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dm btree remove: change a bunch of BUG_ON() calls to proper errors
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Abuse of BUG_ON() is never appropriate, best to propagate errors to
fail gracefully (rather than take the entire system down).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@jthornber @snitm
jthornber authored and snitm committed Jan 4, 2022
1 parent e36649b commit c671ffa
Showing 1 changed file with 122 additions and 51 deletions.
173 changes: 122 additions & 51 deletions drivers/md/persistent-data/dm-btree-remove.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@
#include "dm-transaction-manager.h"

#include <linux/export.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "btree"

/*
* Removing an entry from a btree
Expand Down Expand Up @@ -79,30 +82,43 @@ static void node_shift(struct btree_node *n, int shift)
}
}

static void node_copy(struct btree_node *left, struct btree_node *right, int shift)
static int 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 (value_size != le32_to_cpu(right->header.value_size)) {
DMERR("mismatched value size");
return -EILSEQ;
}

if (shift < 0) {
shift = -shift;
BUG_ON(nr_left + shift > le32_to_cpu(left->header.max_entries));

if (nr_left + shift > le32_to_cpu(left->header.max_entries)) {
DMERR("bad shift");
return -EINVAL;
}

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));
if (shift > le32_to_cpu(right->header.max_entries)) {
DMERR("bad shift");
return -EINVAL;
}

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);
}
return 0;
}

/*
Expand Down Expand Up @@ -170,35 +186,54 @@ 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)
static int shift(struct btree_node *left, struct btree_node *right, int count)
{
int r;
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 (max_entries != r_max_entries) {
DMERR("node max_entries mismatch");
return -EILSEQ;
}

if (nr_left - count > max_entries) {
DMERR("node shift out of bounds");
return -EINVAL;
}

if (nr_right + count > max_entries) {
DMERR("node shift out of bounds");
return -EINVAL;
}

if (!count)
return;
return 0;

if (count > 0) {
node_shift(right, count);
node_copy(left, right, count);
r = node_copy(left, right, count);
if (r)
return r;
} else {
node_copy(left, right, count);
r = node_copy(left, right, count);
if (r)
return r;
node_shift(right, count);
}

left->header.nr_entries = cpu_to_le32(nr_left - count);
right->header.nr_entries = cpu_to_le32(nr_right + count);

return 0;
}

static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *r)
static int __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *r)
{
int ret;
struct btree_node *left = l->n;
struct btree_node *right = r->n;
uint32_t nr_left = le32_to_cpu(left->header.nr_entries);
Expand Down Expand Up @@ -229,9 +264,12 @@ static void __rebalance2(struct dm_btree_info *info, struct btree_node *parent,
* Rebalance.
*/
unsigned target_left = (nr_left + nr_right) / 2;
shift(left, right, nr_left - target_left);
ret = shift(left, right, nr_left - target_left);
if (ret)
return ret;
*key_ptr(parent, r->index) = right->keys[0];
}
return 0;
}

static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
Expand All @@ -253,34 +291,43 @@ static int rebalance2(struct shadow_spine *s, struct dm_btree_info *info,
return r;
}

__rebalance2(info, parent, &left, &right);
r = __rebalance2(info, parent, &left, &right);

exit_child(info, &left);
exit_child(info, &right);

return 0;
return r;
}

/*
* 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)
static int 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);
if (nr_left + shift > max_entries) {
DMERR("node shift out of bounds");
return -EINVAL;
}

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);

if ((nr_right + shift) > max_entries) {
DMERR("node shift out of bounds");
return -EINVAL;
}

node_shift(right, shift);
node_copy(center, right, shift);
right->header.nr_entries = cpu_to_le32(nr_right + shift);
Expand All @@ -291,18 +338,18 @@ static void delete_center_node(struct dm_btree_info *info, struct btree_node *pa
r->index--;

dm_tm_dec(info->tm, dm_block_location(c->block));
__rebalance2(info, parent, l, r);
return __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)
static int 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;
int s, ret;
uint32_t max_entries = le32_to_cpu(left->header.max_entries);
unsigned total = nr_left + nr_center + nr_right;
unsigned target_right = total / 3;
Expand All @@ -317,35 +364,55 @@ static void redistribute3(struct dm_btree_info *info, struct btree_node *parent,

if (s < 0 && nr_center < -s) {
/* not enough in central node */
shift(left, center, -nr_center);
ret = shift(left, center, -nr_center);
if (ret)
return ret;

s += nr_center;
shift(left, right, s);
nr_right += s;
} else
shift(left, center, s);
ret = shift(left, right, s);
if (ret)
return ret;

shift(center, right, target_right - nr_right);
nr_right += s;
} else {
ret = shift(left, center, s);
if (ret)
return ret;
}

ret = shift(center, right, target_right - nr_right);
if (ret)
return ret;
} else {
s = target_right - nr_right;
if (s > 0 && nr_center < s) {
/* not enough in central node */
shift(center, right, nr_center);
ret = shift(center, right, nr_center);
if (ret)
return ret;
s -= nr_center;
shift(left, right, s);
ret = shift(left, right, s);
if (ret)
return ret;
nr_left -= s;
} else
shift(center, right, s);
} else {
ret = shift(center, right, s);
if (ret)
return ret;
}

shift(left, center, nr_left - target_left);
ret = shift(left, center, nr_left - target_left);
if (ret)
return ret;
}

*key_ptr(parent, c->index) = center->keys[0];
*key_ptr(parent, r->index) = right->keys[0];
return 0;
}

static void __rebalance3(struct dm_btree_info *info, struct btree_node *parent,
struct child *l, struct child *c, struct child *r)
static int __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;
Expand All @@ -357,15 +424,19 @@ static void __rebalance3(struct dm_btree_info *info, struct btree_node *parent,

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 ((left->header.max_entries != center->header.max_entries) ||
(center->header.max_entries != right->header.max_entries)) {
DMERR("bad btree metadata, max_entries differ");
return -EILSEQ;
}

if ((nr_left + nr_center + nr_right) < threshold) {
return delete_center_node(info, parent, l, c, r, left, center, right,
nr_left, nr_center, nr_right);
}

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);
return 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,
Expand Down Expand Up @@ -395,13 +466,13 @@ static int rebalance3(struct shadow_spine *s, struct dm_btree_info *info,
return r;
}

__rebalance3(info, parent, &left, &center, &right);
r = __rebalance3(info, parent, &left, &center, &right);

exit_child(info, &left);
exit_child(info, &center);
exit_child(info, &right);

return 0;
return r;
}

static int rebalance_children(struct shadow_spine *s,
Expand Down

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