1531 lines
33 KiB
C
1531 lines
33 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/device-mapper.h>
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#include <linux/delay.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 <linux/log2.h>
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#include <linux/dm-kcopyd.h>
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#include <linux/workqueue.h>
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#include "dm-exception-store.h"
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#define DM_MSG_PREFIX "snapshots"
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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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* Reserve 1MB for each snapshot initially (with minimum of 1 page).
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*/
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#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
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/*
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* The size of the mempool used to track chunks in use.
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*/
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#define MIN_IOS 256
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#define DM_TRACKED_CHUNK_HASH_SIZE 16
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#define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \
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(DM_TRACKED_CHUNK_HASH_SIZE - 1))
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struct exception_table {
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uint32_t hash_mask;
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unsigned hash_shift;
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struct list_head *table;
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};
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struct dm_snapshot {
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struct rw_semaphore lock;
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struct dm_dev *origin;
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/* List of snapshots per Origin */
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struct list_head list;
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/* You can't use a snapshot if this is 0 (e.g. if full) */
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int valid;
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/* Origin writes don't trigger exceptions until this is set */
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int active;
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mempool_t *pending_pool;
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atomic_t pending_exceptions_count;
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struct exception_table pending;
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struct exception_table complete;
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/*
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* pe_lock protects all pending_exception operations and access
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* as well as the snapshot_bios list.
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*/
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spinlock_t pe_lock;
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/* The on disk metadata handler */
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struct dm_exception_store *store;
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struct dm_kcopyd_client *kcopyd_client;
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/* Queue of snapshot writes for ksnapd to flush */
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struct bio_list queued_bios;
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struct work_struct queued_bios_work;
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/* Chunks with outstanding reads */
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mempool_t *tracked_chunk_pool;
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spinlock_t tracked_chunk_lock;
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struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
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};
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static struct workqueue_struct *ksnapd;
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static void flush_queued_bios(struct work_struct *work);
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static sector_t chunk_to_sector(struct dm_exception_store *store,
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chunk_t chunk)
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{
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return chunk << store->chunk_shift;
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}
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static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
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{
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/*
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* There is only ever one instance of a particular block
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* device so we can compare pointers safely.
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*/
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return lhs == rhs;
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}
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struct dm_snap_pending_exception {
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struct dm_snap_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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* Short-term queue of pending exceptions prior to submission.
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*/
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struct list_head list;
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/*
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* The primary pending_exception is the one that holds
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* the ref_count and the list of origin_bios for a
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* group of pending_exceptions. It is always last to get freed.
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* These fields get set up when writing to the origin.
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*/
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struct dm_snap_pending_exception *primary_pe;
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/*
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* Number of pending_exceptions processing this chunk.
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* When this drops to zero we must complete the origin bios.
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* If incrementing or decrementing this, hold pe->snap->lock for
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* the sibling concerned and not pe->primary_pe->snap->lock unless
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* they are the same.
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*/
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atomic_t ref_count;
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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 struct kmem_cache *exception_cache;
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static struct kmem_cache *pending_cache;
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struct dm_snap_tracked_chunk {
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struct hlist_node node;
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chunk_t chunk;
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};
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static struct kmem_cache *tracked_chunk_cache;
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static struct dm_snap_tracked_chunk *track_chunk(struct dm_snapshot *s,
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chunk_t chunk)
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{
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struct dm_snap_tracked_chunk *c = mempool_alloc(s->tracked_chunk_pool,
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GFP_NOIO);
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unsigned long flags;
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c->chunk = chunk;
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spin_lock_irqsave(&s->tracked_chunk_lock, flags);
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hlist_add_head(&c->node,
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)]);
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spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
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return c;
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}
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static void stop_tracking_chunk(struct dm_snapshot *s,
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struct dm_snap_tracked_chunk *c)
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{
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unsigned long flags;
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spin_lock_irqsave(&s->tracked_chunk_lock, flags);
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hlist_del(&c->node);
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spin_unlock_irqrestore(&s->tracked_chunk_lock, flags);
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mempool_free(c, s->tracked_chunk_pool);
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}
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static int __chunk_is_tracked(struct dm_snapshot *s, chunk_t chunk)
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{
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struct dm_snap_tracked_chunk *c;
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struct hlist_node *hn;
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int found = 0;
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spin_lock_irq(&s->tracked_chunk_lock);
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hlist_for_each_entry(c, hn,
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&s->tracked_chunk_hash[DM_TRACKED_CHUNK_HASH(chunk)], node) {
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if (c->chunk == chunk) {
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found = 1;
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break;
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}
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}
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spin_unlock_irq(&s->tracked_chunk_lock);
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return found;
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}
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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("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 unsigned 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, *new_o;
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struct block_device *bdev = snap->origin->bdev;
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new_o = kmalloc(sizeof(*new_o), GFP_KERNEL);
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if (!new_o)
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return -ENOMEM;
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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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kfree(new_o);
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else {
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/* New origin */
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o = new_o;
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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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* The lowest hash_shift bits of the chunk number are ignored, allowing
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* some consecutive chunks to be grouped together.
