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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +00:00
![Martin Schwidefsky](/assets/img/avatar_default.png)
The git commitc2fda5fed8
which added the page_test_and_clear_dirty call to page_mkclean and the git commit7658cc2892
which fixes the "nasty and subtle race in shared mmap'ed page writeback" problem in clear_page_dirty_for_io cause data corruption on s390. The effect of the two changes is that for every call to clear_page_dirty_for_io a page_test_and_clear_dirty is done. If the per page dirty bit is set set_page_dirty is called. Strangly clear_page_dirty_for_io is called for not-uptodate pages, e.g. over this call-chain: [<000000000007c0f2>] clear_page_dirty_for_io+0x12a/0x130 [<000000000007c494>] generic_writepages+0x258/0x3e0 [<000000000007c692>] do_writepages+0x76/0x7c [<00000000000c7a26>] __writeback_single_inode+0xba/0x3e4 [<00000000000c831a>] sync_sb_inodes+0x23e/0x398 [<00000000000c8802>] writeback_inodes+0x12e/0x140 [<000000000007b9ee>] wb_kupdate+0xd2/0x178 [<000000000007cca2>] pdflush+0x162/0x23c The bad news now is that page_test_and_clear_dirty might claim that a not-uptodate page is dirty since SetPageUptodate which resets the per page dirty bit has not yet been called. The page writeback that follows clobbers the data on disk. The simplest solution to this problem is to move the call to page_test_and_clear_dirty under the "if (page_mapped(page))". If a file backed page is mapped it is uptodate. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
941 lines
25 KiB
C
941 lines
25 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 <hugh@veritas.com> 2003, 2004
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*/
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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/kallsyms.h>
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#include <asm/tlbflush.h>
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struct kmem_cache *anon_vma_cachep;
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static inline void validate_anon_vma(struct vm_area_struct *find_vma)
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{
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#ifdef CONFIG_DEBUG_VM
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struct anon_vma *anon_vma = find_vma->anon_vma;
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struct vm_area_struct *vma;
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unsigned int mapcount = 0;
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int found = 0;
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list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
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mapcount++;
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BUG_ON(mapcount > 100000);
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if (vma == find_vma)
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found = 1;
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}
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BUG_ON(!found);
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#endif
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}
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/* This must be called under the mmap_sem. */
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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, *locked;
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anon_vma = find_mergeable_anon_vma(vma);
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if (anon_vma) {
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allocated = NULL;
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locked = anon_vma;
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spin_lock(&locked->lock);
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} else {
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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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locked = NULL;
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}
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|
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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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if (locked)
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spin_unlock(&locked->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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|
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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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validate_anon_vma(vma);
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}
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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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|
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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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validate_anon_vma(vma);
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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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validate_anon_vma(vma);
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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, struct kmem_cache *cachep,
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unsigned long flags)
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{
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if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
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SLAB_CTOR_CONSTRUCTOR) {
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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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}
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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, NULL);
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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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*/
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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 any vma from prio_tree_next */
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BUG_ON(!PageAnon(page));
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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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* 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)
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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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|
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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 (!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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* 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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|
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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);
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if (!pte)
|
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goto out;
|
|
|
|
if (ptep_clear_flush_young(vma, address, pte))
|
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referenced++;
|
|
|
|
/* 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. */
|
|
if (mm != current->mm && has_swap_token(mm) &&
|
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rwsem_is_locked(&mm->mmap_sem))
|
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referenced++;
|
|
|
|
(*mapcount)--;
|
|
pte_unmap_unlock(pte, ptl);
|
|
out:
|
|
return referenced;
|
|
}
|
|
|
|
static int page_referenced_anon(struct page *page)
|
|
{
|
|
unsigned int mapcount;
|
|
struct anon_vma *anon_vma;
|
|
struct vm_area_struct *vma;
|
|
int referenced = 0;
|
|
|
|
anon_vma = page_lock_anon_vma(page);
|
|
if (!anon_vma)
|
|
return referenced;
|
|
|
|
mapcount = page_mapcount(page);
|
|
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
|
|
referenced += page_referenced_one(page, vma, &mapcount);
|
|
if (!mapcount)
|
|
break;
|
|
}
|
|
|
|
page_unlock_anon_vma(anon_vma);
|
|
return referenced;
|
|
}
|
|
|
|
/**
|
|
* page_referenced_file - referenced check for object-based rmap
|
|
* @page: the page we're checking references on.
