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![Sasha Levin](/assets/img/avatar_default.png)
Trivially convert a few VM_BUG_ON calls to VM_BUG_ON_VMA to extract more information when they trigger. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Michel Lespinasse <walken@google.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1758 lines
48 KiB
C
1758 lines
48 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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* mm->mmap_sem
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* page->flags PG_locked (lock_page)
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* mapping->i_mmap_mutex
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* anon_vma->rwsem
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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->i_lock (in set_page_dirty's __mark_inode_dirty)
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* bdi.wb->list_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 bdi.wb->list_lock in __sync_single_inode)
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*
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* anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
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* ->tasklist_lock
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* pte map lock
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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/ksm.h>
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#include <linux/rmap.h>
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#include <linux/rcupdate.h>
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#include <linux/export.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 <linux/hugetlb.h>
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#include <linux/backing-dev.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 struct kmem_cache *anon_vma_chain_cachep;
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static inline struct anon_vma *anon_vma_alloc(void)
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{
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struct anon_vma *anon_vma;
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anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
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if (anon_vma) {
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atomic_set(&anon_vma->refcount, 1);
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/*
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* Initialise the anon_vma root to point to itself. If called
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* from fork, the root will be reset to the parents anon_vma.
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*/
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anon_vma->root = anon_vma;
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}
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return anon_vma;
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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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VM_BUG_ON(atomic_read(&anon_vma->refcount));
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/*
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* Synchronize against page_lock_anon_vma_read() such that
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* we can safely hold the lock without the anon_vma getting
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* freed.
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*
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* Relies on the full mb implied by the atomic_dec_and_test() from
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* put_anon_vma() against the acquire barrier implied by
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* down_read_trylock() from page_lock_anon_vma_read(). This orders:
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*
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* page_lock_anon_vma_read() VS put_anon_vma()
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* down_read_trylock() atomic_dec_and_test()
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* LOCK MB
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* atomic_read() rwsem_is_locked()
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*
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* LOCK should suffice since the actual taking of the lock must
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* happen _before_ what follows.
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*/
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might_sleep();
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if (rwsem_is_locked(&anon_vma->root->rwsem)) {
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anon_vma_lock_write(anon_vma);
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anon_vma_unlock_write(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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static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
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{
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return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
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}
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static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
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{
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kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
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}
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static void anon_vma_chain_link(struct vm_area_struct *vma,
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struct anon_vma_chain *avc,
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struct anon_vma *anon_vma)
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{
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avc->vma = vma;
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avc->anon_vma = anon_vma;
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list_add(&avc->same_vma, &vma->anon_vma_chain);
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anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
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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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* 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_read()
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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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struct anon_vma_chain *avc;
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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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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto out_enomem;
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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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goto out_enomem_free_avc;
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allocated = anon_vma;
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}
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anon_vma_lock_write(anon_vma);
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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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anon_vma_chain_link(vma, avc, anon_vma);
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allocated = NULL;
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avc = NULL;
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}
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spin_unlock(&mm->page_table_lock);
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anon_vma_unlock_write(anon_vma);
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if (unlikely(allocated))
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put_anon_vma(allocated);
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if (unlikely(avc))
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anon_vma_chain_free(avc);
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}
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return 0;
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out_enomem_free_avc:
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anon_vma_chain_free(avc);
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out_enomem:
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return -ENOMEM;
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}
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/*
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* This is a useful helper function for locking the anon_vma root as
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* we traverse the vma->anon_vma_chain, looping over anon_vma's that
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* have the same vma.
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*
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* Such anon_vma's should have the same root, so you'd expect to see
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* just a single mutex_lock for the whole traversal.
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*/
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static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
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{
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struct anon_vma *new_root = anon_vma->root;
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if (new_root != root) {
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if (WARN_ON_ONCE(root))
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up_write(&root->rwsem);
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root = new_root;
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down_write(&root->rwsem);
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}
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return root;
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}
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static inline void unlock_anon_vma_root(struct anon_vma *root)
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{
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if (root)
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up_write(&root->rwsem);
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}
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/*
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* Attach the anon_vmas from src to dst.
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* Returns 0 on success, -ENOMEM on failure.
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*/
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int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
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{
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struct anon_vma_chain *avc, *pavc;
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struct anon_vma *root = NULL;
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list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
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struct anon_vma *anon_vma;
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avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
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if (unlikely(!avc)) {
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unlock_anon_vma_root(root);
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root = NULL;
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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto enomem_failure;
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}
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anon_vma = pavc->anon_vma;
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root = lock_anon_vma_root(root, anon_vma);
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anon_vma_chain_link(dst, avc, anon_vma);
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}
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unlock_anon_vma_root(root);
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return 0;
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enomem_failure:
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unlink_anon_vmas(dst);
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return -ENOMEM;
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}
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/*
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* Attach vma to its own anon_vma, as well as to the anon_vmas that
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* the corresponding VMA in the parent process is attached to.
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* Returns 0 on success, non-zero on failure.
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*/
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int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
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{
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struct anon_vma_chain *avc;
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struct anon_vma *anon_vma;
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/* Don't bother if the parent process has no anon_vma here. */
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if (!pvma->anon_vma)
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return 0;
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/*
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* First, attach the new VMA to the parent VMA's anon_vmas,
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* so rmap can find non-COWed pages in child processes.
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*/
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if (anon_vma_clone(vma, pvma))
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return -ENOMEM;
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/* Then add our own anon_vma. */
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anon_vma = anon_vma_alloc();
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if (!anon_vma)
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goto out_error;
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avc = anon_vma_chain_alloc(GFP_KERNEL);
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if (!avc)
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goto out_error_free_anon_vma;
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/*
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* The root anon_vma's spinlock is the lock actually used when we
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* lock any of the anon_vmas in this anon_vma tree.