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*/
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static int init_exception_table(struct exception_table *et, uint32_t size,
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unsigned hash_shift)
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{
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unsigned int i;
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et->hash_shift = hash_shift;
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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, struct kmem_cache *mem)
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{
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struct list_head *slot;
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struct dm_snap_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 uint32_t exception_hash(struct exception_table *et, chunk_t chunk)
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{
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return (chunk >> et->hash_shift) & et->hash_mask;
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}
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static void insert_exception(struct exception_table *eh,
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struct dm_snap_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 void remove_exception(struct dm_snap_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 dm_snap_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 dm_snap_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 (chunk >= e->old_chunk &&
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chunk <= e->old_chunk + dm_consecutive_chunk_count(e))
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return e;
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return NULL;
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}
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static struct dm_snap_exception *alloc_exception(void)
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{
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struct dm_snap_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 void free_exception(struct dm_snap_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 struct dm_snap_pending_exception *alloc_pending_exception(struct dm_snapshot *s)
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{
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struct dm_snap_pending_exception *pe = mempool_alloc(s->pending_pool,
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GFP_NOIO);
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atomic_inc(&s->pending_exceptions_count);
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pe->snap = s;
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return pe;
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}
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static void free_pending_exception(struct dm_snap_pending_exception *pe)
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{
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struct dm_snapshot *s = pe->snap;
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mempool_free(pe, s->pending_pool);
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smp_mb__before_atomic_dec();
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atomic_dec(&s->pending_exceptions_count);
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}
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static void insert_completed_exception(struct dm_snapshot *s,
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struct dm_snap_exception *new_e)
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{
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struct exception_table *eh = &s->complete;
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struct list_head *l;
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struct dm_snap_exception *e = NULL;
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l = &eh->table[exception_hash(eh, new_e->old_chunk)];
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/* Add immediately if this table doesn't support consecutive chunks */
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if (!eh->hash_shift)
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goto out;
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/* List is ordered by old_chunk */
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list_for_each_entry_reverse(e, l, hash_list) {
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/* Insert after an existing chunk? */
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if (new_e->old_chunk == (e->old_chunk +
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dm_consecutive_chunk_count(e) + 1) &&
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new_e->new_chunk == (dm_chunk_number(e->new_chunk) +
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dm_consecutive_chunk_count(e) + 1)) {
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dm_consecutive_chunk_count_inc(e);
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free_exception(new_e);
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return;
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}
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/* Insert before an existing chunk? */
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if (new_e->old_chunk == (e->old_chunk - 1) &&
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new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
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dm_consecutive_chunk_count_inc(e);
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e->old_chunk--;
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e->new_chunk--;
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free_exception(new_e);
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return;
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}
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if (new_e->old_chunk > e->old_chunk)
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break;
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}
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out:
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list_add(&new_e->hash_list, e ? &e->hash_list : l);
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}
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/*
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* Callback used by the exception stores to load exceptions when
|
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* initialising.
