linux/drivers/md/persistent-data/dm-btree-remove.c
Linus Torvalds e0700ce709 - Revert a dm-multipath change that caused a regression for unprivledged
users (e.g. kvm guests) that issued ioctls when a multipath device had
   no available paths.
 
 - Include Christoph's refactoring of DM's ioctl handling and add support
   for passing through persistent reservations with DM multipath.
 
 - All other changes are very simple cleanups.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQEcBAABAgAGBQJWOp04AAoJEMUj8QotnQNaFLsH/AhMEH/jI1ObOfy4J1Wy4rOx
 ujJT91uS/s0H3pc9cGKQYnuGpFkX6WWU4wMiabIyiTn4sAsoXaflfIGutivLiDJr
 HfecrMrGZgnP4ZlpPPB02BmlxFbcPW8yzAU4ma38xBgQ+Pu30RO/HkvX/2vKOppG
 qwPop/XsNxq3KXgFGM44ToytM6c/MPGluhuvOwbaacAO1HviMuen9qsVjk4kwcf3
 jGYTbEPHATxyu5/6oKDTkQTYhzdwg3B2qHCiKMGw3l1kXhaQLFcaOivOLV8Sf3xh
 bj1070pkGe9OpqaVzMnwDtJ8rnsBl/Nt4wj9oiQPxbX71GYZAmcMIYn9WEkcKFI=
 =AR2D
 -----END PGP SIGNATURE-----

Merge tag 'dm-4.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:
 "Smaller set of DM changes for this merge.  I've based these changes on
  Jens' for-4.4/reservations branch because the associated DM changes
  required it.

   - Revert a dm-multipath change that caused a regression for
     unprivledged users (e.g. kvm guests) that issued ioctls when a
     multipath device had no available paths.

   - Include Christoph's refactoring of DM's ioctl handling and add
     support for passing through persistent reservations with DM
     multipath.

   - All other changes are very simple cleanups"

* tag 'dm-4.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm switch: simplify conditional in alloc_region_table()
  dm delay: document that offsets are specified in sectors
  dm delay: capitalize the start of an delay_ctr() error message
  dm delay: Use DM_MAPIO macros instead of open-coded equivalents
  dm linear: remove redundant target name from error messages
  dm persistent data: eliminate unnecessary return values
  dm: eliminate unused "bioset" process for each bio-based DM device
  dm: convert ffs to __ffs
  dm: drop NULL test before kmem_cache_destroy() and mempool_destroy()
  dm: add support for passing through persistent reservations
  dm: refactor ioctl handling
  Revert "dm mpath: fix stalls when handling invalid ioctls"
  dm: initialize non-blk-mq queue data before queue is used
2015-11-04 21:19:53 -08:00

