Fetching contributors…
Cannot retrieve contributors at this time
654 lines (576 sloc) 19.6 KB
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/mm_types_task.h>
#include <linux/auxvec.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/rbtree.h>
#include <linux/rwsem.h>
#include <linux/completion.h>
#include <linux/cpumask.h>
#include <linux/uprobes.h>
#include <linux/page-flags-layout.h>
#include <linux/workqueue.h>
#include <asm/mmu.h>
struct address_space;
struct mem_cgroup;
struct hmm;
* Each physical page in the system has a struct page associated with
* it to keep track of whatever it is we are using the page for at the
* moment. Note that we have no way to track which tasks are using
* a page, though if it is a pagecache page, rmap structures can tell us
* who is mapping it. If you allocate the page using alloc_pages(), you
* can use some of the space in struct page for your own purposes.
* Pages that were once in the page cache may be found under the RCU lock
* even after they have been recycled to a different purpose. The page
* cache reads and writes some of the fields in struct page to pin the
* page before checking that it's still in the page cache. It is vital
* that all users of struct page:
* 1. Use the first word as PageFlags.
* 2. Clear or preserve bit 0 of page->compound_head. It is used as
* PageTail for compound pages, and the page cache must not see false
* positives. Some users put a pointer here (guaranteed to be at least
* 4-byte aligned), other users avoid using the field altogether.
* 3. page->_refcount must either not be used, or must be used in such a
* way that other CPUs temporarily incrementing and then decrementing the
* refcount does not cause problems. On receiving the page from
* alloc_pages(), the refcount will be positive.
* 4. Either preserve page->_mapcount or restore it to -1 before freeing it.
* If you allocate pages of order > 0, you can use the fields in the struct
* page associated with each page, but bear in mind that the pages may have
* been inserted individually into the page cache, so you must use the above
* four fields in a compatible way for each struct page.
* SLUB uses cmpxchg_double() to atomically update its freelist and
* counters. That requires that freelist & counters be adjacent and
* double-word aligned. We align all struct pages to double-word
* boundaries, and ensure that 'freelist' is aligned within the
* struct.
#define _struct_page_alignment __aligned(2 * sizeof(unsigned long))
#define _slub_counter_t unsigned long
#define _slub_counter_t unsigned int
#define _struct_page_alignment
#define _slub_counter_t unsigned int
struct page {
/* First double word block */
unsigned long flags; /* Atomic flags, some possibly
* updated asynchronously */
union {
/* See page-flags.h for the definition of PAGE_MAPPING_FLAGS */
struct address_space *mapping;
void *s_mem; /* slab first object */
atomic_t compound_mapcount; /* first tail page */
/* page_deferred_list().next -- second tail page */
/* Second double word */
union {
pgoff_t index; /* Our offset within mapping. */
void *freelist; /* sl[aou]b first free object */
/* page_deferred_list().prev -- second tail page */
union {
_slub_counter_t counters;
unsigned int active; /* SLAB */
struct { /* SLUB */
unsigned inuse:16;
unsigned objects:15;
unsigned frozen:1;
int units; /* SLOB */
struct { /* Page cache */
* Count of ptes mapped in mms, to show when
* page is mapped & limit reverse map searches.
* Extra information about page type may be
* stored here for pages that are never mapped,
* in which case the value MUST BE <= -2.
* See page-flags.h for more details.
atomic_t _mapcount;
* Usage count, *USE WRAPPER FUNCTION* when manual
* accounting. See page_ref.h
atomic_t _refcount;
* WARNING: bit 0 of the first word encode PageTail(). That means
* the rest users of the storage space MUST NOT use the bit to
* avoid collision and false-positive PageTail().
union {
struct list_head lru; /* Pageout list, eg. active_list
* protected by zone_lru_lock !
