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Date: Sat, 27 Nov 2010 20:44:41 +1100
From: Nick Piggin <npiggin@...nel.dk>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 11/46] 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@...nel.dk>
---
fs/dcache.c | 38 +++++++++++++++++++++++++++-----------
include/linux/dcache.h | 3 +++
2 files changed, 30 insertions(+), 11 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 4f9ccbe..50c65c7 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -35,12 +35,27 @@
#include <linux/hardirq.h>
#include "internal.h"
+/*
+ * Usage:
+ * dcache_hash_lock protects dcache hash table
+ *
+ * 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);
+__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_hash_lock);
EXPORT_SYMBOL(dcache_lock);
static struct kmem_cache *dentry_cache __read_mostly;
@@ -1195,7 +1210,9 @@ 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);
@@ -1581,7 +1598,9 @@ 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);
}
@@ -1661,8 +1680,6 @@ 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");
@@ -1679,14 +1696,11 @@ 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);
@@ -1883,7 +1897,9 @@ 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:
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 6b5760b..7ce20f5 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -181,6 +181,7 @@ struct dentry_operations {
#define DCACHE_CANT_MOUNT 0x0100
+extern spinlock_t dcache_hash_lock;
extern spinlock_t dcache_lock;
extern seqlock_t rename_lock;
@@ -204,7 +205,9 @@ 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);
}
}
--
1.7.1
--
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