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Subject[patch 19/52] fs: dcache per-bucket dcache hash locking
We can turn the dcache hash locking from a global dcache_hash_lock into
per-bucket locking.

Signed-off-by: Nick Piggin <npiggin@suse.de>
---
fs/dcache.c | 234 +++++++++++++++++++++++++++----------------------
fs/super.c | 3
include/linux/dcache.h | 23 ----
include/linux/fs.h | 3
4 files changed, 141 insertions(+), 122 deletions(-)

Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -33,13 +33,15 @@
#include <linux/bootmem.h>
#include <linux/fs_struct.h>
#include <linux/hardirq.h>
+#include <linux/bit_spinlock.h>
+#include <linux/rculist_bl.h>
#include "internal.h"

/*
* Usage:
* dcache_inode_lock protects:
* - i_dentry, d_alias, d_inode
- * dcache_hash_lock protects:
+ * dcache_hash_bucket lock protects:
* - the dcache hash table
* dcache_lru_lock protects:
* - the dcache lru lists and counters
@@ -57,7 +59,7 @@
* dcache_inode_lock
* dentry->d_lock
* dcache_lru_lock
- * dcache_hash_lock
+ * dcache_hash_bucket lock
*
* If there is an ancestor relationship:
* dentry->d_parent->...->d_parent->d_lock
@@ -74,13 +76,11 @@ int sysctl_vfs_cache_pressure __read_mos
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_inode_lock);
-__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);

EXPORT_SYMBOL(rename_lock);
EXPORT_SYMBOL(dcache_inode_lock);
-EXPORT_SYMBOL(dcache_hash_lock);

static struct kmem_cache *dentry_cache __read_mostly;

@@ -99,7 +99,11 @@ static struct kmem_cache *dentry_cache _

static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
-static struct hlist_head *dentry_hashtable __read_mostly;
+
+struct dcache_hash_bucket {
+ struct hlist_bl_head head;
+};
+static struct dcache_hash_bucket *dentry_hashtable __read_mostly;

/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
@@ -107,6 +111,24 @@ struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};

+static inline struct dcache_hash_bucket *d_hash(struct dentry *parent,
+ unsigned long hash)
+{
+ hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
+ hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
+ return dentry_hashtable + (hash & D_HASHMASK);
+}
+
+static inline void spin_lock_bucket(struct dcache_hash_bucket *b)
+{
+ bit_spin_lock(0, (unsigned long *)b);
+}
+
+static inline void spin_unlock_bucket(struct dcache_hash_bucket *b)
+{
+ __bit_spin_unlock(0, (unsigned long *)b);
+}
+
static void __d_free(struct dentry *dentry)
{
WARN_ON(!list_empty(&dentry->d_alias));
@@ -131,7 +153,7 @@ static void d_free(struct dentry *dentry
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
/* if dentry was never inserted into hash, immediate free is OK */
- if (hlist_unhashed(&dentry->d_hash))
+ if (hlist_bl_unhashed(&dentry->d_hash))
__d_free(dentry);
else
call_rcu(&dentry->d_u.d_rcu, d_callback);
@@ -247,6 +269,81 @@ static struct dentry *d_kill(struct dent
return parent;
}

+void __d_drop(struct dentry *dentry)
+{
+ if (!(dentry->d_flags & DCACHE_UNHASHED)) {
+ struct dcache_hash_bucket *b;
+ b = d_hash(dentry->d_parent, dentry->d_name.hash);
+ /* XXX: put unhashed inside hash lock? (don't need to actually) */
+ dentry->d_flags |= DCACHE_UNHASHED;
+ spin_lock_bucket(b);
+ hlist_bl_del_rcu(&dentry->d_hash);
+ spin_unlock_bucket(b);
+ }
+}
+EXPORT_SYMBOL(__d_drop);
+
+void d_drop(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_drop);
+
+/* This must be called with d_lock held */
+static inline struct dentry * __dget_locked_dlock(struct dentry *dentry)
+{
+ dentry->d_count++;
+ dentry_lru_del_init(dentry);
+ return dentry;
+}
+
+static inline struct dentry * __dget_locked(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __dget_locked_dlock(dentry);
+ spin_unlock(&dentry->d_lock);
+ return dentry;
+}
+
+struct dentry * dget_locked_dlock(struct dentry *dentry)
+{
+ return __dget_locked_dlock(dentry);
+}
+
+struct dentry * dget_locked(struct dentry *dentry)
+{
+ return __dget_locked(dentry);
+}
+EXPORT_SYMBOL(dget_locked);
+
+struct dentry *dget_parent(struct dentry *dentry)
+{
+ struct dentry *ret;
+
+repeat:
+ spin_lock(&dentry->d_lock);
+ ret = dentry->d_parent;
+ if (!ret)
+ goto out;
+ if (dentry == ret) {
+ ret->d_count++;
+ goto out;
+ }
+ if (!spin_trylock(&ret->d_lock)) {
+ spin_unlock(&dentry->d_lock);
+ goto repeat;
+ }
+ BUG_ON(!ret->d_count);
+ ret->d_count++;
+ spin_unlock(&ret->d_lock);
+out:
+ spin_unlock(&dentry->d_lock);
+ return ret;
+}
+EXPORT_SYMBOL(dget_parent);
+
/*
* This is dput
*
@@ -398,60 +495,6 @@ int d_invalidate(struct dentry * dentry)
}
EXPORT_SYMBOL(d_invalidate);