* Can be used as a generic list
* by the page owner.
struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an
* lru or handled by a slab
* allocator, this points to the
* hosting device page map.
struct { /* slub per cpu partial pages */
struct page *next; /* Next partial slab */
#ifdef CONFIG_64BIT
int pages; /* Nr of partial slabs left */
int pobjects; /* Approximate # of objects */
short int pages;
short int pobjects;
struct rcu_head rcu_head; /* Used by SLAB
* when destroying via RCU
/* Tail pages of compound page */
struct {
unsigned long compound_head; /* If bit zero is set */
/* First tail page only */
unsigned char compound_dtor;
unsigned char compound_order;
/* two/six bytes available here */
struct {
unsigned long __pad; /* do not overlay pmd_huge_pte
* with compound_head to avoid
* possible bit 0 collision.
pgtable_t pmd_huge_pte; /* protected by page->ptl */
union {
* Mapping-private opaque data:
* Usually used for buffer_heads if PagePrivate
* Used for swp_entry_t if PageSwapCache
* Indicates order in the buddy system if PageBuddy
unsigned long private;
spinlock_t *ptl;
spinlock_t ptl;
struct kmem_cache *slab_cache; /* SL[AU]B: Pointer to slab */
struct mem_cgroup *mem_cgroup;
* On machines where all RAM is mapped into kernel address space,
* we can simply calculate the virtual address. On machines with
* highmem some memory is mapped into kernel virtual memory
* dynamically, so we need a place to store that address.
* Note that this field could be 16 bits on x86 ... ;)
* Architectures with slow multiplication can define
* WANT_PAGE_VIRTUAL in asm/page.h
#if defined(WANT_PAGE_VIRTUAL)
void *virtual; /* Kernel virtual address (NULL if
not kmapped, ie. highmem) */
#endif /* WANT_PAGE_VIRTUAL */
int _last_cpupid;
} _struct_page_alignment;
struct page_frag_cache {
void * va;
__u16 offset;
__u16 size;
__u32 offset;
/* we maintain a pagecount bias, so that we dont dirty cache line
* containing page->_refcount every time we allocate a fragment.
unsigned int pagecnt_bias;
bool pfmemalloc;
typedef unsigned long vm_flags_t;
* A region containing a mapping of a non-memory backed file under NOMMU
* conditions. These are held in a global tree and are pinned by the VMAs that
* map parts of them.
struct vm_region {
struct rb_node vm_rb; /* link in global region tree */
vm_flags_t vm_flags; /* VMA vm_flags */
unsigned long vm_start; /* start address of region */
unsigned long vm_end; /* region initialised to here */
unsigned long vm_top; /* region allocated to here */
unsigned long vm_pgoff; /* the offset in vm_file corresponding to vm_start */
struct file *vm_file; /* the backing file or NULL */
int vm_usage; /* region usage count (access under nommu_region_sem) */
bool vm_icache_flushed : 1; /* true if the icache has been flushed for
* this region */
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
struct vm_userfaultfd_ctx {
struct userfaultfd_ctx *ctx;
#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
struct vm_userfaultfd_ctx {};
* This struct defines a memory VMM memory area. There is one of these
* per VM-area/task. A VM area is any part of the process virtual memory
* space that has a special rule for the page-fault handlers (ie a shared
* library, the executable area etc).
struct vm_area_struct {
/* The first cache line has the info for VMA tree walking. */
unsigned long vm_start; /* Our start address within vm_mm. */
unsigned long vm_end; /* The first byte after our end address
within vm_mm. */
/* linked list of VM areas per task, sorted by address */
struct vm_area_struct *vm_next, *vm_prev;
struct rb_node vm_rb;
* Largest free memory gap in bytes to the left of this VMA.
* Either between this VMA and vma->vm_prev, or between one of the
* VMAs below us in the VMA rbtree and its ->vm_prev. This helps
* get_unmapped_area find a free area of the right size.
unsigned long rb_subtree_gap;
/* Second cache line starts here. */
struct mm_struct *vm_mm; /* The address space we belong to. */
pgprot_t vm_page_prot; /* Access permissions of this VMA. */
unsigned long vm_flags; /* Flags, see mm.h. */
* For areas with an address space and backing store,
* linkage into the address_space->i_mmap interval tree.
struct {
struct rb_node rb;
unsigned long rb_subtree_last;
} shared;
* A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
* list, after a COW of one of the file pages. A MAP_SHARED vma
* can only be in the i_mmap tree. An anonymous MAP_PRIVATE, stack
* or brk vma (with NULL file) can only be in an anon_vma list.
