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0596661f0a
When suspending a cache the policy is walked and the individual policy
hints written to the metadata via sync_metadata(). This led to this
lock order:
policy->lock
cache_metadata->root_lock
When loading the cache target the policy is populated while the metadata
lock is held:
cache_metadata->root_lock
policy->lock
Fix this potential lock-inversion (ABBA) deadlock in sync_metadata() by
ensuring the cache_metadata root_lock is held whilst all the hints are
written, rather than being repeatedly locked while policy->lock is held
(as was the case with each callout that policy_walk_mappings() made to
the old save_hint() method).
Found by turning on the CONFIG_PROVE_LOCKING ("Lock debugging: prove
locking correctness") build option. However, it is not clear how the
LOCKDEP reported paths can lead to a deadlock since the two paths,
suspending a target and loading a target, never occur at the same time.
But that doesn't mean the same lock-inversion couldn't have occurred
elsewhere.
Reported-by: Marian Csontos <mcsontos@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
141 lines
4.8 KiB
C
141 lines
4.8 KiB
C
/*
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* Copyright (C) 2012 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*/
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#ifndef DM_CACHE_METADATA_H
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#define DM_CACHE_METADATA_H
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#include "dm-cache-block-types.h"
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#include "dm-cache-policy-internal.h"
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/*----------------------------------------------------------------*/
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#define DM_CACHE_METADATA_BLOCK_SIZE 4096
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/* FIXME: remove this restriction */
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/*
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* The metadata device is currently limited in size.
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*
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* We have one block of index, which can hold 255 index entries. Each
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* index entry contains allocation info about 16k metadata blocks.
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*/
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#define DM_CACHE_METADATA_MAX_SECTORS (255 * (1 << 14) * (DM_CACHE_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
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/*
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* A metadata device larger than 16GB triggers a warning.
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*/
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#define DM_CACHE_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))
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/*----------------------------------------------------------------*/
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/*
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* Ext[234]-style compat feature flags.
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*
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* A new feature which old metadata will still be compatible with should
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* define a DM_CACHE_FEATURE_COMPAT_* flag (rarely useful).
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*
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* A new feature that is not compatible with old code should define a
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* DM_CACHE_FEATURE_INCOMPAT_* flag and guard the relevant code with
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* that flag.
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*
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* A new feature that is not compatible with old code accessing the
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* metadata RDWR should define a DM_CACHE_FEATURE_RO_COMPAT_* flag and
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* guard the relevant code with that flag.
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*
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* As these various flags are defined they should be added to the
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* following masks.
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*/
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#define DM_CACHE_FEATURE_COMPAT_SUPP 0UL
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#define DM_CACHE_FEATURE_COMPAT_RO_SUPP 0UL
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#define DM_CACHE_FEATURE_INCOMPAT_SUPP 0UL
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/*
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* Reopens or creates a new, empty metadata volume.
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* Returns an ERR_PTR on failure.
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*/
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struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
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sector_t data_block_size,
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bool may_format_device,
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size_t policy_hint_size);
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void dm_cache_metadata_close(struct dm_cache_metadata *cmd);
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/*
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* The metadata needs to know how many cache blocks there are. We don't
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* care about the origin, assuming the core target is giving us valid
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* origin blocks to map to.
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*/
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int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size);
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dm_cblock_t dm_cache_size(struct dm_cache_metadata *cmd);
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int dm_cache_discard_bitset_resize(struct dm_cache_metadata *cmd,
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sector_t discard_block_size,
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dm_oblock_t new_nr_entries);
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typedef int (*load_discard_fn)(void *context, sector_t discard_block_size,
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dm_oblock_t dblock, bool discarded);
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int dm_cache_load_discards(struct dm_cache_metadata *cmd,
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load_discard_fn fn, void *context);
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int dm_cache_set_discard(struct dm_cache_metadata *cmd, dm_oblock_t dblock, bool discard);
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int dm_cache_remove_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock);
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int dm_cache_insert_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock, dm_oblock_t oblock);
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int dm_cache_changed_this_transaction(struct dm_cache_metadata *cmd);
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typedef int (*load_mapping_fn)(void *context, dm_oblock_t oblock,
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dm_cblock_t cblock, bool dirty,
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uint32_t hint, bool hint_valid);
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int dm_cache_load_mappings(struct dm_cache_metadata *cmd,
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struct dm_cache_policy *policy,
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load_mapping_fn fn,
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void *context);
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int dm_cache_set_dirty(struct dm_cache_metadata *cmd, dm_cblock_t cblock, bool dirty);
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struct dm_cache_statistics {
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uint32_t read_hits;
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uint32_t read_misses;
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uint32_t write_hits;
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uint32_t write_misses;
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};
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void dm_cache_metadata_get_stats(struct dm_cache_metadata *cmd,
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struct dm_cache_statistics *stats);
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void dm_cache_metadata_set_stats(struct dm_cache_metadata *cmd,
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struct dm_cache_statistics *stats);
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int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown);
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int dm_cache_get_free_metadata_block_count(struct dm_cache_metadata *cmd,
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dm_block_t *result);
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int dm_cache_get_metadata_dev_size(struct dm_cache_metadata *cmd,
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dm_block_t *result);
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void dm_cache_dump(struct dm_cache_metadata *cmd);
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/*
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* The policy is invited to save a 32bit hint value for every cblock (eg,
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* for a hit count). These are stored against the policy name. If
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* policies are changed, then hints will be lost. If the machine crashes,
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* hints will be lost.
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*
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* The hints are indexed by the cblock, but many policies will not
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* neccessarily have a fast way of accessing efficiently via cblock. So
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* rather than querying the policy for each cblock, we let it walk its data
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* structures and fill in the hints in whatever order it wishes.
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*/
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int dm_cache_write_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *p);
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/*
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* Query method. Are all the blocks in the cache clean?
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*/
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int dm_cache_metadata_all_clean(struct dm_cache_metadata *cmd, bool *result);
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/*----------------------------------------------------------------*/
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#endif /* DM_CACHE_METADATA_H */
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