-/* This must be called with d_lock held */
-static inline struct dentry * __dget_locked_dlock(struct dentry *dentry)
-{
- dentry->d_count++;
- dentry_lru_del_init(dentry);
- return dentry;
-}
-
-/* This must be called with d_lock held */
-static inline struct dentry * __dget_locked(struct dentry *dentry)
-{
- spin_lock(&dentry->d_lock);
- __dget_locked_dlock(dentry);
- spin_unlock(&dentry->d_lock);
- return dentry;
-}
-
-struct dentry * dget_locked_dlock(struct dentry *dentry)
-{
- return __dget_locked_dlock(dentry);
-}
-
-struct dentry * dget_locked(struct dentry *dentry)
-{
- return __dget_locked(dentry);
-}
-EXPORT_SYMBOL(dget_locked);
-
-struct dentry *dget_parent(struct dentry *dentry)
-{
- struct dentry *ret;
-
-repeat:
- spin_lock(&dentry->d_lock);
- ret = dentry->d_parent;
- if (!ret)
- goto out;
- if (dentry == ret) {
- ret->d_count++;
- goto out;
- }
- if (!spin_trylock(&ret->d_lock)) {
- spin_unlock(&dentry->d_lock);
- goto repeat;
- }
- BUG_ON(!ret->d_count);
- ret->d_count++;
- spin_unlock(&ret->d_lock);
-out:
- spin_unlock(&dentry->d_lock);
- return ret;
-}
-EXPORT_SYMBOL(dget_parent);
-
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
@@ -900,8 +943,8 @@ void shrink_dcache_for_umount(struct sup
spin_unlock(&dentry->d_lock);
shrink_dcache_for_umount_subtree(dentry);

- while (!hlist_empty(&sb->s_anon)) {
- dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
+ while (!hlist_bl_empty(&sb->s_anon)) {
+ dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
shrink_dcache_for_umount_subtree(dentry);
}
}
@@ -1183,7 +1226,7 @@ struct dentry *d_alloc(struct dentry * p
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
dentry->d_mounted = 0;
- INIT_HLIST_NODE(&dentry->d_hash);
+ INIT_HLIST_BL_NODE(&dentry->d_hash);
INIT_LIST_HEAD(&dentry->d_lru);
INIT_LIST_HEAD(&dentry->d_subdirs);
INIT_LIST_HEAD(&dentry->d_alias);
@@ -1348,14 +1391,6 @@ struct dentry * d_alloc_root(struct inod
}
EXPORT_SYMBOL(d_alloc_root);

-static inline struct hlist_head *d_hash(struct dentry *parent,
- unsigned long hash)
-{
- hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
- hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
- return dentry_hashtable + (hash & D_HASHMASK);
-}
-
/**
* d_obtain_alias - find or allocate a dentry for a given inode
* @inode: inode to allocate the dentry for
@@ -1411,7 +1446,7 @@ struct dentry *d_obtain_alias(struct ino
tmp->d_flags |= DCACHE_DISCONNECTED;
tmp->d_flags &= ~DCACHE_UNHASHED;
list_add(&tmp->d_alias, &inode->i_dentry);
- hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
+ hlist_bl_add_head(&tmp->d_hash, &inode->i_sb->s_anon); /* XXX: make s_anon a bl list */
spin_unlock(&tmp->d_lock);
spin_unlock(&dcache_inode_lock);