struct list_head anon_vma_chain; /* Serialized by mmap_sem &
* page_table_lock */
struct anon_vma *anon_vma; /* Serialized by page_table_lock */
/* Function pointers to deal with this struct. */
const struct vm_operations_struct *vm_ops;
/* Information about our backing store: */
unsigned long vm_pgoff; /* Offset (within vm_file) in PAGE_SIZE
units */
struct file * vm_file; /* File we map to (can be NULL). */
void * vm_private_data; /* was vm_pte (shared mem) */
atomic_long_t swap_readahead_info;
#ifndef CONFIG_MMU
struct vm_region *vm_region; /* NOMMU mapping region */
struct mempolicy *vm_policy; /* NUMA policy for the VMA */
struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
} __randomize_layout;
struct core_thread {
struct task_struct *task;
struct core_thread *next;
struct core_state {
atomic_t nr_threads;
struct core_thread dumper;
struct completion startup;
struct kioctx_table;
struct mm_struct {
struct vm_area_struct *mmap; /* list of VMAs */
struct rb_root mm_rb;
u32 vmacache_seqnum; /* per-thread vmacache */
unsigned long (*get_unmapped_area) (struct file *filp,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags);
unsigned long mmap_base; /* base of mmap area */
unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
/* Base adresses for compatible mmap() */
unsigned long mmap_compat_base;
unsigned long mmap_compat_legacy_base;
unsigned long task_size; /* size of task vm space */
unsigned long highest_vm_end; /* highest vma end address */
pgd_t * pgd;
* @mm_users: The number of users including userspace.
* Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
* to 0 (i.e. when the task exits and there are no other temporary
* reference holders), we also release a reference on @mm_count
* (which may then free the &struct mm_struct if @mm_count also
* drops to 0).
atomic_t mm_users;
* @mm_count: The number of references to &struct mm_struct
* (@mm_users count as 1).
* Use mmgrab()/mmdrop() to modify. When this drops to 0, the
* &struct mm_struct is freed.
atomic_t mm_count;
atomic_long_t pgtables_bytes; /* PTE page table pages */
int map_count; /* number of VMAs */
spinlock_t page_table_lock; /* Protects page tables and some counters */
struct rw_semaphore mmap_sem;
struct list_head mmlist; /* List of maybe swapped mm's. These are globally strung
* together off init_mm.mmlist, and are protected
* by mmlist_lock
unsigned long hiwater_rss; /* High-watermark of RSS usage */
unsigned long hiwater_vm; /* High-water virtual memory usage */
unsigned long total_vm; /* Total pages mapped */
unsigned long locked_vm; /* Pages that have PG_mlocked set */
unsigned long pinned_vm; /* Refcount permanently increased */
unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
unsigned long stack_vm; /* VM_STACK */
unsigned long def_flags;
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
unsigned long arg_start, arg_end, env_start, env_end;
unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
* Special counters, in some configurations protected by the
* page_table_lock, in other configurations by being atomic.
struct mm_rss_stat rss_stat;
struct linux_binfmt *binfmt;
cpumask_var_t cpu_vm_mask_var;
/* Architecture-specific MM context */
mm_context_t context;
unsigned long flags; /* Must use atomic bitops to access the bits */
struct core_state *core_state; /* coredumping support */
atomic_t membarrier_state;
spinlock_t ioctx_lock;
struct kioctx_table __rcu *ioctx_table;
* "owner" points to a task that is regarded as the canonical
* user/owner of this mm. All of the following must be true in
* order for it to be changed:
* current == mm->owner
* current->mm != mm
* new_owner->mm == mm
* new_owner->alloc_lock is held
struct task_struct __rcu *owner;
struct user_namespace *user_ns;
/* store ref to file /proc/<pid>/exe symlink points to */
struct file __rcu *exe_file;
struct mmu_notifier_mm *mmu_notifier_mm;
pgtable_t pmd_huge_pte; /* protected by page_table_lock */
struct cpumask cpumask_allocation;
* numa_next_scan is the next time that the PTEs will be marked
* pte_numa. NUMA hinting faults will gather statistics and migrate
* pages to new nodes if necessary.
