mirror of
https://github.com/edk2-porting/linux-next.git
synced 2025-01-16 17:43:56 +08:00
dm ioctl: replace device hash with red-black tree
For high numbers of DM devices the 64-entry hash table has non-trivial overhead. Fix this by replacing the hash table with a red-black tree. Reported-by: Zdenek Kabelac <zkabelac@redhat.com> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka
Mike Snitzer
parent
219a9b5e73
commit
b82096afc8
@ -14,6 +14,7 @@
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#include <linux/init.h>
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#include <linux/wait.h>
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#include <linux/slab.h>
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#include <linux/rbtree.h>
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#include <linux/dm-ioctl.h>
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#include <linux/hdreg.h>
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#include <linux/compat.h>
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@ -36,8 +37,10 @@ struct dm_file {
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* name or uuid.
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*---------------------------------------------------------------*/
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struct hash_cell {
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struct list_head name_list;
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struct list_head uuid_list;
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struct rb_node name_node;
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struct rb_node uuid_node;
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bool name_set;
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bool uuid_set;
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char *name;
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char *uuid;
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@ -53,10 +56,8 @@ struct vers_iter {
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};
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#define NUM_BUCKETS 64
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#define MASK_BUCKETS (NUM_BUCKETS - 1)
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static struct list_head _name_buckets[NUM_BUCKETS];
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static struct list_head _uuid_buckets[NUM_BUCKETS];
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static struct rb_root name_rb_tree = RB_ROOT;
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static struct rb_root uuid_rb_tree = RB_ROOT;
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static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred);
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@ -70,73 +71,110 @@ static DECLARE_RWSEM(_hash_lock);
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*/
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static DEFINE_MUTEX(dm_hash_cells_mutex);
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static void init_buckets(struct list_head *buckets)
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{
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unsigned int i;
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for (i = 0; i < NUM_BUCKETS; i++)
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INIT_LIST_HEAD(buckets + i);
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}
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static int dm_hash_init(void)
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{
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init_buckets(_name_buckets);
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init_buckets(_uuid_buckets);
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return 0;
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}
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static void dm_hash_exit(void)
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{
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dm_hash_remove_all(false, false, false);
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}
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/*-----------------------------------------------------------------
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* Hash function:
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* We're not really concerned with the str hash function being
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* fast since it's only used by the ioctl interface.
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*---------------------------------------------------------------*/
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static unsigned int hash_str(const char *str)
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{
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const unsigned int hash_mult = 2654435387U;
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unsigned int h = 0;
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while (*str)
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h = (h + (unsigned int) *str++) * hash_mult;
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return h & MASK_BUCKETS;
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}
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/*-----------------------------------------------------------------
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* Code for looking up a device by name
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*---------------------------------------------------------------*/
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static struct hash_cell *__get_name_cell(const char *str)
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{
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struct hash_cell *hc;
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unsigned int h = hash_str(str);
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struct rb_node *n = name_rb_tree.rb_node;
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list_for_each_entry (hc, _name_buckets + h, name_list)
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if (!strcmp(hc->name, str)) {
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while (n) {
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struct hash_cell *hc = container_of(n, struct hash_cell, name_node);
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int c = strcmp(hc->name, str);
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if (!c) {
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dm_get(hc->md);
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return hc;
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}
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n = c >= 0 ? n->rb_left : n->rb_right;
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}
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return NULL;
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}
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static struct hash_cell *__get_uuid_cell(const char *str)
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{
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struct hash_cell *hc;
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unsigned int h = hash_str(str);
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struct rb_node *n = uuid_rb_tree.rb_node;
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list_for_each_entry (hc, _uuid_buckets + h, uuid_list)
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if (!strcmp(hc->uuid, str)) {
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while (n) {
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struct hash_cell *hc = container_of(n, struct hash_cell, uuid_node);
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int c = strcmp(hc->uuid, str);
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if (!c) {
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dm_get(hc->md);
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return hc;
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}
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n = c >= 0 ? n->rb_left : n->rb_right;
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}
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return NULL;
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}
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static void __unlink_name(struct hash_cell *hc)
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{
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if (hc->name_set) {
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hc->name_set = false;
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rb_erase(&hc->name_node, &name_rb_tree);
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}
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}
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static void __unlink_uuid(struct hash_cell *hc)
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{
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if (hc->uuid_set) {
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hc->uuid_set = false;
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rb_erase(&hc->uuid_node, &uuid_rb_tree);
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}
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}
