![Alasdair G Kergon](/assets/img/avatar_default.png)
The snapshot and origin targets are incapable of handling barriers and need to indicate this. Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
1225 lines
26 KiB
C
1225 lines
26 KiB
C
/*
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* dm-snapshot.c
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*
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* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
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*
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* This file is released under the GPL.
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*/
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#include <linux/blkdev.h>
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#include <linux/config.h>
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#include <linux/ctype.h>
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#include <linux/device-mapper.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/kdev_t.h>
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#include <linux/list.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include "dm-snap.h"
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#include "dm-bio-list.h"
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#include "kcopyd.h"
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/*
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* The percentage increment we will wake up users at
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*/
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#define WAKE_UP_PERCENT 5
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/*
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* kcopyd priority of snapshot operations
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*/
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#define SNAPSHOT_COPY_PRIORITY 2
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/*
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* Each snapshot reserves this many pages for io
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*/
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#define SNAPSHOT_PAGES 256
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struct pending_exception {
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struct exception e;
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/*
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* Origin buffers waiting for this to complete are held
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* in a bio list
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*/
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struct bio_list origin_bios;
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struct bio_list snapshot_bios;
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/*
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* Other pending_exceptions that are processing this
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* chunk. When this list is empty, we know we can
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* complete the origins.
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*/
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struct list_head siblings;
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/* Pointer back to snapshot context */
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struct dm_snapshot *snap;
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/*
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* 1 indicates the exception has already been sent to
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* kcopyd.
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*/
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int started;
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};
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/*
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* Hash table mapping origin volumes to lists of snapshots and
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* a lock to protect it
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*/
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static kmem_cache_t *exception_cache;
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static kmem_cache_t *pending_cache;
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static mempool_t *pending_pool;
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/*
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* One of these per registered origin, held in the snapshot_origins hash
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*/
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struct origin {
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/* The origin device */
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struct block_device *bdev;
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struct list_head hash_list;
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/* List of snapshots for this origin */
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struct list_head snapshots;
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};
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/*
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* Size of the hash table for origin volumes. If we make this
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* the size of the minors list then it should be nearly perfect
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*/
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#define ORIGIN_HASH_SIZE 256
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#define ORIGIN_MASK 0xFF
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static struct list_head *_origins;
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static struct rw_semaphore _origins_lock;
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static int init_origin_hash(void)
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{
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int i;
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_origins = kmalloc(ORIGIN_HASH_SIZE * sizeof(struct list_head),
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GFP_KERNEL);
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if (!_origins) {
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DMERR("Device mapper: Snapshot: unable to allocate memory");
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return -ENOMEM;
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}
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for (i = 0; i < ORIGIN_HASH_SIZE; i++)
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INIT_LIST_HEAD(_origins + i);
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init_rwsem(&_origins_lock);
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return 0;
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}
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static void exit_origin_hash(void)
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{
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kfree(_origins);
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}
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static inline unsigned int origin_hash(struct block_device *bdev)
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{
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return bdev->bd_dev & ORIGIN_MASK;
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}
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static struct origin *__lookup_origin(struct block_device *origin)
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{
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struct list_head *ol;
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struct origin *o;
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ol = &_origins[origin_hash(origin)];
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list_for_each_entry (o, ol, hash_list)
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if (bdev_equal(o->bdev, origin))
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return o;
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return NULL;
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}
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static void __insert_origin(struct origin *o)
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{
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struct list_head *sl = &_origins[origin_hash(o->bdev)];
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list_add_tail(&o->hash_list, sl);
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}
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/*
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* Make a note of the snapshot and its origin so we can look it
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* up when the origin has a write on it.
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*/
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static int register_snapshot(struct dm_snapshot *snap)
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{
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struct origin *o;
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struct block_device *bdev = snap->origin->bdev;
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down_write(&_origins_lock);
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o = __lookup_origin(bdev);
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if (!o) {
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/* New origin */
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o = kmalloc(sizeof(*o), GFP_KERNEL);
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if (!o) {
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up_write(&_origins_lock);
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return -ENOMEM;
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}
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/* Initialise the struct */
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INIT_LIST_HEAD(&o->snapshots);
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o->bdev = bdev;
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__insert_origin(o);
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}
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list_add_tail(&snap->list, &o->snapshots);
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up_write(&_origins_lock);
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return 0;
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}
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static void unregister_snapshot(struct dm_snapshot *s)
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{
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struct origin *o;
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down_write(&_origins_lock);
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o = __lookup_origin(s->origin->bdev);
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list_del(&s->list);
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if (list_empty(&o->snapshots)) {
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list_del(&o->hash_list);
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kfree(o);
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}
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up_write(&_origins_lock);
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}
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/*
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* Implementation of the exception hash tables.
