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![Baruch Siach](/assets/img/avatar_default.png)
anon_vma_link() is unused since commit 5beb493052
("mm: change anon_vma
linking to fix multi-process server scalability issue").
Link: https://lkml.kernel.org/r/cdce9b00c9ab15f6d02eddf40dcad537d3e9676f.1692877089.git.baruch@tkos.co.il
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
505 lines
16 KiB
C
505 lines
16 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_RMAP_H
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#define _LINUX_RMAP_H
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/*
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* Declarations for Reverse Mapping functions in mm/rmap.c
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*/
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/mm.h>
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#include <linux/rwsem.h>
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#include <linux/memcontrol.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/memremap.h>
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/*
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* The anon_vma heads a list of private "related" vmas, to scan if
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* an anonymous page pointing to this anon_vma needs to be unmapped:
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* the vmas on the list will be related by forking, or by splitting.
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*
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* Since vmas come and go as they are split and merged (particularly
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* in mprotect), the mapping field of an anonymous page cannot point
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* directly to a vma: instead it points to an anon_vma, on whose list
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* the related vmas can be easily linked or unlinked.
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*
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* After unlinking the last vma on the list, we must garbage collect
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* the anon_vma object itself: we're guaranteed no page can be
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* pointing to this anon_vma once its vma list is empty.
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*/
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struct anon_vma {
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struct anon_vma *root; /* Root of this anon_vma tree */
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struct rw_semaphore rwsem; /* W: modification, R: walking the list */
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/*
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* The refcount is taken on an anon_vma when there is no
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* guarantee that the vma of page tables will exist for
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* the duration of the operation. A caller that takes
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* the reference is responsible for clearing up the
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* anon_vma if they are the last user on release
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*/
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atomic_t refcount;
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/*
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* Count of child anon_vmas. Equals to the count of all anon_vmas that
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* have ->parent pointing to this one, including itself.
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*
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* This counter is used for making decision about reusing anon_vma
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* instead of forking new one. See comments in function anon_vma_clone.
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*/
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unsigned long num_children;
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/* Count of VMAs whose ->anon_vma pointer points to this object. */
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unsigned long num_active_vmas;
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struct anon_vma *parent; /* Parent of this anon_vma */
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/*
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* NOTE: the LSB of the rb_root.rb_node is set by
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* mm_take_all_locks() _after_ taking the above lock. So the
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* rb_root must only be read/written after taking the above lock
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* to be sure to see a valid next pointer. The LSB bit itself
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* is serialized by a system wide lock only visible to
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* mm_take_all_locks() (mm_all_locks_mutex).
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*/
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/* Interval tree of private "related" vmas */
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struct rb_root_cached rb_root;
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};
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/*
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* The copy-on-write semantics of fork mean that an anon_vma
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* can become associated with multiple processes. Furthermore,
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* each child process will have its own anon_vma, where new
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* pages for that process are instantiated.
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*
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* This structure allows us to find the anon_vmas associated
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* with a VMA, or the VMAs associated with an anon_vma.
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* The "same_vma" list contains the anon_vma_chains linking
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* all the anon_vmas associated with this VMA.
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* The "rb" field indexes on an interval tree the anon_vma_chains
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* which link all the VMAs associated with this anon_vma.
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*/
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struct anon_vma_chain {
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struct vm_area_struct *vma;
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struct anon_vma *anon_vma;
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struct list_head same_vma; /* locked by mmap_lock & page_table_lock */
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struct rb_node rb; /* locked by anon_vma->rwsem */
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unsigned long rb_subtree_last;
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#ifdef CONFIG_DEBUG_VM_RB
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unsigned long cached_vma_start, cached_vma_last;
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#endif
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};
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enum ttu_flags {
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TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */
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TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */
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TTU_SYNC = 0x10, /* avoid racy checks with PVMW_SYNC */
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TTU_HWPOISON = 0x20, /* do convert pte to hwpoison entry */
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TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible
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* and caller guarantees they will
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* do a final flush if necessary */
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TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock:
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* caller holds it */
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};
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#ifdef CONFIG_MMU
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static inline void get_anon_vma(struct anon_vma *anon_vma)
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{
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atomic_inc(&anon_vma->refcount);
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}
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void __put_anon_vma(struct anon_vma *anon_vma);
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static inline void put_anon_vma(struct anon_vma *anon_vma)
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{
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if (atomic_dec_and_test(&anon_vma->refcount))
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__put_anon_vma(anon_vma);
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}
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static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
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{
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down_write(&anon_vma->root->rwsem);
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}
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static inline void anon_vma_unlock_write(struct anon_vma *anon_vma)
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{
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up_write(&anon_vma->root->rwsem);
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}
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static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
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{
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down_read(&anon_vma->root->rwsem);
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}
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static inline int anon_vma_trylock_read(struct anon_vma *anon_vma)
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{
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return down_read_trylock(&anon_vma->root->rwsem);
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}
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static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
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{
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up_read(&anon_vma->root->rwsem);
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}
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/*
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* anon_vma helper functions.