@@ -1604,14 +1639,14 @@ struct dentry * __d_lookup(struct dentry
unsigned int len = name->len;
unsigned int hash = name->hash;
const unsigned char *str = name->name;
- struct hlist_head *head = d_hash(parent,hash);
+ struct dcache_hash_bucket *b = d_hash(parent, hash);
+ struct hlist_bl_node *node;
struct dentry *found = NULL;
- struct hlist_node *node;
struct dentry *dentry;

rcu_read_lock();

- hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
+ hlist_bl_for_each_entry_rcu(dentry, node, &b->head, d_hash) {
struct qstr *qstr;

if (dentry->d_name.hash != hash)
@@ -1698,8 +1733,9 @@ out:

int d_validate(struct dentry *dentry, struct dentry *dparent)
{
- struct hlist_head *base;
- struct hlist_node *lhp;
+ struct dcache_hash_bucket *b;
+ struct dentry *lhp;
+ struct hlist_bl_node *node;

/* Check whether the ptr might be valid at all.. */
if (!kmem_ptr_validate(dentry_cache, dentry))
@@ -1709,20 +1745,17 @@ int d_validate(struct dentry *dentry, st
goto out;

spin_lock(&dentry->d_lock);
- spin_lock(&dcache_hash_lock);
- base = d_hash(dparent, dentry->d_name.hash);
- hlist_for_each(lhp,base) {
- /* hlist_for_each_entry_rcu() not required for d_hash list
- * as it is parsed under dcache_hash_lock
- */
- if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
- spin_unlock(&dcache_hash_lock);
+ b = d_hash(dparent, dentry->d_name.hash);
+ rcu_read_lock();
+ hlist_bl_for_each_entry_rcu(lhp, node, &b->head, d_hash) {
+ if (dentry == lhp) {
+ rcu_read_unlock();
__dget_locked_dlock(dentry);
spin_unlock(&dentry->d_lock);
return 1;
}
}
- spin_unlock(&dcache_hash_lock);
+ rcu_read_unlock();
spin_unlock(&dentry->d_lock);
out:
return 0;
@@ -1776,11 +1809,12 @@ void d_delete(struct dentry * dentry)
}
EXPORT_SYMBOL(d_delete);

-static void __d_rehash(struct dentry * entry, struct hlist_head *list)
+static void __d_rehash(struct dentry * entry, struct dcache_hash_bucket *b)
{
-
entry->d_flags &= ~DCACHE_UNHASHED;
- hlist_add_head_rcu(&entry->d_hash, list);
+ spin_lock_bucket(b);
+ hlist_bl_add_head_rcu(&entry->d_hash, &b->head);
+ spin_unlock_bucket(b);
}

static void _d_rehash(struct dentry * entry)
@@ -1798,9 +1832,7 @@ static void _d_rehash(struct dentry * en
void d_rehash(struct dentry * entry)
{
spin_lock(&entry->d_lock);
- spin_lock(&dcache_hash_lock);
_d_rehash(entry);
- spin_unlock(&dcache_hash_lock);
spin_unlock(&entry->d_lock);
}
EXPORT_SYMBOL(d_rehash);
@@ -1879,6 +1911,7 @@ static void switch_names(struct dentry *
*/
static void d_move_locked(struct dentry * dentry, struct dentry * target)
{
+ struct dcache_hash_bucket *b;
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");

@@ -1909,11 +1942,13 @@ static void d_move_locked(struct dentry
}

/* Move the dentry to the target hash queue, if on different bucket */
- spin_lock(&dcache_hash_lock);
- if (!d_unhashed(dentry))
- hlist_del_rcu(&dentry->d_hash);
+ if (!d_unhashed(dentry)) {
+ b = d_hash(dentry->d_parent, dentry->d_name.hash);
+ spin_lock_bucket(b);
+ hlist_bl_del_rcu(&dentry->d_hash);
+ spin_unlock_bucket(b);
+ }
__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
- spin_unlock(&dcache_hash_lock);