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*/
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static int dm_add_exception(void *context, chunk_t old, chunk_t new)
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{
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struct dm_snapshot *s = context;
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struct dm_snap_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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/* Consecutive_count is implicitly initialised to zero */
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e->new_chunk = new;
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insert_completed_exception(s, 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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/*
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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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/*
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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->store->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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|
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hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
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hash_size = min(hash_size, max_buckets);
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|
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hash_size = rounddown_pow_of_two(hash_size);
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if (init_exception_table(&s->complete, hash_size,
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DM_CHUNK_CONSECUTIVE_BITS))
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return -ENOMEM;
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|
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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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|
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if (init_exception_table(&s->pending, hash_size, 0)) {
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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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|
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return 0;
|
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}
|
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|
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/*
|
|
* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
|
|
*/
|
|
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
|
|
{
|
|
struct dm_snapshot *s;
|
|
int i;
|
|
int r = -EINVAL;
|
|
char *origin_path;
|
|
struct dm_exception_store *store;
|
|
unsigned args_used;
|
|
|
|
if (argc != 4) {
|
|
ti->error = "requires exactly 4 arguments";
|
|
r = -EINVAL;
|
|
goto bad_args;
|
|
}
|
|
|
|
origin_path = argv[0];
|
|
argv++;
|
|
argc--;
|
|
|
|
r = dm_exception_store_create(ti, argc, argv, &args_used, &store);
|
|
if (r) {
|
|
ti->error = "Couldn't create exception store";
|
|
r = -EINVAL;
|
|
goto bad_args;
|
|
}
|
|
|
|
argv += args_used;
|
|
argc -= args_used;
|
|
|
|
s = kmalloc(sizeof(*s), GFP_KERNEL);
|
|
if (!s) {
|
|
ti->error = "Cannot allocate snapshot context private "
|
|
"structure";
|
|
r = -ENOMEM;
|
|
goto bad_snap;
|
|
}
|
|
|
|
r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
|
|
if (r) {
|
|
ti->error = "Cannot get origin device";
|
|
goto bad_origin;
|
|
}
|
|
|
|
s->store = store;
|
|
s->valid = 1;
|
|
s->active = 0;
|
|
atomic_set(&s->pending_exceptions_count, 0);
|
|
init_rwsem(&s->lock);
|
|
spin_lock_init(&s->pe_lock);
|
|
|
|
/* Allocate hash table for COW data */
|
|
if (init_hash_tables(s)) {
|
|
ti->error = "Unable to allocate hash table space";
|
|
r = -ENOMEM;
|
|
goto bad_hash_tables;
|
|
}
|
|
|
|
r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
|
|
if (r) {
|
|
ti->error = "Could not create kcopyd client";
|
|
goto bad_kcopyd;
|
|
}
|
|
|
|
s->pending_pool = mempool_create_slab_pool(MIN_IOS, pending_cache);
|
|
if (!s->pending_pool) {
|
|
ti->error = "Could not allocate mempool for pending exceptions";
|
|
goto bad_pending_pool;
|
|
}
|
|
|
|
s->tracked_chunk_pool = mempool_create_slab_pool(MIN_IOS,
|
|
tracked_chunk_cache);
|
|
if (!s->tracked_chunk_pool) {
|
|
ti->error = "Could not allocate tracked_chunk mempool for "
|
|
"tracking reads";
|
|
goto bad_tracked_chunk_pool;
|
|
}
|
|
|
