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fs: dcache per-bucket dcache hash locking
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We can turn the dcache hash locking from a global dcache_hash_lock into
per-bucket locking.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
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Nick Piggin committed Jan 7, 2011
1 parent 626d607 commit ceb5bdc
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Showing 4 changed files with 89 additions and 53 deletions.
133 changes: 83 additions & 50 deletions fs/dcache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,14 +33,18 @@
#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:
* - the dcache hash table, s_anon lists
* dcache_hash_bucket lock protects:
* - the dcache hash table
* s_anon bl list spinlock protects:
* - the s_anon list (see __d_drop)
* dcache_lru_lock protects:
* - the dcache lru lists and counters
* d_lock protects:
Expand All @@ -57,7 +61,8 @@
* dcache_inode_lock
* dentry->d_lock
* dcache_lru_lock
* dcache_hash_lock
* dcache_hash_bucket lock
* s_anon lock
*
* If there is an ancestor relationship:
* dentry->d_parent->...->d_parent->d_lock
Expand All @@ -74,7 +79,6 @@ int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_inode_lock);
static __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);

Expand All @@ -96,7 +100,29 @@ static struct kmem_cache *dentry_cache __read_mostly;

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;

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->head.first);
}

static inline void spin_unlock_bucket(struct dcache_hash_bucket *b)
{
__bit_spin_unlock(0, (unsigned long *)&b->head.first);
}

/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
Expand Down Expand Up @@ -144,7 +170,7 @@ static void d_free(struct dentry *dentry)
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->d_u.d_rcu);
else
call_rcu(&dentry->d_u.d_rcu, __d_free);
Expand Down Expand Up @@ -302,11 +328,27 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
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);
dentry_rcuwalk_barrier(dentry);
if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED)) {
bit_spin_lock(0,
(unsigned long *)&dentry->d_sb->s_anon.first);
dentry->d_flags |= DCACHE_UNHASHED;
hlist_bl_del_init(&dentry->d_hash);
__bit_spin_unlock(0,
(unsigned long *)&dentry->d_sb->s_anon.first);
} else {
struct dcache_hash_bucket *b;
b = d_hash(dentry->d_parent, dentry->d_name.hash);
spin_lock_bucket(b);
/*
* We may not actually need to put DCACHE_UNHASHED
* manipulations under the hash lock, but follow
* the principle of least surprise.
*/
dentry->d_flags |= DCACHE_UNHASHED;
hlist_bl_del_rcu(&dentry->d_hash);
spin_unlock_bucket(b);
dentry_rcuwalk_barrier(dentry);
}
}
}
EXPORT_SYMBOL(__d_drop);
Expand Down Expand Up @@ -961,8 +1003,8 @@ void shrink_dcache_for_umount(struct super_block *sb)
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);
}
}
Expand Down Expand Up @@ -1263,7 +1305,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
dentry->d_sb = NULL;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
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);
Expand Down Expand Up @@ -1459,14 +1501,6 @@ struct dentry * d_alloc_root(struct inode * root_inode)
}
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
Expand Down Expand Up @@ -1521,11 +1555,11 @@ struct dentry *d_obtain_alias(struct inode *inode)
tmp->d_sb = inode->i_sb;
tmp->d_inode = inode;
tmp->d_flags |= DCACHE_DISCONNECTED;
tmp->d_flags &= ~DCACHE_UNHASHED;
list_add(&tmp->d_alias, &inode->i_dentry);
spin_lock(&dcache_hash_lock);
hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
spin_unlock(&dcache_hash_lock);
bit_spin_lock(0, (unsigned long *)&tmp->d_sb->s_anon.first);
tmp->d_flags &= ~DCACHE_UNHASHED;
hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
__bit_spin_unlock(0, (unsigned long *)&tmp->d_sb->s_anon.first);
spin_unlock(&tmp->d_lock);
spin_unlock(&dcache_inode_lock);

Expand Down Expand Up @@ -1567,7 +1601,7 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
d_move(new, dentry);
iput(inode);
} else {
/* already taking dcache_inode_lock, so d_add() by hand */
/* already got dcache_inode_lock, so d_add() by hand */
__d_instantiate(dentry, inode);
spin_unlock(&dcache_inode_lock);
security_d_instantiate(dentry, inode);
Expand Down Expand Up @@ -1702,8 +1736,8 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
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 hlist_node *node;
struct dcache_hash_bucket *b = d_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *dentry;

/*
Expand All @@ -1726,7 +1760,7 @@ struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
*
* See Documentation/vfs/dcache-locking.txt for more details.
*/
hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
hlist_bl_for_each_entry_rcu(dentry, node, &b->head, d_hash) {
struct inode *i;
const char *tname;
int tlen;
Expand Down Expand Up @@ -1820,8 +1854,8 @@ struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
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 hlist_node *node;
struct dcache_hash_bucket *b = d_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *found = NULL;
struct dentry *dentry;

Expand All @@ -1847,7 +1881,7 @@ struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
*/
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) {
const char *tname;
int tlen;

Expand Down Expand Up @@ -1998,11 +2032,13 @@ 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)
{

BUG_ON(!d_unhashed(entry));
spin_lock_bucket(b);
entry->d_flags &= ~DCACHE_UNHASHED;
hlist_add_head_rcu(&entry->d_hash, list);
hlist_bl_add_head_rcu(&entry->d_hash, &b->head);
spin_unlock_bucket(b);
}

static void _d_rehash(struct dentry * entry)
Expand All @@ -2020,9 +2056,7 @@ static void _d_rehash(struct dentry * entry)
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);
Expand Down Expand Up @@ -2165,15 +2199,16 @@ void d_move(struct dentry * dentry, struct dentry * target)
write_seqcount_begin(&dentry->d_seq);
write_seqcount_begin(&target->d_seq);

/* 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);
/* __d_drop does write_seqcount_barrier, but they're OK to nest. */

/*
* Move the dentry to the target hash queue. Don't bother checking
* for the same hash queue because of how unlikely it is.
*/
__d_drop(dentry);
__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 does write_seqcount_barrier, but they're OK to nest. */
__d_drop(target);

list_del(&dentry->d_u.d_child);
Expand Down Expand Up @@ -2369,9 +2404,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)

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:
Expand Down Expand Up @@ -2953,7 +2986,7 @@ static void __init dcache_init_early(void)

dentry_hashtable =
alloc_large_system_hash("Dentry cache",
sizeof(struct hlist_head),
sizeof(struct dcache_hash_bucket),
dhash_entries,
13,
HASH_EARLY,
Expand All @@ -2962,7 +2995,7 @@ static void __init dcache_init_early(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);
}

static void __init dcache_init(void)
Expand All @@ -2985,7 +3018,7 @@ 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,
Expand All @@ -2994,7 +3027,7 @@ 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 */
Expand Down
3 changes: 2 additions & 1 deletion fs/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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"


Expand Down Expand Up @@ -71,7 +72,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
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);
Expand Down
3 changes: 2 additions & 1 deletion include/linux/dcache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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/seqlock.h>
#include <linux/cache.h>
Expand Down Expand Up @@ -95,7 +96,7 @@ struct dentry {
/* RCU lookup touched fields */
unsigned int d_flags; /* protected by d_lock */
seqcount_t d_seq; /* per dentry seqlock */
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;
struct inode *d_inode; /* Where the name belongs to - NULL is
Expand Down
3 changes: 2 additions & 1 deletion include/linux/fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -392,6 +392,7 @@ 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>
Expand Down Expand Up @@ -1377,7 +1378,7 @@ 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
Expand Down

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