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*/
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static int init_exception_table(struct exception_table *et, uint32_t size)
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{
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unsigned int i;
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et->hash_mask = size - 1;
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et->table = dm_vcalloc(size, sizeof(struct list_head));
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if (!et->table)
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return -ENOMEM;
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for (i = 0; i < size; i++)
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INIT_LIST_HEAD(et->table + i);
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return 0;
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}
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static void exit_exception_table(struct exception_table *et, kmem_cache_t *mem)
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{
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struct list_head *slot;
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struct exception *ex, *next;
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int i, size;
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size = et->hash_mask + 1;
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for (i = 0; i < size; i++) {
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slot = et->table + i;
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list_for_each_entry_safe (ex, next, slot, hash_list)
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kmem_cache_free(mem, ex);
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}
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vfree(et->table);
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}
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static inline uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
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{
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return chunk & et->hash_mask;
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}
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static void insert_exception(struct exception_table *eh, struct exception *e)
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{
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struct list_head *l = &eh->table[exception_hash(eh, e->old_chunk)];
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list_add(&e->hash_list, l);
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}
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static inline void remove_exception(struct exception *e)
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{
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list_del(&e->hash_list);
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}
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/*
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* Return the exception data for a sector, or NULL if not
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* remapped.
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*/
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static struct exception *lookup_exception(struct exception_table *et,
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chunk_t chunk)
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{
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struct list_head *slot;
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struct exception *e;
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slot = &et->table[exception_hash(et, chunk)];
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list_for_each_entry (e, slot, hash_list)
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if (e->old_chunk == chunk)
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return e;
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return NULL;
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}
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static inline struct exception *alloc_exception(void)
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{
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struct exception *e;
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e = kmem_cache_alloc(exception_cache, GFP_NOIO);
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if (!e)
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e = kmem_cache_alloc(exception_cache, GFP_ATOMIC);
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return e;
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}
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static inline void free_exception(struct exception *e)
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{
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kmem_cache_free(exception_cache, e);
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}
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static inline struct pending_exception *alloc_pending_exception(void)
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{
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return mempool_alloc(pending_pool, GFP_NOIO);
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}
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static inline void free_pending_exception(struct pending_exception *pe)
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{
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mempool_free(pe, pending_pool);
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}
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int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
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{
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struct exception *e;
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e = alloc_exception();
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if (!e)
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return -ENOMEM;
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e->old_chunk = old;
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e->new_chunk = new;
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insert_exception(&s->complete, e);
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return 0;
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}
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/*
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* Hard coded magic.
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*/
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static int calc_max_buckets(void)
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{
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/* use a fixed size of 2MB */
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unsigned long mem = 2 * 1024 * 1024;
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mem /= sizeof(struct list_head);
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return mem;
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}
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/*
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* Rounds a number down to a power of 2.
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*/
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static inline uint32_t round_down(uint32_t n)
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{
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while (n & (n - 1))
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n &= (n - 1);
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return n;
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}
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/*
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* Allocate room for a suitable hash table.
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*/
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static int init_hash_tables(struct dm_snapshot *s)
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{
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sector_t hash_size, cow_dev_size, origin_dev_size, max_buckets;
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/*
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* Calculate based on the size of the original volume or
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* the COW volume...
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*/
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cow_dev_size = get_dev_size(s->cow->bdev);
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origin_dev_size = get_dev_size(s->origin->bdev);
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max_buckets = calc_max_buckets();
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hash_size = min(origin_dev_size, cow_dev_size) >> s->chunk_shift;
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hash_size = min(hash_size, max_buckets);
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/* Round it down to a power of 2 */
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hash_size = round_down(hash_size);
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if (init_exception_table(&s->complete, hash_size))
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return -ENOMEM;
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/*
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* Allocate hash table for in-flight exceptions
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* Make this smaller than the real hash table
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*/
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hash_size >>= 3;
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if (hash_size < 64)
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hash_size = 64;
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if (init_exception_table(&s->pending, hash_size)) {
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exit_exception_table(&s->complete, exception_cache);
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return -ENOMEM;
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}
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return 0;
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}
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/*
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* Round a number up to the nearest 'size' boundary. size must
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* be a power of 2.