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
|
|
INIT_HLIST_HEAD(&s->tracked_chunk_hash[i]);
|
|
|
|
spin_lock_init(&s->tracked_chunk_lock);
|
|
|
|
/* Metadata must only be loaded into one table at once */
|
|
r = s->store->type->read_metadata(s->store, dm_add_exception,
|
|
(void *)s);
|
|
if (r < 0) {
|
|
ti->error = "Failed to read snapshot metadata";
|
|
goto bad_load_and_register;
|
|
} else if (r > 0) {
|
|
s->valid = 0;
|
|
DMWARN("Snapshot is marked invalid.");
|
|
}
|
|
|
|
bio_list_init(&s->queued_bios);
|
|
INIT_WORK(&s->queued_bios_work, flush_queued_bios);
|
|
|
|
/* Add snapshot to the list of snapshots for this origin */
|
|
/* Exceptions aren't triggered till snapshot_resume() is called */
|
|
if (register_snapshot(s)) {
|
|
r = -EINVAL;
|
|
ti->error = "Cannot register snapshot origin";
|
|
goto bad_load_and_register;
|
|
}
|
|
|
|
ti->private = s;
|
|
ti->split_io = s->store->chunk_size;
|
|
ti->num_flush_requests = 1;
|
|
|
|
return 0;
|
|
|
|
bad_load_and_register:
|
|
mempool_destroy(s->tracked_chunk_pool);
|
|
|
|
bad_tracked_chunk_pool:
|
|
mempool_destroy(s->pending_pool);
|
|
|
|
bad_pending_pool:
|
|
dm_kcopyd_client_destroy(s->kcopyd_client);
|
|
|
|
bad_kcopyd:
|
|
exit_exception_table(&s->pending, pending_cache);
|
|
exit_exception_table(&s->complete, exception_cache);
|
|
|
|
bad_hash_tables:
|
|
dm_put_device(ti, s->origin);
|
|
|
|
bad_origin:
|
|
kfree(s);
|
|
|
|
bad_snap:
|
|
dm_exception_store_destroy(store);
|
|
|
|
bad_args:
|
|
return r;
|
|
}
|
|
|
|
static void __free_exceptions(struct dm_snapshot *s)
|
|
{
|
|
dm_kcopyd_client_destroy(s->kcopyd_client);
|
|
s->kcopyd_client = NULL;
|
|
|
|
exit_exception_table(&s->pending, pending_cache);
|
|
exit_exception_table(&s->complete, exception_cache);
|
|
}
|
|
|
|
static void snapshot_dtr(struct dm_target *ti)
|
|
{
|
|
#ifdef CONFIG_DM_DEBUG
|
|
int i;
|
|
#endif
|
|
struct dm_snapshot *s = ti->private;
|
|
|
|
flush_workqueue(ksnapd);
|
|
|
|
/* Prevent further origin writes from using this snapshot. */
|
|
/* After this returns there can be no new kcopyd jobs. */
|
|
unregister_snapshot(s);
|
|
|
|
while (atomic_read(&s->pending_exceptions_count))
|
|
msleep(1);
|
|
/*
|
|
* Ensure instructions in mempool_destroy aren't reordered
|
|
* before atomic_read.
|
|
*/
|
|
smp_mb();
|
|
|
|
#ifdef CONFIG_DM_DEBUG
|
|
for (i = 0; i < DM_TRACKED_CHUNK_HASH_SIZE; i++)
|
|
BUG_ON(!hlist_empty(&s->tracked_chunk_hash[i]));
|
|
#endif
|
|
|
|
mempool_destroy(s->tracked_chunk_pool);
|
|
|
|
__free_exceptions(s);
|
|
|
|
mempool_destroy(s->pending_pool);
|
|
|
|
dm_put_device(ti, s->origin);
|
|
|
|
dm_exception_store_destroy(s->store);
|
|
|
|
kfree(s);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
generic_make_request(bio);
|
|
bio = n;
|
|
}
|
|
}
|
|
|
|
static void flush_queued_bios(struct work_struct *work)
|
|
{
|
|
struct dm_snapshot *s =
|
|
container_of(work, struct dm_snapshot, queued_bios_work);
|
|
struct bio *queued_bios;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&s->pe_lock, flags);
|
|
queued_bios = bio_list_get(&s->queued_bios);
|
|
spin_unlock_irqrestore(&s->pe_lock, flags);
|
|
|
|
flush_bios(queued_bios);
|
|
}
|
|
|
|
/*
|
|
* 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 = n;
|
|
}
|
|
}
|
|
|
|
static void __invalidate_snapshot(struct dm_snapshot *s, int err)
|
|
{
|
|
if (!s->valid)
|
|
return;
|
|
|
|
if (err == -EIO)
|
|
DMERR("Invalidating snapshot: Error reading/writing.");
|
|
else if (err == -ENOMEM)
|
|
DMERR("Invalidating snapshot: Unable to allocate exception.");
|
|
|
|
if (s->store->type->drop_snapshot)
|
|
s->store->type->drop_snapshot(s->store);
|
|
|
|
s->valid = 0;
|
|
|
|
dm_table_event(s->store->ti->table);
|
|
}
|
|
|
|
static void get_pending_exception(struct dm_snap_pending_exception *pe)
|
|
{
|
|
atomic_inc(&pe->ref_count);
|
|
}
|
|
|
|
static struct bio *put_pending_exception(struct dm_snap_pending_exception *pe)
|
|
{
|
|
struct dm_snap_pending_exception *primary_pe;
|
|
struct bio *origin_bios = NULL;
|
|
|
|
primary_pe = pe->primary_pe;
|
|
|
|
/*
|
|
* If this pe is involved in a write to the origin and
|
|
* it is the last sibling to complete then release
|
|
* the bios for the original write to the origin.
|
|
*/
|
|
if (primary_pe &&
|
|
atomic_dec_and_test(&primary_pe->ref_count)) {
|
|
origin_bios = bio_list_get(&primary_pe->origin_bios);
|
|
free_pending_exception(primary_pe);
|
|
}
|
|
|
|
/*
|
|
* Free the pe if it's not linked to an origin write or if
|
|
* it's not itself a primary pe.
