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![Konstantin Khlebnikov](/assets/img/avatar_default.png)
Constantly forking task causes unlimited grow of anon_vma chain. Each
next child allocates new level of anon_vmas and links vma to all
previous levels because pages might be inherited from any level.
This patch adds heuristic which decides to reuse existing anon_vma
instead of forking new one. It adds counter anon_vma->degree which
counts linked vmas and directly descending anon_vmas and reuses anon_vma
if counter is lower than two. As a result each anon_vma has either vma
or at least two descending anon_vmas. In such trees half of nodes are
leafs with alive vmas, thus count of anon_vmas is no more than two times
bigger than count of vmas.
This heuristic reuses anon_vmas as few as possible because each reuse
adds false aliasing among vmas and rmap walker ought to scan more ptes
when it searches where page is might be mapped.
Link: http://lkml.kernel.org/r/20120816024610.GA5350@evergreen.ssec.wisc.edu
Fixes: 5beb493052
("mm: change anon_vma linking to fix multi-process server scalability issue")
[akpm@linux-foundation.org: fix typo, per Rik]
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Reported-by: Daniel Forrest <dan.forrest@ssec.wisc.edu>
Tested-by: Michal Hocko <mhocko@suse.cz>
Tested-by: Jerome Marchand <jmarchan@redhat.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org> [2.6.34+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1817 lines
50 KiB
C
1817 lines
50 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_rwsem
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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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anon_vma->degree = 1; /* Reference for first vma */
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anon_vma->parent = anon_vma;
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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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/* vma reference or self-parent link for new root */
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anon_vma->degree++;
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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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* If dst->anon_vma is NULL this function tries to find and reuse existing
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* anon_vma which has no vmas and only one child anon_vma. This prevents
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* degradation of anon_vma hierarchy to endless linear chain in case of
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* constantly forking task. On the other hand, an anon_vma with more than one
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* child isn't reused even if there was no alive vma, thus rmap walker has a
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* good chance of avoiding scanning the whole hierarchy when it searches where
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* page is mapped.
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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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* Reuse existing anon_vma if its degree lower than two,
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* that means it has no vma and only one anon_vma child.
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*
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* Do not chose parent anon_vma, otherwise first child
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* will always reuse it. Root anon_vma is never reused:
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* it has self-parent reference and at least one child.
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*/
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if (!dst->anon_vma && anon_vma != src->anon_vma &&
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anon_vma->degree < 2)
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dst->anon_vma = anon_vma;
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}
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if (dst->anon_vma)
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dst->anon_vma->degree++;
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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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/*
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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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int error;
|
|
|
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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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/* Drop inherited anon_vma, we'll reuse existing or allocate new. */
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vma->anon_vma = NULL;
|
|
|
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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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error = anon_vma_clone(vma, pvma);
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if (error)
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return error;
|
|
|
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/* An existing anon_vma has been reused, all done then. */
|
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if (vma->anon_vma)
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return 0;
|
|
|
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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);
|
|
if (!avc)
|
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goto out_error_free_anon_vma;
|
|
|
|
/*
|
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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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anon_vma->parent = pvma->anon_vma;
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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->parent->degree++;
|
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anon_vma_unlock_write(anon_vma);
|
|
|
|
return 0;
|
|
|
|
out_error_free_anon_vma:
|
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put_anon_vma(anon_vma);
|
|
out_error:
|
|
unlink_anon_vmas(vma);
|
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return -ENOMEM;
|
|
}
|
|
|
|
void unlink_anon_vmas(struct vm_area_struct *vma)
|
|
{
|
|
struct anon_vma_chain *avc, *next;
|
|
struct anon_vma *root = NULL;
|
|
|
|
/*
|
|
* Unlink each anon_vma chained to the VMA. This list is ordered
|
|
* from newest to oldest, ensuring the root anon_vma gets freed last.
|
|
*/
|
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list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
|
|
struct anon_vma *anon_vma = avc->anon_vma;
|
|
|
|
root = lock_anon_vma_root(root, anon_vma);
|
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anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
|
|
|
|
/*
|
|
* Leave empty anon_vmas on the list - we'll need
|
|
* to free them outside the lock.
