This patch simply transform hlist_head to hlist_bl_head to allow us
to remove dq_list_lock. Later hash lookup will be transformed to
lock less procedure with help of RCU.
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
fs/quota/dquot.c | 56 ++++++++++++++++++++++------------------------
include/linux/list_bl.h | 10 ++++++++
include/linux/quota.h | 3 +-
3 files changed, 39 insertions(+), 30 deletions(-)
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index c06f969..99dc7a3 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -88,7 +88,7 @@
* in inode_add_bytes() and inode_sub_bytes().
*
* The spinlock ordering is hence: dq_data_lock > dq_list_lock > i_lock,
- * dq_list_lock > sb->s_dquot->dq_list_lock
+ * dq_list_lock > sb->s_dquot->dq_list_lock > hlist_bl_head
* Note that some things (eg. sb pointer, type, id) doesn't change during
* the life of the dquot structure and so needn't to be protected by a lock
*
@@ -234,7 +234,7 @@ static void put_quota_format(struct quota_format_type *fmt)
*/
static unsigned int dq_hash_bits, dq_hash_mask;
-static struct hlist_head *dquot_hash;
+static struct hlist_bl_head *dquot_hash;
struct dqstats dqstats;
EXPORT_SYMBOL(dqstats);
@@ -251,29 +251,28 @@ hashfn(const struct super_block *sb, unsigned int id, int type)
return (tmp + (tmp >> dq_hash_bits)) & dq_hash_mask;
}
-/*
- * Following list functions expect dq_list_lock to be held
- */
-static inline void insert_dquot_hash(struct dquot *dquot)
+static inline void insert_dquot_hash(struct dquot *dquot, struct hlist_bl_head *blh)
{
- struct hlist_head *head;
- head = dquot_hash + hashfn(dquot->dq_sb, dquot->dq_id, dquot->dq_type);
- hlist_add_head(&dquot->dq_hash, head);
+ hlist_bl_add_head(&dquot->dq_hash, blh);
}
static inline void remove_dquot_hash(struct dquot *dquot)
{
- hlist_del_init(&dquot->dq_hash);
+ struct hlist_bl_head *blh;
+ blh = dquot_hash + hashfn(dquot->dq_sb, dquot->dq_id, dquot->dq_type);
+ hlist_bl_lock(blh);
+ hlist_bl_del_init(&dquot->dq_hash);
+ hlist_bl_unlock(blh);
}
-static struct dquot *find_dquot(unsigned int hashent, struct super_block *sb,
- unsigned int id, int type)
+static struct dquot *find_dquot(struct hlist_bl_head *blh,
+ struct super_block *sb, unsigned int id,
+ int type)
{
- struct hlist_node *node;
+ struct hlist_bl_node *node;
struct dquot *dquot;
- hlist_for_each (node, dquot_hash+hashent) {
- dquot = hlist_entry(node, struct dquot, dq_hash);
+ hlist_bl_for_each_entry(dquot, node, blh, dq_hash) {
if (dquot->dq_sb == sb && dquot->dq_id == id &&
dquot->dq_type == type)
return dquot;
@@ -830,8 +829,8 @@ static struct dquot *get_empty_dquot(struct super_block *sb, int type)
mutex_init(&dquot->dq_lock);
INIT_LIST_HEAD(&dquot->dq_free);
INIT_LIST_HEAD(&dquot->dq_inuse);
- INIT_HLIST_NODE(&dquot->dq_hash);
INIT_LIST_HEAD(&dquot->dq_dirty);
+ INIT_HLIST_BL_NODE(&dquot->dq_hash);
init_waitqueue_head(&dquot->dq_wait_unused);
dquot->dq_sb = sb;
dquot->dq_type = type;
@@ -850,7 +849,7 @@ static struct dquot *get_empty_dquot(struct super_block *sb, int type)
*/
struct dquot *dqget(struct super_block *sb, unsigned int id, int type)
{
- unsigned int hashent = hashfn(sb, id, type);
+ struct hlist_bl_head * blh = dquot_hash + hashfn(sb, id, type);
struct dquot *dquot = NULL, *empty = NULL;