|
|
*/
|
|
if (!primary_pe || primary_pe != pe)
|
|
free_pending_exception(pe);
|
|
|
|
return origin_bios;
|
|
}
|
|
|
|
static void pending_complete(struct dm_snap_pending_exception *pe, int success)
|
|
{
|
|
struct dm_snap_exception *e;
|
|
struct dm_snapshot *s = pe->snap;
|
|
struct bio *origin_bios = NULL;
|
|
struct bio *snapshot_bios = NULL;
|
|
int error = 0;
|
|
|
|
if (!success) {
|
|
/* Read/write error - snapshot is unusable */
|
|
down_write(&s->lock);
|
|
__invalidate_snapshot(s, -EIO);
|
|
error = 1;
|
|
goto out;
|
|
}
|
|
|
|
e = alloc_exception();
|
|
if (!e) {
|
|
down_write(&s->lock);
|
|
__invalidate_snapshot(s, -ENOMEM);
|
|
error = 1;
|
|
goto out;
|
|
}
|
|
*e = pe->e;
|
|
|
|
down_write(&s->lock);
|
|
if (!s->valid) {
|
|
free_exception(e);
|
|
error = 1;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Check for conflicting reads. This is extremely improbable,
|
|
* so msleep(1) is sufficient and there is no need for a wait queue.
|
|
*/
|
|
while (__chunk_is_tracked(s, pe->e.old_chunk))
|
|
msleep(1);
|
|
|
|
/*
|
|
* Add a proper exception, and remove the
|
|
* in-flight exception from the list.
|
|
*/
|
|
insert_completed_exception(s, e);
|
|
|
|
out:
|
|
remove_exception(&pe->e);
|
|
snapshot_bios = bio_list_get(&pe->snapshot_bios);
|
|
origin_bios = put_pending_exception(pe);
|
|
|
|
up_write(&s->lock);
|
|
|
|
/* Submit any pending write bios */
|
|
if (error)
|
|
error_bios(snapshot_bios);
|
|
else
|
|
flush_bios(snapshot_bios);
|
|
|
|
flush_bios(origin_bios);
|
|
}
|
|
|
|
static void commit_callback(void *context, int success)
|
|
{
|
|
struct dm_snap_pending_exception *pe = 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 long write_err, void *context)
|
|
{
|
|
struct dm_snap_pending_exception *pe = 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->type->commit_exception(s->store, &pe->e,
|
|
commit_callback, pe);
|
|
}
|
|
|
|
/*
|
|
* Dispatches the copy operation to kcopyd.
|
|
*/
|
|
static void start_copy(struct dm_snap_pending_exception *pe)
|
|
{
|
|
struct dm_snapshot *s = pe->snap;
|
|
struct dm_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->store, pe->e.old_chunk);
|
|
src.count = min(s->store->chunk_size, dev_size - src.sector);
|
|
|
|
dest.bdev = s->store->cow->bdev;
|
|
dest.sector = chunk_to_sector(s->store, pe->e.new_chunk);
|
|
dest.count = src.count;
|
|
|
|
/* Hand over to kcopyd */
|
|
dm_kcopyd_copy(s->kcopyd_client,
|
|
&src, 1, &dest, 0, copy_callback, pe);
|
|
}
|
|
|
|
static struct dm_snap_pending_exception *
|
|
__lookup_pending_exception(struct dm_snapshot *s, chunk_t chunk)
|
|
{
|
|
struct dm_snap_exception *e = lookup_exception(&s->pending, chunk);
|
|
|
|
if (!e)
|
|
return NULL;
|
|
|
|
return container_of(e, struct dm_snap_pending_exception, e);
|
|
}
|
|
|
|
/*
|
|
* 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 dm_snap_pending_exception *
|
|
__find_pending_exception(struct dm_snapshot *s,
|
|
struct dm_snap_pending_exception *pe, chunk_t chunk)
|
|
{
|
|
struct dm_snap_pending_exception *pe2;
|
|
|
|
pe2 = __lookup_pending_exception(s, chunk);
|
|
if (pe2) {
|
|
free_pending_exception(pe);
|
|
return pe2;
|
|
}
|
|
|
|
pe->e.old_chunk = chunk;
|
|
bio_list_init(&pe->origin_bios);
|
|
bio_list_init(&pe->snapshot_bios);
|
|
pe->primary_pe = NULL;
|
|
atomic_set(&pe->ref_count, 0);
|
|
pe->started = 0;
|
|
|
|
if (s->store->type->prepare_exception(s->store, &pe->e)) {
|
|
free_pending_exception(pe);
|
|
return NULL;
|
|
}
|
|
|
|
get_pending_exception(pe);
|
|
insert_exception(&s->pending, &pe->e);