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*/
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anon_vma->root = pvma->anon_vma->root;
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/*
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* With refcounts, an anon_vma can stay around longer than the
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* process it belongs to. The root anon_vma needs to be pinned until
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* this anon_vma is freed, because the lock lives in the root.
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*/
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get_anon_vma(anon_vma->root);
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/* Mark this anon_vma as the one where our new (COWed) pages go. */
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vma->anon_vma = anon_vma;
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anon_vma_lock_write(anon_vma);
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anon_vma_chain_link(vma, avc, anon_vma);
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anon_vma_unlock_write(anon_vma);
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return 0;
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out_error_free_anon_vma:
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put_anon_vma(anon_vma);
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out_error:
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unlink_anon_vmas(vma);
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return -ENOMEM;
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}
|
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|
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void unlink_anon_vmas(struct vm_area_struct *vma)
|
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{
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struct anon_vma_chain *avc, *next;
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struct anon_vma *root = NULL;
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|
|
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/*
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* Unlink each anon_vma chained to the VMA. This list is ordered
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* from newest to oldest, ensuring the root anon_vma gets freed last.
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*/
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list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
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struct anon_vma *anon_vma = avc->anon_vma;
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|
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root = lock_anon_vma_root(root, anon_vma);
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anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
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|
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/*
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* Leave empty anon_vmas on the list - we'll need
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* to free them outside the lock.
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*/
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if (RB_EMPTY_ROOT(&anon_vma->rb_root))
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continue;
|
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|
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list_del(&avc->same_vma);
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anon_vma_chain_free(avc);
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}
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unlock_anon_vma_root(root);
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|
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/*
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* Iterate the list once more, it now only contains empty and unlinked
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* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
|
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* needing to write-acquire the anon_vma->root->rwsem.
|
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*/
|
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list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
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struct anon_vma *anon_vma = avc->anon_vma;
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|
|
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put_anon_vma(anon_vma);
|
|
|
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list_del(&avc->same_vma);
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anon_vma_chain_free(avc);
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}
|
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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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|
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init_rwsem(&anon_vma->rwsem);
|
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atomic_set(&anon_vma->refcount, 0);
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anon_vma->rb_root = RB_ROOT;
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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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anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
|
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}
|
|
|
|
/*
|
|
* Getting a lock on a stable anon_vma from a page off the LRU is tricky!
|
|
*
|
|
* Since there is no serialization what so ever against page_remove_rmap()
|
|
* the best this function can do is return a locked anon_vma that might
|
|
* have been relevant to this page.
|
|
*
|
|
* The page might have been remapped to a different anon_vma or the anon_vma
|
|
* returned may already be freed (and even reused).
|
|
*
|
|
* In case it was remapped to a different anon_vma, the new anon_vma will be a
|
|
* child of the old anon_vma, and the anon_vma lifetime rules will therefore
|
|
* ensure that any anon_vma obtained from the page will still be valid for as
|
|
* long as we observe page_mapped() [ hence all those page_mapped() tests ].
|
|
*
|
|
* All users of this function must be very careful when walking the anon_vma
|
|
* chain and verify that the page in question is indeed mapped in it
|
|
* [ something equivalent to page_mapped_in_vma() ].
|
|
*
|
|
* Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
|
|
* that the anon_vma pointer from page->mapping is valid if there is a
|
|
* mapcount, we can dereference the anon_vma after observing those.
|
|
*/
|
|
struct anon_vma *page_get_anon_vma(struct page *page)
|
|
{
|
|
struct anon_vma *anon_vma = NULL;
|
|
unsigned long anon_mapping;
|
|
|
|
rcu_read_lock();
|
|
anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
|
|
if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
|
|
goto out;
|
|
if (!page_mapped(page))
|
|
goto out;
|
|
|
|
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
|
|
if (!atomic_inc_not_zero(&anon_vma->refcount)) {
|
|
anon_vma = NULL;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* If this page is still mapped, then its anon_vma cannot have been
|
|
* freed. But if it has been unmapped, we have no security against the
|
|
* anon_vma structure being freed and reused (for another anon_vma:
|
|
* SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
|
|
* above cannot corrupt).
|
|
*/
|
|
if (!page_mapped(page)) {
|
|
rcu_read_unlock();
|
|
put_anon_vma(anon_vma);
|
|
return NULL;
|
|
}
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return anon_vma;
|
|
}
|
|
|
|
/*
|
|
* Similar to page_get_anon_vma() except it locks the anon_vma.
|
|
*
|
|
* Its a little more complex as it tries to keep the fast path to a single
|
|
* atomic op -- the trylock. If we fail the trylock, we fall back to getting a
|
|
* reference like with page_get_anon_vma() and then block on the mutex.
|
|
*/
|
|
struct anon_vma *page_lock_anon_vma_read(struct page *page)
|
|
{
|
|
struct anon_vma *anon_vma = NULL;
|
|
struct anon_vma *root_anon_vma;
|
|
unsigned long anon_mapping;
|
|
|
|
rcu_read_lock();
|
|
anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
|
|
if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
|
|
goto out;
|
|
if (!page_mapped(page))
|
|
goto out;
|
|
|
|
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
|
|
root_anon_vma = ACCESS_ONCE(anon_vma->root);
|
|
if (down_read_trylock(&root_anon_vma->rwsem)) {
|
|
/*
|
|
* If the page is still mapped, then this anon_vma is still
|
|
* its anon_vma, and holding the mutex ensures that it will
|
|
* not go away, see anon_vma_free().