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*/
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static inline ulong round_up(ulong n, ulong size)
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{
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size--;
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return (n + size) & ~size;
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}
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static void read_snapshot_metadata(struct dm_snapshot *s)
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{
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if (s->store.read_metadata(&s->store)) {
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down_write(&s->lock);
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s->valid = 0;
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up_write(&s->lock);
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}
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}
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/*
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* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
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*/
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static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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{
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struct dm_snapshot *s;
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unsigned long chunk_size;
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int r = -EINVAL;
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char persistent;
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char *origin_path;
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char *cow_path;
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char *value;
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int blocksize;
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if (argc < 4) {
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ti->error = "dm-snapshot: requires exactly 4 arguments";
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r = -EINVAL;
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goto bad1;
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}
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origin_path = argv[0];
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cow_path = argv[1];
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persistent = toupper(*argv[2]);
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if (persistent != 'P' && persistent != 'N') {
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ti->error = "Persistent flag is not P or N";
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r = -EINVAL;
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goto bad1;
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}
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chunk_size = simple_strtoul(argv[3], &value, 10);
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if (chunk_size == 0 || value == NULL) {
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ti->error = "Invalid chunk size";
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r = -EINVAL;
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goto bad1;
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}
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s = kmalloc(sizeof(*s), GFP_KERNEL);
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if (s == NULL) {
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ti->error = "Cannot allocate snapshot context private "
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"structure";
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r = -ENOMEM;
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goto bad1;
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}
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r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
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if (r) {
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ti->error = "Cannot get origin device";
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goto bad2;
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}
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r = dm_get_device(ti, cow_path, 0, 0,
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FMODE_READ | FMODE_WRITE, &s->cow);
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if (r) {
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dm_put_device(ti, s->origin);
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ti->error = "Cannot get COW device";
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goto bad2;
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}
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/*
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* Chunk size must be multiple of page size. Silently
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* round up if it's not.
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*/
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chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
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/* Validate the chunk size against the device block size */
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blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
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if (chunk_size % (blocksize >> 9)) {
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ti->error = "Chunk size is not a multiple of device blocksize";
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r = -EINVAL;
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goto bad3;
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}
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/* Check chunk_size is a power of 2 */
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if (chunk_size & (chunk_size - 1)) {
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ti->error = "Chunk size is not a power of 2";
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r = -EINVAL;
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goto bad3;
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}
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s->chunk_size = chunk_size;
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s->chunk_mask = chunk_size - 1;
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s->type = persistent;
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s->chunk_shift = ffs(chunk_size) - 1;
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s->valid = 1;
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s->active = 0;
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s->last_percent = 0;
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init_rwsem(&s->lock);
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s->table = ti->table;
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|
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/* Allocate hash table for COW data */
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if (init_hash_tables(s)) {
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ti->error = "Unable to allocate hash table space";
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r = -ENOMEM;
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goto bad3;
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}
|
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|
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/*
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* Check the persistent flag - done here because we need the iobuf
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* to check the LV header
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*/
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s->store.snap = s;
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|
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if (persistent == 'P')
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r = dm_create_persistent(&s->store, chunk_size);
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else
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r = dm_create_transient(&s->store, s, blocksize);
|
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|
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if (r) {
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ti->error = "Couldn't create exception store";
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r = -EINVAL;
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goto bad4;
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}
|
|
|
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r = kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
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if (r) {
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ti->error = "Could not create kcopyd client";
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goto bad5;
|
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}
|
|
|
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/* Metadata must only be loaded into one table at once */
|
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read_snapshot_metadata(s);
|
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|
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/* Add snapshot to the list of snapshots for this origin */
|
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/* Exceptions aren't triggered till snapshot_resume() is called */
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if (register_snapshot(s)) {
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r = -EINVAL;
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ti->error = "Cannot register snapshot origin";
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goto bad6;
|
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}
|
|
|
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ti->private = s;
|
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ti->split_io = chunk_size;
|
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|
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return 0;
|
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|
|
bad6:
|
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kcopyd_client_destroy(s->kcopyd_client);
|
|
|
|
bad5:
|
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s->store.destroy(&s->store);
|
|
|
|
bad4:
|
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exit_exception_table(&s->pending, pending_cache);
|
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exit_exception_table(&s->complete, exception_cache);
|
|
|
|
bad3:
|
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dm_put_device(ti, s->cow);
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dm_put_device(ti, s->origin);
|
|
|
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bad2:
|
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kfree(s);
|
|
|
|
bad1:
|
|
return r;
|
|
}
|
|
|
|
static void snapshot_dtr(struct dm_target *ti)
|
|
{
|
|
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
|
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|
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unregister_snapshot(s);
|
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|
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exit_exception_table(&s->pending, pending_cache);
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exit_exception_table(&s->complete, exception_cache);
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|
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/* Deallocate memory used */
|
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s->store.destroy(&s->store);
|
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|
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dm_put_device(ti, s->origin);
|
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dm_put_device(ti, s->cow);
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kcopyd_client_destroy(s->kcopyd_client);
|
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kfree(s);
|
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}
|
|
|
|
/*
|
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* Flush a list of buffers.