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static void __link_name(struct hash_cell *new_hc)
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{
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struct rb_node **n, *parent;
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__unlink_name(new_hc);
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new_hc->name_set = true;
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n = &name_rb_tree.rb_node;
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parent = NULL;
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while (*n) {
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struct hash_cell *hc = container_of(*n, struct hash_cell, name_node);
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int c = strcmp(hc->name, new_hc->name);
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BUG_ON(!c);
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parent = *n;
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n = c >= 0 ? &hc->name_node.rb_left : &hc->name_node.rb_right;
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}
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rb_link_node(&new_hc->name_node, parent, n);
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rb_insert_color(&new_hc->name_node, &name_rb_tree);
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}
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static void __link_uuid(struct hash_cell *new_hc)
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{
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struct rb_node **n, *parent;
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__unlink_uuid(new_hc);
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new_hc->uuid_set = true;
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n = &uuid_rb_tree.rb_node;
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parent = NULL;
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while (*n) {
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struct hash_cell *hc = container_of(*n, struct hash_cell, uuid_node);
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int c = strcmp(hc->uuid, new_hc->uuid);
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BUG_ON(!c);
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parent = *n;
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n = c > 0 ? &hc->uuid_node.rb_left : &hc->uuid_node.rb_right;
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}
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rb_link_node(&new_hc->uuid_node, parent, n);
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rb_insert_color(&new_hc->uuid_node, &uuid_rb_tree);
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}
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static struct hash_cell *__get_dev_cell(uint64_t dev)
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{
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struct mapped_device *md;
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@ -185,8 +223,7 @@ static struct hash_cell *alloc_cell(const char *name, const char *uuid,
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}
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}
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INIT_LIST_HEAD(&hc->name_list);
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INIT_LIST_HEAD(&hc->uuid_list);
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hc->name_set = hc->uuid_set = false;
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hc->md = md;
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hc->new_map = NULL;
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return hc;
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@ -226,16 +263,16 @@ static int dm_hash_insert(const char *name, const char *uuid, struct mapped_devi
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goto bad;
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}
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list_add(&cell->name_list, _name_buckets + hash_str(name));
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__link_name(cell);
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if (uuid) {
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hc = __get_uuid_cell(uuid);
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if (hc) {
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list_del(&cell->name_list);
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__unlink_name(cell);
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dm_put(hc->md);
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goto bad;
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}
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list_add(&cell->uuid_list, _uuid_buckets + hash_str(uuid));
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__link_uuid(cell);
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}
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dm_get(md);
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mutex_lock(&dm_hash_cells_mutex);
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@ -256,9 +293,9 @@ static struct dm_table *__hash_remove(struct hash_cell *hc)
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struct dm_table *table;
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int srcu_idx;
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/* remove from the dev hash */
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list_del(&hc->uuid_list);
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list_del(&hc->name_list);
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/* remove from the dev trees */
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__unlink_name(hc);
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__unlink_uuid(hc);
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mutex_lock(&dm_hash_cells_mutex);
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dm_set_mdptr(hc->md, NULL);
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mutex_unlock(&dm_hash_cells_mutex);
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@ -279,7 +316,8 @@ static struct dm_table *__hash_remove(struct hash_cell *hc)
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static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred)
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{
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int i, dev_skipped;
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int dev_skipped;
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struct rb_node *n;
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struct hash_cell *hc;
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struct mapped_device *md;
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struct dm_table *t;
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@ -289,40 +327,39 @@ retry:
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down_write(&_hash_lock);
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for (i = 0; i < NUM_BUCKETS; i++) {
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list_for_each_entry(hc, _name_buckets + i, name_list) {
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md = hc->md;
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dm_get(md);
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for (n = rb_first(&name_rb_tree); n; n = rb_next(n)) {
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hc = container_of(n, struct hash_cell, name_node);
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md = hc->md;
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dm_get(md);
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if (keep_open_devices &&
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dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
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dm_put(md);
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dev_skipped++;
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continue;
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}
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t = __hash_remove(hc);
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up_write(&_hash_lock);
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if (t) {
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dm_sync_table(md);
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dm_table_destroy(t);
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}
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if (keep_open_devices &&
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dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
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dm_put(md);
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if (likely(keep_open_devices))
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dm_destroy(md);
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else
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dm_destroy_immediate(md);
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/*
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* Some mapped devices may be using other mapped
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* devices, so repeat until we make no further
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* progress. If a new mapped device is created
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* here it will also get removed.
