Linux中如何使用tmpfs内存文件系统

什么是tmpfs内存文件系统

tmpfs(Temporary File System,临时文件系统)是一种基于内存的文件系统，它将文件存储在内存中，而不是磁盘上，当文件被创建或访问时，它们会暂时存储在内存中，直到被关闭或删除，tmpfs可以提高文件系统的性能，特别是在处理大量小文件时，在Linux系统中，tmpfs通常用于挂载点，以便用户可以将临时文件存储在内存中，而不是磁盘上。

如何在Linux中使用tmpfs内存文件系统

1、创建一个空的tmpfs挂载点

要使用tmpfs,首先需要创建一个空的挂载点，可以使用mkdir命令创建一个目录，并使用mount命令将其挂载到tmpfs。

sudo mkdir /mnt/tmpfs
sudo mount -t tmpfs tmpfs /mnt/tmpfs

2、格式化tmpfs文件系统

如果需要对tmpfs进行格式化，可以使用mkfs命令，要将tmpfs格式化为ext4文件系统，可以使用以下命令：

sudo mkfs.ext4 /dev/sdb1

注意：请根据实际情况替换/dev/sdb1。

3、将设备挂载到tmpfs

要将设备挂载到tmpfs,可以使用mount命令，要将U盘挂载到tmpfs,可以使用以下命令：

sudo mount /dev/sdb1 /mnt/tmpfs

注意：请根据实际情况替换/dev/sdb1和/mnt/tmpfs。

4、在程序中使用tmpfs

要在程序中使用tmpfs,可以使用fopen函数打开一个指向内存中的文件。

include <stdio.h>
include <sys/mman.h>
include <unistd.h>
include <fcntl.h>
include <stdlib.h>
include <string.h>
include <errno.h>
include <sys/stat.h>
include <sys/types.h>
include <linux/limits.h>
include <linux/kernel.h>
include <linux/module.h>
include <linux/fs.h>
include <linux/uaccess.h>
include <linux/mm.h>
include <linux/high_memory.h>
include <asm/segment.h>
include <asm/io.h>
include <asm/irq.h>
include <asm/dma.h>
include <asm/system.h>
include <asm/page.h>
include <asm/bitops.h>
include <linux/init.h>
include <linux/module.h>
include <linux/kernel.h>
include <linux/fs.h>
include <linux/cdev.h>
include <linux/device.h>
include <linux/uaccess.h>
include <linux/slab.h>
include <linux/vmalloc.h>
include <linux/highmem.h>
include <linux/mm.h>
include <linux/file.h>
include <linux/proc_fs.h>
include <linux/string.h>
include <linux/sched.h>
include <linux/delayqueue.h>
include <linux/timer_list.h>
include <linux/namei.h>
include <linux/nsswitch.h>
include <linux/xattr.h>
include <linux/blkdev.h>
define TMPFS_NAME "tmpfs" /* Name of the tmpfs device */
static int major_number; /* Device number (set by module_init() function) */
static struct cdev tmpfs_cdev; /* The character device structure */    /* Create a new tmpfs device */                    /* and add it to the list of registered devices */    int tmpfs_init(void);                       /* Unregister the tmpfs device */        int tmpfs_cleanup(void);                       /* Register the tmpfs device */        static struct file_operations tmpfs_fops = {                /* Open, read, write and release functions */    int (*open)(struct inode *inode, struct file *file);    int (*release)(struct inode *inode, struct file *file);    ssize_t (*read)(struct file *file, char __user *buf, size_t count, loff_t *ppos);    ssize_t (*write)(struct file *file, const char __user *buf, size_t count, loff_t *ppos);};                                                                                  /* Set up the device operations for this class */                                                                                  struct class *tmpfs_class = NULL;                                                                                  int major_number;                                                             int tmpfs_init(void) {                                          int result;                                       char name[32];                                       result = register_chrdev(0, TMPFS_NAME, &tmpfs_fops);                                           if (result < 0) printk("Failed to register tmpfs device
"); else {                                           major_number = result;                                           strcpy(name, TMPFS_NAME);                                           tmpfs_class = class_create(THIS_MODULE, name);                                           } return result; }                                                                                  void tmpfs_cleanup(void) {                                        unregister_chrdev(major_number, TMPFS_NAME);                                           class_destroy(tmpfs_class);                                           }                                                                                                                /* The actual open function for the tmpfs device */                                                                                                                int open(struct inode *inode, struct file *file) {                                                                                                                char path[256];                                                                                                                sprintf(path, "/%d", getpid());                                                                                                                int res = syscall(__NR_shmat, (void *)getpid(), (void *)path, OBJAT | SHM_RDONLY | SHM_ANON | SHM_CREAT | SHM_PERMS, 0777 & ~IPC_LOCK);                                                                                                                if (res == -1) return -1;                                                                                                                file->f_mode = 4200755;                                                                                                                file->f_pos = 0;                                                                                                                file->f_flags = O_RDONLY;                                                                                                                return res; }                                                                                                                /* The actual read function for the tmpfs device */                                                                                                                ssize_t read(struct file *file, char __user *buf, size_t count, loff_t *ppos) {                                                                                                                char path[256];                                                                                                                char *ptr;                                                                                                                int res = syscall(__NR_shmat, (void *)getpid(), (void *)path, OBJAT | SHM_RDONLY | SHM_ANON | SHM_CREAT | SHM_PERMS, 0777 & ~IPC_LOCK);                                                                                                                if (res == -1) return -1;                                                                                                                ptr = mmap((void *)path + offsetof(struct shmid_ds, shm_addr), count, PROT_READ, MAP_SHARED, (unsigned long)file->f_mapping);                                                                                                                if (ptr == MAP_FAILED) return -1;                                                                                                                memcpy(buf, ptr + *ppos % count, count);                                                                                                                *ppos += count;                                                                                                                munmap((void *)path + offsetof(struct shmid_ds, shm_addr), count);                                                                                                                return count; }                                                                                                                /* The actual write function for the tmpfs device */                                                                                                                ssize_t write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) {                                                                                                                char path[256];                                                                                                                char *ptr;                                                                                                                int res = syscall(__NR_shmat, (void *)getpid(), (void *)path, OBJAT | SHM_RDONLY | SHM_ANON | SHM_CREAT | SHM_PERMS, 0777 & ~IPC_LOCK);                                                                                                                if (res == -1) return -1;                                                                                                                ptr = mmap((void *)path + offsetof(struct shmid_ds, shm_addr), count, PROT_WRITE | PROT_READ, MAP_SHARED, (unsigned long)file->f_mapping);                                                                                                                if (ptr == MAP_FAILED) return -1;                                                                                                                memcpy((void *)ptr + *ppos % count, buf, count);                                                                                                                *ppos += count;                                                                                                                munmap((void *)path + offsetof(struct shmid_ds, shm_addr), count);                                                                                                                return count