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*/
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void anon_vma_init(void); /* create anon_vma_cachep */
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int __anon_vma_prepare(struct vm_area_struct *);
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void unlink_anon_vmas(struct vm_area_struct *);
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int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
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int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
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static inline int anon_vma_prepare(struct vm_area_struct *vma)
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{
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if (likely(vma->anon_vma))
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return 0;
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return __anon_vma_prepare(vma);
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}
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static inline void anon_vma_merge(struct vm_area_struct *vma,
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struct vm_area_struct *next)
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{
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VM_BUG_ON_VMA(vma->anon_vma != next->anon_vma, vma);
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unlink_anon_vmas(next);
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}
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struct anon_vma *folio_get_anon_vma(struct folio *folio);
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/* RMAP flags, currently only relevant for some anon rmap operations. */
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typedef int __bitwise rmap_t;
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/*
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* No special request: if the page is a subpage of a compound page, it is
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* mapped via a PTE. The mapped (sub)page is possibly shared between processes.
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*/
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#define RMAP_NONE ((__force rmap_t)0)
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/* The (sub)page is exclusive to a single process. */
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#define RMAP_EXCLUSIVE ((__force rmap_t)BIT(0))
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/*
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* The compound page is not mapped via PTEs, but instead via a single PMD and
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* should be accounted accordingly.
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*/
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#define RMAP_COMPOUND ((__force rmap_t)BIT(1))
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/*
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* rmap interfaces called when adding or removing pte of page
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*/
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void page_move_anon_rmap(struct page *, struct vm_area_struct *);
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void page_add_anon_rmap(struct page *, struct vm_area_struct *,
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unsigned long address, rmap_t flags);
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void page_add_new_anon_rmap(struct page *, struct vm_area_struct *,
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unsigned long address);
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void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
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unsigned long address);
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void page_add_file_rmap(struct page *, struct vm_area_struct *,
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bool compound);
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void folio_add_file_rmap_range(struct folio *, struct page *, unsigned int nr,
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struct vm_area_struct *, bool compound);
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void page_remove_rmap(struct page *, struct vm_area_struct *,
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bool compound);
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void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
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unsigned long address, rmap_t flags);
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void hugepage_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
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unsigned long address);
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static inline void __page_dup_rmap(struct page *page, bool compound)
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{
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if (compound) {
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struct folio *folio = (struct folio *)page;
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VM_BUG_ON_PAGE(compound && !PageHead(page), page);
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atomic_inc(&folio->_entire_mapcount);
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} else {
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atomic_inc(&page->_mapcount);
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}
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}
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static inline void page_dup_file_rmap(struct page *page, bool compound)
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{
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__page_dup_rmap(page, compound);
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}
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/**
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* page_try_dup_anon_rmap - try duplicating a mapping of an already mapped
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* anonymous page
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* @page: the page to duplicate the mapping for
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* @compound: the page is mapped as compound or as a small page
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* @vma: the source vma
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*
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* The caller needs to hold the PT lock and the vma->vma_mm->write_protect_seq.
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*
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* Duplicating the mapping can only fail if the page may be pinned; device
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* private pages cannot get pinned and consequently this function cannot fail.
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*
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* If duplicating the mapping succeeds, the page has to be mapped R/O into
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* the parent and the child. It must *not* get mapped writable after this call.
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*
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* Returns 0 if duplicating the mapping succeeded. Returns -EBUSY otherwise.
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*/
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static inline int page_try_dup_anon_rmap(struct page *page, bool compound,
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struct vm_area_struct *vma)
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{
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VM_BUG_ON_PAGE(!PageAnon(page), page);
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/*
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* No need to check+clear for already shared pages, including KSM
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* pages.
