linux/drivers/md/dm-exception-store.h
Linus Torvalds 311f71281f - Improve DM snapshot target's scalability by using finer grained
locking.  Requires some list_bl interface improvements.
 
 - Add ability for DM integrity to use a bitmap mode, that tracks regions
   where data and metadata are out of sync, instead of using a journal.
 
 - Improve DM thin provisioning target to not write metadata changes to
   disk if the thin-pool and associated thin devices are merely
   activated but not used.  This avoids metadata corruption due to
   concurrent activation of thin devices across different OS instances
   (e.g. split brain scenarios, which ultimately would be avoided if
   proper device filters were used -- but not having proper filtering has
   proven a very common configuration mistake)
 
 - Fix missing call to path selector type->end_io in DM multipath.  This
   fixes reported performance problems due to inaccurate path selector IO
   accounting causing an imbalance of IO (e.g. avoiding issuing IO to
   particular path due to it seemingly being heavily used).
 
 - Fix bug in DM cache metadata's loading of its discard bitset that
   could lead to all cache blocks being discarded if the very first cache
   block was discarded (thankfully in practice the first cache block is
   generally in use; be it FS superblock, partition table, disk label,
   etc).
 
 - Add testing-only DM dust target which simulates a device that has
   failing sectors and/or read failures.
 
 - Fix a DM init error path reference count hang that caused boot hangs
   if user supplied malformed input on kernel commandline.
 
 - Fix a couple issues with DM crypt target's logging being overly
   verbose or lacking context.
 
 - Various other small fixes to DM init, DM multipath, DM zoned, and DM
   crypt.
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Merge tag 'for-5.2/dm-changes-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:

 - Improve DM snapshot target's scalability by using finer grained
   locking. Requires some list_bl interface improvements.

 - Add ability for DM integrity to use a bitmap mode, that tracks
   regions where data and metadata are out of sync, instead of using a
   journal.

 - Improve DM thin provisioning target to not write metadata changes to
   disk if the thin-pool and associated thin devices are merely
   activated but not used. This avoids metadata corruption due to
   concurrent activation of thin devices across different OS instances
   (e.g. split brain scenarios, which ultimately would be avoided if
   proper device filters were used -- but not having proper filtering
   has proven a very common configuration mistake)

 - Fix missing call to path selector type->end_io in DM multipath. This
   fixes reported performance problems due to inaccurate path selector
   IO accounting causing an imbalance of IO (e.g. avoiding issuing IO to
   particular path due to it seemingly being heavily used).

 - Fix bug in DM cache metadata's loading of its discard bitset that
   could lead to all cache blocks being discarded if the very first
   cache block was discarded (thankfully in practice the first cache
   block is generally in use; be it FS superblock, partition table, disk
   label, etc).

 - Add testing-only DM dust target which simulates a device that has
   failing sectors and/or read failures.

 - Fix a DM init error path reference count hang that caused boot hangs
   if user supplied malformed input on kernel commandline.

 - Fix a couple issues with DM crypt target's logging being overly
   verbose or lacking context.

 - Various other small fixes to DM init, DM multipath, DM zoned, and DM
   crypt.

* tag 'for-5.2/dm-changes-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (42 commits)
  dm: fix a couple brace coding style issues
  dm crypt: print device name in integrity error message
  dm crypt: move detailed message into debug level
  dm ioctl: fix hang in early create error condition
  dm integrity: whitespace, coding style and dead code cleanup
  dm integrity: implement synchronous mode for reboot handling
  dm integrity: handle machine reboot in bitmap mode
  dm integrity: add a bitmap mode
  dm integrity: introduce a function add_new_range_and_wait()
  dm integrity: allow large ranges to be described
  dm ingerity: pass size to dm_integrity_alloc_page_list()
  dm integrity: introduce rw_journal_sectors()
  dm integrity: update documentation
  dm integrity: don't report unused options
  dm integrity: don't check null pointer before kvfree and vfree
  dm integrity: correctly calculate the size of metadata area
  dm dust: Make dm_dust_init and dm_dust_exit static
  dm dust: remove redundant unsigned comparison to less than zero
  dm mpath: always free attached_handler_name in parse_path()
  dm init: fix max devices/targets checks
  ...
2019-05-16 15:55:48 -07:00

