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fs/mbcache.c: doucple the locking of local from global data 

The patch increases the parallelism of mbcache by using the built-in
lock in the hlist_bl_node to protect the mb_cache's local block and
index hash chains.  The global data mb_cache_lru_list and
mb_cache_list continue to be protected by the global
mb_cache_spinlock.

New block group spinlock, mb_cache_bg_lock is also added to serialize
accesses to mb_cache_entry's local data.

A new member e_refcnt is added to the mb_cache_entry structure to help
preventing an mb_cache_entry from being deallocated by a free while it
is being referenced by either mb_cache_entry_get() or
mb_cache_entry_find().

Signed-off-by: T. Makphaibulchoke <tmac@hp.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
T Makphaibulchoke 2014-03-18 19:23:20 -04:00 committed by Theodore Ts'o
parent 3e037e5211
commit 1f3e55fe02
1 changed files with 303 additions and 118 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

367
fs/mbcache.c
View File

@ -26,6 +26,41 @@
* back on the lru list. * back on the lru list.
*/ */
/*
* Lock descriptions and usage:
*
* Each hash chain of both the block and index hash tables now contains
* a built-in lock used to serialize accesses to the hash chain.
*
* Accesses to global data structures mb_cache_list and mb_cache_lru_list
* are serialized via the global spinlock mb_cache_spinlock.
*
* Each mb_cache_entry contains a spinlock, e_entry_lock, to serialize
* accesses to its local data, such as e_used and e_queued.
*
* Lock ordering:
*
* Each block hash chain's lock has the highest lock order, followed by an
* index hash chain's lock, mb_cache_bg_lock (used to implement mb_cache_entry's
* lock), and mb_cach_spinlock, with the lowest order. While holding
* either a block or index hash chain lock, a thread can acquire an
* mc_cache_bg_lock, which in turn can also acquire mb_cache_spinlock.
*
* Synchronization:
*
* Since both mb_cache_entry_get and mb_cache_entry_find scan the block and
* index hash chian, it needs to lock the corresponding hash chain. For each
* mb_cache_entry within the chain, it needs to lock the mb_cache_entry to
* prevent either any simultaneous release or free on the entry and also
* to serialize accesses to either the e_used or e_queued member of the entry.
*
* To avoid having a dangling reference to an already freed
* mb_cache_entry, an mb_cache_entry is only freed when it is not on a
* block hash chain and also no longer being referenced, both e_used,
* and e_queued are 0's. When an mb_cache_entry is explicitly freed it is
* first removed from a block hash chain.
*/
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/module.h> #include <linux/module.h>
@ -37,6 +72,7 @@
#include <linux/list_bl.h> #include <linux/list_bl.h>
#include <linux/mbcache.h> #include <linux/mbcache.h>
#include <linux/init.h> #include <linux/init.h>
#include <linux/blockgroup_lock.h>
#ifdef MB_CACHE_DEBUG #ifdef MB_CACHE_DEBUG
# define mb_debug(f...) do { \ # define mb_debug(f...) do { \
@ -57,7 +93,12 @@
#define MB_CACHE_WRITER ((unsigned short)~0U >> 1) #define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS)
#define MB_CACHE_ENTRY_LOCK_INDEX(ce) \
(hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS))
static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue); static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
static struct blockgroup_lock *mb_cache_bg_lock;
MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>"); MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
MODULE_DESCRIPTION("Meta block cache (for extended attributes)"); MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
@ -86,6 +127,20 @@ static LIST_HEAD(mb_cache_list);
static LIST_HEAD(mb_cache_lru_list); static LIST_HEAD(mb_cache_lru_list);
static DEFINE_SPINLOCK(mb_cache_spinlock); static DEFINE_SPINLOCK(mb_cache_spinlock);
static inline void
__spin_lock_mb_cache_entry(struct mb_cache_entry *ce)
{
spin_lock(bgl_lock_ptr(mb_cache_bg_lock,
MB_CACHE_ENTRY_LOCK_INDEX(ce)));
}
static inline void
__spin_unlock_mb_cache_entry(struct mb_cache_entry *ce)
{
spin_unlock(bgl_lock_ptr(mb_cache_bg_lock,
MB_CACHE_ENTRY_LOCK_INDEX(ce)));
}
static inline int static inline int
__mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce) __mb_cache_entry_is_block_hashed(struct mb_cache_entry *ce)
{ {
@ -113,11 +168,21 @@ __mb_cache_entry_unhash_index(struct mb_cache_entry *ce)
hlist_bl_del_init(&ce->e_index.o_list); hlist_bl_del_init(&ce->e_index.o_list);
} }
/*
* __mb_cache_entry_unhash_unlock()
*
* This function is called to unhash both the block and index hash
* chain.