|
|
|
|
return pe;
|
|
}
|
|
|
|
static void remap_exception(struct dm_snapshot *s, struct dm_snap_exception *e,
|
|
struct bio *bio, chunk_t chunk)
|
|
{
|
|
bio->bi_bdev = s->store->cow->bdev;
|
|
bio->bi_sector = chunk_to_sector(s->store,
|
|
dm_chunk_number(e->new_chunk) +
|
|
(chunk - e->old_chunk)) +
|
|
(bio->bi_sector &
|
|
s->store->chunk_mask);
|
|
}
|
|
|
|
static int snapshot_map(struct dm_target *ti, struct bio *bio,
|
|
union map_info *map_context)
|
|
{
|
|
struct dm_snap_exception *e;
|
|
struct dm_snapshot *s = ti->private;
|
|
int r = DM_MAPIO_REMAPPED;
|
|
chunk_t chunk;
|
|
struct dm_snap_pending_exception *pe = NULL;
|
|
|
|
if (unlikely(bio_empty_barrier(bio))) {
|
|
bio->bi_bdev = s->store->cow->bdev;
|
|
return DM_MAPIO_REMAPPED;
|
|
}
|
|
|
|
chunk = sector_to_chunk(s->store, bio->bi_sector);
|
|
|
|
/* Full snapshots are not usable */
|
|
/* To get here the table must be live so s->active is always set. */
|
|
if (!s->valid)
|
|
return -EIO;
|
|
|
|
/* FIXME: should only take write lock if we need
|
|
* to copy an exception */
|
|
down_write(&s->lock);
|
|
|
|
if (!s->valid) {
|
|
r = -EIO;
|
|
goto out_unlock;
|
|
}
|
|
|
|
/* If the block is already remapped - use that, else remap it */
|
|
e = lookup_exception(&s->complete, chunk);
|
|
if (e) {
|
|
remap_exception(s, e, bio, chunk);
|
|
goto out_unlock;
|
|
}
|
|
|
|
/*
|
|
* 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) {
|
|
pe = __lookup_pending_exception(s, chunk);
|
|
if (!pe) {
|
|
up_write(&s->lock);
|
|
pe = alloc_pending_exception(s);
|
|
down_write(&s->lock);
|
|
|
|
if (!s->valid) {
|
|
free_pending_exception(pe);
|
|
r = -EIO;
|
|
goto out_unlock;
|
|
}
|
|
|
|
e = lookup_exception(&s->complete, chunk);
|
|
if (e) {
|
|
free_pending_exception(pe);
|
|
remap_exception(s, e, bio, chunk);
|
|
goto out_unlock;
|
|
}
|
|
|
|
pe = __find_pending_exception(s, pe, chunk);
|
|
if (!pe) {
|
|
__invalidate_snapshot(s, -ENOMEM);
|
|
r = -EIO;
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
|
|
remap_exception(s, &pe->e, bio, chunk);
|
|
bio_list_add(&pe->snapshot_bios, bio);
|
|
|
|
r = DM_MAPIO_SUBMITTED;
|
|
|
|
if (!pe->started) {
|
|
/* this is protected by snap->lock */
|
|
pe->started = 1;
|
|
up_write(&s->lock);
|
|
start_copy(pe);
|
|
goto out;
|
|
}
|
|
} else {
|
|
bio->bi_bdev = s->origin->bdev;
|
|
map_context->ptr = track_chunk(s, chunk);
|
|
}
|
|
|
|
out_unlock:
|
|
up_write(&s->lock);
|
|
out:
|
|
return r;
|
|
}
|
|
|
|
static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
|
|
int error, union map_info *map_context)
|
|
{
|
|
struct dm_snapshot *s = ti->private;
|
|
struct dm_snap_tracked_chunk *c = map_context->ptr;
|
|
|
|
if (c)
|
|
stop_tracking_chunk(s, c);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void snapshot_resume(struct dm_target *ti)
|
|
{
|
|
struct dm_snapshot *s = 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)
|
|
{
|
|
unsigned sz = 0;
|
|
struct dm_snapshot *snap = ti->private;
|
|
|
|
switch (type) {
|
|
case STATUSTYPE_INFO:
|
|
if (!snap->valid)
|
|
DMEMIT("Invalid");
|
|
else {
|
|
if (snap->store->type->fraction_full) {
|
|
sector_t numerator, denominator;
|
|
snap->store->type->fraction_full(snap->store,
|
|
&numerator,
|
|
&denominator);
|
|
DMEMIT("%llu/%llu",
|
|
(unsigned long long)numerator,
|
|
(unsigned long long)denominator);
|
|
}
|
|
else
|
|
DMEMIT("Unknown");
|
|
}
|
|
break;
|
|
|
|
case STATUSTYPE_TABLE:
|
|
/*
|
|
* kdevname returns a static pointer so we need
|
|
* to make private copies if the output is to
|
|
* make sense.
