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fs/mbcache.c: change block and index hash chain to hlist_bl_node
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This patch changes each mb_cache's both block and index hash chains to
use a hlist_bl_node, which contains a built-in lock.  This is the
first step in decoupling of locks serializing accesses to mb_cache
global data and each mb_cache_entry local data.

Signed-off-by: T. Makphaibulchoke <tmac@hp.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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T Makphaibulchoke authored and Theodore Ts'o committed Mar 18, 2014
1 parent b8a8684 commit 3e037e5
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Showing 2 changed files with 85 additions and 44 deletions.
117 changes: 78 additions & 39 deletions fs/mbcache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,9 +34,9 @@
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/list_bl.h>
#include <linux/mbcache.h>

#include <linux/init.h>

#ifdef MB_CACHE_DEBUG
# define mb_debug(f...) do { \
Expand Down Expand Up @@ -87,21 +87,38 @@ static LIST_HEAD(mb_cache_lru_list);
static DEFINE_SPINLOCK(mb_cache_spinlock);

static inline int
__mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
{
return !list_empty(&ce->e_block_list);
return !hlist_bl_unhashed(&ce->e_block_list);
}


static void
__mb_cache_entry_unhash(struct mb_cache_entry *ce)
static inline void
__mb_cache_entry_unhash_block(struct mb_cache_entry *ce)
{
if (__mb_cache_entry_is_hashed(ce)) {
list_del_init(&ce->e_block_list);
list_del(&ce->e_index.o_list);
}
if (__mb_cache_entry_is_block_hashed(ce))
hlist_bl_del_init(&ce->e_block_list);
}

static inline int
__mb_cache_entry_is_index_hashed(struct mb_cache_entry *ce)
{
return !hlist_bl_unhashed(&ce->e_index.o_list);
}

static inline void
__mb_cache_entry_unhash_index(struct mb_cache_entry *ce)
{
if (__mb_cache_entry_is_index_hashed(ce))
hlist_bl_del_init(&ce->e_index.o_list);
}

static inline void
__mb_cache_entry_unhash(struct mb_cache_entry *ce)
{
__mb_cache_entry_unhash_index(ce);
__mb_cache_entry_unhash_block(ce);
}

static void
__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
Expand All @@ -125,7 +142,7 @@ __mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
ce->e_used -= MB_CACHE_WRITER;
ce->e_used--;
if (!(ce->e_used || ce->e_queued)) {
if (!__mb_cache_entry_is_hashed(ce))
if (!__mb_cache_entry_is_block_hashed(ce))
goto forget;
mb_assert(list_empty(&ce->e_lru_list));
list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
Expand Down Expand Up @@ -221,18 +238,18 @@ mb_cache_create(const char *name, int bucket_bits)
cache->c_name = name;
atomic_set(&cache->c_entry_count, 0);
cache->c_bucket_bits = bucket_bits;
cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
GFP_KERNEL);
cache->c_block_hash = kmalloc(bucket_count *
sizeof(struct hlist_bl_head), GFP_KERNEL);
if (!cache->c_block_hash)
goto fail;
for (n=0; n<bucket_count; n++)
INIT_LIST_HEAD(&cache->c_block_hash[n]);
cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head),
GFP_KERNEL);
INIT_HLIST_BL_HEAD(&cache->c_block_hash[n]);
cache->c_index_hash = kmalloc(bucket_count *
sizeof(struct hlist_bl_head), GFP_KERNEL);
if (!cache->c_index_hash)
goto fail;
for (n=0; n<bucket_count; n++)
INIT_LIST_HEAD(&cache->c_index_hash[n]);
INIT_HLIST_BL_HEAD(&cache->c_index_hash[n]);
cache->c_entry_cache = kmem_cache_create(name,
sizeof(struct mb_cache_entry), 0,
SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
Expand Down Expand Up @@ -364,10 +381,13 @@ mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
return NULL;
atomic_inc(&cache->c_entry_count);
INIT_LIST_HEAD(&ce->e_lru_list);
INIT_LIST_HEAD(&ce->e_block_list);
INIT_HLIST_BL_NODE(&ce->e_block_list);
INIT_HLIST_BL_NODE(&ce->e_index.o_list);
ce->e_cache = cache;
ce->e_queued = 0;
}
ce->e_block_hash_p = &cache->c_block_hash[0];
ce->e_index_hash_p = &cache->c_index_hash[0];
ce->e_used = 1 + MB_CACHE_WRITER;
return ce;
}
Expand All @@ -393,25 +413,32 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
{
struct mb_cache *cache = ce->e_cache;
unsigned int bucket;
struct list_head *l;
struct hlist_bl_node *l;
int error = -EBUSY;
struct hlist_bl_head *block_hash_p;
struct hlist_bl_head *index_hash_p;
struct mb_cache_entry *lce;

