOCKED) &&
|
|
page_mapped_in_vma(page, vma)))
|
|
continue; /* must visit all unlocked vmas */
|
|
ret = SWAP_MLOCK; /* saw at least one mlocked vma */
|
|
} else {
|
|
ret = try_to_unmap_one(page, vma, migration);
|
|
if (ret == SWAP_FAIL || !page_mapped(page))
|
|
break;
|
|
}
|
|
if (ret == SWAP_MLOCK) {
|
|
mlocked = try_to_mlock_page(page, vma);
|
|
if (mlocked)
|
|
break; /* stop if actually mlocked page */
|
|
}
|
|
}
|
|
|
|
page_unlock_anon_vma(anon_vma);
|
|
|
|
if (mlocked)
|
|
ret = SWAP_MLOCK; /* actually mlocked the page */
|
|
else if (ret == SWAP_MLOCK)
|
|
ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* try_to_unmap_file - unmap/unlock file page using the object-based rmap method
|
|
* @page: the page to unmap/unlock
|
|
* @unlock: request for unlock rather than unmap [unlikely]
|
|
* @migration: unmapping for migration - ignored if @unlock
|
|
*
|
|
* Find all the mappings of a page using the mapping pointer and the vma chains
|
|
* contained in the address_space struct it points to.
|
|
*
|
|
* This function is only called from try_to_unmap/try_to_munlock for
|
|
* object-based pages.
|
|
* When called from try_to_munlock(), the mmap_sem of the mm containing the vma
|
|
* where the page was found will be held for write. So, we won't recheck
|
|
* vm_flags for that VMA. That should be OK, because that vma shouldn't be
|
|
* 'LOCKED.
|
|
*/
|
|
static int try_to_unmap_file(struct page *page, int unlock, int migration)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
|
|
struct vm_area_struct *vma;
|
|
struct prio_tree_iter iter;
|
|
int ret = SWAP_AGAIN;
|
|
unsigned long cursor;
|
|
unsigned long max_nl_cursor = 0;
|
|
unsigned long max_nl_size = 0;
|
|
unsigned int mapcount;
|
|
unsigned int mlocked = 0;
|
|
|
|
if (MLOCK_PAGES && unlikely(unlock))
|
|
ret = SWAP_SUCCESS; /* default for try_to_munlock() */
|
|
|
|
spin_lock(&mapping->i_mmap_lock);
|
|
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
|
|
if (MLOCK_PAGES && unlikely(unlock)) {
|
|
if (!((vma->vm_flags & VM_LOCKED) &&
|
|
page_mapped_in_vma(page, vma)))
|
|
continue; /* must visit all vmas */
|
|
ret = SWAP_MLOCK;
|
|
} else {
|
|
ret = try_to_unmap_one(page, vma, migration);
|
|
if (ret == SWAP_FAIL || !page_mapped(page))
|
|
goto out;
|
|
}
|
|
if (ret == SWAP_MLOCK) {
|
|
mlocked = try_to_mlock_page(page, vma);
|
|
if (mlocked)
|
|
break; /* stop if actually mlocked page */
|
|
}
|
|
}
|
|
|
|
if (mlocked)
|
|
goto out;
|
|
|
|
if (list_empty(&mapping->i_mmap_nonlinear))
|
|
goto out;
|
|
|
|
list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
|
|
shared.vm_set.list) {
|
|
if (MLOCK_PAGES && unlikely(unlock)) {
|
|
if (!(vma->vm_flags & VM_LOCKED))
|
|
continue; /* must visit all vmas */
|
|
ret = SWAP_MLOCK; /* leave mlocked == 0 */
|
|
goto out; /* no need to look further */
|
|
}
|
|
if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED))
|
|
continue;
|
|
cursor = (unsigned long) vma->vm_private_data;
|
|
if (cursor > max_nl_cursor)
|
|
max_nl_cursor = cursor;
|
|
cursor = vma->vm_end - vma->vm_start;
|
|
if (cursor > max_nl_size)
|
|
max_nl_size = cursor;
|
|
}
|
|
|
|
if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
|
|
ret = SWAP_FAIL;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* We don't try to search for this page in the nonlinear vmas,
|
|
* and page_referenced wouldn't have found it anyway. Instead
|
|
* just walk the nonlinear vmas trying to age and unmap some.
