los_vm_filemap.h

/*
 * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
 * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of
 *    conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list
 *    of conditions and the following disclaimer in the documentation and/or other materials
 *    provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors may be used
 *    to endorse or promote products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @defgroup los_vm_filemap vm filemap definition
 * @ingroup kernel
 */

#ifndef __LOS_VM_FILEMAP_H__
#define __LOS_VM_FILEMAP_H__

#include "fs/file.h"
#include "los_vm_map.h"
#include "los_vm_page.h"
#include "los_vm_common.h"
#include "los_vm_phys.h"

#ifdef __cplusplus
#if __cplusplus
extern "C" {
#endif /* __cplusplus */
#endif /* __cplusplus */

/**************************************************************************************************
 磁盘高速缓存是一种软件机制，它允许系统把通常存放在磁盘上的一些数据保留在 RAM 中，以便对那些数据的
 进一步访问不用再访问磁盘而能尽快得到满足。
 页高速缓存中的信息单位是一个完整的页。
 一个页包含的磁盘块在物理上不一定相邻，所以不能用设备号和块号标识，而是通过页的所有者和所有者数据中的索引来识别。
 页高速缓存可以缓存以下内容
 A.普通文件数据
 B.含有目录的页 
 C.直接从快设备读取的页 
 D.用户进程数据的页
 E.特殊文件系统的文件页
**************************************************************************************************/
#if 0 //@note_#if0 
//page_mapping描述的是一个文件在内存中被映射了多少页,<文件,文件页的关系>
/* file mapped in VMM pages */
struct page_mapping {//记录文件页和文件关系的结构体,叫文件页映射
  LOS_DL_LIST                           page_list;    /* all pages */ //链表上挂的是属于该文件的所有FilePage，这些页的内容都来源同一个文件
  SPIN_LOCK_S                           list_lock;    /* lock protecting it */ //操作page_list的自旋锁
  LosMux                                mux_lock;     /* mutex lock */	//		//操作page_mapping的互斥量
  unsigned long                         nrpages;      /* number of total pages */ //page_list的节点数量	
  unsigned long                         flags;			//@note_why 全量代码中也没查到源码中对其操作	
  Atomic                                ref;          /* reference counting */	//引用次数(自增/自减),对应add_mapping/dec_mapping
  struct file                           *host;        /* owner of this mapping *///属于哪个文件的映射
};

/* map: full_path(owner) <-> mapping */ //叫文件映射
struct file_map { //为在内核层面文件在内存的身份证,每个需映射到内存的文件必须创建一个file_map，都挂到全局g_file_mapping链表上
  LOS_DL_LIST           head;		//链表节点,用于挂到g_file_mapping上
  LosMux                lock;         /* lock to protect this mapping */
  struct page_mapping   mapping;	//每个文件都有唯一的page_mapping标识其在内存的身份
  char                  *owner;     /* owner: full path of file *///文件全路径来标识唯一性
};

#endif

//文件页结构体
typedef struct FilePage {
    LOS_DL_LIST             node;		//节点,节点挂到page_mapping.page_list上,链表以 pgoff 从小到大方式排序.
    LOS_DL_LIST             lru;		//lru节点, 结合 LosVmPhysSeg: LOS_DL_LIST lruList[VM_NR_LRU_LISTS] 理解
    LOS_DL_LIST             i_mmap;     /* list of mappings */ //链表记录文件页被哪些进程映射 MapInfo.node挂上来
    UINT32                  n_maps;       /* num of mapping */ //记录被进程映射的次数
    struct VmPhysSeg        *physSeg;      /* physical memory that file page belongs to */ //物理段:物理页框 = 1:N
    struct VmPage           *vmPage;	//物理页框
    struct page_mapping     *mapping;	//此结构由文件系统提供，用于描述装入点 见于 ..\third_party\NuttX\include\nuttx\fs\fs.h
    VM_OFFSET_T             pgoff;		//页标，文件被切成一页一页读到内存
    UINT32                  flags;		//标签
    UINT16                  dirtyOff;	//脏页的页内偏移地址
    UINT16                  dirtyEnd;	//脏页的结束位置
} LosFilePage;
//虚拟地址和文件页的映射信息
typedef struct MapInfo {//在一个进程使用文件页之前,需要提前做好文件页在此内存空间的映射关系,如此通过虚拟内存就可以对文件页读写操作.
    LOS_DL_LIST             node;	//节点,挂到page->i_mmap链表上.链表上记录要操作文件页的进程对这个page的映射信息
    VADDR_T                 vaddr;	//虚拟地址.每个进程访问同一个文件页的虚拟地址都是不一样的
    LosFilePage             *page;	//文件页中只记录物理地址,是不会变的.但它是需要被多个进程访问,和映射的.
    LosArchMmu              *archMmu;//mmu完成vaddr和page->vmPage->physAddr物理地址的映射
} LosMapInfo;
//Flags由 bitmap 管理
enum OsPageFlags {
    FILE_PAGE_FREE,			//空闲页	
    FILE_PAGE_LOCKED,		//被锁页
    FILE_PAGE_REFERENCED,   //被引用页
    FILE_PAGE_DIRTY,		//脏页
    FILE_PAGE_LRU,			//LRU置换页
    FILE_PAGE_ACTIVE,		//活动页
    FILE_PAGE_SHARED,		//共享页
};