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*/
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if (!PageAnonExclusive(page))
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goto dup;
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/*
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* If this page may have been pinned by the parent process,
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* don't allow to duplicate the mapping but instead require to e.g.,
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* copy the page immediately for the child so that we'll always
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* guarantee the pinned page won't be randomly replaced in the
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* future on write faults.
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*/
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if (likely(!is_device_private_page(page) &&
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unlikely(page_needs_cow_for_dma(vma, page))))
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return -EBUSY;
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ClearPageAnonExclusive(page);
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/*
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* It's okay to share the anon page between both processes, mapping
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* the page R/O into both processes.
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*/
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dup:
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__page_dup_rmap(page, compound);
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return 0;
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}
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/**
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* page_try_share_anon_rmap - try marking an exclusive anonymous page possibly
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* shared to prepare for KSM or temporary unmapping
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* @page: the exclusive anonymous page to try marking possibly shared
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*
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* The caller needs to hold the PT lock and has to have the page table entry
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* cleared/invalidated.
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*
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* This is similar to page_try_dup_anon_rmap(), however, not used during fork()
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* to duplicate a mapping, but instead to prepare for KSM or temporarily
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* unmapping a page (swap, migration) via page_remove_rmap().
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*
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* Marking the page shared can only fail if the page may be pinned; device
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* private pages cannot get pinned and consequently this function cannot fail.
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*
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* Returns 0 if marking the page possibly shared succeeded. Returns -EBUSY
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* otherwise.
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*/
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static inline int page_try_share_anon_rmap(struct page *page)
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{
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VM_BUG_ON_PAGE(!PageAnon(page) || !PageAnonExclusive(page), page);
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/* device private pages cannot get pinned via GUP. */
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if (unlikely(is_device_private_page(page))) {
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ClearPageAnonExclusive(page);
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return 0;
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}
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/*
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* We have to make sure that when we clear PageAnonExclusive, that
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* the page is not pinned and that concurrent GUP-fast won't succeed in
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* concurrently pinning the page.
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*
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* Conceptually, PageAnonExclusive clearing consists of:
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* (A1) Clear PTE
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* (A2) Check if the page is pinned; back off if so.
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* (A3) Clear PageAnonExclusive
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* (A4) Restore PTE (optional, but certainly not writable)
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*
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* When clearing PageAnonExclusive, we cannot possibly map the page
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* writable again, because anon pages that may be shared must never
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* be writable. So in any case, if the PTE was writable it cannot
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* be writable anymore afterwards and there would be a PTE change. Only
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* if the PTE wasn't writable, there might not be a PTE change.
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*
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* Conceptually, GUP-fast pinning of an anon page consists of:
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* (B1) Read the PTE
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* (B2) FOLL_WRITE: check if the PTE is not writable; back off if so.
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* (B3) Pin the mapped page
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* (B4) Check if the PTE changed by re-reading it; back off if so.
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* (B5) If the original PTE is not writable, check if
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* PageAnonExclusive is not set; back off if so.
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*
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* If the PTE was writable, we only have to make sure that GUP-fast
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* observes a PTE change and properly backs off.
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*
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* If the PTE was not writable, we have to make sure that GUP-fast either
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* detects a (temporary) PTE change or that PageAnonExclusive is cleared
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* and properly backs off.
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*
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* Consequently, when clearing PageAnonExclusive(), we have to make
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* sure that (A1), (A2)/(A3) and (A4) happen in the right memory
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* order. In GUP-fast pinning code, we have to make sure that (B3),(B4)
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* and (B5) happen in the right memory order.
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*
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* We assume that there might not be a memory barrier after
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* clearing/invalidating the PTE (A1) and before restoring the PTE (A4),
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* so we use explicit ones here.
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*/
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/* Paired with the memory barrier in try_grab_folio(). */
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if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
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smp_mb();
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if (unlikely(page_maybe_dma_pinned(page)))
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return -EBUSY;
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ClearPageAnonExclusive(page);
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/*
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* This is conceptually a smp_wmb() paired with the smp_rmb() in
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* gup_must_unshare().
