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lvm2/lib/cache/lvmcache.h
David Teigland d9a77e8bb4 lvmcache: simplify metadata cache 
The copy of VG metadata stored in lvmcache was not being used
in general.  It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation.  There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.

This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.

This is a way of passing the VG from suspend to resume in
clvmd.  Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.)  The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo.  These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd.  The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.

suspend has both old (current) and new (precommitted)
copies of the VG metadata.  It stashes both of these in
the vginfo prior to suspending devices.  When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.

resume grabs the VG stashed by suspend.  If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG.  The VG is then used to resume
LVs.

This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.

Sequence of operations:

- lv_suspend() has both vg_old and vg_new
  and stashes a copy of each onto the vginfo:
  lvmcache_save_suspended_vg(vg_old);
  lvmcache_save_suspended_vg(vg_new);

- vg_commit() happens, which causes all clvmd
  instances to call lvmcache_commit_metadata(vg).
  A flag is set in the vginfo indicating the
  transition from the old to new VG:
  vginfo->suspended_vg_committed = 1;

- lv_resume() needs either vg_old or vg_new
  to use in resuming LVs.  It doesn't want to
  read the VG from disk since devices are
  suspended, so it gets the VG stashed by
  lv_suspend:
  vg = lvmcache_get_suspended_vg(vgid);

If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
2018-04-20 11:22:45 -05:00