|
|
*
|
|
* For an object-based mapped page, find all the places it is mapped and
|
|
* check/clear the referenced flag. This is done by following the page->mapping
|
|
* pointer, then walking the chain of vmas it holds. It returns the number
|
|
* of references it found.
|
|
*
|
|
* This function is only called from page_referenced for object-based pages.
|
|
*/
|
|
static int page_referenced_file(struct page *page)
|
|
{
|
|
unsigned int mapcount;
|
|
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 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
|
|
* excludes the case just before it gets set on an anon page.
|
|
*/
|
|
BUG_ON(PageAnon(page));
|
|
|
|
/*
|
|
* The page lock not only makes sure that page->mapping cannot
|
|
* suddenly be NULLified by truncation, it makes sure that the
|
|
* structure at mapping cannot be freed and reused yet,
|
|
* so we can safely take mapping->i_mmap_lock.
|
|
*/
|
|
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 ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
|
|
== (VM_LOCKED|VM_MAYSHARE)) {
|
|
referenced++;
|
|
break;
|
|
}
|
|
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
|
|
*
|
|
* 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)
|
|
{
|
|
int referenced = 0;
|
|
|
|
if (page_test_and_clear_young(page))
|
|
referenced++;
|
|
|
|
if (TestClearPageReferenced(page))
|
|
referenced++;
|
|
|
|
if (page_mapped(page) && page->mapping) {
|
|
if (PageAnon(page))
|
|
referenced += page_referenced_anon(page);
|
|
else if (is_locked)
|
|
referenced += page_referenced_file(page);
|
|
else if (TestSetPageLocked(page))
|
|
referenced++;
|
|
else {
|
|
if (page->mapping)
|
|
referenced += page_referenced_file(page);
|
|
unlock_page(page);
|
|
}
|
|
}
|
|
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);
|
|
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(vma, address, pte);
|
|
entry = pte_wrprotect(entry);
|
|
entry = pte_mkclean(entry);
|
|
set_pte_at(mm, address, pte, entry);
|
|
lazy_mmu_prot_update(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_and_clear_dirty(page))
|
|
ret = 1;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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_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.
|
|
*/
|
|
void page_add_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
if (atomic_inc_and_test(&page->_mapcount))
|
|
__page_set_anon_rmap(page, vma, address);
|
|
/* else checking page index and mapping is racy */
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
void page_add_new_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */
|
|
__page_set_anon_rmap(page, vma, address);
|
|
}
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
|
|
/**
|
|
* 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, struct vm_area_struct *vma)
|
|
{
|
|
if (atomic_add_negative(-1, &page->_mapcount)) {
|
|
if (unlikely(page_mapcount(page) < 0)) {
|
|
printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
|
|
printk (KERN_EMERG " page pfn = %lx\n", page_to_pfn(page));
|
|
printk (KERN_EMERG " page->flags = %lx\n", page->flags);
|
|
printk (KERN_EMERG " page->count = %x\n", page_count(page));
|
|
printk (KERN_EMERG " page->mapping = %p\n", page->mapping);
|
|
print_symbol (KERN_EMERG " vma->vm_ops = %s\n", (unsigned long)vma->vm_ops);
|
|
if (vma->vm_ops)
|
|
print_symbol (KERN_EMERG " vma->vm_ops->nopage = %s\n", (unsigned long)vma->vm_ops->nopage);
|
|
if (vma->vm_file && vma->vm_file->f_op)
|
|
print_symbol (KERN_EMERG " vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap);
|
|
BUG();
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (page_test_and_clear_dirty(page))
|
|
set_page_dirty(page);
|
|
__dec_zone_page_state(page,
|
|
PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
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 && ((vma->vm_flags & VM_LOCKED) ||
|
|
(ptep_clear_flush_young(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(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);
|
|
#ifdef CONFIG_MIGRATION
|
|
} else {
|
|
/*
|
|
* 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));
|
|
#endif
|
|
}
|
|
set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
|
|
BUG_ON(pte_file(*pte));
|
|
} else
|
|
#ifdef CONFIG_MIGRATION
|
|
if (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
|
|
#endif
|
|
dec_mm_counter(mm, file_rss);
|
|
|
|
|
|
page_remove_rmap(page, vma);
|
|
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.