|
|
*/
|
|
if (!page_mapped(page)) {
|
|
up_read(&root_anon_vma->rwsem);
|
|
anon_vma = NULL;
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
/* trylock failed, we got to sleep */
|
|
if (!atomic_inc_not_zero(&anon_vma->refcount)) {
|
|
anon_vma = NULL;
|
|
goto out;
|
|
}
|
|
|
|
if (!page_mapped(page)) {
|
|
rcu_read_unlock();
|
|
put_anon_vma(anon_vma);
|
|
return NULL;
|
|
}
|
|
|
|
/* we pinned the anon_vma, its safe to sleep */
|
|
rcu_read_unlock();
|
|
anon_vma_lock_read(anon_vma);
|
|
|
|
if (atomic_dec_and_test(&anon_vma->refcount)) {
|
|
/*
|
|
* Oops, we held the last refcount, release the lock
|
|
* and bail -- can't simply use put_anon_vma() because
|
|
* we'll deadlock on the anon_vma_lock_write() recursion.
|
|
*/
|
|
anon_vma_unlock_read(anon_vma);
|
|
__put_anon_vma(anon_vma);
|
|
anon_vma = NULL;
|
|
}
|
|
|
|
return anon_vma;
|
|
|
|
out:
|
|
rcu_read_unlock();
|
|
return anon_vma;
|
|
}
|
|
|
|
void page_unlock_anon_vma_read(struct anon_vma *anon_vma)
|
|
{
|
|
anon_vma_unlock_read(anon_vma);
|
|
}
|
|
|
|
/*
|
|
* At what user virtual address is page expected in @vma?
|
|
*/
|
|
static inline unsigned long
|
|
__vma_address(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
pgoff_t pgoff = page_to_pgoff(page);
|
|
return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
|
|
}
|
|
|
|
inline unsigned long
|
|
vma_address(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
unsigned long address = __vma_address(page, vma);
|
|
|
|
/* page should be within @vma mapping range */
|
|
VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
|
|
|
|
return address;
|
|
}
|
|
|
|
/*
|
|
* At what user virtual address is page expected in vma?
|
|
* Caller should check the page is actually part of the vma.
|
|
*/
|
|
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
unsigned long address;
|
|
if (PageAnon(page)) {
|
|
struct anon_vma *page__anon_vma = page_anon_vma(page);
|
|
/*
|
|
* Note: swapoff's unuse_vma() is more efficient with this
|
|
* check, and needs it to match anon_vma when KSM is active.
|
|
*/
|
|
if (!vma->anon_vma || !page__anon_vma ||
|
|
vma->anon_vma->root != page__anon_vma->root)
|
|
return -EFAULT;
|
|
} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
|
|
if (!vma->vm_file ||
|
|
vma->vm_file->f_mapping != page->mapping)
|
|
return -EFAULT;
|
|
} else
|
|
return -EFAULT;
|
|
address = __vma_address(page, vma);
|
|
if (unlikely(address < vma->vm_start || address >= vma->vm_end))
|
|
return -EFAULT;
|
|
return address;
|
|
}
|
|
|
|
pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
|
|
{
|
|
pgd_t *pgd;
|
|
pud_t *pud;
|
|
pmd_t *pmd = NULL;
|
|
pmd_t pmde;
|
|
|
|
pgd = pgd_offset(mm, address);
|
|
if (!pgd_present(*pgd))
|
|
goto out;
|
|
|
|
pud = pud_offset(pgd, address);
|
|
if (!pud_present(*pud))
|
|
goto out;
|
|
|
|
pmd = pmd_offset(pud, address);
|
|
/*
|
|
* Some THP functions use the sequence pmdp_clear_flush(), set_pmd_at()
|
|
* without holding anon_vma lock for write. So when looking for a
|
|
* genuine pmde (in which to find pte), test present and !THP together.
|
|
*/
|
|
pmde = ACCESS_ONCE(*pmd);
|
|
if (!pmd_present(pmde) || pmd_trans_huge(pmde))
|
|
pmd = NULL;
|
|
out:
|
|
return pmd;
|
|
}
|
|
|
|
/*
|
|
* Check that @page is mapped at @address into @mm.
|
|
*
|
|
* If @sync is false, page_check_address may perform a racy check to avoid
|
|
* the page table lock when the pte is not present (helpful when reclaiming
|
|
* highly shared pages).
|
|
*
|
|
* On success returns with pte mapped and locked.
|
|
*/
|
|
pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
|
|
unsigned long address, spinlock_t **ptlp, int sync)
|
|
{
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
spinlock_t *ptl;
|
|
|
|
if (unlikely(PageHuge(page))) {
|
|
/* when pud is not present, pte will be NULL */
|
|
pte = huge_pte_offset(mm, address);
|
|
if (!pte)
|
|
return NULL;
|
|
|
|
ptl = huge_pte_lockptr(page_hstate(page), mm, pte);
|
|
goto check;
|
|
}
|
|
|
|
pmd = mm_find_pmd(mm, address);
|
|
if (!pmd)
|
|
return NULL;
|
|
|
|
pte = pte_offset_map(pmd, address);
|
|
/* Make a quick check before getting the lock */
|
|
if (!sync && !pte_present(*pte)) {
|
|
pte_unmap(pte);
|
|
return NULL;
|
|
}
|
|
|
|
ptl = pte_lockptr(mm, pmd);
|
|
check:
|
|
spin_lock(ptl);
|
|
if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
|
|
*ptlp = ptl;
|
|
return pte;
|
|
}
|
|
pte_unmap_unlock(pte, ptl);
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* page_mapped_in_vma - check whether a page is really mapped in a VMA
|
|
* @page: the page to test
|
|
* @vma: the VMA to test
|
|
*
|
|
* Returns 1 if the page is mapped into the page tables of the VMA, 0
|
|
* if the page is not mapped into the page tables of this VMA. Only
|
|
* valid for normal file or anonymous VMAs.
