Use the rosebush instead of a custom hashtable. This is a deliberately
awful patch because I wouldn't want anyone applying it yet. We need to
figure out how to implement d_unhashed() properly, and what to do about
IS_ROOT() dentries.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
fs/dcache.c | 152 +++++++++++++++++++---------------------------------
1 file changed, 54 insertions(+), 98 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 407095188f83..5c2ba8d5f8ff 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -26,6 +26,7 @@
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/export.h>
+#include <linux/rosebush.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/memblock.h>
@@ -87,23 +88,7 @@ EXPORT_SYMBOL(slash_name);
const struct qstr dotdot_name = QSTR_INIT("..", 2);
EXPORT_SYMBOL(dotdot_name);
-/*
- * This is the single most critical data structure when it comes
- * to the dcache: the hashtable for lookups. Somebody should try
- * to make this good - I've just made it work.
- *
- * This hash-function tries to avoid losing too many bits of hash
- * information, yet avoid using a prime hash-size or similar.
- */
-
-static unsigned int d_hash_shift __ro_after_init;
-
-static struct hlist_bl_head *dentry_hashtable __ro_after_init;
-
-static inline struct hlist_bl_head *d_hash(unsigned int hash)
-{
- return dentry_hashtable + (hash >> d_hash_shift);
-}
+static DEFINE_ROSEBUSH(all_dentries);
#define IN_LOOKUP_SHIFT 10
static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
@@ -486,20 +471,22 @@ static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
static void ___d_drop(struct dentry *dentry)
{
- struct hlist_bl_head *b;
/*
* Hashed dentries are normally on the dentry hashtable,
* with the exception of those newly allocated by
* d_obtain_root, which are always IS_ROOT:
*/
- if (unlikely(IS_ROOT(dentry)))
- b = &dentry->d_sb->s_roots;
- else
- b = d_hash(dentry->d_name.hash);
+ if (unlikely(IS_ROOT(dentry))) {
+ struct hlist_bl_head *b = &dentry->d_sb->s_roots;
+ hlist_bl_lock(b);
+ __hlist_bl_del(&dentry->d_hash);
+ hlist_bl_unlock(b);
+ } else {
+ dentry->d_hash.pprev = NULL;
+ }
- hlist_bl_lock(b);
- __hlist_bl_del(&dentry->d_hash);
- hlist_bl_unlock(b);
+//printk("removing dentry %p at %x\n", dentry, dentry->d_name.hash);
+ rbh_remove(&all_dentries, dentry->d_name.hash, dentry);
}
void __d_drop(struct dentry *dentry)
@@ -2104,15 +2091,14 @@ static noinline struct dentry *__d_lookup_rcu_op_compare(
unsigned *seqp)
{
u64 hashlen = name->hash_len;
- struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
- struct hlist_bl_node *node;
+ RBH_ITER(iter, &all_dentries, hashlen_hash(hashlen));
struct dentry *dentry;
- hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+ while ((dentry = rbh_next(&iter)) != NULL) {
int tlen;
const char *tname;
unsigned seq;
-
+//printk("%s: got dentry %p with hash %x\n", __func__, dentry, dentry->d_name.hash);
seqretry:
seq = raw_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent)
@@ -2131,9 +2117,9 @@ static noinline struct dentry *__d_lookup_rcu_op_compare(
if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
continue;
*seqp = seq;
- return dentry;
+ break;
}
- return NULL;
+ return dentry;
}
/**
@@ -2171,8 +2157,7 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
{
u64 hashlen = name->hash_len;
const unsigned char *str = name->name;
- struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
- struct hlist_bl_node *node;
+ RBH_ITER(iter, &all_dentries, hashlen_hash(hashlen));
struct dentry *dentry;
/*
@@ -2182,6 +2167,8 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
* Keep the two functions in sync.
*/
+//printk("%s: Looking up %s with hash %x\n", __func__, name->name, name->hash);
+
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
return __d_lookup_rcu_op_compare(parent, name, seqp);
@@ -2198,9 +2185,10 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
*
* See Documentation/filesystems/path-lookup.txt for more details.
*/
- hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+ while ((dentry = rbh_next(&iter)) != NULL) {
unsigned seq;
+//printk("%s: got dentry %p with hash %x\n", __func__, dentry, dentry->d_name.hash);
/*
* The dentry sequence count protects us from concurrent
* renames, and thus protects parent and name fields.
@@ -2228,9 +2216,10 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
continue;
*seqp = seq;
- return dentry;
+ break;
}
- return NULL;
+//printk("%s: found %p\n", __func__, dentry);
+ return dentry;
}
/**
@@ -2276,10 +2265,7 @@ EXPORT_SYMBOL(d_lookup);
*/
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
{
- unsigned int hash = name->hash;
- struct hlist_bl_head *b = d_hash(hash);
- struct hlist_bl_node *node;
- struct dentry *found = NULL;
+ RBH_ITER(iter, &all_dentries, name->hash);
struct dentry *dentry;
/*
@@ -2289,6 +2275,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
* Keep the two functions in sync.
*/
+//printk("%s: Looking up %s with hash %x\n", __func__, name->name, name->hash);
+
/*
* The hash list is protected using RCU.
*
@@ -2303,12 +2291,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
* See Documentation/filesystems/path-lookup.txt for more details.