|
|
*/
|
|
DMEMIT("%s", snap->origin->name);
|
|
snap->store->type->status(snap->store, type, result + sz,
|
|
maxlen - sz);
|
|
break;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*-----------------------------------------------------------------
|
|
* Origin methods
|
|
*---------------------------------------------------------------*/
|
|
static int __origin_write(struct list_head *snapshots, struct bio *bio)
|
|
{
|
|
int r = DM_MAPIO_REMAPPED, first = 0;
|
|
struct dm_snapshot *snap;
|
|
struct dm_snap_exception *e;
|
|
struct dm_snap_pending_exception *pe, *next_pe, *primary_pe = NULL;
|
|
chunk_t chunk;
|
|
LIST_HEAD(pe_queue);
|
|
|
|
/* Do all the snapshots on this origin */
|
|
list_for_each_entry (snap, snapshots, list) {
|
|
|
|
down_write(&snap->lock);
|
|
|
|
/* Only deal with valid and active snapshots */
|
|
if (!snap->valid || !snap->active)
|
|
goto next_snapshot;
|
|
|
|
/* Nothing to do if writing beyond end of snapshot */
|
|
if (bio->bi_sector >= dm_table_get_size(snap->store->ti->table))
|
|
goto next_snapshot;
|
|
|
|
/*
|
|
* Remember, different snapshots can have
|
|
* different chunk sizes.
|
|
*/
|
|
chunk = sector_to_chunk(snap->store, bio->bi_sector);
|
|
|
|
/*
|
|
* Check exception table to see if block
|
|
* is already remapped in this snapshot
|
|
* and trigger an exception if not.
|
|
*
|
|
* ref_count is initialised to 1 so pending_complete()
|
|
* won't destroy the primary_pe while we're inside this loop.
|
|
*/
|
|
e = lookup_exception(&snap->complete, chunk);
|
|
if (e)
|
|
goto next_snapshot;
|
|
|
|
pe = __lookup_pending_exception(snap, chunk);
|
|
if (!pe) {
|
|
up_write(&snap->lock);
|
|
pe = alloc_pending_exception(snap);
|
|
down_write(&snap->lock);
|
|
|
|
if (!snap->valid) {
|
|
free_pending_exception(pe);
|
|
goto next_snapshot;
|
|
}
|
|
|
|
e = lookup_exception(&snap->complete, chunk);
|
|
if (e) {
|
|
free_pending_exception(pe);
|
|
goto next_snapshot;
|
|
}
|
|
|
|
pe = __find_pending_exception(snap, pe, chunk);
|
|
if (!pe) {
|
|
__invalidate_snapshot(snap, -ENOMEM);
|
|
goto next_snapshot;
|
|
}
|
|
}
|
|
|
|
if (!primary_pe) {
|
|
/*
|
|
* Either every pe here has same
|
|
* primary_pe or none has one yet.