|
|
*/
|
|
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
|
|
{
|
|
unsigned long address;
|
|
pte_t *pte;
|
|
spinlock_t *ptl;
|
|
|
|
address = __vma_address(page, vma);
|
|
if (unlikely(address < vma->vm_start || address >= vma->vm_end))
|
|
return 0;
|
|
pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
|
|
if (!pte) /* the page is not in this mm */
|
|
return 0;
|
|
pte_unmap_unlock(pte, ptl);
|
|
|
|
return 1;
|
|
}
|
|
|
|
struct page_referenced_arg {
|
|
int mapcount;
|
|
int referenced;
|
|
unsigned long vm_flags;
|
|
struct mem_cgroup *memcg;
|
|
};
|
|
/*
|
|
* arg: page_referenced_arg will be passed
|
|
*/
|
|
static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
|
|
unsigned long address, void *arg)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
spinlock_t *ptl;
|
|
int referenced = 0;
|
|
struct page_referenced_arg *pra = arg;
|
|
|
|
if (unlikely(PageTransHuge(page))) {
|
|
pmd_t *pmd;
|
|
|
|
/*
|
|
* rmap might return false positives; we must filter
|
|
* these out using page_check_address_pmd().
|
|
*/
|
|
pmd = page_check_address_pmd(page, mm, address,
|
|
PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
|
|
if (!pmd)
|
|
return SWAP_AGAIN;
|
|
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
spin_unlock(ptl);
|
|
pra->vm_flags |= VM_LOCKED;
|
|
return SWAP_FAIL; /* To break the loop */
|
|
}
|
|
|
|
/* go ahead even if the pmd is pmd_trans_splitting() */
|
|
if (pmdp_clear_flush_young_notify(vma, address, pmd))
|
|
referenced++;
|
|
spin_unlock(ptl);
|
|
} else {
|
|
pte_t *pte;
|
|
|
|
/*
|
|
* rmap might return false positives; we must filter
|
|
* these out using page_check_address().
|
|
*/
|
|
pte = page_check_address(page, mm, address, &ptl, 0);
|
|
if (!pte)
|
|
return SWAP_AGAIN;
|
|
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
pte_unmap_unlock(pte, ptl);
|
|
pra->vm_flags |= VM_LOCKED;
|
|
return SWAP_FAIL; /* To break the loop */
|
|
}
|
|
|
|
if (ptep_clear_flush_young_notify(vma, address, pte)) {
|
|
/*
|
|
* Don't treat a reference through a sequentially read
|
|
* mapping as such. If the page has been used in
|
|
* another mapping, we will catch it; if this other
|
|
* mapping is already gone, the unmap path will have
|
|
* set PG_referenced or activated the page.
|
|
*/
|
|
if (likely(!(vma->vm_flags & VM_SEQ_READ)))
|
|
referenced++;
|
|
}
|
|
pte_unmap_unlock(pte, ptl);
|
|
}
|
|
|
|
if (referenced) {
|
|
pra->referenced++;
|
|
pra->vm_flags |= vma->vm_flags;
|
|
}
|
|
|
|
pra->mapcount--;
|
|
if (!pra->mapcount)
|
|
return SWAP_SUCCESS; /* To break the loop */
|
|
|
|
return SWAP_AGAIN;
|
|
}
|
|
|
|
static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
|
|
{
|
|
struct page_referenced_arg *pra = arg;
|
|
struct mem_cgroup *memcg = pra->memcg;
|
|
|
|
if (!mm_match_cgroup(vma->vm_mm, memcg))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* page_referenced - test if the page was referenced
|
|
* @page: the page to test
|
|
* @is_locked: caller holds lock on the page
|
|
* @memcg: target memory cgroup
|
|
* @vm_flags: collect encountered vma->vm_flags who actually referenced 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,
|
|
struct mem_cgroup *memcg,
|
|
unsigned long *vm_flags)
|
|
{
|
|
int ret;
|
|
int we_locked = 0;
|
|
struct page_referenced_arg pra = {
|
|
.mapcount = page_mapcount(page),
|
|
.memcg = memcg,
|
|
};
|
|
struct rmap_walk_control rwc = {
|
|
.rmap_one = page_referenced_one,
|
|
.arg = (void *)&pra,
|
|
.anon_lock = page_lock_anon_vma_read,
|
|
};
|
|
|
|
*vm_flags = 0;
|
|
if (!page_mapped(page))
|
|
return 0;
|
|
|
|
if (!page_rmapping(page))
|
|
return 0;
|
|
|
|
if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
|
|
we_locked = trylock_page(page);
|
|
if (!we_locked)
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* If we are reclaiming on behalf of a cgroup, skip
|
|
* counting on behalf of references from different
|
|
* cgroups
|
|
*/
|
|
if (memcg) {
|
|
rwc.invalid_vma = invalid_page_referenced_vma;
|
|
}
|
|
|
|
ret = rmap_walk(page, &rwc);
|
|
*vm_flags = pra.vm_flags;
|
|
|
|
if (we_locked)
|
|
unlock_page(page);
|
|
|
|
return pra.referenced;
|
|
}
|
|
|
|
static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
|
|
unsigned long address, void *arg)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
pte_t *pte;
|
|
spinlock_t *ptl;
|
|
int ret = 0;
|
|
int *cleaned = arg;
|
|
|
|
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(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);
|
|
|
|
if (ret) {
|
|
mmu_notifier_invalidate_page(mm, address);
|
|
(*cleaned)++;
|
|
}
|
|
out:
|
|
return SWAP_AGAIN;
|
|
}
|
|
|
|
static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
|
|
{
|
|
if (vma->vm_flags & VM_SHARED)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
int page_mkclean(struct page *page)
|
|
{
|
|
int cleaned = 0;
|
|
struct address_space *mapping;
|
|
struct rmap_walk_control rwc = {
|
|
.arg = (void *)&cleaned,
|
|
.rmap_one = page_mkclean_one,
|
|
.invalid_vma = invalid_mkclean_vma,
|
|
};
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
|
|
if (!page_mapped(page))
|
|
return 0;
|
|
|
|
mapping = page_mapping(page);
|
|
if (!mapping)
|
|
return 0;
|
|
|
|
rmap_walk(page, &rwc);
|
|
|
|
return cleaned;
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_mkclean);
|
|
|
|
/**
|
|
* page_move_anon_rmap - move a page to our anon_vma
|
|
* @page: the page to move to our anon_vma
|
|
* @vma: the vma the page belongs to
|
|
* @address: the user virtual address mapped
|
|
*
|
|
* When a page belongs exclusively to one process after a COW event,
|
|
* that page can be moved into the anon_vma that belongs to just that
|
|
* process, so the rmap code will not search the parent or sibling
|
|
* processes.
