/*
 *  linux/fs/ext2/file.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * 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
 * 	(jj@sunsite.ms.mff.cuni.cz)
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/sched.h>



#define	NBUF	32

#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))

static long long ext2_file_lseek(struct file *, long long, int);
#if BITS_PER_LONG < 64
static int ext2_open_file (struct inode *, struct file *);
#endif

#define EXT2_MAX_SIZE(bits)							\
	(((EXT2_NDIR_BLOCKS + (1LL << (bits - 2)) + 				\
	   (1LL << (bits - 2)) * (1LL << (bits - 2)) + 				\
	   (1LL << (bits - 2)) * (1LL << (bits - 2)) * (1LL << (bits - 2))) * 	\
	  (1LL << bits)) - 1)

static long long ext2_max_sizes[] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
EXT2_MAX_SIZE(10), EXT2_MAX_SIZE(11), EXT2_MAX_SIZE(12), EXT2_MAX_SIZE(13)
};

/*
 * Make sure the offset never goes beyond the 32-bit mark..
 */
static long long ext2_file_lseek(
	struct file *file,
	long long offset,
	int origin)
{
	struct inode *inode = file->f_dentry->d_inode;

	switch (origin) {
		case 2:
			offset += inode->i_size;
			break;
		case 1:
			offset += file->f_pos;
	}
	if (offset<0)
		return -EINVAL;
	if (((unsigned long long) offset >> 32) != 0) {
		if (offset > ext2_max_sizes[EXT2_BLOCK_SIZE_BITS(inode->i_sb)])
			return -EINVAL;
	} 
	if (offset != file->f_pos) {
		file->f_pos = offset;
		file->f_reada = 0;
		file->f_version = ++event;
	}
	return offset;
}

static inline void remove_suid(struct inode *inode)
{
	unsigned int mode;

	/* set S_IGID if S_IXGRP is set, and always set S_ISUID */
	mode = (inode->i_mode & S_IXGRP)*(S_ISGID/S_IXGRP) | S_ISUID;

	/* was any of the uid bits set? */
	mode &= inode->i_mode;
	if (mode && !capable(CAP_FSETID)) {
		inode->i_mode &= ~mode;
		mark_inode_dirty(inode);
	}
}

/*
 * Write to a file (through the page cache).
 */
static ssize_t
ext2_file_write(struct file *file, const char *buf, size_t count, loff_t *ppos)
{
	ssize_t retval;

	retval = generic_file_write(file, buf, count,
						 ppos, block_write_partial_page);
	if (retval > 0) {
		struct inode *inode = file->f_dentry->d_inode;
		remove_suid(inode);
		inode->i_ctime = inode->i_mtime = CURRENT_TIME;
		mark_inode_dirty(inode);
	}
	return retval;
}

/*
 * Called when an inode is released. Note that this is different
 * from ext2_file_open: open gets called at every open, but release
 * gets called only when /all/ the files are closed.
 */
static int ext2_release_file (struct inode * inode, struct file * filp)
{
	if (filp->f_mode & FMODE_WRITE)
		ext2_discard_prealloc (inode);
	return 0;
}

#if BITS_PER_LONG < 64
/*
 * Called when an inode is about to be open.
 * We use this to disallow opening RW large files on 32bit systems if
 * the caller didn't specify O_LARGEFILE.
 */
static int ext2_open_file (struct inode * inode, struct file * filp)
{
	if (inode->u.ext2_i.i_high_size && !(filp->f_flags & O_LARGEFILE))
		return -EFBIG;
	return 0;
}
#endif

/*
 * We have mostly NULL's here: the current defaults are ok for
 * the ext2 filesystem.
 */
static struct file_operations ext2_file_operations = {
	ext2_file_lseek,	/* lseek */
	generic_file_read,	/* read */
	ext2_file_write,	/* write */
	NULL,			/* readdir - bad */
	NULL,			/* poll - default */
	ext2_ioctl,		/* ioctl */
	generic_file_mmap,	/* mmap */
#if BITS_PER_LONG == 64	
	NULL,			/* no special open is needed */
#else
	ext2_open_file,
#endif
	NULL,			/* flush */
	ext2_release_file,	/* release */
	ext2_sync_file,		/* fsync */
	NULL,			/* fasync */
	NULL,			/* check_media_change */
	NULL			/* revalidate */
};

struct inode_operations ext2_file_inode_operations = {
	&ext2_file_operations,/* default file operations */
	NULL,			/* create */
	NULL,			/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	NULL,			/* readlink */
	NULL,			/* follow_link */
	ext2_get_block,		/* get_block */
	block_read_full_page,	/* readpage */
	block_write_full_page,	/* writepage */
	block_flushpage,	/* flushpage */
	ext2_truncate,		/* truncate */
	ext2_permission,	/* permission */
	NULL,			/* smap */
	NULL,			/* revalidate */
};