|
|
*/
|
|
if (pe->primary_pe)
|
|
primary_pe = pe->primary_pe;
|
|
else {
|
|
primary_pe = pe;
|
|
first = 1;
|
|
}
|
|
|
|
bio_list_add(&primary_pe->origin_bios, bio);
|
|
|
|
r = DM_MAPIO_SUBMITTED;
|
|
}
|
|
|
|
if (!pe->primary_pe) {
|
|
pe->primary_pe = primary_pe;
|
|
get_pending_exception(primary_pe);
|
|
}
|
|
|
|
if (!pe->started) {
|
|
pe->started = 1;
|
|
list_add_tail(&pe->list, &pe_queue);
|
|
}
|
|
|
|
next_snapshot:
|
|
up_write(&snap->lock);
|
|
}
|
|
|
|
if (!primary_pe)
|
|
return r;
|
|
|
|
/*
|
|
* If this is the first time we're processing this chunk and
|
|
* ref_count is now 1 it means all the pending exceptions
|
|
* got completed while we were in the loop above, so it falls to
|
|
* us here to remove the primary_pe and submit any origin_bios.
|
|
*/
|
|
|
|
if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
|
|
flush_bios(bio_list_get(&primary_pe->origin_bios));
|
|
free_pending_exception(primary_pe);
|
|
/* If we got here, pe_queue is necessarily empty. */
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
* Now that we have a complete pe list we can start the copying.
|
|
*/
|
|
list_for_each_entry_safe(pe, next_pe, &pe_queue, list)
|
|
start_copy(pe);
|
|
|
|
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 = DM_MAPIO_REMAPPED;
|
|
|
|
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 = "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;
|
|
ti->num_flush_requests = 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void origin_dtr(struct dm_target *ti)
|
|
{
|
|
struct dm_dev *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 = ti->private;
|
|
bio->bi_bdev = dev->bdev;
|
|
|
|
if (unlikely(bio_empty_barrier(bio)))
|
|
return DM_MAPIO_REMAPPED;
|
|
|
|
/* Only tell snapshots if this is a write */
|
|
return (bio_rw(bio) == WRITE) ? do_origin(dev, bio) : DM_MAPIO_REMAPPED;
|
|
}
|
|
|
|
#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 = 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->store->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 = 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, 6, 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, 6, 0},
|
|
.module = THIS_MODULE,
|
|
.ctr = snapshot_ctr,
|
|
.dtr = snapshot_dtr,
|
|
.map = snapshot_map,
|
|
.end_io = snapshot_end_io,
|
|
.resume = snapshot_resume,
|
|
.status = snapshot_status,
|
|
};
|
|
|
|
static int __init dm_snapshot_init(void)
|
|
{
|
|
int r;
|
|
|
|
r = dm_exception_store_init();
|
|
if (r) {
|
|
DMERR("Failed to initialize exception stores");
|
|
return 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("Origin target register failed %d", r);
|
|
goto bad1;
|
|
}
|
|
|
|
r = init_origin_hash();
|
|
if (r) {
|
|
DMERR("init_origin_hash failed.");
|
|
goto bad2;
|
|
}
|
|
|
|
exception_cache = KMEM_CACHE(dm_snap_exception, 0);
|
|
if (!exception_cache) {
|
|
DMERR("Couldn't create exception cache.");
|
|
r = -ENOMEM;
|
|
goto bad3;
|
|
}
|
|
|
|
pending_cache = KMEM_CACHE(dm_snap_pending_exception, 0);
|
|
if (!pending_cache) {
|
|
DMERR("Couldn't create pending cache.");
|
|
r = -ENOMEM;
|
|
goto bad4;
|
|
}
|
|
|
|
tracked_chunk_cache = KMEM_CACHE(dm_snap_tracked_chunk, 0);
|
|
if (!tracked_chunk_cache) {
|
|
DMERR("Couldn't create cache to track chunks in use.");
|
|
r = -ENOMEM;
|
|
goto bad5;
|
|
}
|
|
|
|
ksnapd = create_singlethread_workqueue("ksnapd");
|
|
if (!ksnapd) {
|
|
DMERR("Failed to create ksnapd workqueue.");
|
|
r = -ENOMEM;
|
|
goto bad_pending_pool;
|
|
}
|
|
|
|
return 0;
|
|
|
|
bad_pending_pool:
|
|
kmem_cache_destroy(tracked_chunk_cache);
|
|
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)
|
|
{
|
|
destroy_workqueue(ksnapd);
|
|
|
|
dm_unregister_target(&snapshot_target);
|
|
dm_unregister_target(&origin_target);
|
|
|
|
exit_origin_hash();
|
|
kmem_cache_destroy(pending_cache);
|
|
kmem_cache_destroy(exception_cache);
|
|
kmem_cache_destroy(tracked_chunk_cache);
|
|
|
|
dm_exception_store_exit();
|
|
}
|
|
|
|
/* 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");
|