682 lines
17 KiB
C

/*
* Copyright (C) 2011 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#include "dm-btree.h"
#include "dm-btree-internal.h"
#include "dm-transaction-manager.h"
#include <linux/export.h>
/*
* Removing an entry from a btree
* ==============================
*
* A very important constraint for our btree is that no node, except the
* root, may have fewer than a certain number of entries.
* (MIN_ENTRIES <= nr_entries <= MAX_ENTRIES).
*
* Ensuring this is complicated by the way we want to only ever hold the
* locks on 2 nodes concurrently, and only change nodes in a top to bottom
* fashion.
*
* Each node may have a left or right sibling. When decending the spine,
* if a node contains only MIN_ENTRIES then we try and increase this to at
* least MIN_ENTRIES + 1. We do this in the following ways:
*
* [A] No siblings => this can only happen if the node is the root, in which
* case we copy the childs contents over the root.
*
* [B] No left sibling
* ==> rebalance(node, right sibling)
*
* [C] No right sibling
* ==> rebalance(left sibling, node)
*
* [D] Both siblings, total_entries(left, node, right) <= DEL_THRESHOLD
* ==> delete node adding it's contents to left and right
*
* [E] Both siblings, total_entries(left, node, right) > DEL_THRESHOLD
* ==> rebalance(left, node, right)
*
* After these operations it's possible that the our original node no
* longer contains the desired sub tree. For this reason this rebalancing
* is performed on the children of the current node. This also avoids
* having a special case for the root.
*
* Once this rebalancing has occurred we can then step into the child node
* for internal nodes. Or delete the entry for leaf nodes.
*/
/*
* Some little utilities for moving node data around.
*/
static void node_shift(struct btree_node *n, int shift)
{
uint32_t nr_entries = le32_to_cpu(n->header.nr_entries);
uint32_t value_size = le32_to_cpu(n->header.value_size);
if (shift < 0) {
shift = -shift;
BUG_ON(shift > nr_entries);
BUG_ON((void *) key_ptr(n, shift) >= value_ptr(n, shift));
memmove(key_ptr(n, 0),
key_ptr(n, shift),
(nr_entries - shift) * sizeof(__le64));
memmove(value_ptr(n, 0),
value_ptr(n, shift),
(nr_entries - shift) * value_size);
} else {
BUG_ON(nr_entries + shift > le32_to_cpu(n->header.max_entries));
memmove(key_ptr(n, shift),
key_ptr(n, 0),
nr_entries * sizeof(__le64));
memmove(value_ptr(n, shift),
value_ptr(n, 0),
nr_entries * value_size);
}
}
static void node_copy(struct btree_node *left, struct btree_node *right, int shift)
{
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
uint32_t value_size = le32_to_cpu(left->header.value_size);
BUG_ON(value_size != le32_to_cpu(right->header.value_size));
if (shift < 0) {
shift = -shift;
BUG_ON(nr_left + shift > le32_to_cpu(left->header.max_entries));
memcpy(key_ptr(left, nr_left),
key_ptr(right, 0),
shift * sizeof(__le64));
memcpy(value_ptr(left, nr_left),
value_ptr(right, 0),
shift * value_size);
} else {
BUG_ON(shift > le32_to_cpu(right->header.max_entries));
memcpy(key_ptr(right, 0),
key_ptr(left, nr_left - shift),
shift * sizeof(__le64));
memcpy(value_ptr(right, 0),
value_ptr(left, nr_left - shift),
shift * value_size);
}
}
/*
* Delete a specific entry from a leaf node.
*/
static void delete_at(struct btree_node *n, unsigned index)
{
unsigned nr_entries = le32_to_cpu(n->header.nr_entries);
unsigned nr_to_copy = nr_entries - (index + 1);
uint32_t value_size = le32_to_cpu(n->header.value_size);
BUG_ON(index >= nr_entries);
if (nr_to_copy) {
memmove(key_ptr(n, index),
key_ptr(n, index + 1),
nr_to_copy * sizeof(__le64));
memmove(value_ptr(n, index),
value_ptr(n, index + 1),
nr_to_copy * value_size);
}
n->header.nr_entries = cpu_to_le32(nr_entries - 1);
}
static unsigned merge_threshold(struct btree_node *n)
{
return le32_to_cpu(n->header.max_entries) / 3;
}
struct child {
unsigned index;
struct dm_block *block;
struct btree_node *n;
};
static int init_child(struct dm_btree_info *info, struct dm_btree_value_type *vt,
struct btree_node *parent,
