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lvm2/lib/metadata/snapshot_manip.c
Zdenek Kabelac 63c50ced89 snapshot: relocate common code validation for snapshot origin
Since both lvcreate and lvconvert needs to check for same
type of allowed origin for snapshot - move the code into
a single function.

This way we also fix several inconsitencies where snapshot
has been allowed by mistake either through lvcreate or
lvconvert path.
2017-10-27 17:07:42 +02:00

433 lines
12 KiB
C

/*
* Copyright (C) 2002-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2006 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
*/
#include "lib.h"
#include "metadata.h"
#include "segtype.h"
#include "locking.h"
#include "toolcontext.h"
#include "lv_alloc.h"
#include "activate.h"
#define SNAPSHOT_MIN_CHUNKS 3 /* Minimum number of chunks in snapshot */
int lv_is_origin(const struct logical_volume *lv)
{
return lv->origin_count ? 1 : 0;
}
int lv_is_cow(const struct logical_volume *lv)
{
/* Make sure a merging thin origin isn't confused as a cow LV */
return (!lv_is_thin_volume(lv) && !lv_is_origin(lv) && lv->snapshot) ? 1 : 0;
}
struct logical_volume *find_cow(const struct logical_volume *snap)
{
return first_seg(snap)->cow;
}
/*
* Some kernels have a bug that they may leak space in the snapshot on crash.
* If the kernel is buggy, we add some extra space.
*/
static uint64_t _cow_extra_chunks(struct cmd_context *cmd, uint64_t n_chunks)
{
const struct segment_type *segtype;
unsigned attrs = 0;
if (activation() &&
(segtype = get_segtype_from_string(cmd, SEG_TYPE_NAME_SNAPSHOT)) &&
segtype->ops->target_present &&
segtype->ops->target_present(cmd, NULL, &attrs) &&
(attrs & SNAPSHOT_FEATURE_FIXED_LEAK))
return 0;
return (n_chunks + 63) / 64;
}
static uint64_t _cow_max_size(struct cmd_context *cmd, uint64_t origin_size, uint32_t chunk_size)
{
/* Snapshot disk layout:
* COW is divided into chunks
* 1st. chunk is reserved for header
* 2nd. chunk is the 1st. metadata chunk
* 3rd. chunk is the 1st. data chunk
*/
uint64_t origin_chunks = (origin_size + chunk_size - 1) / chunk_size;
uint64_t chunks_per_metadata_area = (uint64_t)chunk_size << (SECTOR_SHIFT - 4);
/*
* Note: if origin_chunks is divisible by chunks_per_metadata_area, we
* need one extra metadata chunk as a terminator.
*/
uint64_t metadata_chunks = (origin_chunks + chunks_per_metadata_area) / chunks_per_metadata_area;
uint64_t n_chunks = 1 + origin_chunks + metadata_chunks;
return (n_chunks + _cow_extra_chunks(cmd, n_chunks)) * chunk_size;
}
uint32_t cow_max_extents(const struct logical_volume *origin, uint32_t chunk_size)
{
uint64_t size = _cow_max_size(origin->vg->cmd, origin->size, chunk_size);
uint32_t extent_size = origin->vg->extent_size;
uint64_t max_size = (uint64_t) MAX_EXTENT_COUNT * extent_size;
if (size % extent_size)
size += extent_size - size % extent_size;
if (size > max_size)
size = max_size; /* Origin is too big for 100% snapshot anyway */
return (uint32_t) (size / extent_size);
}
int cow_has_min_chunks(const struct volume_group *vg, uint32_t cow_extents, uint32_t chunk_size)
{
if (((uint64_t)vg->extent_size * cow_extents) >= (SNAPSHOT_MIN_CHUNKS * chunk_size))
return 1;
log_error("Snapshot volume cannot be smaller than " DM_TO_STRING(SNAPSHOT_MIN_CHUNKS)
" chunks (%u extents, %s).", (unsigned)
(((uint64_t) SNAPSHOT_MIN_CHUNKS * chunk_size +
vg->extent_size - 1) / vg->extent_size),
display_size(vg->cmd, (uint64_t) SNAPSHOT_MIN_CHUNKS * chunk_size));
return 0;
}
