linux/drivers/md/persistent-data/dm-space-map-metadata.h
Mike Snitzer 7d48935eff dm thin: allow metadata space larger than supported to go unused
It was always intended that a user could provide a thin metadata device
that is larger than the max supported by the on-disk format.  The extra
space would just go unused.

Unfortunately that never worked.  If the user attempted to use a larger
metadata device on creation they would get an error like the following:

 device-mapper: space map common: space map too large
 device-mapper: transaction manager: couldn't create metadata space map
 device-mapper: thin metadata: tm_create_with_sm failed
 device-mapper: table: 252:17: thin-pool: Error creating metadata object
 device-mapper: ioctl: error adding target to table

Fix this by allowing the initial metadata space map creation to cap its
size at the max number of blocks supported (DM_SM_METADATA_MAX_BLOCKS).
get_metadata_dev_size() must also impose DM_SM_METADATA_MAX_BLOCKS (via
THIN_METADATA_MAX_SECTORS), otherwise extending metadata would cap at
THIN_METADATA_MAX_SECTORS_WARNING (which is larger than supported).

Also, the calculation for THIN_METADATA_MAX_SECTORS didn't account for
the sizeof the disk_bitmap_header.  So the supported maximum metadata
size is a bit smaller (reduced from 33423360 to 33292800 sectors).

Lastly, remove the "excess space will not be used" warning message from
get_metadata_dev_size(); it resulted in printing the warning multiple
times.  Factor out warn_if_metadata_device_too_big(), call it from
pool_ctr() and maybe_resize_metadata_dev().

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
2014-02-27 11:49:08 -05:00

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1.1 KiB
C

/*
* Copyright (C) 2011 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#ifndef DM_SPACE_MAP_METADATA_H
#define DM_SPACE_MAP_METADATA_H
#include "dm-transaction-manager.h"
#define DM_SM_METADATA_BLOCK_SIZE (4096 >> SECTOR_SHIFT)
/*
* The metadata device is currently limited in size.
*
* We have one block of index, which can hold 255 index entries. Each
* index entry contains allocation info about ~16k metadata blocks.
*/
#define DM_SM_METADATA_MAX_BLOCKS (255 * ((1 << 14) - 64))
#define DM_SM_METADATA_MAX_SECTORS (DM_SM_METADATA_MAX_BLOCKS * DM_SM_METADATA_BLOCK_SIZE)
/*
* Unfortunately we have to use two-phase construction due to the cycle
* between the tm and sm.
*/
struct dm_space_map *dm_sm_metadata_init(void);
/*
* Create a fresh space map.
*/
int dm_sm_metadata_create(struct dm_space_map *sm,
struct dm_transaction_manager *tm,
dm_block_t nr_blocks,
dm_block_t superblock);
/*
* Open from a previously-recorded root.
*/
int dm_sm_metadata_open(struct dm_space_map *sm,
struct dm_transaction_manager *tm,
void *root_le, size_t len);
#endif /* DM_SPACE_MAP_METADATA_H */