mb_assert(ce);
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits);
block_hash_p = &cache->c_block_hash[bucket];
spin_lock(&mb_cache_spinlock);
list_for_each_prev(l, &cache->c_block_hash[bucket]) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry, e_block_list);
if (ce->e_bdev == bdev && ce->e_block == block)
hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
if (lce->e_bdev == bdev && lce->e_block == block)
goto out;
}
mb_assert(!__mb_cache_entry_is_block_hashed(ce));
__mb_cache_entry_unhash(ce);
ce->e_bdev = bdev;
ce->e_block = block;
list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
ce->e_block_hash_p = block_hash_p;
ce->e_index.o_key = key;
bucket = hash_long(key, cache->c_bucket_bits);
list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]);
index_hash_p = &cache->c_index_hash[bucket];
ce->e_index_hash_p = index_hash_p;
hlist_bl_add_head(&ce->e_index.o_list, index_hash_p);
hlist_bl_add_head(&ce->e_block_list, block_hash_p);
error = 0;
out:
spin_unlock(&mb_cache_spinlock);
Expand Down Expand Up @@ -463,14 +490,16 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
sector_t block)
{
unsigned int bucket;
struct list_head *l;
struct hlist_bl_node *l;
struct mb_cache_entry *ce;
struct hlist_bl_head *block_hash_p;

bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits);
block_hash_p = &cache->c_block_hash[bucket];
spin_lock(&mb_cache_spinlock);
list_for_each(l, &cache->c_block_hash[bucket]) {
ce = list_entry(l, struct mb_cache_entry, e_block_list);
hlist_bl_for_each_entry(ce, l, block_hash_p, e_block_list) {
mb_assert(ce->e_block_hash_p == block_hash_p);
if (ce->e_bdev == bdev && ce->e_block == block) {
DEFINE_WAIT(wait);

Expand All @@ -489,7 +518,7 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
finish_wait(&mb_cache_queue, &wait);
ce->e_used += 1 + MB_CACHE_WRITER;

if (!__mb_cache_entry_is_hashed(ce)) {
if (!__mb_cache_entry_is_block_hashed(ce)) {
__mb_cache_entry_release_unlock(ce);
return NULL;
}
Expand All @@ -506,12 +535,14 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)

static struct mb_cache_entry *
__mb_cache_entry_find(struct list_head *l, struct list_head *head,
__mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head,
struct block_device *bdev, unsigned int key)
{
while (l != head) {
while (l != NULL) {
struct mb_cache_entry *ce =
list_entry(l, struct mb_cache_entry, e_index.o_list);
hlist_bl_entry(l, struct mb_cache_entry,
e_index.o_list);
mb_assert(ce->e_index_hash_p == head);
if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
DEFINE_WAIT(wait);

Expand All @@ -532,7 +563,7 @@ __mb_cache_entry_find(struct list_head *l, struct list_head *head,
}
finish_wait(&mb_cache_queue, &wait);

if (!__mb_cache_entry_is_hashed(ce)) {
if (!__mb_cache_entry_is_block_hashed(ce)) {
__mb_cache_entry_release_unlock(ce);
spin_lock(&mb_cache_spinlock);
return ERR_PTR(-EAGAIN);
Expand Down Expand Up @@ -562,12 +593,16 @@ mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
unsigned int key)
{
unsigned int bucket = hash_long(key, cache->c_bucket_bits);
struct list_head *l;
struct mb_cache_entry *ce;
struct hlist_bl_node *l;
struct mb_cache_entry *ce = NULL;
struct hlist_bl_head *index_hash_p;

index_hash_p = &cache->c_index_hash[bucket];
spin_lock(&mb_cache_spinlock);
l = cache->c_index_hash[bucket].next;
ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
if (!hlist_bl_empty(index_hash_p)) {
l = hlist_bl_first(index_hash_p);
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
}
spin_unlock(&mb_cache_spinlock);
return ce;
}
Expand Down Expand Up @@ -597,12 +632,16 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev,
{
struct mb_cache *cache = prev->e_cache;
unsigned int bucket = hash_long(key, cache->c_bucket_bits);
struct list_head *l;
struct hlist_bl_node *l;
struct mb_cache_entry *ce;
struct hlist_bl_head *index_hash_p;

index_hash_p = &cache->c_index_hash[bucket];
mb_assert(prev->e_index_hash_p == index_hash_p);
spin_lock(&mb_cache_spinlock);
mb_assert(!hlist_bl_empty(index_hash_p));
l = prev->e_index.o_list.next;
ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
__mb_cache_entry_release_unlock(prev);
return ce;
}
Expand Down
12 changes: 7 additions & 5 deletions include/linux/mbcache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,19 +3,21 @@
(C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
*/

struct mb_cache_entry {
struct list_head e_lru_list;
struct mb_cache *e_cache;
unsigned short e_used;
unsigned short e_queued;
atomic_t e_refcnt;
struct block_device *e_bdev;
sector_t e_block;
struct list_head e_block_list;
struct hlist_bl_node e_block_list;
struct {
struct list_head o_list;
struct hlist_bl_node o_list;
unsigned int o_key;
} e_index;
struct hlist_bl_head *e_block_hash_p;
struct hlist_bl_head *e_index_hash_p;
};

struct mb_cache {
Expand All @@ -25,8 +27,8 @@ struct mb_cache {
int c_max_entries;
int c_bucket_bits;
struct kmem_cache *c_entry_cache;
struct list_head *c_block_hash;
struct list_head *c_index_hash;
struct hlist_bl_head *c_block_hash;
struct hlist_bl_head *c_index_hash;
};

/* Functions on caches */
Expand Down

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