|
|
*/
|
|
static void flush_bios(struct bio *bio)
|
|
{
|
|
struct bio *n;
|
|
|
|
while (bio) {
|
|
n = bio->bi_next;
|
|
bio->bi_next = NULL;
|
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generic_make_request(bio);
|
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bio = n;
|
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}
|
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}
|
|
|
|
/*
|
|
* Error a list of buffers.
|
|
*/
|
|
static void error_bios(struct bio *bio)
|
|
{
|
|
struct bio *n;
|
|
|
|
while (bio) {
|
|
n = bio->bi_next;
|
|
bio->bi_next = NULL;
|
|
bio_io_error(bio, bio->bi_size);
|
|
bio = n;
|
|
}
|
|
}
|
|
|
|
static struct bio *__flush_bios(struct pending_exception *pe)
|
|
{
|
|
struct pending_exception *sibling;
|
|
|
|
if (list_empty(&pe->siblings))
|
|
return bio_list_get(&pe->origin_bios);
|
|
|
|
sibling = list_entry(pe->siblings.next,
|
|
struct pending_exception, siblings);
|
|
|
|
list_del(&pe->siblings);
|
|
|
|
/* This is fine as long as kcopyd is single-threaded. If kcopyd
|
|
* becomes multi-threaded, we'll need some locking here.
|
|
*/
|
|
bio_list_merge(&sibling->origin_bios, &pe->origin_bios);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static void pending_complete(struct pending_exception *pe, int success)
|
|
{
|
|
struct exception *e;
|
|
struct dm_snapshot *s = pe->snap;
|
|
struct bio *flush = NULL;
|
|
|
|
if (success) {
|
|
e = alloc_exception();
|
|
if (!e) {
|
|
DMWARN("Unable to allocate exception.");
|
|
down_write(&s->lock);
|
|
s->store.drop_snapshot(&s->store);
|
|
s->valid = 0;
|
|
flush = __flush_bios(pe);
|
|
up_write(&s->lock);
|
|
|
|
error_bios(bio_list_get(&pe->snapshot_bios));
|
|
goto out;
|
|
}
|
|
*e = pe->e;
|
|
|
|
/*
|
|
* Add a proper exception, and remove the
|
|
* in-flight exception from the list.
|
|
*/
|
|
down_write(&s->lock);
|
|
insert_exception(&s->complete, e);
|
|
remove_exception(&pe->e);
|
|
flush = __flush_bios(pe);
|
|
|
|
/* Submit any pending write bios */
|
|
up_write(&s->lock);
|
|
|
|
flush_bios(bio_list_get(&pe->snapshot_bios));
|
|
} else {
|
|
/* Read/write error - snapshot is unusable */
|
|
down_write(&s->lock);
|
|
if (s->valid)
|
|
DMERR("Error reading/writing snapshot");
|
|
s->store.drop_snapshot(&s->store);
|
|
s->valid = 0;
|
|
remove_exception(&pe->e);
|
|
flush = __flush_bios(pe);
|
|
up_write(&s->lock);
|
|
|
|
error_bios(bio_list_get(&pe->snapshot_bios));
|
|
|
|
dm_table_event(s->table);
|
|
}
|
|
|
|
out:
|
|
free_pending_exception(pe);
|
|
|
|
if (flush)
|
|
flush_bios(flush);
|
|
}
|
|
|
|
static void commit_callback(void *context, int success)
|
|
{
|
|
struct pending_exception *pe = (struct pending_exception *) context;
|
|
pending_complete(pe, success);
|
|
}
|
|
|
|
/*
|
|
* Called when the copy I/O has finished. kcopyd actually runs
|
|
* this code so don't block.
|
|
*/
|
|
static void copy_callback(int read_err, unsigned int write_err, void *context)
|
|
{
|
|
struct pending_exception *pe = (struct pending_exception *) context;
|
|
struct dm_snapshot *s = pe->snap;
|
|
|
|
if (read_err || write_err)
|
|
pending_complete(pe, 0);
|
|
|
|
else
|
|
/* Update the metadata if we are persistent */
|
|
s->store.commit_exception(&s->store, &pe->e, commit_callback,
|
|
pe);
|
|
}
|
|
|
|
/*
|
|
* Dispatches the copy operation to kcopyd.