|
|
*/
|
|
void page_move_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
VM_BUG_ON_VMA(!anon_vma, vma);
|
|
VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
|
|
|
|
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
|
|
page->mapping = (struct address_space *) anon_vma;
|
|
}
|
|
|
|
/**
|
|
* __page_set_anon_rmap - set up new anonymous rmap
|
|
* @page: Page to add to rmap
|
|
* @vma: VM area to add page to.
|
|
* @address: User virtual address of the mapping
|
|
* @exclusive: the page is exclusively owned by the current process
|
|
*/
|
|
static void __page_set_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address, int exclusive)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
|
|
BUG_ON(!anon_vma);
|
|
|
|
if (PageAnon(page))
|
|
return;
|
|
|
|
/*
|
|
* If the page isn't exclusively mapped into this vma,
|
|
* we must use the _oldest_ possible anon_vma for the
|
|
* page mapping!
|
|
*/
|
|
if (!exclusive)
|
|
anon_vma = anon_vma->root;
|
|
|
|
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
|
|
page->mapping = (struct address_space *) anon_vma;
|
|
page->index = linear_page_index(vma, address);
|
|
}
|
|
|
|
/**
|
|
* __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.
|
|
*/
|
|
BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
|
|
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 in
|
|
* the anon_vma case: to serialize mapping,index checking after setting,
|
|
* and to ensure that PageAnon is not being upgraded racily to PageKsm
|
|
* (but PageKsm is never downgraded to PageAnon).
|
|
*/
|
|
void page_add_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
do_page_add_anon_rmap(page, vma, address, 0);
|
|
}
|
|
|
|
/*
|
|
* Special version of the above for do_swap_page, which often runs
|
|
* into pages that are exclusively owned by the current process.
|
|
* Everybody else should continue to use page_add_anon_rmap above.
|
|
*/
|
|
void do_page_add_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address, int exclusive)
|
|
{
|
|
int first = atomic_inc_and_test(&page->_mapcount);
|
|
if (first) {
|
|
/*
|
|
* We use the irq-unsafe __{inc|mod}_zone_page_stat because
|
|
* these counters are not modified in interrupt context, and
|
|
* pte lock(a spinlock) is held, which implies preemption
|
|
* disabled.
|
|
*/
|
|
if (PageTransHuge(page))
|
|
__inc_zone_page_state(page,
|
|
NR_ANON_TRANSPARENT_HUGEPAGES);
|
|
__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
|
|
hpage_nr_pages(page));
|
|
}
|
|
if (unlikely(PageKsm(page)))
|
|
return;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
/* address might be in next vma when migration races vma_adjust */
|
|
if (first)
|
|
__page_set_anon_rmap(page, vma, address, exclusive);
|
|
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_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
|
|
SetPageSwapBacked(page);
|
|
atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
|
|
if (PageTransHuge(page))
|
|
__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
|
|
__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
|
|
hpage_nr_pages(page));
|
|
__page_set_anon_rmap(page, vma, address, 1);
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
bool locked;
|
|
unsigned long flags;
|
|
|
|
mem_cgroup_begin_update_page_stat(page, &locked, &flags);
|
|
if (atomic_inc_and_test(&page->_mapcount)) {
|
|
__inc_zone_page_state(page, NR_FILE_MAPPED);
|
|
mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
|
|
}
|
|
mem_cgroup_end_update_page_stat(page, &locked, &flags);
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
bool anon = PageAnon(page);
|
|
bool locked;
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* The anon case has no mem_cgroup page_stat to update; but may
|
|
* uncharge_page() below, where the lock ordering can deadlock if
|
|
* we hold the lock against page_stat move: so avoid it on anon.
|
|
*/
|
|
if (!anon)
|
|
mem_cgroup_begin_update_page_stat(page, &locked, &flags);
|
|
|
|
/* page still mapped by someone else? */
|
|
if (!atomic_add_negative(-1, &page->_mapcount))
|
|
goto out;
|
|
|
|
/*
|
|
* Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
|
|
* and not charged by memcg for now.
|
|
*
|
|
* We use the irq-unsafe __{inc|mod}_zone_page_stat because
|
|
* these counters are not modified in interrupt context, and
|
|
* these counters are not modified in interrupt context, and
|
|
* pte lock(a spinlock) is held, which implies preemption disabled.