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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License v.2.1.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _LVM_CACHE_H
#define _LVM_CACHE_H
#include "dev-cache.h"
#include "dev-type.h"
#include "uuid.h"
#include "label.h"
#include "locking.h"
#define ORPHAN_PREFIX VG_ORPHANS
#define ORPHAN_VG_NAME(fmt) ORPHAN_PREFIX "_" fmt
/* LVM specific per-volume info */
/* Eventual replacement for struct physical_volume perhaps? */
struct cmd_context;
struct format_type;
struct volume_group;
struct physical_volume;
struct dm_config_tree;
struct format_instance;
struct metadata_area;
struct disk_locn;
struct lvmcache_vginfo;
/*
* vgsummary represents a summary of the VG that is read
* without a lock. The info does not come through vg_read(),
* but through reading mdas. It provides information about
* the VG that is needed to lock the VG and then read it fully
* with vg_read(), after which the VG summary should be checked
* against the full VG metadata to verify it was correct (since
* it was read without a lock.)
*
* Once read, vgsummary information is saved in lvmcache_vginfo.
*/
struct lvmcache_vgsummary {
const char *vgname;
struct id vgid;
uint64_t vgstatus;
char *creation_host;
const char *system_id;
const char *lock_type;
uint32_t mda_checksum;
size_t mda_size;
};
int lvmcache_init(void);
void lvmcache_allow_reads_with_lvmetad(void);
void lvmcache_destroy(struct cmd_context *cmd, int retain_orphans, int reset);
/*
* lvmcache_label_scan() will scan labels the first time it's
* called, but not on subsequent calls, unless
* lvmcache_force_next_label_scan() is called first
* to force the next lvmcache_label_scan() to scan again.
*/
void lvmcache_force_next_label_scan(void);
int lvmcache_label_scan(struct cmd_context *cmd);
int lvmcache_label_rescan_vg(struct cmd_context *cmd, const char *vgname, const char *vgid);
/* Add/delete a device */
struct lvmcache_info *lvmcache_add(struct labeller *labeller, const char *pvid,
struct device *dev,
const char *vgname, const char *vgid,
uint32_t vgstatus);
int lvmcache_add_orphan_vginfo(const char *vgname, struct format_type *fmt);
void lvmcache_del(struct lvmcache_info *info);
/* Update things */
int lvmcache_update_vgname_and_id(struct lvmcache_info *info,
struct lvmcache_vgsummary *vgsummary);
int lvmcache_update_vg(struct volume_group *vg, unsigned precommitted);
void lvmcache_lock_vgname(const char *vgname, int read_only);
void lvmcache_unlock_vgname(const char *vgname);
int lvmcache_verify_lock_order(const char *vgname);
/* Queries */
const struct format_type *lvmcache_fmt_from_vgname(struct cmd_context *cmd, const char *vgname, const char *vgid, unsigned revalidate_labels);
int lvmcache_lookup_mda(struct lvmcache_vgsummary *vgsummary);
/* Decrement and test if there are still vg holders in vginfo. */
int lvmcache_vginfo_holders_dec_and_test_for_zero(struct lvmcache_vginfo *vginfo);
struct lvmcache_vginfo *lvmcache_vginfo_from_vgname(const char *vgname,
const char *vgid);
struct lvmcache_vginfo *lvmcache_vginfo_from_vgid(const char *vgid);
struct lvmcache_info *lvmcache_info_from_pvid(const char *pvid, struct device *dev, int valid_only);
const char *lvmcache_vgname_from_vgid(struct dm_pool *mem, const char *vgid);
const char *lvmcache_vgid_from_vgname(struct cmd_context *cmd, const char *vgname);
struct device *lvmcache_device_from_pvid(struct cmd_context *cmd, const struct id *pvid, uint64_t *label_sector);
const char *lvmcache_pvid_from_devname(struct cmd_context *cmd, const char *devname);
char *lvmcache_vgname_from_pvid(struct cmd_context *cmd, const char *pvid);
const char *lvmcache_vgname_from_info(struct lvmcache_info *info);
const struct format_type *lvmcache_fmt_from_info(struct lvmcache_info *info);
int lvmcache_vgs_locked(void);
int lvmcache_vgname_is_locked(const char *vgname);
void lvmcache_seed_infos_from_lvmetad(struct cmd_context *cmd);
/* Returns list of struct dm_str_list containing pool-allocated copy of vgnames */
/* If include_internal is not set, return only proper vg names. */
struct dm_list *lvmcache_get_vgnames(struct cmd_context *cmd,
int include_internal);
/* Returns list of struct dm_str_list containing pool-allocated copy of vgids */
/* If include_internal is not set, return only proper vg ids. */
struct dm_list *lvmcache_get_vgids(struct cmd_context *cmd,
int include_internal);
int lvmcache_get_vgnameids(struct cmd_context *cmd, int include_internal,
struct dm_list *vgnameids);
/* Returns list of struct dm_str_list containing pool-allocated copy of pvids */
struct dm_list *lvmcache_get_pvids(struct cmd_context *cmd, const char *vgname,
const char *vgid);
void lvmcache_drop_metadata(const char *vgname, int drop_precommitted);
void lvmcache_commit_metadata(const char *vgname);
int lvmcache_pvid_is_locked(const char *pvid);
int lvmcache_fid_add_mdas(struct lvmcache_info *info, struct format_instance *fid,
const char *id, int id_len);
int lvmcache_fid_add_mdas_pv(struct lvmcache_info *info, struct format_instance *fid);
int lvmcache_fid_add_mdas_vg(struct lvmcache_vginfo *vginfo, struct format_instance *fid);
int lvmcache_populate_pv_fields(struct lvmcache_info *info,
struct volume_group *vg,
struct physical_volume *pv);
int lvmcache_check_format(struct lvmcache_info *info, const struct format_type *fmt);
void lvmcache_del_mdas(struct lvmcache_info *info);
void lvmcache_del_das(struct lvmcache_info *info);
void lvmcache_del_bas(struct lvmcache_info *info);
int lvmcache_add_mda(struct lvmcache_info *info, struct device *dev,
uint64_t start, uint64_t size, unsigned ignored);
int lvmcache_add_da(struct lvmcache_info *info, uint64_t start, uint64_t size);
int lvmcache_add_ba(struct lvmcache_info *info, uint64_t start, uint64_t size);
void lvmcache_set_ext_version(struct lvmcache_info *info, uint32_t version);
uint32_t lvmcache_ext_version(struct lvmcache_info *info);
void lvmcache_set_ext_flags(struct lvmcache_info *info, uint32_t flags);
uint32_t lvmcache_ext_flags(struct lvmcache_info *info);
const struct format_type *lvmcache_fmt(struct lvmcache_info *info);
struct label *lvmcache_get_label(struct lvmcache_info *info);
void lvmcache_update_pv(struct lvmcache_info *info, struct physical_volume *pv,
const struct format_type *fmt);
int lvmcache_update_das(struct lvmcache_info *info, struct physical_volume *pv);
int lvmcache_update_bas(struct lvmcache_info *info, struct physical_volume *pv);
int lvmcache_foreach_mda(struct lvmcache_info *info,
int (*fun)(struct metadata_area *, void *),
void *baton);
int lvmcache_foreach_da(struct lvmcache_info *info,
int (*fun)(struct disk_locn *, void *),
void *baton);
int lvmcache_foreach_ba(struct lvmcache_info *info,
int (*fun)(struct disk_locn *, void *),
void *baton);
int lvmcache_foreach_pv(struct lvmcache_vginfo *vginfo,
int (*fun)(struct lvmcache_info *, void *), void * baton);
uint64_t lvmcache_device_size(struct lvmcache_info *info);
void lvmcache_set_device_size(struct lvmcache_info *info, uint64_t size);
struct device *lvmcache_device(struct lvmcache_info *info);
void lvmcache_make_valid(struct lvmcache_info *info);
int lvmcache_is_orphan(struct lvmcache_info *info);
int lvmcache_uncertain_ownership(struct lvmcache_info *info);
unsigned lvmcache_mda_count(struct lvmcache_info *info);
int lvmcache_vgid_is_cached(const char *vgid);
uint64_t lvmcache_smallest_mda_size(struct lvmcache_info *info);
int lvmcache_found_duplicate_pvs(void);
int lvmcache_get_unused_duplicate_devs(struct cmd_context *cmd, struct dm_list *head);
int vg_has_duplicate_pvs(struct volume_group *vg);
int lvmcache_contains_lock_type_sanlock(struct cmd_context *cmd);
void lvmcache_get_max_name_lengths(struct cmd_context *cmd,
unsigned *pv_max_name_len, unsigned *vg_max_name_len);
int lvmcache_vg_is_foreign(struct cmd_context *cmd, const char *vgname, const char *vgid);
void lvmcache_lock_ordering(int enable);
int lvmcache_dev_is_unchosen_duplicate(struct device *dev);
void lvmcache_remove_unchosen_duplicate(struct device *dev);
int lvmcache_pvid_in_unchosen_duplicates(const char *pvid);
int lvmcache_get_vg_devs(struct cmd_context *cmd,
struct lvmcache_vginfo *vginfo,
struct dm_list *devs);
void lvmcache_set_independent_location(const char *vgname);
void lvmcache_save_suspended_vg(struct volume_group *vg, int precommitted);
struct volume_group *lvmcache_get_suspended_vg(const char *vgid);
void lvmcache_drop_suspended_vg(struct volume_group *vg);
#endif
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