int lv_is_cow_covering_origin(const struct logical_volume *lv)
{
return lv_is_cow(lv) &&
(lv->size >= _cow_max_size(lv->vg->cmd, origin_from_cow(lv)->size,
find_snapshot(lv)->chunk_size));
}
int lv_is_visible(const struct logical_volume *lv)
{
if (lv_is_historical(lv))
return 1;
if (lv_is_snapshot(lv))
return 0;
if (lv_is_cow(lv)) {
if (lv_is_virtual_origin(origin_from_cow(lv)))
return 1;
if (lv_is_merging_cow(lv))
return 0;
return lv_is_visible(origin_from_cow(lv));
}
return lv->status & VISIBLE_LV ? 1 : 0;
}
int lv_is_merging_cow(const struct logical_volume *cow)
{
struct lv_segment *snap_seg;
if (!lv_is_cow(cow))
return 0;
snap_seg = find_snapshot(cow);
/* checks lv_segment's status to see if snapshot is merging */
return (snap_seg && (snap_seg->status & MERGING)) ? 1 : 0;
}
struct lv_segment *find_snapshot(const struct logical_volume *lv)
{
return lv->snapshot;
}
/* Given a cow LV, return its origin */
struct logical_volume *origin_from_cow(const struct logical_volume *lv)
{
if (lv->snapshot)
return lv->snapshot->origin;
return NULL;
}
void init_snapshot_seg(struct lv_segment *seg, struct logical_volume *origin,
struct logical_volume *cow, uint32_t chunk_size, int merge)
{
seg->chunk_size = chunk_size;
seg->origin = origin;
seg->cow = cow;
lv_set_hidden(cow);
cow->snapshot = seg;
origin->origin_count++;
/* FIXME Assumes an invisible origin belongs to a sparse device */
if (!lv_is_visible(origin))
origin->status |= VIRTUAL_ORIGIN;
seg->lv->status |= (SNAPSHOT | VIRTUAL);
if (merge)
init_snapshot_merge(seg, origin);
dm_list_add(&origin->snapshot_segs, &seg->origin_list);
}
void init_snapshot_merge(struct lv_segment *snap_seg,
struct logical_volume *origin)
{
snap_seg->status |= MERGING;
origin->snapshot = snap_seg;
origin->status |= MERGING;
if (seg_is_thin_volume(snap_seg)) {
snap_seg->merge_lv = origin;
/* Making thin LV invisible with regular log */
lv_set_hidden(snap_seg->lv);
return;
}
/*
* Even though lv_is_visible(snap_seg->lv) returns 0,
* the snap_seg->lv (name: snapshotX) is _not_ hidden;
* this is part of the lvm2 snapshot fiction. Must
* clear VISIBLE_LV directly (lv_set_visible can't)
* - snap_seg->lv->status is used to control whether 'lv'
* (with user provided snapshot LV name) is visible
* - this also enables vg_validate() to succeed with
* merge metadata (snap_seg->lv is now "internal")
*/
snap_seg->lv->status &= ~VISIBLE_LV;
}
void clear_snapshot_merge(struct logical_volume *origin)
{
/* clear merge attributes */
if (origin->snapshot->merge_lv)
/* Removed thin volume has to be visible */
lv_set_visible(origin->snapshot->lv);
origin->snapshot->merge_lv = NULL;
origin->snapshot->status &= ~MERGING;
origin->snapshot = NULL;
origin->status &= ~MERGING;
}
static struct lv_segment *_alloc_snapshot_seg(struct logical_volume *lv)
{
struct lv_segment *seg;
const struct segment_type *segtype;
segtype = get_segtype_from_string(lv->vg->cmd, SEG_TYPE_NAME_SNAPSHOT);
if (!segtype) {
log_error("Failed to find snapshot segtype");
return NULL;
}
if (!(seg = alloc_lv_segment(segtype, lv, 0, lv->le_count, 0, 0, 0,
NULL, 0, lv->le_count, 0, 0, 0, 0, NULL))) {
log_error("Couldn't allocate new snapshot segment.");
return NULL;
}
dm_list_add(&lv->segments, &seg->list);
return seg;
}
int vg_add_snapshot(struct logical_volume *origin,
struct logical_volume *cow, union lvid *lvid,
uint32_t extent_count, uint32_t chunk_size)
{
struct logical_volume *snap;
struct lv_segment *seg;
/*
* Is the cow device already being used ?