|
|
*/
|
|
if (unlikely(PageHuge(page)))
|
|
goto out;
|
|
if (anon) {
|
|
if (PageTransHuge(page))
|
|
__dec_zone_page_state(page,
|
|
NR_ANON_TRANSPARENT_HUGEPAGES);
|
|
__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
|
|
-hpage_nr_pages(page));
|
|
} else {
|
|
__dec_zone_page_state(page, NR_FILE_MAPPED);
|
|
mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED);
|
|
mem_cgroup_end_update_page_stat(page, &locked, &flags);
|
|
}
|
|
if (unlikely(PageMlocked(page)))
|
|
clear_page_mlock(page);
|
|
/*
|
|
* 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.
|
|
*/
|
|
return;
|
|
out:
|
|
if (!anon)
|
|
mem_cgroup_end_update_page_stat(page, &locked, &flags);
|
|
}
|
|
|
|
/*
|
|
* @arg: enum ttu_flags will be passed to this argument
|
|
*/
|
|
static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
|
|
unsigned long address, void *arg)
|
|
{
|
|
struct mm_struct *mm = vma->vm_mm;
|
|
pte_t *pte;
|
|
pte_t pteval;
|
|
spinlock_t *ptl;
|
|
int ret = SWAP_AGAIN;
|
|
enum ttu_flags flags = (enum ttu_flags)arg;
|
|
|
|
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 (!(flags & TTU_IGNORE_MLOCK)) {
|
|
if (vma->vm_flags & VM_LOCKED)
|
|
goto out_mlock;
|
|
|
|
if (flags & TTU_MUNLOCK)
|
|
goto out_unmap;
|
|
}
|
|
if (!(flags & TTU_IGNORE_ACCESS)) {
|
|
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(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 (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
|
|
if (!PageHuge(page)) {
|
|
if (PageAnon(page))
|
|
dec_mm_counter(mm, MM_ANONPAGES);
|
|
else
|
|
dec_mm_counter(mm, MM_FILEPAGES);
|
|
}
|
|
set_pte_at(mm, address, pte,
|
|
swp_entry_to_pte(make_hwpoison_entry(page)));
|
|
} else if (pte_unused(pteval)) {
|
|
/*
|
|
* The guest indicated that the page content is of no
|
|
* interest anymore. Simply discard the pte, vmscan
|
|
* will take care of the rest.
|
|
*/
|
|
if (PageAnon(page))
|
|
dec_mm_counter(mm, MM_ANONPAGES);
|
|
else
|
|
dec_mm_counter(mm, MM_FILEPAGES);
|
|
} else if (PageAnon(page)) {
|
|
swp_entry_t entry = { .val = page_private(page) };
|
|
pte_t swp_pte;
|
|
|
|
if (PageSwapCache(page)) {
|
|
/*
|
|
* Store the swap location in the pte.
|
|
* See handle_pte_fault() ...
|
|
*/
|
|
if (swap_duplicate(entry) < 0) {
|
|
set_pte_at(mm, address, pte, pteval);
|
|
ret = SWAP_FAIL;
|
|
goto out_unmap;
|
|
}
|
|
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, MM_ANONPAGES);
|
|
inc_mm_counter(mm, MM_SWAPENTS);
|
|
} else if (IS_ENABLED(CONFIG_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(!(flags & TTU_MIGRATION));
|
|
entry = make_migration_entry(page, pte_write(pteval));
|
|
}
|
|
swp_pte = swp_entry_to_pte(entry);
|
|
if (pte_soft_dirty(pteval))
|
|
swp_pte = pte_swp_mksoft_dirty(swp_pte);
|
|
set_pte_at(mm, address, pte, swp_pte);
|
|
BUG_ON(pte_file(*pte));
|
|
} else if (IS_ENABLED(CONFIG_MIGRATION) &&
|
|
(flags & TTU_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, MM_FILEPAGES);
|
|
|
|
page_remove_rmap(page);
|
|
page_cache_release(page);
|
|
|
|
out_unmap:
|
|
pte_unmap_unlock(pte, ptl);
|
|
if (ret != SWAP_FAIL && !(flags & TTU_MUNLOCK))
|
|
mmu_notifier_invalidate_page(mm, address);
|
|
out:
|
|
return ret;
|
|
|
|
out_mlock:
|
|
pte_unmap_unlock(pte, ptl);
|
|
|
|
|
|
/*
|
|
* We need mmap_sem locking, Otherwise VM_LOCKED check makes
|
|
* unstable result and race. Plus, We can't wait here because
|
|
* we now hold anon_vma->rwsem or mapping->i_mmap_mutex.
|
|
* if trylock failed, the page remain in evictable lru and later
|
|
* vmscan could retry to move the page to unevictable lru if the
|
|
* page is actually mlocked.
|
|
*/
|
|
if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
|
|
if (vma->vm_flags & VM_LOCKED) {
|
|
mlock_vma_page(page);
|
|
ret = SWAP_MLOCK;
|
|
}
|
|
up_read(&vma->vm_mm->mmap_sem);
|
|
}
|
|
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;
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
pte_t pteval;
|
|
spinlock_t *ptl;
|
|
struct page *page;
|
|
unsigned long address;
|
|
unsigned long mmun_start; /* For mmu_notifiers */
|
|
unsigned long mmun_end; /* For mmu_notifiers */
|
|
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;
|
|
|
|
pmd = mm_find_pmd(mm, address);
|
|
if (!pmd)
|
|
return ret;
|
|
|
|
mmun_start = address;
|
|
mmun_end = end;
|
|
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
|
|
|
|
/*
|
|
* 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 (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) {
|
|
if (page == check_page) {
|
|
/* we know we have check_page locked */
|
|
mlock_vma_page(page);
|
|
ret = SWAP_MLOCK;
|
|
} else if (trylock_page(page)) {
|
|
/*
|
|
* If we can lock the page, perform mlock.