unsigned index, struct child *result)
{
int r, inc;
dm_block_t root;
result->index = index;
root = value64(parent, index);
r = dm_tm_shadow_block(info->tm, root, &btree_node_validator,
&result->block, &inc);
if (r)
return r;
result->n = dm_block_data(result->block);
if (inc)
inc_children(info->tm, result->n, vt);
*((__le64 *) value_ptr(parent, index)) =
cpu_to_le64(dm_block_location(result->block));
return 0;
}
static void exit_child(struct dm_btree_info *info, struct child *c)
{
dm_tm_unlock(info->tm, c->block);
}
static void shift(struct btree_node *left, struct btree_node *right, int count)
{
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
uint32_t max_entries = le32_to_cpu(left->header.max_entries);
uint32_t r_max_entries = le32_to_cpu(right->header.max_entries);
BUG_ON(max_entries != r_max_entries);
BUG_ON(nr_left - count > max_entries);
BUG_ON(nr_right + count > max_entries);
if (!count)
return;
if (count > 0) {
node_shift(right, count);
node_copy(left, right, count);
} else {
node_copy(left, right, count);
node_shift(right, count);
}
left->header.nr_entries = cpu_to_le32(nr_left - count);
right->header.nr_entries = cpu_to_le32(nr_right + count);
}
static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *r)
{
struct btree_node *left = l->n;
struct btree_node *right = r->n;
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
unsigned threshold = 2 * merge_threshold(left) + 1;
if (nr_left + nr_right < threshold) {
/*
* Merge
*/
node_copy(left, right, -nr_right);
left->header.nr_entries = cpu_to_le32(nr_left + nr_right);
delete_at(parent, r->index);
/*
* We need to decrement the right block, but not it's
* children, since they're still referenced by left.
*/
dm_tm_dec(info->tm, dm_block_location(r->block));
} else {
/*
* Rebalance.
*/
unsigned target_left = (nr_left + nr_right) / 2;
shift(left, right, nr_left - target_left);
*key_ptr(parent, r->index) = right->keys[0];
}
}
static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
struct dm_btree_value_type *vt, unsigned left_index)
{
int r;
struct btree_node *parent;
struct child left, right;
parent = dm_block_data(shadow_current(s));
r = init_child(info, vt, parent, left_index, &left);
if (r)
return r;
r = init_child(info, vt, parent, left_index + 1, &right);
if (r) {
exit_child(info, &left);
return r;
}
__rebalance2(info, parent, &left, &right);
exit_child(info, &left);
exit_child(info, &right);
return 0;
}
/*
* We dump as many entries from center as possible into left, then the rest
* in right, then rebalance2. This wastes some cpu, but I want something
* simple atm.
*/
static void delete_center_node(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *c, struct child *r,
struct btree_node *left, struct btree_node *center, struct btree_node *right,
uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
{
uint32_t max_entries = le32_to_cpu(left->header.max_entries);
unsigned shift = min(max_entries - nr_left, nr_center);
BUG_ON(nr_left + shift > max_entries);
node_copy(left, center, -shift);
left->header.nr_entries = cpu_to_le32(nr_left + shift);
if (shift != nr_center) {
shift = nr_center - shift;
BUG_ON((nr_right + shift) > max_entries);
node_shift(right, shift);
node_copy(center, right, shift);
right->header.nr_entries = cpu_to_le32(nr_right + shift);
}
*key_ptr(parent, r->index) = right->keys[0];
delete_at(parent, c->index);
r->index--;
dm_tm_dec(info->tm, dm_block_location(c->block));
__rebalance2(info, parent, l, r);
}
/*
* Redistributes entries among 3 sibling nodes.
*/
static void redistribute3(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *c, struct child *r,
struct btree_node *left, struct btree_node *center, struct btree_node *right,
uint32_t nr_left, uint32_t nr_center, uint32_t nr_right)
{
int s;
uint32_t max_entries = le32_to_cpu(left->header.max_entries);
unsigned total = nr_left + nr_center + nr_right;
unsigned target_right = total / 3;
unsigned remainder = (target_right * 3) != total;
unsigned target_left = target_right + remainder;