unsigned long numa_next_scan;
/* Restart point for scanning and setting pte_numa */
unsigned long numa_scan_offset;
/* numa_scan_seq prevents two threads setting pte_numa */
int numa_scan_seq;
* An operation with batched TLB flushing is going on. Anything that
* can move process memory needs to flush the TLB when moving a
* PROT_NONE or PROT_NUMA mapped page.
atomic_t tlb_flush_pending;
/* See flush_tlb_batched_pending() */
bool tlb_flush_batched;
struct uprobes_state uprobes_state;
atomic_long_t hugetlb_usage;
struct work_struct async_put_work;
/* HMM needs to track a few things per mm */
struct hmm *hmm;
} __randomize_layout;
extern struct mm_struct init_mm;
static inline void mm_init_cpumask(struct mm_struct *mm)
mm->cpu_vm_mask_var = &mm->cpumask_allocation;
/* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
return mm->cpu_vm_mask_var;
struct mmu_gather;
extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
unsigned long start, unsigned long end);
extern void tlb_finish_mmu(struct mmu_gather *tlb,
unsigned long start, unsigned long end);
static inline void init_tlb_flush_pending(struct mm_struct *mm)
atomic_set(&mm->tlb_flush_pending, 0);
static inline void inc_tlb_flush_pending(struct mm_struct *mm)
* The only time this value is relevant is when there are indeed pages
* to flush. And we'll only flush pages after changing them, which
* requires the PTL.
* So the ordering here is:
* atomic_inc(&mm->tlb_flush_pending);
* spin_lock(&ptl);
* ...
* set_pte_at();
* spin_unlock(&ptl);
* spin_lock(&ptl)
* mm_tlb_flush_pending();
* ....
* spin_unlock(&ptl);
* flush_tlb_range();
* atomic_dec(&mm->tlb_flush_pending);
* Where the increment if constrained by the PTL unlock, it thus
* ensures that the increment is visible if the PTE modification is
* visible. After all, if there is no PTE modification, nobody cares
* about TLB flushes either.
* This very much relies on users (mm_tlb_flush_pending() and
* mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
* therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
* locks (PPC) the unlock of one doesn't order against the lock of
* another PTL.
* The decrement is ordered by the flush_tlb_range(), such that
* mm_tlb_flush_pending() will not return false unless all flushes have
* completed.
static inline void dec_tlb_flush_pending(struct mm_struct *mm)
* See inc_tlb_flush_pending().
* This cannot be smp_mb__before_atomic() because smp_mb() simply does
* not order against TLB invalidate completion, which is what we need.
* Therefore we must rely on tlb_flush_*() to guarantee order.
static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
* Must be called after having acquired the PTL; orders against that
* PTLs release and therefore ensures that if we observe the modified
* PTE we must also observe the increment from inc_tlb_flush_pending().
* That is, it only guarantees to return true if there is a flush
* pending for _this_ PTL.
return atomic_read(&mm->tlb_flush_pending);
static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
* Similar to mm_tlb_flush_pending(), we must have acquired the PTL
* for which there is a TLB flush pending in order to guarantee
* we've seen both that PTE modification and the increment.
* (no requirement on actually still holding the PTL, that is irrelevant)
return atomic_read(&mm->tlb_flush_pending) > 1;
struct vm_fault;
struct vm_special_mapping {
const char *name; /* The name, e.g. "[vdso]". */
* If .fault is not provided, this points to a
* NULL-terminated array of pages that back the special mapping.
* This must not be NULL unless .fault is provided.
struct page **pages;
* If non-NULL, then this is called to resolve page faults
* on the special mapping. If used, .pages is not checked.
int (*fault)(const struct vm_special_mapping *sm,
struct vm_area_struct *vma,
struct vm_fault *vmf);
int (*mremap)(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma);
enum tlb_flush_reason {
* A swap entry has to fit into a "unsigned long", as the entry is hidden
* in the "index" field of the swapper address space.
typedef struct {
unsigned long val;
} swp_entry_t;
#endif /* _LINUX_MM_TYPES_H */