|
|
* Otherwise leave the page alone, it will be
|
|
* eventually encountered again later.
|
|
*/
|
|
mlock_vma_page(page);
|
|
unlock_page(page);
|
|
}
|
|
continue; /* don't unmap */
|
|
}
|
|
|
|
/*
|
|
* No need for _notify because we're within an
|
|
* mmu_notifier_invalidate_range_ {start|end} scope.
|
|
*/
|
|
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)) {
|
|
pte_t ptfile = pgoff_to_pte(page->index);
|
|
if (pte_soft_dirty(pteval))
|
|
ptfile = pte_file_mksoft_dirty(ptfile);
|
|
set_pte_at(mm, address, pte, ptfile);
|
|
}
|
|
|
|
/* 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, MM_FILEPAGES);
|
|
(*mapcount)--;
|
|
}
|
|
pte_unmap_unlock(pte - 1, ptl);
|
|
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
|
|
if (locked_vma)
|
|
up_read(&vma->vm_mm->mmap_sem);
|
|
return ret;
|
|
}
|
|
|
|
static int try_to_unmap_nonlinear(struct page *page,
|
|
struct address_space *mapping, void *arg)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
int ret = SWAP_AGAIN;
|
|
unsigned long cursor;
|
|
unsigned long max_nl_cursor = 0;
|
|
unsigned long max_nl_size = 0;
|
|
unsigned int mapcount;
|
|
|
|
list_for_each_entry(vma,
|
|
&mapping->i_mmap_nonlinear, shared.nonlinear) {
|
|
|
|
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 ? */
|
|
return SWAP_FAIL;
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
return ret;
|
|
|
|
cond_resched();
|
|
|
|
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.nonlinear) {
|
|
|
|
cursor = (unsigned long) vma->vm_private_data;
|
|
while (cursor < max_nl_cursor &&
|
|
cursor < vma->vm_end - vma->vm_start) {
|
|
if (try_to_unmap_cluster(cursor, &mapcount,
|
|
vma, page) == SWAP_MLOCK)
|
|
ret = SWAP_MLOCK;
|
|
cursor += CLUSTER_SIZE;
|
|
vma->vm_private_data = (void *) cursor;
|
|
if ((int)mapcount <= 0)
|
|
return ret;
|
|
}
|
|
vma->vm_private_data = (void *) max_nl_cursor;
|
|
}
|
|
cond_resched();
|
|
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.nonlinear)
|
|
vma->vm_private_data = NULL;
|
|
|
|
return ret;
|
|
}
|
|
|
|
bool is_vma_temporary_stack(struct vm_area_struct *vma)
|
|
{
|
|
int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
|
|
|
|
if (!maybe_stack)
|
|
return false;
|
|
|
|
if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
|
|
VM_STACK_INCOMPLETE_SETUP)
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
|
|
{
|
|
return is_vma_temporary_stack(vma);
|
|
}
|
|
|
|
static int page_not_mapped(struct page *page)
|
|
{
|
|
return !page_mapped(page);
|
|
};
|
|
|
|
/**
|
|
* try_to_unmap - try to remove all page table mappings to a page
|
|
* @page: the page to get unmapped
|
|
* @flags: action and flags
|
|
*
|
|
* 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, enum ttu_flags flags)
|
|
{
|
|
int ret;
|
|
struct rmap_walk_control rwc = {
|
|
.rmap_one = try_to_unmap_one,
|
|
.arg = (void *)flags,
|
|
.done = page_not_mapped,
|
|
.file_nonlinear = try_to_unmap_nonlinear,
|
|
.anon_lock = page_lock_anon_vma_read,
|
|
};
|
|
|
|
VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page);
|
|
|
|
/*
|
|
* During exec, a temporary VMA is setup and later moved.
|
|
* The VMA is moved under the anon_vma lock but not the
|
|
* page tables leading to a race where migration cannot
|
|
* find the migration ptes. Rather than increasing the
|
|
* locking requirements of exec(), migration skips
|
|
* temporary VMAs until after exec() completes.
|
|
*/
|
|
if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page))
|
|
rwc.invalid_vma = invalid_migration_vma;
|
|
|
|
ret = rmap_walk(page, &rwc);
|
|
|
|
if (ret != SWAP_MLOCK && !page_mapped(page))
|
|
ret = SWAP_SUCCESS;
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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_AGAIN - no vma is holding page mlocked, or,
|
|
* SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem
|
|
* SWAP_FAIL - page cannot be located at present
|
|
* SWAP_MLOCK - page is now mlocked.
|
|
*/
|
|
int try_to_munlock(struct page *page)
|
|
{
|
|
int ret;
|
|
struct rmap_walk_control rwc = {
|
|
.rmap_one = try_to_unmap_one,
|
|
.arg = (void *)TTU_MUNLOCK,
|
|
.done = page_not_mapped,
|
|
/*
|
|
* We don't bother to try to find the munlocked page in
|
|
* nonlinears. It's costly. Instead, later, page reclaim logic
|
|
* may call try_to_unmap() and recover PG_mlocked lazily.