/* Unhash the target: dput() will then get rid of it */
__d_drop(target);
@@ -2121,9 +2156,7 @@ struct dentry *d_materialise_unique(stru
found_lock:
spin_lock(&actual->d_lock);
found:
- spin_lock(&dcache_hash_lock);
_d_rehash(actual);
- spin_unlock(&dcache_hash_lock);
spin_unlock(&actual->d_lock);
spin_unlock(&dcache_inode_lock);
out_nolock:
@@ -2631,7 +2664,7 @@ static void __init dcache_init_early(voi

dentry_hashtable =
alloc_large_system_hash("Dentry cache",
- sizeof(struct hlist_head),
+ sizeof(struct dcache_hash_bucket),
dhash_entries,
13,
HASH_EARLY,
@@ -2640,7 +2673,7 @@ static void __init dcache_init_early(voi
0);

for (loop = 0; loop < (1 << d_hash_shift); loop++)
- INIT_HLIST_HEAD(&dentry_hashtable[loop]);
+ INIT_HLIST_BL_HEAD(&dentry_hashtable[loop].head);
}

static void __init dcache_init(void)
@@ -2663,7 +2696,7 @@ static void __init dcache_init(void)

dentry_hashtable =
alloc_large_system_hash("Dentry cache",
- sizeof(struct hlist_head),
+ sizeof(struct dcache_hash_bucket),
dhash_entries,
13,
0,
@@ -2672,7 +2705,7 @@ static void __init dcache_init(void)
0);

for (loop = 0; loop < (1 << d_hash_shift); loop++)
- INIT_HLIST_HEAD(&dentry_hashtable[loop]);
+ INIT_HLIST_BL_HEAD(&dentry_hashtable[loop].head);
}

/* SLAB cache for __getname() consumers */
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h
+++ linux-2.6/include/linux/dcache.h
@@ -4,6 +4,7 @@
#include <asm/atomic.h>
#include <linux/list.h>
#include <linux/rculist.h>
+#include <linux/rculist_bl.h>
#include <linux/spinlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
@@ -97,7 +98,7 @@ struct dentry {
* The next three fields are touched by __d_lookup. Place them here
* so they all fit in a cache line.
*/
- struct hlist_node d_hash; /* lookup hash list */
+ struct hlist_bl_node d_hash; /* lookup hash list */
struct dentry *d_parent; /* parent directory */
struct qstr d_name;

@@ -190,7 +191,6 @@ d_iput: no no yes
#define DCACHE_GENOCIDE 0x0200

extern spinlock_t dcache_inode_lock;
-extern spinlock_t dcache_hash_lock;
extern seqlock_t rename_lock;

/**
@@ -208,23 +208,8 @@ extern seqlock_t rename_lock;
*
* __d_drop requires dentry->d_lock.
*/
-
-static inline void __d_drop(struct dentry *dentry)
-{
- if (!(dentry->d_flags & DCACHE_UNHASHED)) {
- dentry->d_flags |= DCACHE_UNHASHED;
- spin_lock(&dcache_hash_lock);
- hlist_del_rcu(&dentry->d_hash);
- spin_unlock(&dcache_hash_lock);
- }
-}
-
-static inline void d_drop(struct dentry *dentry)
-{
- spin_lock(&dentry->d_lock);
- __d_drop(dentry);
- spin_unlock(&dentry->d_lock);
-}
+void d_drop(struct dentry *dentry);
+void __d_drop(struct dentry *dentry);

static inline int dname_external(struct dentry *dentry)
{
Index: linux-2.6/fs/super.c
===================================================================
--- linux-2.6.orig/fs/super.c
+++ linux-2.6/fs/super.c
@@ -30,6 +30,7 @@
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
+#include <linux/rculist_bl.h>
#include "internal.h"


@@ -71,7 +72,7 @@ static struct super_block *alloc_super(s
INIT_LIST_HEAD(&s->s_files);
#endif
INIT_LIST_HEAD(&s->s_instances);
- INIT_HLIST_HEAD(&s->s_anon);
+ INIT_HLIST_BL_HEAD(&s->s_anon);
INIT_LIST_HEAD(&s->s_inodes);
INIT_LIST_HEAD(&s->s_dentry_lru);
init_rwsem(&s->s_umount);
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h
+++ linux-2.6/include/linux/fs.h
@@ -382,6 +382,7 @@ struct inodes_stat_t {
#include <linux/capability.h>
#include <linux/semaphore.h>
#include <linux/fiemap.h>
+#include <linux/rculist_bl.h>

#include <asm/atomic.h>
#include <asm/byteorder.h>
@@ -1341,7 +1342,7 @@ struct super_block {
const struct xattr_handler **s_xattr;

struct list_head s_inodes; /* all inodes */
- struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
+ struct hlist_bl_head s_anon; /* anonymous dentries for (nfs) exporting */
#ifdef CONFIG_SMP
struct list_head __percpu *s_files;
#else



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