#define PGOFF_MAX                       2000
#define MAX_SHRINK_PAGECACHE_TRY        2
#define VM_FILEMAP_MAX_SCAN             (SYS_MEM_SIZE_DEFAULT >> PAGE_SHIFT) //扫描文件映射页最大数量
#define VM_FILEMAP_MIN_SCAN             32 //扫描文件映射页最小数量
//给页面贴上被锁的标签
STATIC INLINE VOID OsSetPageLocked(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_LOCKED);
}
//给页面撕掉被锁的标签
STATIC INLINE VOID OsCleanPageLocked(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_LOCKED);
}
//给页面贴上数据被修改的标签
STATIC INLINE VOID OsSetPageDirty(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_DIRTY);
}
//给页面撕掉数据被修改的标签
STATIC INLINE VOID OsCleanPageDirty(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_DIRTY);
}
//给页面贴上活动的标签
STATIC INLINE VOID OsSetPageActive(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_ACTIVE);
}
//给页面撕掉活动的标签
STATIC INLINE VOID OsCleanPageActive(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_ACTIVE);
}
//给页面贴上置换页的标签
STATIC INLINE VOID OsSetPageLRU(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_LRU);
}
//给页面贴上被释放的标签
STATIC INLINE VOID OsSetPageFree(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_FREE);
}
//给页面撕掉被释放的标签
STATIC INLINE VOID OsCleanPageFree(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_FREE);
}
//给页面贴上被引用的标签
STATIC INLINE VOID OsSetPageReferenced(LosVmPage *page)
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_REFERENCED);
}
//给页面撕掉被引用的标签
STATIC INLINE VOID OsCleanPageReferenced(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_REFERENCED);
}
//页面是否活动
STATIC INLINE BOOL OsIsPageActive(LosVmPage *page)
{
    return BIT_GET(page->flags, FILE_PAGE_ACTIVE);
}
//页面是否被锁
STATIC INLINE BOOL OsIsPageLocked(LosVmPage *page)
{
    return BIT_GET(page->flags, FILE_PAGE_LOCKED);
}
//页面是否被引用，只被一个进程引用的页叫私有页，多个进程引用就是共享页，此为共享内存的本质所在
STATIC INLINE BOOL OsIsPageReferenced(LosVmPage *page)
{
    return BIT_GET(page->flags, FILE_PAGE_REFERENCED);
}
//页面是否为脏页，所谓脏页就是页内数据是否被更新过，只有脏页才会有写时拷贝
STATIC INLINE BOOL OsIsPageDirty(LosVmPage *page)
{
    return BIT_GET(page->flags, FILE_PAGE_DIRTY);
}
//文件页是否映射过了
STATIC INLINE BOOL OsIsPageMapped(LosFilePage *page)
{
    return (page->n_maps != 0);//由映射的次数来判断
}

/* The follow three functions is used to SHM module */
STATIC INLINE VOID OsSetPageShared(LosVmPage *page)//给页面贴上共享页标签
{
    LOS_BitmapSet(&page->flags, FILE_PAGE_SHARED);//设为共享页面,共享页位 置0
}
//给页面撕掉共享页标签
STATIC INLINE VOID OsCleanPageShared(LosVmPage *page)
{
    LOS_BitmapClr(&page->flags, FILE_PAGE_SHARED);//共享页位 置0
}
//是否为共享页
STATIC INLINE BOOL OsIsPageShared(LosVmPage *page)
{
    return BIT_GET(page->flags, FILE_PAGE_SHARED);
}

INT32 OsVfsFileMmap(struct file *filep, LosVmMapRegion *region);
LosFilePage *OsPageCacheAlloc(struct page_mapping *mapping, VM_OFFSET_T pgoff);
LosFilePage *OsFindGetEntry(struct page_mapping *mapping, VM_OFFSET_T pgoff);
LosMapInfo *OsGetMapInfo(LosFilePage *page, LosArchMmu *archMmu, VADDR_T vaddr);
VOID OsAddMapInfo(LosFilePage *page, LosArchMmu *archMmu, VADDR_T vaddr);
VOID OsDelMapInfo(LosVmMapRegion *region, LosVmPgFault *pgFault, BOOL cleanDirty);
VOID OsFileCacheFlush(struct page_mapping *mapping);
VOID OsFileCacheRemove(struct page_mapping *mapping);
VOID OsUnmapPageLocked(LosFilePage *page, LosMapInfo *info);
VOID OsUnmapAllLocked(LosFilePage *page);
VOID OsLruCacheAdd(LosFilePage *fpage, enum OsLruList lruType);
VOID OsLruCacheDel(LosFilePage *fpage);
LosFilePage *OsDumpDirtyPage(LosFilePage *oldPage);
VOID OsDoFlushDirtyPage(LosFilePage *fpage);
VOID OsDeletePageCacheLru(LosFilePage *page);
STATUS_T OsNamedMMap(struct file *filep, LosVmMapRegion *region);
VOID OsPageRefDecNoLock(LosFilePage *page);
VOID OsPageRefIncLocked(LosFilePage *page);
int OsTryShrinkMemory(size_t nPage);
VOID OsMarkPageDirty(LosFilePage *fpage, LosVmMapRegion *region, int off, int len);

typedef struct ProcessCB LosProcessCB;
VOID OsVmmFileRegionFree(struct file *filep, LosProcessCB *processCB);
#ifdef __cplusplus
#if __cplusplus
}
#endif /* __cplusplus */
#endif /* __cplusplus */

#endif /* __LOS_VM_FILEMAP_H__ */