|
|
*/
|
|
.file_nonlinear = NULL,
|
|
.anon_lock = page_lock_anon_vma_read,
|
|
|
|
};
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page);
|
|
|
|
ret = rmap_walk(page, &rwc);
|
|
return ret;
|
|
}
|
|
|
|
void __put_anon_vma(struct anon_vma *anon_vma)
|
|
{
|
|
struct anon_vma *root = anon_vma->root;
|
|
|
|
anon_vma_free(anon_vma);
|
|
if (root != anon_vma && atomic_dec_and_test(&root->refcount))
|
|
anon_vma_free(root);
|
|
}
|
|
|
|
static struct anon_vma *rmap_walk_anon_lock(struct page *page,
|
|
struct rmap_walk_control *rwc)
|
|
{
|
|
struct anon_vma *anon_vma;
|
|
|
|
if (rwc->anon_lock)
|
|
return rwc->anon_lock(page);
|
|
|
|
/*
|
|
* Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
|
|
* because that depends on page_mapped(); but not all its usages
|
|
* are holding mmap_sem. Users without mmap_sem are required to
|
|
* take a reference count to prevent the anon_vma disappearing
|
|
*/
|
|
anon_vma = page_anon_vma(page);
|
|
if (!anon_vma)
|
|
return NULL;
|
|
|
|
anon_vma_lock_read(anon_vma);
|
|
return anon_vma;
|
|
}
|
|
|
|
/*
|
|
* rmap_walk_anon - do something to anonymous page using the object-based
|
|
* rmap method
|
|
* @page: the page to be handled
|
|
* @rwc: control variable according to each walk type
|
|
*
|
|
* Find all the mappings of a page using the mapping pointer and the vma chains
|
|
* contained in the anon_vma struct it points to.
|
|
*
|
|
* 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 rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
|
|
{
|
|
struct anon_vma *anon_vma;
|
|
pgoff_t pgoff = page_to_pgoff(page);
|
|
struct anon_vma_chain *avc;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
anon_vma = rmap_walk_anon_lock(page, rwc);
|
|
if (!anon_vma)
|
|
return ret;
|
|
|
|
anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
|
|
struct vm_area_struct *vma = avc->vma;
|
|
unsigned long address = vma_address(page, vma);
|
|
|
|
if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
|
|
continue;
|
|
|
|
ret = rwc->rmap_one(page, vma, address, rwc->arg);
|
|
if (ret != SWAP_AGAIN)
|
|
break;
|
|
if (rwc->done && rwc->done(page))
|
|
break;
|
|
}
|
|
anon_vma_unlock_read(anon_vma);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* rmap_walk_file - do something to file page using the object-based rmap method
|
|
* @page: the page to be handled
|
|
* @rwc: control variable according to each walk type
|
|
*
|
|
* Find all the mappings of a page using the mapping pointer and the vma chains
|
|
* contained in the address_space struct it points to.
|
|
*
|
|
* 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 rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
pgoff_t pgoff = page_to_pgoff(page);
|
|
struct vm_area_struct *vma;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
/*
|
|
* 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_mutex.
|
|
*/
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
|
|
if (!mapping)
|
|
return ret;
|
|
mutex_lock(&mapping->i_mmap_mutex);
|
|
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
|
|
unsigned long address = vma_address(page, vma);
|
|
|
|
if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
|
|
continue;
|
|
|
|
ret = rwc->rmap_one(page, vma, address, rwc->arg);
|
|
if (ret != SWAP_AGAIN)
|
|
goto done;
|
|
if (rwc->done && rwc->done(page))
|
|
goto done;
|
|
}
|
|
|
|
if (!rwc->file_nonlinear)
|
|
goto done;
|
|
|
|
if (list_empty(&mapping->i_mmap_nonlinear))
|
|
goto done;
|
|
|
|
ret = rwc->file_nonlinear(page, mapping, rwc->arg);
|
|
|
|
done:
|
|
mutex_unlock(&mapping->i_mmap_mutex);
|
|
return ret;
|
|
}
|
|
|
|
int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
|
|
{
|
|
if (unlikely(PageKsm(page)))
|
|
return rmap_walk_ksm(page, rwc);
|
|
else if (PageAnon(page))
|
|
return rmap_walk_anon(page, rwc);
|
|
else
|
|
return rmap_walk_file(page, rwc);
|
|
}
|
|
|
|
#ifdef CONFIG_HUGETLB_PAGE
|
|
/*
|
|
* The following three functions are for anonymous (private mapped) hugepages.
|
|
* Unlike common anonymous pages, anonymous hugepages have no accounting code
|
|
* and no lru code, because we handle hugepages differently from common pages.
|
|
*/
|
|
static void __hugepage_set_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address, int exclusive)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
|
|
BUG_ON(!anon_vma);
|
|
|
|
if (PageAnon(page))
|
|
return;
|
|
if (!exclusive)
|
|
anon_vma = anon_vma->root;
|
|
|
|
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
|
|
page->mapping = (struct address_space *) anon_vma;
|
|
page->index = linear_page_index(vma, address);
|
|
}
|
|
|
|
void hugepage_add_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
struct anon_vma *anon_vma = vma->anon_vma;
|
|
int first;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
BUG_ON(!anon_vma);
|
|
/* address might be in next vma when migration races vma_adjust */
|
|
first = atomic_inc_and_test(&page->_mapcount);
|
|
if (first)
|
|
__hugepage_set_anon_rmap(page, vma, address, 0);
|
|
}
|
|
|
|
void hugepage_add_new_anon_rmap(struct page *page,
|
|
struct vm_area_struct *vma, unsigned long address)
|
|
{
|
|
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
|
|
atomic_set(&page->_mapcount, 0);
|
|
__hugepage_set_anon_rmap(page, vma, address, 1);
|
|
}
|
|
#endif /* CONFIG_HUGETLB_PAGE */
|