|
|
*/
|
|
#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE)
|
|
#define CLUSTER_MASK (~(CLUSTER_SIZE - 1))
|
|
|
|
static void try_to_unmap_cluster(unsigned long cursor,
|
|
unsigned int *mapcount, struct vm_area_struct *vma)
|
|
{
|
|
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;
|
|
|
|
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;
|
|
|
|
pud = pud_offset(pgd, address);
|
|
if (!pud_present(*pud))
|
|
return;
|
|
|
|
pmd = pmd_offset(pud, address);
|
|
if (!pmd_present(*pmd))
|
|
return;
|
|
|
|
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 (ptep_clear_flush_young(vma, address, pte))
|
|
continue;
|
|
|
|
/* Nuke the page table entry. */
|
|
flush_cache_page(vma, address, pte_pfn(*pte));
|
|
pteval = ptep_clear_flush(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, vma);
|
|
page_cache_release(page);
|
|
dec_mm_counter(mm, file_rss);
|
|
(*mapcount)--;
|
|
}
|
|
pte_unmap_unlock(pte - 1, ptl);
|
|
}
|
|
|
|
static int try_to_unmap_anon(struct page *page, int migration)
|
|
{
|
|
struct anon_vma *anon_vma;
|
|
struct vm_area_struct *vma;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
anon_vma = page_lock_anon_vma(page);
|
|
if (!anon_vma)
|
|
return ret;
|
|
|
|
list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
|
|
ret = try_to_unmap_one(page, vma, migration);
|
|
if (ret == SWAP_FAIL || !page_mapped(page))
|
|
break;
|
|
}
|
|
|
|
page_unlock_anon_vma(anon_vma);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* try_to_unmap_file - unmap file page using the object-based rmap method
|
|
* @page: the page to unmap
|
|
*
|
|
* 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 for object-based pages.
|
|
*/
|
|
static int try_to_unmap_file(struct page *page, 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;
|
|
|
|
spin_lock(&mapping->i_mmap_lock);
|
|
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
|
|
ret = try_to_unmap_one(page, vma, migration);
|
|
if (ret == SWAP_FAIL || !page_mapped(page))
|
|
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 ((vma->vm_flags & VM_LOCKED) && !migration)
|
|
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) { /* any 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 ((vma->vm_flags & VM_LOCKED) && !migration)
|
|
continue;
|
|
cursor = (unsigned long) vma->vm_private_data;
|
|
while ( cursor < max_nl_cursor &&
|
|
cursor < vma->vm_end - vma->vm_start) {
|
|
try_to_unmap_cluster(cursor, &mapcount, vma);
|
|
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);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* try_to_unmap - try to remove all page table mappings to a page
|
|
* @page: the page to get unmapped
|
|
*
|
|
* 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
|
|
*/
|
|
int try_to_unmap(struct page *page, int migration)
|
|
{
|
|
int ret;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (PageAnon(page))
|
|
ret = try_to_unmap_anon(page, migration);
|
|
else
|
|
ret = try_to_unmap_file(page, migration);
|
|
|
|
if (!page_mapped(page))
|
|
ret = SWAP_SUCCESS;
|
|
return ret;
|
|
}
|
|
|