/* * dm-snapshot.c * * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * * This file is released under the GPL. */#include<linux/blkdev.h>#include<linux/ctype.h>#include<linux/device-mapper.h>#include<linux/delay.h>#include<linux/fs.h>#include<linux/init.h>#include<linux/kdev_t.h>#include<linux/list.h>#include<linux/mempool.h>#include<linux/module.h>#include<linux/slab.h>#include<linux/vmalloc.h>#include<linux/log2.h>#include<linux/dm-kcopyd.h>#include"dm-exception-store.h"#include"dm-snap.h"#include"dm-bio-list.h"#define DM_MSG_PREFIX "snapshots"/* * The percentage increment we will wake up users at */#define WAKE_UP_PERCENT 5/* * kcopyd priority of snapshot operations */#define SNAPSHOT_COPY_PRIORITY 2/* * Reserve 1MB for each snapshot initially (with minimum of 1 page). */#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)/* * The size of the mempool used to track chunks in use. */#define MIN_IOS 256staticstructworkqueue_struct*ksnapd;staticvoidflush_queued_bios(structwork_struct*work);structdm_snap_pending_exception{structdm_snap_exceptione;/* * Origin buffers waiting for this to complete are held * in a bio list */structbio_listorigin_bios;structbio_listsnapshot_bios;/* * Short-term queue of pending exceptions prior to submission. */structlist_headlist;/* * The primary pending_exception is the one