|
|
*/
|
|
if (RB_EMPTY_ROOT(&anon_vma->rb_root)) {
|
|
anon_vma->parent->degree--;
|
|
continue;
|
|
}
|
|
|
|
list_del(&avc->same_vma);
|
|
anon_vma_chain_free(avc);
|
|
}
|
|
if (vma->anon_vma)
|
|
vma->anon_vma->degree--;
|
|
unlock_anon_vma_root(root);
|
|
|
|
/*
|
|
* Iterate the list once more, it now only contains empty and unlinked
|
|
* anon_vmas, destroy them. Could not do before due to __put_anon_vma()
|
|
* needing to write-acquire the anon_vma->root->rwsem.
|
|
*/
|
|
list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
|
|
struct anon_vma *anon_vma = avc->anon_vma;
|
|
|
|
BUG_ON(anon_vma->degree);
|
|
put_anon_vma(anon_vma);
|
|
|
|
list_del(&avc->same_vma);
|
|
anon_vma_chain_free(avc);
|
|
}
|
|
}
|
|
|
|
static void anon_vma_ctor(void *data)
|
|
{
|
|
struct anon_vma *anon_vma = data;
|
|
|
|
init_rwsem(&anon_vma->rwsem);
|
|
atomic_set(&anon_vma->refcount, 0);
|
|
anon_vma->rb_root = RB_ROOT;
|
|
}
|
|
|
|
void __init anon_vma_init(void)
|
|
{
|
|
anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
|
|
0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
|
|
anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
|
|
}
|
|
|
|
/*
|
|
* 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 = *pmd;
|
|
barrier();
|
|
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)
|
|
{
|
|
struct mem_cgroup *memcg;
|
|
unsigned long flags;
|
|
bool locked;
|
|
|
|
memcg = mem_cgroup_begin_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(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
|
|
}
|
|
mem_cgroup_end_page_stat(memcg, &locked, &flags);
|
|
}
|
|
|
|
static void page_remove_file_rmap(struct page *page)
|
|
{
|
|
struct mem_cgroup *memcg;
|
|
unsigned long flags;
|
|
bool locked;
|
|
|
|
memcg = mem_cgroup_begin_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_FILE_MAPPED for now. */
|
|
if (unlikely(PageHuge(page)))
|
|
goto out;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
__dec_zone_page_state(page, NR_FILE_MAPPED);
|
|
mem_cgroup_dec_page_stat(memcg, MEM_CGROUP_STAT_FILE_MAPPED);
|
|
|
|
if (unlikely(PageMlocked(page)))
|
|
clear_page_mlock(page);
|
|
out:
|
|
mem_cgroup_end_page_stat(memcg, &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)
|
|
{
|
|
if (!PageAnon(page)) {
|
|
page_remove_file_rmap(page);
|
|
return;
|
|
}
|
|
|
|
/* page still mapped by someone else? */
|
|
if (!atomic_add_negative(-1, &page->_mapcount))
|
|
return;
|
|
|
|
/* Hugepages are not counted in NR_ANON_PAGES for now. */
|
|
if (unlikely(PageHuge(page)))
|
|
return;
|
|
|
|
/*
|
|
* 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))
|
|
__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
|
|
|
|
__mod_zone_page_state(page_zone(page), NR_ANON_PAGES,
|
|
-hpage_nr_pages(page));
|
|
|
|
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.
|
|
*/
|
|
}
|
|
|
|
/*
|
|
* @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_rwsem.
|
|
* 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_notify(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;
|
|
struct anon_vma_chain *avc;
|
|
int ret = SWAP_AGAIN;
|
|
|
|
anon_vma = rmap_walk_anon_lock(page, rwc);
|
|
if (!anon_vma)
|
|
return ret;
|
|
|
|
pgoff = page_to_pgoff(page);
|
|
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;
|
|
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_rwsem.
|
|
*/
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
|
|
if (!mapping)
|
|
return ret;
|
|
|
|
pgoff = page_to_pgoff(page);
|
|
i_mmap_lock_read(mapping);
|
|
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:
|
|
i_mmap_unlock_read(mapping);
|
|
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 */
|