*/
rcu_read_lock();
-
- hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
-
- if (dentry->d_name.hash != hash)
- continue;
-
+ while ((dentry = rbh_next(&iter)) != NULL) {
+//printk("%s: got dentry %p with hash %x\n", __func__, dentry, dentry->d_name.hash);
spin_lock(&dentry->d_lock);
if (dentry->d_parent != parent)
goto next;
@@ -2319,15 +2303,15 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
goto next;
dentry->d_lockref.count++;
- found = dentry;
spin_unlock(&dentry->d_lock);
break;
next:
spin_unlock(&dentry->d_lock);
- }
- rcu_read_unlock();
+ }
+ rcu_read_unlock();
- return found;
+//printk("%s: found %p\n", __func__, dentry);
+ return dentry;
}
/**
@@ -2397,11 +2381,10 @@ EXPORT_SYMBOL(d_delete);
static void __d_rehash(struct dentry *entry)
{
- struct hlist_bl_head *b = d_hash(entry->d_name.hash);
-
- hlist_bl_lock(b);
- hlist_bl_add_head_rcu(&entry->d_hash, b);
- hlist_bl_unlock(b);
+//printk("%s: using dentry %p at %x\n", __func__, entry, entry->d_name.hash);
+
+ entry->d_hash.pprev = (void *)&all_dentries;
+ rbh_use(&all_dentries, entry->d_name.hash, entry);
}
/**
@@ -2413,6 +2396,8 @@ static void __d_rehash(struct dentry *entry)
void d_rehash(struct dentry * entry)
{
+//printk("%s: reserving dentry %p at %x\n", __func__, entry, entry->d_name.hash);
+ rbh_reserve(&all_dentries, entry->d_name.hash);
spin_lock(&entry->d_lock);
__d_rehash(entry);
spin_unlock(&entry->d_lock);
@@ -2601,6 +2586,7 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
wait_queue_head_t *d_wait;
struct inode *dir = NULL;
unsigned n;
+
spin_lock(&dentry->d_lock);
if (unlikely(d_in_lookup(dentry))) {
dir = dentry->d_parent->d_inode;
@@ -2625,20 +2611,21 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
/**
* d_add - add dentry to hash queues
- * @entry: dentry to add
+ * @dentry: dentry to add
* @inode: The inode to attach to this dentry
*
* This adds the entry to the hash queues and initializes @inode.
* The entry was actually filled in earlier during d_alloc().
*/
-
-void d_add(struct dentry *entry, struct inode *inode)
+void d_add(struct dentry *dentry, struct inode *inode)
{
+//printk("%s: reserving dentry %p at %x\n", __func__, dentry, dentry->d_name.hash);
+ rbh_reserve(&all_dentries, dentry->d_name.hash);
if (inode) {
- security_d_instantiate(entry, inode);
+ security_d_instantiate(dentry, inode);
spin_lock(&inode->i_lock);
}
- __d_add(entry, inode);
+ __d_add(dentry, inode);
}
EXPORT_SYMBOL(d_add);
@@ -2658,6 +2645,8 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
struct dentry *alias;
unsigned int hash = entry->d_name.hash;
+//printk("%s: reserving dentry %p at %x\n", __func__, entry, hash);
+ rbh_reserve(&all_dentries, hash);
spin_lock(&inode->i_lock);
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
/*
@@ -2675,6 +2664,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
if (!d_unhashed(alias)) {
spin_unlock(&alias->d_lock);
alias = NULL;
+ rbh_release(&all_dentries, hash);
} else {
dget_dlock(alias);
__d_rehash(alias);
@@ -2684,6 +2674,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
return alias;
}
spin_unlock(&inode->i_lock);
+ rbh_release(&all_dentries, hash);
return NULL;
}
EXPORT_SYMBOL(d_exact_alias);
@@ -2967,6 +2958,8 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
BUG_ON(!d_unhashed(dentry));
+//printk("%s: reserving dentry %p at %x\n", __func__, dentry, dentry->d_name.hash);
+ rbh_reserve(&all_dentries, dentry->d_name.hash);
if (!inode)
goto out;
@@ -3002,6 +2995,7 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
write_sequnlock(&rename_lock);
}
iput(inode);
+ rbh_release(&all_dentries, dentry->d_name.hash);
return new;
}
}
@@ -3110,27 +3104,6 @@ static int __init set_dhash_entries(char *str)
}
__setup("dhash_entries=", set_dhash_entries);
-static void __init dcache_init_early(void)
-{
- /* If hashes are distributed across NUMA nodes, defer
- * hash allocation until vmalloc space is available.
- */
- if (hashdist)
- return;
-
- dentry_hashtable =
- alloc_large_system_hash("Dentry cache",
- sizeof(struct hlist_bl_head),
- dhash_entries,
- 13,
- HASH_EARLY | HASH_ZERO,
- &d_hash_shift,
- NULL,
- 0,
- 0);
- d_hash_shift = 32 - d_hash_shift;
-}
-
static void __init dcache_init(void)
{
/*
@@ -3141,22 +3114,6 @@ static void __init dcache_init(void)
dentry_cache = KMEM_CACHE_USERCOPY(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
d_iname);
-
- /* Hash may have been set up in dcache_init_early */
- if (!hashdist)
- return;
-
- dentry_hashtable =
- alloc_large_system_hash("Dentry cache",
- sizeof(struct hlist_bl_head),
- dhash_entries,
- 13,
- HASH_ZERO,
- &d_hash_shift,
- NULL,
- 0,
- 0);
- d_hash_shift = 32 - d_hash_shift;
}
/* SLAB cache for __getname() consumers */
@@ -3170,7 +3127,6 @@ void __init vfs_caches_init_early(void)
for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
- dcache_init_early();
inode_init_early();
}
--
2.43.0