|
|
* The mapcount of the page we came in with is irrelevant,
|
|
* but even so use it as a guide to how hard we should try?
|
|
*/
|
|
mapcount = page_mapcount(page);
|
|
if (!mapcount)
|
|
goto out;
|
|
cond_resched_lock(&mapping->i_mmap_lock);
|
|
|
|
max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
|
|
if (max_nl_cursor == 0)
|
|
max_nl_cursor = CLUSTER_SIZE;
|
|
|
|
do {
|
|
list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
|
|
shared.vm_set.list) {
|
|
if (!MLOCK_PAGES && !migration &&
|
|
(vma->vm_flags & VM_LOCKED))
|
|
continue;
|
|
cursor = (unsigned long) vma->vm_private_data;
|
|
while ( cursor < max_nl_cursor &&
|
|
cursor < vma->vm_end - vma->vm_start) {
|
|
ret = try_to_unmap_cluster(cursor, &mapcount,
|
|
vma, page);
|
|
if (ret == SWAP_MLOCK)
|
|
mlocked = 2; /* to return below */
|
|
cursor += CLUSTER_SIZE;
|
|
vma->vm_private_data = (void *) cursor;
|
|
if ((int)mapcount <= 0)
|
|
goto out;
|
|
}
|
|
vma->vm_private_data = (void *) max_nl_cursor;
|
|
}
|
|
cond_resched_lock(&mapping->i_mmap_lock);
|
|
max_nl_cursor += CLUSTER_SIZE;
|
|
} while (max_nl_cursor <= max_nl_size);
|
|
|
|
/*
|
|
* Don't loop forever (perhaps all the remaining pages are
|
|
* in locked vmas). Reset cursor on all unreserved nonlinear
|
|
* vmas, now forgetting on which ones it had fallen behind.
|
|
*/
|
|
list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
|
|
vma->vm_private_data = NULL;
|
|
out:
|
|
spin_unlock(&mapping->i_mmap_lock);
|
|
if (mlocked)
|
|
ret = SWAP_MLOCK; /* actually mlocked the page */
|
|
else if (ret == SWAP_MLOCK)
|
|
ret = SWAP_AGAIN; /* saw VM_LOCKED vma */
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* try_to_unmap - try to remove all page table mappings to a page
|
|
* @page: the page to get unmapped
|
|
* @migration: migration flag
|
|
*
|
|
* Tries to remove all the page table entries which are mapping this
|
|
* page, used in the pageout path. Caller must hold the page lock.
|
|
* Return values are:
|
|
*
|
|
* SWAP_SUCCESS - we succeeded in removing all mappings
|
|
* SWAP_AGAIN - we missed a mapping, try again later
|
|
* SWAP_FAIL - the page is unswappable
|
|
* SWAP_MLOCK - page is mlocked.
|
|
*/
|
|
int try_to_unmap(struct page *page, int migration)
|
|
{
|
|
int ret;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (PageAnon(page))
|
|
ret = try_to_unmap_anon(page, 0, migration);
|
|
else
|
|
ret = try_to_unmap_file(page, 0, migration);
|
|
if (ret != SWAP_MLOCK && !page_mapped(page))
|
|
ret = SWAP_SUCCESS;
|
|
return ret;
|
|
}
|
|
|
|
#ifdef CONFIG_UNEVICTABLE_LRU
|
|
/**
|
|
* try_to_munlock - try to munlock a page
|
|
* @page: the page to be munlocked
|
|
*
|
|
* Called from munlock code. Checks all of the VMAs mapping the page
|
|
* to make sure nobody else has this page mlocked. The page will be
|
|
* returned with PG_mlocked cleared if no other vmas have it mlocked.
|
|
*
|
|
* Return values are:
|
|
*
|
|
* SWAP_SUCCESS - no vma's holding page mlocked.
|
|
* SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
|
|
* SWAP_MLOCK - page is now mlocked.
|
|
*/
|
|
int try_to_munlock(struct page *page)
|
|
{
|
|
VM_BUG_ON(!PageLocked(page) || PageLRU(page));
|
|
|
|
if (PageAnon(page))
|
|
return try_to_unmap_anon(page, 1, 0);
|
|
else
|
|
return try_to_unmap_file(page, 1, 0);
|
|
}
|
|
#endif
|