7513c2a761
The logging API needs an extra function to make cluster mirroring possible. This new function allows us to check whether a mirror region is being recovered on another machine in the cluster. This helps us prevent simultaneous recovery I/O and process I/O to the same locations on disk. Cluster-aware log modules will implement this function. Single machine log modules will not. So, there is no performance penalty for single machine mirrors. Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Acked-by: Heinz Mauelshagen <heinzm@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
144 lines
3.9 KiB
C
144 lines
3.9 KiB
C
/*
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* Copyright (C) 2003 Sistina Software
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* Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
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*
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* Device-Mapper dirty region log.
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*
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* This file is released under the LGPL.
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*/
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#ifndef _LINUX_DM_DIRTY_LOG
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#define _LINUX_DM_DIRTY_LOG
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#ifdef __KERNEL__
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#include <linux/types.h>
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#include <linux/device-mapper.h>
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typedef sector_t region_t;
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struct dm_dirty_log_type;
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struct dm_dirty_log {
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struct dm_dirty_log_type *type;
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void *context;
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};
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struct dm_dirty_log_type {
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const char *name;
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struct module *module;
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/* For internal device-mapper use */
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struct list_head list;
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int (*ctr)(struct dm_dirty_log *log, struct dm_target *ti,
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unsigned argc, char **argv);
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void (*dtr)(struct dm_dirty_log *log);
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/*
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* There are times when we don't want the log to touch
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* the disk.
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*/
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int (*presuspend)(struct dm_dirty_log *log);
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int (*postsuspend)(struct dm_dirty_log *log);
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int (*resume)(struct dm_dirty_log *log);
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/*
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* Retrieves the smallest size of region that the log can
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* deal with.
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*/
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uint32_t (*get_region_size)(struct dm_dirty_log *log);
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/*
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* A predicate to say whether a region is clean or not.
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* May block.
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*/
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int (*is_clean)(struct dm_dirty_log *log, region_t region);
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/*
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* Returns: 0, 1, -EWOULDBLOCK, < 0
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*
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* A predicate function to check the area given by
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* [sector, sector + len) is in sync.
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*
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* If -EWOULDBLOCK is returned the state of the region is
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* unknown, typically this will result in a read being
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* passed to a daemon to deal with, since a daemon is
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* allowed to block.
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*/
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int (*in_sync)(struct dm_dirty_log *log, region_t region,
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int can_block);
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/*
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* Flush the current log state (eg, to disk). This
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* function may block.
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*/
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int (*flush)(struct dm_dirty_log *log);
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/*
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* Mark an area as clean or dirty. These functions may
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* block, though for performance reasons blocking should
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* be extremely rare (eg, allocating another chunk of
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* memory for some reason).
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*/
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void (*mark_region)(struct dm_dirty_log *log, region_t region);
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void (*clear_region)(struct dm_dirty_log *log, region_t region);
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/*
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* Returns: <0 (error), 0 (no region), 1 (region)
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*
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* The mirrord will need perform recovery on regions of
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* the mirror that are in the NOSYNC state. This
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* function asks the log to tell the caller about the
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* next region that this machine should recover.
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*
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* Do not confuse this function with 'in_sync()', one
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* tells you if an area is synchronised, the other
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* assigns recovery work.
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*/
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int (*get_resync_work)(struct dm_dirty_log *log, region_t *region);
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/*
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* This notifies the log that the resync status of a region
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* has changed. It also clears the region from the recovering
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* list (if present).
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*/
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void (*set_region_sync)(struct dm_dirty_log *log,
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region_t region, int in_sync);
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/*
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* Returns the number of regions that are in sync.
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*/
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region_t (*get_sync_count)(struct dm_dirty_log *log);
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/*
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* Support function for mirror status requests.
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*/
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int (*status)(struct dm_dirty_log *log, status_type_t status_type,
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char *result, unsigned maxlen);
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/*
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* is_remote_recovering is necessary for cluster mirroring. It provides
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* a way to detect recovery on another node, so we aren't writing
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* concurrently. This function is likely to block (when a cluster log
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* is used).
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*
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* Returns: 0, 1
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*/
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int (*is_remote_recovering)(struct dm_dirty_log *log, region_t region);
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};
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int dm_dirty_log_type_register(struct dm_dirty_log_type *type);
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int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type);
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/*
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* Make sure you use these two functions, rather than calling
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* type->constructor/destructor() directly.
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*/
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struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
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struct dm_target *ti,
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unsigned argc, char **argv);
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void dm_dirty_log_destroy(struct dm_dirty_log *log);
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#endif /* __KERNEL__ */
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#endif /* _LINUX_DM_DIRTY_LOG_H */
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