|
|
*/
|
|
static void start_copy(struct pending_exception *pe)
|
|
{
|
|
struct dm_snapshot *s = pe->snap;
|
|
struct io_region src, dest;
|
|
struct block_device *bdev = s->origin->bdev;
|
|
sector_t dev_size;
|
|
|
|
dev_size = get_dev_size(bdev);
|
|
|
|
src.bdev = bdev;
|
|
src.sector = chunk_to_sector(s, pe->e.old_chunk);
|
|
src.count = min(s->chunk_size, dev_size - src.sector);
|
|
|
|
dest.bdev = s->cow->bdev;
|
|
dest.sector = chunk_to_sector(s, pe->e.new_chunk);
|
|
dest.count = src.count;
|
|
|
|
/* Hand over to kcopyd */
|
|
kcopyd_copy(s->kcopyd_client,
|
|
&src, 1, &dest, 0, copy_callback, pe);
|
|
}
|
|
|
|
/*
|
|
* Looks to see if this snapshot already has a pending exception
|
|
* for this chunk, otherwise it allocates a new one and inserts
|
|
* it into the pending table.
|
|
*
|
|
* NOTE: a write lock must be held on snap->lock before calling
|
|
* this.
|
|
*/
|
|
static struct pending_exception *
|
|
__find_pending_exception(struct dm_snapshot *s, struct bio *bio)
|
|
{
|
|
struct exception *e;
|
|
struct pending_exception *pe;
|
|
chunk_t chunk = sector_to_chunk(s, bio->bi_sector);
|
|
|
|
/*
|
|
* Is there a pending exception for this already ?
|
|
*/
|
|
e = lookup_exception(&s->pending, chunk);
|
|
if (e) {
|
|
/* cast the exception to a pending exception */
|
|
pe = container_of(e, struct pending_exception, e);
|
|
|
|
} else {
|
|
/*
|
|
* Create a new pending exception, we don't want
|
|
* to hold the lock while we do this.
|
|
*/
|
|
up_write(&s->lock);
|
|
pe = alloc_pending_exception();
|
|
down_write(&s->lock);
|
|
|
|
e = lookup_exception(&s->pending, chunk);
|
|
if (e) {
|
|
free_pending_exception(pe);
|
|
pe = container_of(e, struct pending_exception, e);
|
|
} else {
|
|
pe->e.old_chunk = chunk;
|
|
bio_list_init(&pe->origin_bios);
|
|
bio_list_init(&pe->snapshot_bios);
|
|
INIT_LIST_HEAD(&pe->siblings);
|
|
pe->snap = s;
|
|
pe->started = 0;
|
|
|
|
if (s->store.prepare_exception(&s->store, &pe->e)) {
|
|
free_pending_exception(pe);
|
|
s->valid = 0;
|
|
return NULL;
|
|
}
|
|
|
|
insert_exception(&s->pending, &pe->e);
|
|
}
|
|
}
|
|
|
|
return pe;
|
|
}
|
|
|
|
static inline void remap_exception(struct dm_snapshot *s, struct exception *e,
|
|
struct bio *bio)
|
|
{
|
|
bio->bi_bdev = s->cow->bdev;
|
|
bio->bi_sector = chunk_to_sector(s, e->new_chunk) +
|
|
(bio->bi_sector & s->chunk_mask);
|
|
}
|
|
|
|
static int snapshot_map(struct dm_target *ti, struct bio *bio,
|
|
union map_info *map_context)
|
|
{
|
|
struct exception *e;
|
|
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
|
|
int r = 1;
|
|
chunk_t chunk;
|
|
struct pending_exception *pe;
|
|
|
|
chunk = sector_to_chunk(s, bio->bi_sector);
|
|
|
|
/* Full snapshots are not usable */
|
|
if (!s->valid)
|
|
return -EIO;
|
|
|
|
if (unlikely(bio_barrier(bio)))
|
|
return -EOPNOTSUPP;
|
|
|
|
/*
|
|
* Write to snapshot - higher level takes care of RW/RO
|
|
* flags so we should only get this if we are
|
|
* writeable.