* It assumes both the block and index hash chain is locked upon entry.
* It also unlock both hash chains both exit
*/
static inline void static inline void
__mb_cache_entry_unhash(struct mb_cache_entry *ce) __mb_cache_entry_unhash_unlock(struct mb_cache_entry *ce)
{ {
__mb_cache_entry_unhash_index(ce); __mb_cache_entry_unhash_index(ce);
hlist_bl_unlock(ce->e_index_hash_p);
__mb_cache_entry_unhash_block(ce); __mb_cache_entry_unhash_block(ce);
hlist_bl_unlock(ce->e_block_hash_p);
} }
static void static void
@ -125,36 +190,47 @@ __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
{ {
struct mb_cache *cache = ce->e_cache; struct mb_cache *cache = ce->e_cache;
mb_assert(!(ce->e_used || ce->e_queued)); mb_assert(!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt)));
kmem_cache_free(cache->c_entry_cache, ce); kmem_cache_free(cache->c_entry_cache, ce);
atomic_dec(&cache->c_entry_count); atomic_dec(&cache->c_entry_count);
} }
static void static void
__mb_cache_entry_release_unlock(struct mb_cache_entry *ce) __mb_cache_entry_release(struct mb_cache_entry *ce)
__releases(mb_cache_spinlock)
{ {
/* First lock the entry to serialize access to its local data. */
__spin_lock_mb_cache_entry(ce);
/* Wake up all processes queuing for this cache entry. */ /* Wake up all processes queuing for this cache entry. */
if (ce->e_queued) if (ce->e_queued)
wake_up_all(&mb_cache_queue); wake_up_all(&mb_cache_queue);
if (ce->e_used >= MB_CACHE_WRITER) if (ce->e_used >= MB_CACHE_WRITER)
ce->e_used -= MB_CACHE_WRITER; ce->e_used -= MB_CACHE_WRITER;
/*
* Make sure that all cache entries on lru_list have
* both e_used and e_qued of 0s.
*/
ce->e_used--; ce->e_used--;
if (!(ce->e_used || ce->e_queued)) { if (!(ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))) {
if (!__mb_cache_entry_is_block_hashed(ce)) if (!__mb_cache_entry_is_block_hashed(ce)) {
__spin_unlock_mb_cache_entry(ce);
goto forget; goto forget;
mb_assert(list_empty(&ce->e_lru_list));
list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
} }
/*
* Need access to lru list, first drop entry lock,
* then reacquire the lock in the proper order.
