move_extent.c File Reference

#include <linux/fs.h>
#include <linux/quotaops.h>
#include <linux/slab.h>
#include "ext4_jbd2.h"
#include "ext4.h"

Go to the source code of this file.

Functions
int	ext4_move_extents (struct file *o_filp, struct file *d_filp, __u64 orig_start, __u64 donor_start, __u64 len, __u64 *moved_len)

Function Documentation

int ext4_move_extents	(	struct file *	o_filp,
		struct file *	d_filp,
		__u64	orig_start,
		__u64	donor_start,
		__u64	len,
		__u64 *	moved_len
	)

ext4_move_extents - Exchange the specified range of a file

: file structure of the original file : file structure of the donor file : start offset in block for orig : start offset in block for donor : the number of blocks to be moved : moved block length

This function returns 0 and moved block length is set in moved_len if succeed, otherwise returns error value.

Note: ext4_move_extents() proceeds the following order. 1:ext4_move_extents() calculates the last block number of moving extent function by the start block number (orig_start) and the number of blocks to be moved (len) specified as arguments. If the {orig, donor}_start points a hole, the extent's start offset pointed by ext_cur (current extent), holecheck_path, orig_path are set after hole behind. 2:Continue step 3 to step 5, until the holecheck_path points to last_extent or the ext_cur exceeds the block_end which is last logical block number. 3:To get the length of continues area, call mext_next_extent() specified with the ext_cur (initial value is holecheck_path) re-cursive, until find un-continuous extent, the start logical block number exceeds the block_end or the extent points to the last extent. 4:Exchange the original inode data with donor inode data from orig_page_offset to seq_end_page. The start indexes of data are specified as arguments. That of the original inode is orig_page_offset, and the donor inode is also orig_page_offset (To easily handle blocksize != pagesize case, the offset for the donor inode is block unit). 5:Update holecheck_path and orig_path to points a next proceeding extent, then returns to step 2. 6:Release holecheck_path, orig_path and set the len to moved_len which shows the number of moved blocks. The moved_len is useful for the command to calculate the file offset for starting next move extent ioctl. 7:Return 0 on success, or a negative error value on failure.

Definition at line 1277 of file move_extent.c.