Linux下一个简单的文件系统实现

#include <linux/kernel.h> #include <linux/init.h> #include <linux/module.h> #include <linux/pagemap.h> /* PAGE_CACHE_SIZE */ #include <linux/fs.h> /* This is where libfs stuff is declared */ #include <asm/atomic.h> #include <asm/uaccess.h> /* copy_to_user */ #include <linux/pagemap.h> #include <linux/buffer_head.h> /* * Wen Hui. * Just for linux 2.6 * * desp: * innux 3.2, get_sb --> mount, * get_sb_single --> mount_single. */ MODULE_LICENSE("GPL"); MODULE_AUTHOR("Wen Hui"); #define XORFS_MAGIC 0x20120418 #define FILE_INODE_NUMBER 2 /** * system_file_type */ /* get_sb */ static struct super_block * xorfs_get_sb(struct file_system_type *fs_type, int flags, const char *devname, void *data, struct vfsmount* mnt); /* kill_sb */ static void xorfs_kill_sb(struct super_block *super); static int xorfs_fill_super(struct super_block* sb, void *data, int silent); /** * super_operations */ static int xorfs_super_write_inode(struct inode *inode, struct writeback_control *wbc); /*static void xorfs_super_read_inode(struct inode *inode);*/ /** * inode_operations */ /* lookup */ static struct dentry* xorfs_inode_lookup(struct inode*, struct dentry *, struct nameidata *); static struct inode* xorfs_iget(struct super_block *sp, unsigned long ino); /** * file_operations */ static int xorfs_file_open(struct inode *inode, struct file *file); static int xorfs_file_readdir(struct file *file, void *dirent, filldir_t filldir); static int xorfs_file_release(struct inode* ino, struct file *file); static ssize_t xorfs_file_read(struct file *file, char *buf, size_t max, loff_t* offset); static ssize_t xorfs_file_write(struct file *file, const char *buf, size_t max, loff_t* offset); /** * address_space_operations */ /* readpage * old version: ->prepare_write(),->commit_write(), * ->sync_page(),and ->readpage() * new version (LSF'08'): try use vm_operations * instead of address_space_operations, * and a small/dummpy ->readpage is still needed because * ->generic_file_mmap, still check * for the existence of the ->readpage method. */ static int xorfs_readpage(struct file *file, struct page *page); /* write page */ static int xorfs_writepage(struct page *page, struct writeback_control *wbc); /* write_beign */ static int xorfs_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata); /* write_end */ static int xorfs_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata); /* * Data declarations */ static struct super_operations xorfs_sops = { // .read_inode = xorfs_super_read_inode .statfs = simple_statfs, .write_inode = &xorfs_super_write_inode }; // struct xorfs_sops static struct inode_operations xorfs_iops = { .lookup = xorfs_inode_lookup }; // struct xorfs_iops static struct file_operations xorfs_fops = { .open = xorfs_file_open, .read = &xorfs_file_read, .readdir = &xorfs_file_readdir, .write = &xorfs_file_write, .release = &xorfs_file_release, .fsync = &generic_file_fsync }; // struct xorfs_fops static struct file_system_type xorfs = { name : "xorfs", get_sb : xorfs_get_sb, kill_sb : xorfs_kill_sb, owner : THIS_MODULE }; // struct file_system_type static struct address_space_operations xorfs_aops = { .readpage = xorfs_readpage, .writepage = xorfs_writepage, .write_begin = xorfs_write_begin, .write_end = xorfs_write_end }; // struct xorfs_aops static struct inode *xorfs_root_inode; static char file_buf[PAGE_SIZE] = "Hello World\n"; static int file_size = 12; /** * system_file_type */ static struct super_block * xorfs_get_sb(struct file_system_type *fs_type, int flags, const char *devname, void *data, struct vfsmount* mnt) { printk("XORFS:xorfs_get_sb\n"); return get_sb_single(fs_type, flags, data, &xorfs_fill_super, mnt); } // xorfs_get_sb static void xorfs_kill_sb(struct super_block *super) { printk("XORFS: xorfs_kill_sb\n"); kill_anon_super(super); } // xorfs_kill_sb /* call the get_sb_single(), and callback the fn() */ static int xorfs_fill_super(struct super_block* sb, void *data, int silent) { printk("XORFS: xorfs_fill_super\n"); sb->s_blocksize = 1024; sb->s_blocksize_bits = 10; sb->s_magic = XORFS_MAGIC; sb->s_op = &xorfs_sops; // super block operation sb->s_type = &xorfs; // file_system_type // xorfs_root_inode = iget_locked(sb, 1); // allocate 1 node xorfs_root_inode = xorfs_iget(sb, 1); // allocate 1 node xorfs_root_inode->i_op = &xorfs_iops; // set the inode ops xorfs_root_inode->i_mode = S_IFDIR | S_IRWXU; xorfs_root_inode->i_fop = &xorfs_fops; // set the inode file operations // xorfs_root_inode->i_mapping->a_ops = &xorfs_aops; if(!(sb->s_root = d_alloc_root(xorfs_root_inode))) { iput( xorfs_root_inode ); return -ENOMEM; } // if return 0; } // xorfs_fill_super /** * super_operations */ static int xorfs_super_write_inode(struct inode *inode, struct writeback_control *wbc) { printk("XORFS: xorfs_super_write_inode (i_ino=%d) = %d\n", (int) inode->i_ino, (int) i_size_read(inode)); if(inode->i_ino == FILE_INODE_NUMBER) { file_size = i_size_read(inode); } return 0; } // xorfs_super_write_inode /** static void* xorfs_super_read_inode(struct super_block *sp, struct inode *inode) { inode->i_mapping->a_ops = &xorfs_aops; } // xorfs_super_read_inode */ /** * inode_operations */ static char filename[] = "hello.txt"; static int filename_len = sizeof(filename) - 1; static struct dentry* xorfs_inode_lookup(struct inode* parent_inode, struct dentry *dentry, struct nameidata *nameidata) { struct inode *file_inode; printk("XORFS: xorfs_inode_lookup\n"); if(parent_inode->i_ino != xorfs_root_inode->i_ino || dentry->d_name.len != filename_len || strncmp(dentry->d_name.name, filename, dentry->d_name.len)) { d_add(dentry, NULL); return NULL; } // if file_inode = xorfs_iget(parent_inode->i_sb, FILE_INODE_NUMBER); if(!file_inode) return ERR_PTR(-EACCES); file_inode->i_size = file_size; file_inode->i_mode = S_IFREG | S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH; file_inode->i_fop = &xorfs_fops; d_add(dentry, file_inode); return NULL; } // xorfs_inode_lookup static struct inode* xorfs_iget(struct super_block *sb, unsigned long ino) { struct inode *inode; int ret; printk("XORFS: xorfs_iget\n"); inode = iget_locked(sb, ino); if(!inode) return ERR_PTR(-ENOMEM); if(!(inode->i_state & I_NEW)) return inode; inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; inode->i_mapping->a_ops = &xorfs_aops; unlock_new_inode(inode); return inode; } // xorfs_iget /** * file_operations */ static int xorfs_file_open(struct inode *inode, struct file *file) { printk("XORFS: @xorfs_file_open max_readahead = %d (size = %d)\n", (int) file->f_ra.ra_pages, file_size); file->f_ra.ra_pages = 0; /* No read-ahead */ return generic_file_open(inode, file); } // xorfs_file_open static ssize_t xorfs_file_write(struct file *file, const char *buf, size_t maxlen, loff_t* offset) { int count; if(*offset > 0) { printk("XORFS: @xorfs_file_write Positive offset %d\n", *offset); return 0; } // if count = maxlen > sizeof(file_buf) ? sizeof(file_buf) : maxlen; //__generic_copy_from_user(file_buf, buf, count); copy_from_user(file_buf, buf, maxlen); printk("XORFS: xorfs_file_write called with maxlen=%d, offset=%d\n", maxlen, *offset); *offset += count; if(*offset > file_size) file_size = *offset; return count; } // xorfs_file_write static ssize_t xorfs_file_read(struct file *file, char *buf, size_t max, loff_t* offset){ int i; int buflen; if(*offset > 0) return 0; printk("XORFS: xorfs_file_read called [%d] [%d]\n", max, *offset); buflen = (file_size > max) ? max : file_size; copy_to_user(buf, file_buf, buflen); *offset += buflen; return buflen; } // xorfs_file_read static int xorfs_file_readdir(struct file *f