*/
spin_lock(&mb_cache_spinlock);
if (list_empty(&ce->e_lru_list))
list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
spin_unlock(&mb_cache_spinlock); spin_unlock(&mb_cache_spinlock);
}
__spin_unlock_mb_cache_entry(ce);
return; return;
forget: forget:
spin_unlock(&mb_cache_spinlock); mb_assert(list_empty(&ce->e_lru_list));
__mb_cache_entry_forget(ce, GFP_KERNEL); __mb_cache_entry_forget(ce, GFP_KERNEL);
} }
/* /*
* mb_cache_shrink_scan() memory pressure callback * mb_cache_shrink_scan() memory pressure callback
* *
@ -177,17 +253,34 @@ mb_cache_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
mb_debug("trying to free %d entries", nr_to_scan); mb_debug("trying to free %d entries", nr_to_scan);
spin_lock(&mb_cache_spinlock); spin_lock(&mb_cache_spinlock);
while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) { while ((nr_to_scan-- > 0) && !list_empty(&mb_cache_lru_list)) {
struct mb_cache_entry *ce = struct mb_cache_entry *ce =
list_entry(mb_cache_lru_list.next, list_entry(mb_cache_lru_list.next,
struct mb_cache_entry, e_lru_list); struct mb_cache_entry, e_lru_list);
list_move_tail(&ce->e_lru_list, &free_list); list_del_init(&ce->e_lru_list);
__mb_cache_entry_unhash(ce); if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt))
freed++; continue;
spin_unlock(&mb_cache_spinlock);
/* Prevent any find or get operation on the entry */
hlist_bl_lock(ce->e_block_hash_p);
hlist_bl_lock(ce->e_index_hash_p);
/* Ignore if it is touched by a find/get */
if (ce->e_used || ce->e_queued || atomic_read(&ce->e_refcnt) ||
!list_empty(&ce->e_lru_list)) {
hlist_bl_unlock(ce->e_index_hash_p);
hlist_bl_unlock(ce->e_block_hash_p);
spin_lock(&mb_cache_spinlock);
continue;
}
__mb_cache_entry_unhash_unlock(ce);
list_add_tail(&ce->e_lru_list, &free_list);
spin_lock(&mb_cache_spinlock);
} }
spin_unlock(&mb_cache_spinlock); spin_unlock(&mb_cache_spinlock);
list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) { list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
__mb_cache_entry_forget(entry, gfp_mask); __mb_cache_entry_forget(entry, gfp_mask);
freed++;
} }
return freed; return freed;
} }
@ -232,6 +325,14 @@ mb_cache_create(const char *name, int bucket_bits)
int n, bucket_count = 1 << bucket_bits; int n, bucket_count = 1 << bucket_bits;
struct mb_cache *cache = NULL; struct mb_cache *cache = NULL;
if (!mb_cache_bg_lock) {
mb_cache_bg_lock = kmalloc(sizeof(struct blockgroup_lock),
GFP_KERNEL);
if (!mb_cache_bg_lock)
return NULL;
bgl_lock_init(mb_cache_bg_lock);
}
cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL); cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
if (!cache) if (!cache)
return NULL; return NULL;
@ -290,21 +391,47 @@ void
mb_cache_shrink(struct block_device *bdev) mb_cache_shrink(struct block_device *bdev)
{ {
LIST_HEAD(free_list); LIST_HEAD(free_list);
struct list_head *l, *ltmp; struct list_head *l;
struct mb_cache_entry *ce, *tmp;
l = &mb_cache_lru_list;
spin_lock(&mb_cache_spinlock); spin_lock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &mb_cache_lru_list) { while (!list_is_last(l, &mb_cache_lru_list)) {
struct mb_cache_entry *ce = l = l->next;
list_entry(l, struct mb_cache_entry, e_lru_list); ce = list_entry(l, struct mb_cache_entry, e_lru_list);
if (ce->e_bdev == bdev) { if (ce->e_bdev == bdev) {
list_move_tail(&ce->e_lru_list, &free_list); list_del_init(&ce->e_lru_list);
__mb_cache_entry_unhash(ce); if (ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt))
continue;
spin_unlock(&mb_cache_spinlock);
/*
* Prevent any find or get operation on the entry.