*/
if (lv_is_cow(cow)) {
log_error("'%s' is already in use as a snapshot.", cow->name);
return 0;
}
if (cow == origin) {
log_error("Snapshot and origin LVs must differ.");
return 0;
}
if (!(snap = lv_create_empty("snapshot%d",
lvid, LVM_READ | LVM_WRITE | VISIBLE_LV,
ALLOC_INHERIT, origin->vg)))
return_0;
snap->le_count = extent_count;
if (!(seg = _alloc_snapshot_seg(snap)))
return_0;
init_snapshot_seg(seg, origin, cow, chunk_size, 0);
return 1;
}
int vg_remove_snapshot(struct logical_volume *cow)
{
int merging_snapshot = 0;
struct logical_volume *origin = origin_from_cow(cow);
int is_origin_active = lv_is_active(origin);
if (is_origin_active &&
lv_is_virtual_origin(origin)) {
if (!deactivate_lv(origin->vg->cmd, origin)) {
log_error("Failed to deactivate logical volume \"%s\"",
origin->name);
return 0;
}
is_origin_active = 0;
}
dm_list_del(&cow->snapshot->origin_list);
origin->origin_count--;
if (lv_is_merging_origin(origin) &&
(find_snapshot(origin) == find_snapshot(cow))) {
clear_snapshot_merge(origin);
/*
* preload origin IFF "snapshot-merge" target is active
* - IMPORTANT: avoids preload if inactivate merge is pending
*/
if (lv_has_target_type(origin->vg->vgmem, origin, NULL,
TARGET_NAME_SNAPSHOT_MERGE)) {
/*
* preload origin to:
* - allow proper release of -cow
* - avoid allocations with other devices suspended
* when transitioning from "snapshot-merge" to
* "snapshot-origin after a merge completes.
*/
merging_snapshot = 1;
}
}
if (!lv_remove(cow->snapshot->lv)) {
log_error("Failed to remove internal snapshot LV %s",
cow->snapshot->lv->name);
return 0;
}
cow->snapshot = NULL;
lv_set_visible(cow);
/* format1 must do the change in one step, with the commit last. */
if (!(origin->vg->fid->fmt->features & FMT_MDAS)) {
/* Get the lock for COW volume */
if (is_origin_active && !activate_lv(cow->vg->cmd, cow)) {
log_error("Unable to activate logical volume \"%s\"",
cow->name);
return 0;
}
return 1;
}
if (!vg_write(origin->vg))
return_0;
/* Skip call suspend, if device is not active */
if (is_origin_active && !suspend_lv(origin->vg->cmd, origin)) {
log_error("Failed to refresh %s without snapshot.",
origin->name);
vg_revert(origin->vg);
return 0;
}
if (!vg_commit(origin->vg))
return_0;
if (is_origin_active) {
/*
* If the snapshot was active and the COW LV is taken away
* the LV lock on cluster has to be grabbed, so use
* activate_lv() which resumes suspend cow device.
*/
if (!merging_snapshot && !activate_lv(cow->vg->cmd, cow)) {
log_error("Failed to activate %s.", cow->name);
return 0;
}
if (!resume_lv(origin->vg->cmd, origin)) {
log_error("Failed to resume %s.", origin->name);
return 0;
}
/*
* For merged snapshot and clustered VG activate cow LV so
* the following call to deactivate_lv() can clean-up table
* entries. For this clustered lock need to be held.
*/
if (vg_is_clustered(cow->vg) &&
merging_snapshot && !activate_lv(cow->vg->cmd, cow)) {
log_error("Failed to activate %s.", cow->name);
return 0;
}
}
return 1;
}
/* Check if given LV is usable as snapshot origin LV */
int validate_snapshot_origin(const struct logical_volume *origin_lv)
{
const char *err = NULL; /* For error string */
if (lv_is_cow(origin_lv))
err = "snapshots";
else if (lv_is_locked(origin_lv))
err = "locked volumes";
else if (lv_is_pvmove(origin_lv))
err = "pvmoved volumes";
else if (!lv_is_visible(origin_lv))
err = "hidden volumes";
else if (lv_is_merging_origin(origin_lv))
err = "an origin that has a merging snapshot";
else if (lv_is_cache_type(origin_lv) && !lv_is_cache(origin_lv))
err = "cache type volumes";
else if (lv_is_thin_type(origin_lv) && !lv_is_thin_volume(origin_lv))
err = "thin pool type volumes";
else if (lv_is_mirror_type(origin_lv)) {
if (!lv_is_mirror(origin_lv))
err = "mirror subvolumes";
else {
log_warn("WARNING: Snapshots of mirrors can deadlock under rare device failures.");
log_warn("WARNING: Consider using the raid1 mirror type to avoid this.");
log_warn("WARNING: See global/mirror_segtype_default in lvm.conf.");
}
} else if (lv_is_raid_type(origin_lv) && !lv_is_raid(origin_lv))
err = "raid subvolumes";
if (err) {
log_error("Snapshots of %s are not supported.", err);
return 0;
}
if (vg_is_clustered(origin_lv->vg) && lv_is_active(origin_lv) &&
!lv_is_active_exclusive_locally(origin_lv)) {
log_error("Snapshot origin must be active exclusively.");
return 0;
}
return 1;
}