|
|
*/
|
|
if (bio_rw(bio) == WRITE) {
|
|
|
|
/* FIXME: should only take write lock if we need
|
|
* to copy an exception */
|
|
down_write(&s->lock);
|
|
|
|
/* If the block is already remapped - use that, else remap it */
|
|
e = lookup_exception(&s->complete, chunk);
|
|
if (e) {
|
|
remap_exception(s, e, bio);
|
|
up_write(&s->lock);
|
|
|
|
} else {
|
|
pe = __find_pending_exception(s, bio);
|
|
|
|
if (!pe) {
|
|
if (s->store.drop_snapshot)
|
|
s->store.drop_snapshot(&s->store);
|
|
s->valid = 0;
|
|
r = -EIO;
|
|
up_write(&s->lock);
|
|
} else {
|
|
remap_exception(s, &pe->e, bio);
|
|
bio_list_add(&pe->snapshot_bios, bio);
|
|
|
|
if (!pe->started) {
|
|
/* this is protected by snap->lock */
|
|
pe->started = 1;
|
|
up_write(&s->lock);
|
|
start_copy(pe);
|
|
} else
|
|
up_write(&s->lock);
|
|
r = 0;
|
|
}
|
|
}
|
|
|
|
} else {
|
|
/*
|
|
* FIXME: this read path scares me because we
|
|
* always use the origin when we have a pending
|
|
* exception. However I can't think of a
|
|
* situation where this is wrong - ejt.
|
|
*/
|
|
|
|
/* Do reads */
|
|
down_read(&s->lock);
|
|
|
|
/* See if it it has been remapped */
|
|
e = lookup_exception(&s->complete, chunk);
|
|
if (e)
|
|
remap_exception(s, e, bio);
|
|
else
|
|
bio->bi_bdev = s->origin->bdev;
|
|
|
|
up_read(&s->lock);
|
|
}
|
|
|
|
return r;
|
|
}
|
|
|
|
static void snapshot_resume(struct dm_target *ti)
|
|
{
|
|
struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
|
|
|
|
down_write(&s->lock);
|
|
s->active = 1;
|
|
up_write(&s->lock);
|
|
}
|
|
|
|
static int snapshot_status(struct dm_target *ti, status_type_t type,
|
|
char *result, unsigned int maxlen)
|
|
{
|
|
struct dm_snapshot *snap = (struct dm_snapshot *) ti->private;
|
|
|
|
switch (type) {
|
|
case STATUSTYPE_INFO:
|
|
if (!snap->valid)
|
|
snprintf(result, maxlen, "Invalid");
|
|
else {
|
|
if (snap->store.fraction_full) {
|
|
sector_t numerator, denominator;
|
|
snap->store.fraction_full(&snap->store,
|
|
&numerator,
|
|
&denominator);
|
|
snprintf(result, maxlen,
|
|
SECTOR_FORMAT "/" SECTOR_FORMAT,
|
|
numerator, denominator);
|
|
}
|
|
else
|
|
snprintf(result, maxlen, "Unknown");
|
|
}
|
|
break;
|
|
|
|
case STATUSTYPE_TABLE:
|
|
/*
|
|
* kdevname returns a static pointer so we need
|
|
* to make private copies if the output is to
|
|
* make sense.
|
|
*/
|
|
snprintf(result, maxlen, "%s %s %c " SECTOR_FORMAT,
|
|
snap->origin->name, snap->cow->name,
|
|
snap->type, snap->chunk_size);
|
|
break;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*-----------------------------------------------------------------
|
|
* Origin methods
|
|
*---------------------------------------------------------------*/
|
|
static void list_merge(struct list_head *l1, struct list_head *l2)
|
|
{
|
|
struct list_head *l1_n, *l2_p;
|
|
|
|
l1_n = l1->next;
|
|
l2_p = l2->prev;
|
|
|
|
l1->next = l2;
|
|
l2->prev = l1;
|
|
|
|
l2_p->next = l1_n;
|
|
l1_n->prev = l2_p;
|
|
}
|
|
|
|
static int __origin_write(struct list_head *snapshots, struct bio *bio)
|
|
{
|
|
int r = 1, first = 1;
|
|
struct dm_snapshot *snap;
|
|
struct exception *e;
|
|
struct pending_exception *pe, *last = NULL;
|
|
chunk_t chunk;
|
|
|
|
/* Do all the snapshots on this origin */
|
|
list_for_each_entry (snap, snapshots, list) {
|
|
|
|
/* Only deal with valid and active snapshots */
|
|
if (!snap->valid || !snap->active)
|
|
continue;
|
|
|
|
/* Nothing to do if writing beyond end of snapshot */
|
|
if (bio->bi_sector >= dm_table_get_size(snap->table))
|
|
continue;
|
|
|
|
down_write(&snap->lock);
|
|
|
|
/*
|
|
* Remember, different snapshots can have
|
|
* different chunk sizes.