*/
hlist_bl_lock(ce->e_block_hash_p);
hlist_bl_lock(ce->e_index_hash_p);
/* Ignore if it is touched by a find/get */
if (ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt) ||
!list_empty(&ce->e_lru_list)) {
hlist_bl_unlock(ce->e_index_hash_p);
hlist_bl_unlock(ce->e_block_hash_p);
l = &mb_cache_lru_list;
spin_lock(&mb_cache_spinlock);
continue;
}
__mb_cache_entry_unhash_unlock(ce);
mb_assert(!(ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt)));
list_add_tail(&ce->e_lru_list, &free_list);
l = &mb_cache_lru_list;
spin_lock(&mb_cache_spinlock);
} }
} }
spin_unlock(&mb_cache_spinlock); spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
e_lru_list), GFP_KERNEL); __mb_cache_entry_forget(ce, GFP_KERNEL);
} }
} }
@ -320,23 +447,27 @@ void
mb_cache_destroy(struct mb_cache *cache) mb_cache_destroy(struct mb_cache *cache)
{ {
LIST_HEAD(free_list); LIST_HEAD(free_list);
struct list_head *l, *ltmp; struct mb_cache_entry *ce, *tmp;
spin_lock(&mb_cache_spinlock); spin_lock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &mb_cache_lru_list) { list_for_each_entry_safe(ce, tmp, &mb_cache_lru_list, e_lru_list) {
struct mb_cache_entry *ce = if (ce->e_cache == cache)
list_entry(l, struct mb_cache_entry, e_lru_list);
if (ce->e_cache == cache) {
list_move_tail(&ce->e_lru_list, &free_list); list_move_tail(&ce->e_lru_list, &free_list);
__mb_cache_entry_unhash(ce);
}
} }
list_del(&cache->c_cache_list); list_del(&cache->c_cache_list);
spin_unlock(&mb_cache_spinlock); spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) { list_for_each_entry_safe(ce, tmp, &free_list, e_lru_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, list_del_init(&ce->e_lru_list);
e_lru_list), GFP_KERNEL); /*
* Prevent any find or get operation on the entry.
*/
hlist_bl_lock(ce->e_block_hash_p);
hlist_bl_lock(ce->e_index_hash_p);
mb_assert(!(ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt)));
__mb_cache_entry_unhash_unlock(ce);
__mb_cache_entry_forget(ce, GFP_KERNEL);
} }
if (atomic_read(&cache->c_entry_count) > 0) { if (atomic_read(&cache->c_entry_count) > 0) {
@ -345,8 +476,6 @@ mb_cache_destroy(struct mb_cache *cache)
atomic_read(&cache->c_entry_count)); atomic_read(&cache->c_entry_count));
} }
kmem_cache_destroy(cache->c_entry_cache);
kfree(cache->c_index_hash); kfree(cache->c_index_hash);
kfree(cache->c_block_hash); kfree(cache->c_block_hash);
kfree(cache); kfree(cache);
@ -363,19 +492,48 @@ mb_cache_destroy(struct mb_cache *cache)
struct mb_cache_entry * struct mb_cache_entry *
mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags) mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
{ {
struct mb_cache_entry *ce = NULL; struct mb_cache_entry *ce;
if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) { if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
struct list_head *l;
l = &mb_cache_lru_list;
spin_lock(&mb_cache_spinlock); spin_lock(&mb_cache_spinlock);
if (!list_empty(&mb_cache_lru_list)) { while (!list_is_last(l, &mb_cache_lru_list)) {
ce = list_entry(mb_cache_lru_list.next, l = l->next;
struct mb_cache_entry, e_lru_list); ce = list_entry(l, struct mb_cache_entry, e_lru_list);
if (ce->e_cache == cache) {
list_del_init(&ce->e_lru_list); list_del_init(&ce->e_lru_list);
__mb_cache_entry_unhash(ce); if (ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt))
continue;
spin_unlock(&mb_cache_spinlock);
/*
* Prevent any find or get operation on the
* entry.