BUG_ON(target_left > max_entries);
BUG_ON(target_right > max_entries);
if (nr_left < nr_right) {
s = nr_left - target_left;
if (s < 0 && nr_center < -s) {
/* not enough in central node */
shift(left, center, -nr_center);
s += nr_center;
shift(left, right, s);
nr_right += s;
} else
shift(left, center, s);
shift(center, right, target_right - nr_right);
} else {
s = target_right - nr_right;
if (s > 0 && nr_center < s) {
/* not enough in central node */
shift(center, right, nr_center);
s -= nr_center;
shift(left, right, s);
nr_left -= s;
} else
shift(center, right, s);
shift(left, center, nr_left - target_left);
}
*key_ptr(parent, c->index) = center->keys[0];
*key_ptr(parent, r->index) = right->keys[0];
}
static void __rebalance3(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *c, struct child *r)
{
struct btree_node *left = l->n;
struct btree_node *center = c->n;
struct btree_node *right = r->n;
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
uint32_t nr_center = le32_to_cpu(center->header.nr_entries);
uint32_t nr_right = le32_to_cpu(right->header.nr_entries);
unsigned threshold = merge_threshold(left) * 4 + 1;
BUG_ON(left->header.max_entries != center->header.max_entries);
BUG_ON(center->header.max_entries != right->header.max_entries);
if ((nr_left + nr_center + nr_right) < threshold)
delete_center_node(info, parent, l, c, r, left, center, right,
nr_left, nr_center, nr_right);
else
redistribute3(info, parent, l, c, r, left, center, right,
nr_left, nr_center, nr_right);
}
static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
struct dm_btree_value_type *vt, unsigned left_index)
{
int r;
struct btree_node *parent = dm_block_data(shadow_current(s));
struct child left, center, right;
/*
* FIXME: fill out an array?
*/
r = init_child(info, vt, parent, left_index, &left);
if (r)
return r;
r = init_child(info, vt, parent, left_index + 1, &center);
if (r) {
exit_child(info, &left);
return r;
}
r = init_child(info, vt, parent, left_index + 2, &right);
if (r) {
exit_child(info, &left);
exit_child(info, &center);
return r;
}
__rebalance3(info, parent, &left, &center, &right);
exit_child(info, &left);
exit_child(info, &center);
exit_child(info, &right);
return 0;
}
static int rebalance_children(struct shadow_spine *s,
struct dm_btree_info *info,
struct dm_btree_value_type *vt, uint64_t key)
{
int i, r, has_left_sibling, has_right_sibling;
struct btree_node *n;
n = dm_block_data(shadow_current(s));
if (le32_to_cpu(n->header.nr_entries) == 1) {
struct dm_block *child;
dm_block_t b = value64(n, 0);
r = dm_tm_read_lock(info->tm, b, &btree_node_validator, &child);
if (r)
return r;
memcpy(n, dm_block_data(child),
dm_bm_block_size(dm_tm_get_bm(info->tm)));
dm_tm_unlock(info->tm, child);
dm_tm_dec(info->tm, dm_block_location(child));
return 0;
}
i = lower_bound(n, key);
if (i < 0)
return -ENODATA;
has_left_sibling = i > 0;
has_right_sibling = i < (le32_to_cpu(n->header.nr_entries) - 1);
if (!has_left_sibling)
r = rebalance2(s, info, vt, i);
else if (!has_right_sibling)
r = rebalance2(s, info, vt, i - 1);
else
r = rebalance3(s, info, vt, i - 1);
return r;
}
static int do_leaf(struct btree_node *n, uint64_t key, unsigned *index)
{
int i = lower_bound(n, key);
if ((i < 0) ||
(i >= le32_to_cpu(n->header.nr_entries)) ||
(le64_to_cpu(n->keys[i]) != key))
return -ENODATA;
*index = i;
return 0;
}
/*
* Prepares for removal from one level of the hierarchy. The caller must
* call delete_at() to remove the entry at index.
*/
static int remove_raw(struct shadow_spine *s, struct dm_btree_info *info,
struct dm_btree_value_type *vt, dm_block_t root,
uint64_t key, unsigned *index)
{
int i = *index, r;
struct btree_node *n;
for (;;) {
r = shadow_step(s, root, vt);
if (r < 0)
break;
/*
* We have to patch up the parent node, ugly, but I don't
* see a way to do this automatically as part of the spine
* op.
*/
if (shadow_has_parent(s)) {
__le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
&location, sizeof(__le64));
}