|
|
*/
|
|
chunk = sector_to_chunk(snap, bio->bi_sector);
|
|
|
|
/*
|
|
* Check exception table to see if block
|
|
* is already remapped in this snapshot
|
|
* and trigger an exception if not.
|
|
*/
|
|
e = lookup_exception(&snap->complete, chunk);
|
|
if (!e) {
|
|
pe = __find_pending_exception(snap, bio);
|
|
if (!pe) {
|
|
snap->store.drop_snapshot(&snap->store);
|
|
snap->valid = 0;
|
|
|
|
} else {
|
|
if (last)
|
|
list_merge(&pe->siblings,
|
|
&last->siblings);
|
|
|
|
last = pe;
|
|
r = 0;
|
|
}
|
|
}
|
|
|
|
up_write(&snap->lock);
|
|
}
|
|
|
|
/*
|
|
* Now that we have a complete pe list we can start the copying.
|
|
*/
|
|
if (last) {
|
|
pe = last;
|
|
do {
|
|
down_write(&pe->snap->lock);
|
|
if (first)
|
|
bio_list_add(&pe->origin_bios, bio);
|
|
if (!pe->started) {
|
|
pe->started = 1;
|
|
up_write(&pe->snap->lock);
|
|
start_copy(pe);
|
|
} else
|
|
up_write(&pe->snap->lock);
|
|
first = 0;
|
|
pe = list_entry(pe->siblings.next,
|
|
struct pending_exception, siblings);
|
|
|
|
} while (pe != last);
|
|
}
|
|
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
* Called on a write from the origin driver.
|
|
*/
|
|
static int do_origin(struct dm_dev *origin, struct bio *bio)
|
|
{
|
|
struct origin *o;
|
|
int r = 1;
|
|
|
|
down_read(&_origins_lock);
|
|
o = __lookup_origin(origin->bdev);
|
|
if (o)
|
|
r = __origin_write(&o->snapshots, bio);
|
|
up_read(&_origins_lock);
|
|
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
* Origin: maps a linear range of a device, with hooks for snapshotting.
|
|
*/
|
|
|
|
/*
|
|
* Construct an origin mapping: <dev_path>
|
|
* The context for an origin is merely a 'struct dm_dev *'
|
|
* pointing to the real device.
|
|
*/
|
|
static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
|
|
{
|
|
int r;
|
|
struct dm_dev *dev;
|
|
|
|
if (argc != 1) {
|
|
ti->error = "dm-origin: incorrect number of arguments";
|
|
return -EINVAL;
|
|
}
|
|
|
|
r = dm_get_device(ti, argv[0], 0, ti->len,
|
|
dm_table_get_mode(ti->table), &dev);
|
|
if (r) {
|
|
ti->error = "Cannot get target device";
|
|
return r;
|
|
}
|
|
|
|
ti->private = dev;
|
|
return 0;
|
|
}
|
|
|
|
static void origin_dtr(struct dm_target *ti)
|
|
{
|
|
struct dm_dev *dev = (struct dm_dev *) ti->private;
|
|
dm_put_device(ti, dev);
|
|
}
|
|
|
|
static int origin_map(struct dm_target *ti, struct bio *bio,
|
|
union map_info *map_context)
|
|
{
|
|
struct dm_dev *dev = (struct dm_dev *) ti->private;
|
|
bio->bi_bdev = dev->bdev;
|
|
|
|
if (unlikely(bio_barrier(bio)))
|
|
return -EOPNOTSUPP;
|
|
|
|
/* Only tell snapshots if this is a write */
|
|
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : 1;
|
|
}
|
|
|
|
#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
|
|
|
|
/*
|
|
* Set the target "split_io" field to the minimum of all the snapshots'
|
|
* chunk sizes.