*/
hlist_bl_lock(ce->e_block_hash_p);
hlist_bl_lock(ce->e_index_hash_p);
/* Ignore if it is touched by a find/get */
if (ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt) ||
!list_empty(&ce->e_lru_list)) {
hlist_bl_unlock(ce->e_index_hash_p);
hlist_bl_unlock(ce->e_block_hash_p);
l = &mb_cache_lru_list;
spin_lock(&mb_cache_spinlock);
continue;
}
mb_assert(list_empty(&ce->e_lru_list));
mb_assert(!(ce->e_used || ce->e_queued ||
atomic_read(&ce->e_refcnt)));
__mb_cache_entry_unhash_unlock(ce);
goto found;
}
} }
spin_unlock(&mb_cache_spinlock); spin_unlock(&mb_cache_spinlock);
} }
if (!ce) {
ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags); ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
if (!ce) if (!ce)
return NULL; return NULL;
@ -385,7 +543,8 @@ mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
INIT_HLIST_BL_NODE(&ce->e_index.o_list); INIT_HLIST_BL_NODE(&ce->e_index.o_list);
ce->e_cache = cache; ce->e_cache = cache;
ce->e_queued = 0; ce->e_queued = 0;
} atomic_set(&ce->e_refcnt, 0);
found:
ce->e_block_hash_p = &cache->c_block_hash[0]; ce->e_block_hash_p = &cache->c_block_hash[0];
ce->e_index_hash_p = &cache->c_index_hash[0]; ce->e_index_hash_p = &cache->c_index_hash[0];
ce->e_used = 1 + MB_CACHE_WRITER; ce->e_used = 1 + MB_CACHE_WRITER;
@ -414,7 +573,6 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
struct mb_cache *cache = ce->e_cache; struct mb_cache *cache = ce->e_cache;
unsigned int bucket; unsigned int bucket;
struct hlist_bl_node *l; struct hlist_bl_node *l;
int error = -EBUSY;
struct hlist_bl_head *block_hash_p; struct hlist_bl_head *block_hash_p;
struct hlist_bl_head *index_hash_p; struct hlist_bl_head *index_hash_p;
struct mb_cache_entry *lce; struct mb_cache_entry *lce;
@ -423,26 +581,29 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits); cache->c_bucket_bits);
block_hash_p = &cache->c_block_hash[bucket]; block_hash_p = &cache->c_block_hash[bucket];
spin_lock(&mb_cache_spinlock); hlist_bl_lock(block_hash_p);
hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) { hlist_bl_for_each_entry(lce, l, block_hash_p, e_block_list) {
if (lce->e_bdev == bdev && lce->e_block == block) if (lce->e_bdev == bdev && lce->e_block == block) {
goto out; hlist_bl_unlock(block_hash_p);
return -EBUSY;
}
} }
mb_assert(!__mb_cache_entry_is_block_hashed(ce)); mb_assert(!__mb_cache_entry_is_block_hashed(ce));
__mb_cache_entry_unhash(ce); __mb_cache_entry_unhash_block(ce);
__mb_cache_entry_unhash_index(ce);
ce->e_bdev = bdev; ce->e_bdev = bdev;
ce->e_block = block; ce->e_block = block;
ce->e_block_hash_p = block_hash_p; ce->e_block_hash_p = block_hash_p;
ce->e_index.o_key = key; ce->e_index.o_key = key;
hlist_bl_add_head(&ce->e_block_list, block_hash_p);
hlist_bl_unlock(block_hash_p);
bucket = hash_long(key, cache->c_bucket_bits); bucket = hash_long(key, cache->c_bucket_bits);
index_hash_p = &cache->c_index_hash[bucket]; index_hash_p = &cache->c_index_hash[bucket];
hlist_bl_lock(index_hash_p);
ce->e_index_hash_p = index_hash_p; 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_index.o_list, index_hash_p);
hlist_bl_add_head(&ce->e_block_list, block_hash_p); hlist_bl_unlock(index_hash_p);
error = 0; return 0;
out:
spin_unlock(&mb_cache_spinlock);
return error;
} }
@ -456,24 +617,26 @@ mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
void void
mb_cache_entry_release(struct mb_cache_entry *ce) mb_cache_entry_release(struct mb_cache_entry *ce)
{ {
spin_lock(&mb_cache_spinlock); __mb_cache_entry_release(ce);
__mb_cache_entry_release_unlock(ce);
} }
/* /*
* mb_cache_entry_free() * mb_cache_entry_free()
* *
* This is equivalent to the sequence mb_cache_entry_takeout() --
* mb_cache_entry_release().