n = dm_block_data(shadow_current(s));
if (le32_to_cpu(n->header.flags) & LEAF_NODE)
return do_leaf(n, key, index);
r = rebalance_children(s, info, vt, key);
if (r)
break;
n = dm_block_data(shadow_current(s));
if (le32_to_cpu(n->header.flags) & LEAF_NODE)
return do_leaf(n, key, index);
i = lower_bound(n, key);
/*
* We know the key is present, or else
* rebalance_children would have returned
* -ENODATA
*/
root = value64(n, i);
}
return r;
}
int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
uint64_t *keys, dm_block_t *new_root)
{
unsigned level, last_level = info->levels - 1;
int index = 0, r = 0;
struct shadow_spine spine;
struct btree_node *n;
struct dm_btree_value_type le64_vt;
init_le64_type(info->tm, &le64_vt);
init_shadow_spine(&spine, info);
for (level = 0; level < info->levels; level++) {
r = remove_raw(&spine, info,
(level == last_level ?
&info->value_type : &le64_vt),
root, keys[level], (unsigned *)&index);
if (r < 0)
break;
n = dm_block_data(shadow_current(&spine));
if (level != last_level) {
root = value64(n, index);
continue;
}
BUG_ON(index < 0 || index >= le32_to_cpu(n->header.nr_entries));
if (info->value_type.dec)
info->value_type.dec(info->value_type.context,
value_ptr(n, index));
delete_at(n, index);
}
*new_root = shadow_root(&spine);
exit_shadow_spine(&spine);
return r;
}
EXPORT_SYMBOL_GPL(dm_btree_remove);
/*----------------------------------------------------------------*/
static int remove_nearest(struct shadow_spine *s, struct dm_btree_info *info,
struct dm_btree_value_type *vt, dm_block_t root,
uint64_t key, int *index)
{
int i = *index, r;
struct btree_node *n;
for (;;) {
r = shadow_step(s, root, vt);
if (r < 0)
break;
/*
* We have to patch up the parent node, ugly, but I don't
* see a way to do this automatically as part of the spine
* op.
*/
if (shadow_has_parent(s)) {
__le64 location = cpu_to_le64(dm_block_location(shadow_current(s)));
memcpy(value_ptr(dm_block_data(shadow_parent(s)), i),
&location, sizeof(__le64));
}
n = dm_block_data(shadow_current(s));
if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
*index = lower_bound(n, key);
return 0;
}
r = rebalance_children(s, info, vt, key);
if (r)
break;
n = dm_block_data(shadow_current(s));
if (le32_to_cpu(n->header.flags) & LEAF_NODE) {
*index = lower_bound(n, key);
return 0;
}
i = lower_bound(n, key);
/*
* We know the key is present, or else
* rebalance_children would have returned
* -ENODATA
*/
root = value64(n, i);
}
return r;
}
static int remove_one(struct dm_btree_info *info, dm_block_t root,
uint64_t *keys, uint64_t end_key,
dm_block_t *new_root, unsigned *nr_removed)
{
unsigned level, last_level = info->levels - 1;
int index = 0, r = 0;
struct shadow_spine spine;
struct btree_node *n;
struct dm_btree_value_type le64_vt;
uint64_t k;
init_le64_type(info->tm, &le64_vt);
init_shadow_spine(&spine, info);
for (level = 0; level < last_level; level++) {
r = remove_raw(&spine, info, &le64_vt,
root, keys[level], (unsigned *) &index);
if (r < 0)
goto out;
n = dm_block_data(shadow_current(&spine));
root = value64(n, index);
}
r = remove_nearest(&spine, info, &info->value_type,
root, keys[last_level], &index);
if (r < 0)
goto out;
n = dm_block_data(shadow_current(&spine));
if (index < 0)
index = 0;
if (index >= le32_to_cpu(n->header.nr_entries)) {
r = -ENODATA;
goto out;
}
k = le64_to_cpu(n->keys[index]);
if (k >= keys[last_level] && k < end_key) {
if (info->value_type.dec)
info->value_type.dec(info->value_type.context,
value_ptr(n, index));
delete_at(n, index);
keys[last_level] = k + 1ull;
} else
r = -ENODATA;
out:
*new_root = shadow_root(&spine);
exit_shadow_spine(&spine);
return r;
}
int dm_btree_remove_leaves(struct dm_btree_info *info, dm_block_t root,
uint64_t *first_key, uint64_t end_key,
dm_block_t *new_root, unsigned *nr_removed)
{
int r;
*nr_removed = 0;
do {
r = remove_one(info, root, first_key, end_key, &root, nr_removed);
if (!r)
(*nr_removed)++;
} while (!r);
*new_root = root;
return r == -ENODATA ? 0 : r;
}
EXPORT_SYMBOL_GPL(dm_btree_remove_leaves);