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fs: dcache scale hash 

Add a new lock, dcache_hash_lock, to protect the dcache hash table from
concurrent modification. d_hash is also protected by d_lock.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:30 +11:00
parent ec2447c278
commit 789680d1ee
2 changed files with 64 additions and 44 deletions
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73
fs/dcache.c
View File

@ -35,10 +35,24 @@
#include <linux/hardirq.h>
#include "internal.h"
/*
* Usage:
* dcache_hash_lock protects dcache hash table, s_anon lists
*
* Ordering:
* dcache_lock
* dentry->d_lock
* dcache_hash_lock
*
* if (dentry1 < dentry2)
* dentry1->d_lock
* dentry2->d_lock
*/
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
EXPORT_SYMBOL(dcache_lock);
@ -196,6 +210,42 @@ static struct dentry *d_kill(struct dentry *dentry)
return parent;
}
/**
* d_drop - drop a dentry
* @dentry: dentry to drop
*
* d_drop() unhashes the entry from the parent dentry hashes, so that it won't
* be found through a VFS lookup any more. Note that this is different from
* deleting the dentry - d_delete will try to mark the dentry negative if
* possible, giving a successful _negative_ lookup, while d_drop will
* just make the cache lookup fail.
*
* d_drop() is used mainly for stuff that wants to invalidate a dentry for some
* reason (NFS timeouts or autofs deletes).
*
* __d_drop requires dentry->d_lock.
*/
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);
}
}
EXPORT_SYMBOL(__d_drop);
void d_drop(struct dentry *dentry)
{
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
EXPORT_SYMBOL(d_drop);
/*
* This is dput
*
@ -1199,7 +1249,9 @@ struct dentry *d_obtain_alias(struct 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);
spin_unlock(&tmp->d_lock);
spin_unlock(&dcache_lock);
@ -1585,7 +1637,9 @@ void d_rehash(struct dentry * entry)
{
spin_lock(&dcache_lock);
spin_lock(&entry->d_lock);
spin_lock(&dcache_hash_lock);
_d_rehash(entry);
spin_unlock(&dcache_hash_lock);
spin_unlock(&entry->d_lock);
spin_unlock(&dcache_lock);
}
@ -1692,8 +1746,6 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
*/
static void d_move_locked(struct dentry * dentry, struct dentry * target)
{
struct hlist_head *list;
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
@ -1710,14 +1762,11 @@ static void d_move_locked(struct dentry * dentry, struct dentry * target)
}
/* Move the dentry to the target hash queue, if on different bucket */
if (d_unhashed(dentry))
goto already_unhashed;
hlist_del_rcu(&dentry->d_hash);
already_unhashed:
list = d_hash(target->d_parent, target->d_name.hash);
__d_rehash(dentry, list);
spin_lock(&dcache_hash_lock);
if (!d_unhashed(dentry))
hlist_del_rcu(&dentry->d_hash);
__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);
@ -1914,7 +1963,9 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
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_lock);
out_nolock:

35
include/linux/dcache.h
View File

@ -184,39 +184,6 @@ struct dentry_operations {
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
/**
* d_drop - drop a dentry
* @dentry: dentry to drop
*
* d_drop() unhashes the entry from the parent dentry hashes, so that it won't
* be found through a VFS lookup any more. Note that this is different from
* deleting the dentry - d_delete will try to mark the dentry negative if
* possible, giving a successful _negative_ lookup, while d_drop will
* just make the cache lookup fail.
*
* d_drop() is used mainly for stuff that wants to invalidate a dentry for some
* reason (NFS timeouts or autofs deletes).
*
* __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;
hlist_del_rcu(&dentry->d_hash);
}
}
static inline void d_drop(struct dentry *dentry)
{
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
static inline int dname_external(struct dentry *dentry)
{
return dentry->d_name.name != dentry->d_iname;
@ -228,6 +195,8 @@ static inline int dname_external(struct dentry *dentry)
extern void d_instantiate(struct dentry *, struct inode *);
extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
extern void __d_drop(struct dentry *dentry);
extern void d_drop(struct dentry *dentry);
extern void d_delete(struct dentry *);
/* allocate/de-allocate */