EXT2 file system file.c with my comments

/* *  linux/fs/ext2/file.c * * Copyright (C) 1992, 1993, 1994, 1995 * Remy Card ([e-mail]) * Laboratoire MASI - Institut Blaise Pascal * Universite Pierre et Marie Curie (Paris VI) * *  from * *  linux/fs/minix/file.c * *  Copyright (C) 1991, 1992  Linus Torvalds * *  ext2 fs regular file handling primitives * *  64-bit file support on 64-bit platforms by Jakub Jelinek * ([e-mail]) */#include <linux/time.h>#include <linux/pagemap.h>#include <linux/quotaops.h>#include "ext2.h"#include "xattr.h"#include "acl.h"/* * Called when filp is released. This happens when all file descriptors * for a single struct file are closed. Note that different open() calls * for the same file yield different struct file structures. */static int ext2_release_file (struct inode * inode, struct file * filp){if (filp->f_mode & FMODE_WRITE) {mutex_lock(&EXT2_I(inode)->truncate_mutex);/*discard(free) block reservation window on last file close, or truncate* or at last iput().*/ext2_discard_reservation(inode);mutex_unlock(&EXT2_I(inode)->truncate_mutex);}return 0;}/*synchnorinize the file inode data to disk, now the data is already write to disk*/int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync){int ret;struct super_block *sb = file->f_mapping->host->i_sb;struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;ret = generic_file_fsync(file, start, end, datasync); /*call the general method, it is very complex*/if (ret == -EIO || test_and_clear_bit(AS_EIO, &mapping->flags)) {/* We don't really know where the IO error happened... */ext2_error(sb, __func__,   "detected IO error when writing metadata buffers");ret = -EIO;}return ret;}/* * We have mostly NULL's here: the current defaults are ok for * the ext2 filesystem. * most of the methods are in the linux/fs, they are the general methods */const struct file_operations ext2_file_operations = {.llseek= generic_file_llseek,.read= do_sync_read,.write= do_sync_write,.aio_read= generic_file_aio_read,.aio_write= generic_file_aio_write,.unlocked_ioctl = ext2_ioctl,#ifdef CONFIG_COMPAT.compat_ioctl= ext2_compat_ioctl,#endif.mmap= generic_file_mmap,.open= dquot_file_open,.release= ext2_release_file,.fsync= ext2_fsync,.splice_read= generic_file_splice_read,.splice_write= generic_file_splice_write,};#ifdef CONFIG_EXT2_FS_XIPconst struct file_operations ext2_xip_file_operations = {.llseek= generic_file_llseek,.read= xip_file_read,.write= xip_file_write,.unlocked_ioctl = ext2_ioctl,#ifdef CONFIG_COMPAT.compat_ioctl= ext2_compat_ioctl,#endif.mmap= xip_file_mmap,.open= dquot_file_open,.release= ext2_release_file,.fsync= ext2_fsync,};#endifconst struct inode_operations ext2_file_inode_operations = {#ifdef CONFIG_EXT2_FS_XATTR.setxattr= generic_setxattr,.getxattr= generic_getxattr,.listxattr= ext2_listxattr,.removexattr= generic_removexattr,#endif.setattr= ext2_setattr,.get_acl= ext2_get_acl,.fiemap= ext2_fiemap,};