*/ */
void void
mb_cache_entry_free(struct mb_cache_entry *ce) mb_cache_entry_free(struct mb_cache_entry *ce)
{ {
spin_lock(&mb_cache_spinlock); mb_assert(ce);
mb_assert(list_empty(&ce->e_lru_list)); mb_assert(list_empty(&ce->e_lru_list));
__mb_cache_entry_unhash(ce); hlist_bl_lock(ce->e_index_hash_p);
__mb_cache_entry_release_unlock(ce); __mb_cache_entry_unhash_index(ce);
hlist_bl_unlock(ce->e_index_hash_p);
hlist_bl_lock(ce->e_block_hash_p);
__mb_cache_entry_unhash_block(ce);
hlist_bl_unlock(ce->e_block_hash_p);
__mb_cache_entry_release(ce);
} }
@ -497,40 +660,49 @@ mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
cache->c_bucket_bits); cache->c_bucket_bits);
block_hash_p = &cache->c_block_hash[bucket]; block_hash_p = &cache->c_block_hash[bucket];
spin_lock(&mb_cache_spinlock); /* First serialize access to the block corresponding hash chain. */
hlist_bl_lock(block_hash_p);
hlist_bl_for_each_entry(ce, l, block_hash_p, 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); mb_assert(ce->e_block_hash_p == block_hash_p);
if (ce->e_bdev == bdev && ce->e_block == block) { if (ce->e_bdev == bdev && ce->e_block == block) {
/*
* Prevent a free from removing the entry.
*/
atomic_inc(&ce->e_refcnt);
hlist_bl_unlock(block_hash_p);
__spin_lock_mb_cache_entry(ce);
atomic_dec(&ce->e_refcnt);
if (ce->e_used > 0) {
DEFINE_WAIT(wait); DEFINE_WAIT(wait);
if (!list_empty(&ce->e_lru_list))
list_del_init(&ce->e_lru_list);
while (ce->e_used > 0) { while (ce->e_used > 0) {
ce->e_queued++; ce->e_queued++;
prepare_to_wait(&mb_cache_queue, &wait, prepare_to_wait(&mb_cache_queue, &wait,
TASK_UNINTERRUPTIBLE); TASK_UNINTERRUPTIBLE);
spin_unlock(&mb_cache_spinlock); __spin_unlock_mb_cache_entry(ce);
schedule(); schedule();
spin_lock(&mb_cache_spinlock); __spin_lock_mb_cache_entry(ce);
ce->e_queued--; ce->e_queued--;
} }
finish_wait(&mb_cache_queue, &wait); finish_wait(&mb_cache_queue, &wait);
}
ce->e_used += 1 + MB_CACHE_WRITER; ce->e_used += 1 + MB_CACHE_WRITER;
__spin_unlock_mb_cache_entry(ce);
if (!list_empty(&ce->e_lru_list)) {
spin_lock(&mb_cache_spinlock);
list_del_init(&ce->e_lru_list);
spin_unlock(&mb_cache_spinlock);
}
if (!__mb_cache_entry_is_block_hashed(ce)) { if (!__mb_cache_entry_is_block_hashed(ce)) {
__mb_cache_entry_release_unlock(ce); __mb_cache_entry_release(ce);
return NULL; return NULL;
} }
goto cleanup;
}
}
ce = NULL;
cleanup:
spin_unlock(&mb_cache_spinlock);
return ce; return ce;
} }
}
hlist_bl_unlock(block_hash_p);
return NULL;
}
#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) #if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
@ -538,40 +710,53 @@ static struct mb_cache_entry *
__mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head, __mb_cache_entry_find(struct hlist_bl_node *l, struct hlist_bl_head *head,
struct block_device *bdev, unsigned int key) struct block_device *bdev, unsigned int key)
{ {
/* The index hash chain is alredy acquire by caller. */
while (l != NULL) { while (l != NULL) {
struct mb_cache_entry *ce = struct mb_cache_entry *ce =
hlist_bl_entry(l, struct mb_cache_entry, hlist_bl_entry(l, struct mb_cache_entry,
e_index.o_list); e_index.o_list);
mb_assert(ce->e_index_hash_p == head); mb_assert(ce->e_index_hash_p == head);
if (ce->e_bdev == bdev && ce->e_index.o_key == key) { if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
DEFINE_WAIT(wait); /*
* Prevent a free from removing the entry.