|
|
*/
|
|
static void origin_resume(struct dm_target *ti)
|
|
{
|
|
struct dm_dev *dev = (struct dm_dev *) ti->private;
|
|
struct dm_snapshot *snap;
|
|
struct origin *o;
|
|
chunk_t chunk_size = 0;
|
|
|
|
down_read(&_origins_lock);
|
|
o = __lookup_origin(dev->bdev);
|
|
if (o)
|
|
list_for_each_entry (snap, &o->snapshots, list)
|
|
chunk_size = min_not_zero(chunk_size, snap->chunk_size);
|
|
up_read(&_origins_lock);
|
|
|
|
ti->split_io = chunk_size;
|
|
}
|
|
|
|
static int origin_status(struct dm_target *ti, status_type_t type, char *result,
|
|
unsigned int maxlen)
|
|
{
|
|
struct dm_dev *dev = (struct dm_dev *) ti->private;
|
|
|
|
switch (type) {
|
|
case STATUSTYPE_INFO:
|
|
result[0] = '\0';
|
|
break;
|
|
|
|
case STATUSTYPE_TABLE:
|
|
snprintf(result, maxlen, "%s", dev->name);
|
|
break;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct target_type origin_target = {
|
|
.name = "snapshot-origin",
|
|
.version = {1, 1, 0},
|
|
.module = THIS_MODULE,
|
|
.ctr = origin_ctr,
|
|
.dtr = origin_dtr,
|
|
.map = origin_map,
|
|
.resume = origin_resume,
|
|
.status = origin_status,
|
|
};
|
|
|
|
static struct target_type snapshot_target = {
|
|
.name = "snapshot",
|
|
.version = {1, 1, 0},
|
|
.module = THIS_MODULE,
|
|
.ctr = snapshot_ctr,
|
|
.dtr = snapshot_dtr,
|
|
.map = snapshot_map,
|
|
.resume = snapshot_resume,
|
|
.status = snapshot_status,
|
|
};
|
|
|
|
static int __init dm_snapshot_init(void)
|
|
{
|
|
int r;
|
|
|
|
r = dm_register_target(&snapshot_target);
|
|
if (r) {
|
|
DMERR("snapshot target register failed %d", r);
|
|
return r;
|
|
}
|
|
|
|
r = dm_register_target(&origin_target);
|
|
if (r < 0) {
|
|
DMERR("Device mapper: Origin: register failed %d\n", r);
|
|
goto bad1;
|
|
}
|
|
|
|
r = init_origin_hash();
|
|
if (r) {
|
|
DMERR("init_origin_hash failed.");
|
|
goto bad2;
|
|
}
|
|
|
|
exception_cache = kmem_cache_create("dm-snapshot-ex",
|
|
sizeof(struct exception),
|
|
__alignof__(struct exception),
|
|
0, NULL, NULL);
|
|
if (!exception_cache) {
|
|
DMERR("Couldn't create exception cache.");
|
|
r = -ENOMEM;
|
|
goto bad3;
|
|
}
|
|
|
|
pending_cache =
|
|
kmem_cache_create("dm-snapshot-in",
|
|
sizeof(struct pending_exception),
|
|
__alignof__(struct pending_exception),
|
|
0, NULL, NULL);
|
|
if (!pending_cache) {
|
|
DMERR("Couldn't create pending cache.");
|
|
r = -ENOMEM;
|
|
goto bad4;
|
|
}
|
|
|
|
pending_pool = mempool_create(128, mempool_alloc_slab,
|
|
mempool_free_slab, pending_cache);
|
|
if (!pending_pool) {
|
|
DMERR("Couldn't create pending pool.");
|
|
r = -ENOMEM;
|
|
goto bad5;
|
|
}
|
|
|
|
return 0;
|
|
|
|
bad5:
|
|
kmem_cache_destroy(pending_cache);
|
|
bad4:
|
|
kmem_cache_destroy(exception_cache);
|
|
bad3:
|
|
exit_origin_hash();
|
|
bad2:
|
|
dm_unregister_target(&origin_target);
|
|
bad1:
|
|
dm_unregister_target(&snapshot_target);
|
|
return r;
|
|
}
|
|
|
|
static void __exit dm_snapshot_exit(void)
|
|
{
|
|
int r;
|
|
|
|
r = dm_unregister_target(&snapshot_target);
|
|
if (r)
|
|
DMERR("snapshot unregister failed %d", r);
|
|
|
|
r = dm_unregister_target(&origin_target);
|
|
if (r)
|
|
DMERR("origin unregister failed %d", r);
|
|
|
|
exit_origin_hash();
|
|
mempool_destroy(pending_pool);
|
|
kmem_cache_destroy(pending_cache);
|
|
kmem_cache_destroy(exception_cache);
|
|
}
|
|
|
|
/* Module hooks */
|
|
module_init(dm_snapshot_init);
|
|
module_exit(dm_snapshot_exit);
|
|
|
|
MODULE_DESCRIPTION(DM_NAME " snapshot target");
|
|
MODULE_AUTHOR("Joe Thornber");
|
|
MODULE_LICENSE("GPL");
|