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*/
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if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
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smp_mb__after_atomic();
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return 0;
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}
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/*
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* Called from mm/vmscan.c to handle paging out
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*/
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int folio_referenced(struct folio *, int is_locked,
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struct mem_cgroup *memcg, unsigned long *vm_flags);
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void try_to_migrate(struct folio *folio, enum ttu_flags flags);
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void try_to_unmap(struct folio *, enum ttu_flags flags);
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int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
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unsigned long end, struct page **pages,
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void *arg);
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/* Avoid racy checks */
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#define PVMW_SYNC (1 << 0)
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/* Look for migration entries rather than present PTEs */
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#define PVMW_MIGRATION (1 << 1)
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struct page_vma_mapped_walk {
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unsigned long pfn;
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unsigned long nr_pages;
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pgoff_t pgoff;
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struct vm_area_struct *vma;
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unsigned long address;
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pmd_t *pmd;
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pte_t *pte;
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spinlock_t *ptl;
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unsigned int flags;
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};
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#define DEFINE_PAGE_VMA_WALK(name, _page, _vma, _address, _flags) \
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struct page_vma_mapped_walk name = { \
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.pfn = page_to_pfn(_page), \
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.nr_pages = compound_nr(_page), \
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.pgoff = page_to_pgoff(_page), \
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.vma = _vma, \
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.address = _address, \
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.flags = _flags, \
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}
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#define DEFINE_FOLIO_VMA_WALK(name, _folio, _vma, _address, _flags) \
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struct page_vma_mapped_walk name = { \
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.pfn = folio_pfn(_folio), \
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.nr_pages = folio_nr_pages(_folio), \
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.pgoff = folio_pgoff(_folio), \
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.vma = _vma, \
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.address = _address, \
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.flags = _flags, \
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}
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static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
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{
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/* HugeTLB pte is set to the relevant page table entry without pte_mapped. */
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if (pvmw->pte && !is_vm_hugetlb_page(pvmw->vma))
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pte_unmap(pvmw->pte);
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if (pvmw->ptl)
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spin_unlock(pvmw->ptl);
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}
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bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
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/*
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* Used by swapoff to help locate where page is expected in vma.
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*/
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unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);
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/*
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* Cleans the PTEs of shared mappings.
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* (and since clean PTEs should also be readonly, write protects them too)
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*
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* returns the number of cleaned PTEs.
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*/
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int folio_mkclean(struct folio *);
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int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
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struct vm_area_struct *vma);
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void remove_migration_ptes(struct folio *src, struct folio *dst, bool locked);
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int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
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/*
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* rmap_walk_control: To control rmap traversing for specific needs
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*
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* arg: passed to rmap_one() and invalid_vma()
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* try_lock: bail out if the rmap lock is contended
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* contended: indicate the rmap traversal bailed out due to lock contention
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* rmap_one: executed on each vma where page is mapped
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* done: for checking traversing termination condition
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* anon_lock: for getting anon_lock by optimized way rather than default
|
|
* invalid_vma: for skipping uninterested vma
|
|
*/
|
|
struct rmap_walk_control {
|
|
void *arg;
|
|
bool try_lock;
|
|
bool contended;
|
|
/*
|
|
* Return false if page table scanning in rmap_walk should be stopped.
|
|
* Otherwise, return true.
|
|
*/
|
|
bool (*rmap_one)(struct folio *folio, struct vm_area_struct *vma,
|
|
unsigned long addr, void *arg);
|
|
int (*done)(struct folio *folio);
|
|
struct anon_vma *(*anon_lock)(struct folio *folio,
|
|
struct rmap_walk_control *rwc);
|
|
bool (*invalid_vma)(struct vm_area_struct *vma, void *arg);
|
|
};
|
|
|
|
void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc);
|
|
void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc);
|
|
struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
|
|
struct rmap_walk_control *rwc);
|
|
|
|
#else /* !CONFIG_MMU */
|
|
|
|
#define anon_vma_init() do {} while (0)
|
|
#define anon_vma_prepare(vma) (0)
|
|
|
|
static inline int folio_referenced(struct folio *folio, int is_locked,
|
|
struct mem_cgroup *memcg,
|
|
unsigned long *vm_flags)
|
|
{
|
|
*vm_flags = 0;
|
|
return 0;
|
|
}
|
|
|
|
static inline void try_to_unmap(struct folio *folio, enum ttu_flags flags)
|
|
{
|
|
}
|
|
|
|
static inline int folio_mkclean(struct folio *folio)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif /* CONFIG_MMU */
|
|
|
|
static inline int page_mkclean(struct page *page)
|
|
{
|
|
return folio_mkclean(page_folio(page));
|
|
}
|
|
#endif /* _LINUX_RMAP_H */
|