if (!list_empty(&ce->e_lru_list)) */
list_del_init(&ce->e_lru_list); atomic_inc(&ce->e_refcnt);
hlist_bl_unlock(head);
__spin_lock_mb_cache_entry(ce);
atomic_dec(&ce->e_refcnt);
ce->e_used++;
/* Incrementing before holding the lock gives readers /* Incrementing before holding the lock gives readers
priority over writers. */ priority over writers. */
ce->e_used++; if (ce->e_used >= MB_CACHE_WRITER) {
DEFINE_WAIT(wait);
while (ce->e_used >= MB_CACHE_WRITER) { while (ce->e_used >= MB_CACHE_WRITER) {
ce->e_queued++; ce->e_queued++;
prepare_to_wait(&mb_cache_queue, &wait, prepare_to_wait(&mb_cache_queue, &wait,
TASK_UNINTERRUPTIBLE); TASK_UNINTERRUPTIBLE);
spin_unlock(&mb_cache_spinlock); __spin_unlock_mb_cache_entry(ce);
schedule(); schedule();
spin_lock(&mb_cache_spinlock); __spin_lock_mb_cache_entry(ce);
ce->e_queued--; ce->e_queued--;
} }
finish_wait(&mb_cache_queue, &wait); finish_wait(&mb_cache_queue, &wait);
}
if (!__mb_cache_entry_is_block_hashed(ce)) { __spin_unlock_mb_cache_entry(ce);
__mb_cache_entry_release_unlock(ce); if (!list_empty(&ce->e_lru_list)) {
spin_lock(&mb_cache_spinlock); spin_lock(&mb_cache_spinlock);
list_del_init(&ce->e_lru_list);
spin_unlock(&mb_cache_spinlock);
}
if (!__mb_cache_entry_is_block_hashed(ce)) {
__mb_cache_entry_release(ce);
return ERR_PTR(-EAGAIN); return ERR_PTR(-EAGAIN);
} }
return ce; return ce;
} }
l = l->next; l = l->next;
} }
hlist_bl_unlock(head);
return NULL; return NULL;
} }
@ -598,12 +783,12 @@ mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
struct hlist_bl_head *index_hash_p; struct hlist_bl_head *index_hash_p;
index_hash_p = &cache->c_index_hash[bucket]; index_hash_p = &cache->c_index_hash[bucket];
spin_lock(&mb_cache_spinlock); hlist_bl_lock(index_hash_p);
if (!hlist_bl_empty(index_hash_p)) { if (!hlist_bl_empty(index_hash_p)) {
l = hlist_bl_first(index_hash_p); l = hlist_bl_first(index_hash_p);
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key); ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
} } else
spin_unlock(&mb_cache_spinlock); hlist_bl_unlock(index_hash_p);
return ce; return ce;
} }
@ -638,11 +823,11 @@ mb_cache_entry_find_next(struct mb_cache_entry *prev,
index_hash_p = &cache->c_index_hash[bucket]; index_hash_p = &cache->c_index_hash[bucket];
mb_assert(prev->e_index_hash_p == index_hash_p); mb_assert(prev->e_index_hash_p == index_hash_p);
spin_lock(&mb_cache_spinlock); hlist_bl_lock(index_hash_p);
mb_assert(!hlist_bl_empty(index_hash_p)); mb_assert(!hlist_bl_empty(index_hash_p));
l = prev->e_index.o_list.next; l = prev->e_index.o_list.next;
ce = __mb_cache_entry_find(l, index_hash_p, bdev, key); ce = __mb_cache_entry_find(l, index_hash_p, bdev, key);
__mb_cache_entry_release_unlock(prev); __mb_cache_entry_release(prev);
return ce; return ce;
} }