struct quota_info *dqopt;
int idx;
@@ -871,9 +870,11 @@ we_slept:
spin_unlock(&dq_list_lock);
goto out;
}
- dquot = find_dquot(hashent, sb, id, type);
+ hlist_bl_lock(blh);
+ dquot = find_dquot(blh, sb, id, type);
if (!dquot) {
if (!empty) {
+ hlist_bl_unlock(blh);
spin_unlock(&dqopt->dq_list_lock);
spin_unlock(&dq_list_lock);
empty = get_empty_dquot(sb, type);
@@ -884,10 +885,11 @@ we_slept:
dquot = empty;
empty = NULL;
dquot->dq_id = id;
+ /* hash it first so it can be found */
+ insert_dquot_hash(dquot, blh);
+ hlist_bl_unlock(blh);
/* all dquots go on the inuse_list */
put_inuse(dquot);
- /* hash it first so it can be found */
- insert_dquot_hash(dquot);
spin_unlock(&dqopt->dq_list_lock);
spin_unlock(&dq_list_lock);
dqstats_inc(DQST_LOOKUPS);
@@ -895,6 +897,7 @@ we_slept:
if (!atomic_read(&dquot->dq_count))
remove_free_dquot(dquot);
atomic_inc(&dquot->dq_count);
+ hlist_bl_unlock(blh);
spin_unlock(&dqopt->dq_list_lock);
spin_unlock(&dq_list_lock);
dqstats_inc(DQST_CACHE_HITS);
@@ -2802,7 +2805,7 @@ static int __init dquot_init(void)
NULL);
order = 0;
- dquot_hash = (struct hlist_head *)__get_free_pages(GFP_ATOMIC, order);
+ dquot_hash = (struct hlist_bl_head *)__get_free_pages(GFP_ATOMIC, order);
if (!dquot_hash)
panic("Cannot create dquot hash table");
@@ -2813,17 +2816,12 @@ static int __init dquot_init(void)
}
/* Find power-of-two hlist_heads which can fit into allocation */
- nr_hash = (1UL << order) * PAGE_SIZE / sizeof(struct hlist_head);
- dq_hash_bits = 0;
- do {
- dq_hash_bits++;
- } while (nr_hash >> dq_hash_bits);
- dq_hash_bits--;
-
+ nr_hash = (1UL << order) * PAGE_SIZE / sizeof(*dquot_hash);
+ dq_hash_bits = ilog2(nr_hash);
nr_hash = 1UL << dq_hash_bits;
dq_hash_mask = nr_hash - 1;
for (i = 0; i < nr_hash; i++)
- INIT_HLIST_HEAD(dquot_hash + i);
+ INIT_HLIST_BL_HEAD(dquot_hash + i);
printk("Dquot-cache hash table entries: %ld (order %ld, %ld bytes)\n",
nr_hash, order, (PAGE_SIZE << order));
diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
index cf8acfc..bea750f 100644
--- a/include/linux/list_bl.h
+++ b/include/linux/list_bl.h
@@ -110,6 +110,16 @@ static inline void hlist_bl_del_init(struct hlist_bl_node *n)
}
}
+static inline void hlist_bl_lock(struct hlist_bl_head *b)
+{
+ bit_spin_lock(0, (unsigned long *)b);
+}
+
+static inline void hlist_bl_unlock(struct hlist_bl_head *b)
+{
+ __bit_spin_unlock(0, (unsigned long *)b);
+}
+
/**
* hlist_bl_for_each_entry - iterate over list of given type
* @tpos: the type * to use as a loop cursor.
diff --git a/include/linux/quota.h b/include/linux/quota.h
index 4ca03aa..1661afa 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -170,6 +170,7 @@ enum {
#ifdef __KERNEL__
#include <linux/list.h>
+#include <linux/list_bl.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/spinlock.h>
@@ -284,7 +285,7 @@ static inline void dqstats_dec(unsigned int type)
* clear them when it sees fit. */
struct dquot {
- struct hlist_node dq_hash; /* Hash list in memory */
+ struct hlist_bl_node dq_hash; /* Hash list in memory */
struct list_head dq_inuse; /* List of all quotas */
struct list_head dq_free; /* Free list element */
struct list_head dq_dirty; /* List of dirty dquots */
--
1.6.5.2
--
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