206 lines
5.3 KiB
C

/*
* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
* Copyright (C) 2008 Red Hat, Inc. All rights reserved.
*
* Device-mapper snapshot exception store.
*
* This file is released under the GPL.
*/
#ifndef _LINUX_DM_EXCEPTION_STORE
#define _LINUX_DM_EXCEPTION_STORE
#include <linux/blkdev.h>
#include <linux/list_bl.h>
#include <linux/device-mapper.h>
/*
* The snapshot code deals with largish chunks of the disk at a
* time. Typically 32k - 512k.
*/
typedef sector_t chunk_t;
/*
* An exception is used where an old chunk of data has been
* replaced by a new one.
* If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
* of chunks that follow contiguously. Remaining bits hold the number of the
* chunk within the device.
*/
struct dm_exception {
struct hlist_bl_node hash_list;
chunk_t old_chunk;
chunk_t new_chunk;
};
/*
* Abstraction to handle the meta/layout of exception stores (the
* COW device).
*/
struct dm_exception_store;
struct dm_exception_store_type {
const char *name;
struct module *module;
int (*ctr) (struct dm_exception_store *store, char *options);
/*
* Destroys this object when you've finished with it.
*/
void (*dtr) (struct dm_exception_store *store);
/*
* The target shouldn't read the COW device until this is
* called. As exceptions are read from the COW, they are
* reported back via the callback.
*/
int (*read_metadata) (struct dm_exception_store *store,
int (*callback)(void *callback_context,
chunk_t old, chunk_t new),
void *callback_context);
/*
* Find somewhere to store the next exception.
*/
int (*prepare_exception) (struct dm_exception_store *store,
struct dm_exception *e);
/*
* Update the metadata with this exception.
*/
void (*commit_exception) (struct dm_exception_store *store,
struct dm_exception *e, int valid,
void (*callback) (void *, int success),
void *callback_context);
/*
* Returns 0 if the exception store is empty.
*
* If there are exceptions still to be merged, sets
* *last_old_chunk and *last_new_chunk to the most recent
* still-to-be-merged chunk and returns the number of
* consecutive previous ones.
*/
int (*prepare_merge) (struct dm_exception_store *store,
chunk_t *last_old_chunk, chunk_t *last_new_chunk);
/*
* Clear the last n exceptions.
* nr_merged must be <= the value returned by prepare_merge.
*/
int (*commit_merge) (struct dm_exception_store *store, int nr_merged);
/*
* The snapshot is invalid, note this in the metadata.
*/
void (*drop_snapshot) (struct dm_exception_store *store);
unsigned (*status) (struct dm_exception_store *store,
status_type_t status, char *result,
unsigned maxlen);
/*
* Return how full the snapshot is.
*/
void (*usage) (struct dm_exception_store *store,
sector_t *total_sectors, sector_t *sectors_allocated,
sector_t *metadata_sectors);
/* For internal device-mapper use only. */
struct list_head list;
};
struct dm_snapshot;
struct dm_exception_store {
struct dm_exception_store_type *type;
struct dm_snapshot *snap;
/* Size of data blocks saved - must be a power of 2 */
unsigned chunk_size;
unsigned chunk_mask;
unsigned chunk_shift;
void *context;
bool userspace_supports_overflow;
};
/*
* Obtain the origin or cow device used by a given snapshot.
*/
struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
/*
* Funtions to manipulate consecutive chunks
*/
#define DM_CHUNK_CONSECUTIVE_BITS 8
#define DM_CHUNK_NUMBER_BITS 56
static inline chunk_t dm_chunk_number(chunk_t chunk)
{
return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
}
static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
{
return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
}
static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
{
e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
BUG_ON(!dm_consecutive_chunk_count(e));
}
static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
{
BUG_ON(!dm_consecutive_chunk_count(e));
e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
}
/*
* Return the number of sectors in the device.
*/
static inline sector_t get_dev_size(struct block_device *bdev)
{
return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
}
static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
sector_t sector)
{
return sector >> store->chunk_shift;
}
int dm_exception_store_type_register(struct dm_exception_store_type *type);
int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
unsigned chunk_size,
char **error);
int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
struct dm_snapshot *snap,
unsigned *args_used,
struct dm_exception_store **store);
void dm_exception_store_destroy(struct dm_exception_store *store);
int dm_exception_store_init(void);
void dm_exception_store_exit(void);
/*
* Two exception store implementations.
*/
int dm_persistent_snapshot_init(void);
void dm_persistent_snapshot_exit(void);
int dm_transient_snapshot_init(void);
void dm_transient_snapshot_exit(void);
#endif /* _LINUX_DM_EXCEPTION_STORE */