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*/
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goto retry;
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dev_skipped++;
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continue;
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}
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t = __hash_remove(hc);
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up_write(&_hash_lock);
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if (t) {
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dm_sync_table(md);
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dm_table_destroy(t);
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}
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dm_put(md);
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if (likely(keep_open_devices))
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dm_destroy(md);
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else
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dm_destroy_immediate(md);
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/*
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* Some mapped devices may be using other mapped
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* devices, so repeat until we make no further
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* progress. If a new mapped device is created
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* here it will also get removed.
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*/
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goto retry;
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}
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up_write(&_hash_lock);
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@ -340,7 +377,7 @@ static void __set_cell_uuid(struct hash_cell *hc, char *new_uuid)
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hc->uuid = new_uuid;
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mutex_unlock(&dm_hash_cells_mutex);
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list_add(&hc->uuid_list, _uuid_buckets + hash_str(new_uuid));
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__link_uuid(hc);
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}
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/*
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@ -354,14 +391,14 @@ static char *__change_cell_name(struct hash_cell *hc, char *new_name)
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/*
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* Rename and move the name cell.
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*/
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list_del(&hc->name_list);
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__unlink_name(hc);
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old_name = hc->name;
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mutex_lock(&dm_hash_cells_mutex);
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hc->name = new_name;
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mutex_unlock(&dm_hash_cells_mutex);
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list_add(&hc->name_list, _name_buckets + hash_str(new_name));
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__link_name(hc);
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return old_name;
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}
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@ -505,7 +542,7 @@ static void *get_result_buffer(struct dm_ioctl *param, size_t param_size,
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static int list_devices(struct file *filp, struct dm_ioctl *param, size_t param_size)
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{
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unsigned int i;
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struct rb_node *n;
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struct hash_cell *hc;
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size_t len, needed = 0;
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struct gendisk *disk;
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@ -518,11 +555,10 @@ static int list_devices(struct file *filp, struct dm_ioctl *param, size_t param_
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* Loop through all the devices working out how much
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* space we need.
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*/
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for (i = 0; i < NUM_BUCKETS; i++) {
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list_for_each_entry (hc, _name_buckets + i, name_list) {
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needed += align_val(offsetof(struct dm_name_list, name) + strlen(hc->name) + 1);
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needed += align_val(sizeof(uint32_t));
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}
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for (n = rb_first(&name_rb_tree); n; n = rb_next(n)) {
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hc = container_of(n, struct hash_cell, name_node);
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needed += align_val(offsetof(struct dm_name_list, name) + strlen(hc->name) + 1);
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needed += align_val(sizeof(uint32_t));
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}
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/*
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@ -540,21 +576,20 @@ static int list_devices(struct file *filp, struct dm_ioctl *param, size_t param_
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/*
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* Now loop through filling out the names.
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*/
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for (i = 0; i < NUM_BUCKETS; i++) {
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list_for_each_entry (hc, _name_buckets + i, name_list) {
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if (old_nl)
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old_nl->next = (uint32_t) ((void *) nl -
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(void *) old_nl);
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disk = dm_disk(hc->md);
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nl->dev = huge_encode_dev(disk_devt(disk));
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nl->next = 0;
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strcpy(nl->name, hc->name);
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for (n = rb_first(&name_rb_tree); n; n = rb_next(n)) {
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hc = container_of(n, struct hash_cell, name_node);
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if (old_nl)
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old_nl->next = (uint32_t) ((void *) nl -
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(void *) old_nl);
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disk = dm_disk(hc->md);
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nl->dev = huge_encode_dev(disk_devt(disk));
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nl->next = 0;
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strcpy(nl->name, hc->name);
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old_nl = nl;
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event_nr = align_ptr(nl->name + strlen(hc->name) + 1);
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*event_nr = dm_get_event_nr(hc->md);
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nl = align_ptr(event_nr + 1);
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}
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old_nl = nl;
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event_nr = align_ptr(nl->name + strlen(hc->name) + 1);
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*event_nr = dm_get_event_nr(hc->md);
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nl = align_ptr(event_nr + 1);
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}
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/*
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* If mismatch happens, security may be compromised due to buffer
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@ -1991,14 +2026,9 @@ int __init dm_interface_init(void)
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{
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int r;
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r = dm_hash_init();
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if (r)
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return r;
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r = misc_register(&_dm_misc);
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if (r) {
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DMERR("misc_register failed for control device");
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dm_hash_exit();
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return r;
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}
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