From 9999e48639b3cecb08ffb37358bcba3b48161b29 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Fri, 10 May 2024 08:50:17 +0000
Subject: [PATCH] add ax88772_rst
---
kernel/fs/mbcache.c | 121 +++++++++++++++++++++++++++------------
1 files changed, 83 insertions(+), 38 deletions(-)
diff --git a/kernel/fs/mbcache.c b/kernel/fs/mbcache.c
index 97c54d3..95b0472 100644
--- a/kernel/fs/mbcache.c
+++ b/kernel/fs/mbcache.c
@@ -11,7 +11,7 @@
/*
* Mbcache is a simple key-value store. Keys need not be unique, however
* key-value pairs are expected to be unique (we use this fact in
- * mb_cache_entry_delete()).
+ * mb_cache_entry_delete_or_get()).
*
* Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
* Ext4 also uses it for deduplication of xattr values stored in inodes.
@@ -90,12 +90,19 @@
return -ENOMEM;
INIT_LIST_HEAD(&entry->e_list);
- /* One ref for hash, one ref returned */
- atomic_set(&entry->e_refcnt, 1);
+ /*
+ * We create entry with two references. One reference is kept by the
+ * hash table, the other reference is used to protect us from
+ * mb_cache_entry_delete_or_get() until the entry is fully setup. This
+ * avoids nesting of cache->c_list_lock into hash table bit locks which
+ * is problematic for RT.
+ */
+ atomic_set(&entry->e_refcnt, 2);
entry->e_key = key;
entry->e_value = value;
- entry->e_reusable = reusable;
- entry->e_referenced = 0;
+ entry->e_flags = 0;
+ if (reusable)
+ set_bit(MBE_REUSABLE_B, &entry->e_flags);
head = mb_cache_entry_head(cache, key);
hlist_bl_lock(head);
hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) {
@@ -107,23 +114,40 @@
}
hlist_bl_add_head(&entry->e_hash_list, head);
hlist_bl_unlock(head);
-
spin_lock(&cache->c_list_lock);
list_add_tail(&entry->e_list, &cache->c_list);
- /* Grab ref for LRU list */
- atomic_inc(&entry->e_refcnt);
cache->c_entry_count++;
spin_unlock(&cache->c_list_lock);
+ mb_cache_entry_put(cache, entry);
return 0;
}
EXPORT_SYMBOL(mb_cache_entry_create);
-void __mb_cache_entry_free(struct mb_cache_entry *entry)
+void __mb_cache_entry_free(struct mb_cache *cache, struct mb_cache_entry *entry)
{
+ struct hlist_bl_head *head;
+
+ head = mb_cache_entry_head(cache, entry->e_key);
+ hlist_bl_lock(head);
+ hlist_bl_del(&entry->e_hash_list);
+ hlist_bl_unlock(head);
kmem_cache_free(mb_entry_cache, entry);
}
EXPORT_SYMBOL(__mb_cache_entry_free);
+
+/*
+ * mb_cache_entry_wait_unused - wait to be the last user of the entry
+ *
+ * @entry - entry to work on
+ *
+ * Wait to be the last user of the entry.
+ */
+void mb_cache_entry_wait_unused(struct mb_cache_entry *entry)
+{
+ wait_var_event(&entry->e_refcnt, atomic_read(&entry->e_refcnt) <= 2);
+}
+EXPORT_SYMBOL(mb_cache_entry_wait_unused);
static struct mb_cache_entry *__entry_find(struct mb_cache *cache,
struct mb_cache_entry *entry,
@@ -142,10 +166,10 @@
while (node) {
entry = hlist_bl_entry(node, struct mb_cache_entry,
e_hash_list);
- if (entry->e_key == key && entry->e_reusable) {
- atomic_inc(&entry->e_refcnt);
+ if (entry->e_key == key &&
+ test_bit(MBE_REUSABLE_B, &entry->e_flags) &&
+ atomic_inc_not_zero(&entry->e_refcnt))
goto out;
- }
node = node->next;
}
entry = NULL;
@@ -205,10 +229,9 @@
head = mb_cache_entry_head(cache, key);
hlist_bl_lock(head);
hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
- if (entry->e_key == key && entry->e_value == value) {
- atomic_inc(&entry->e_refcnt);
+ if (entry->e_key == key && entry->e_value == value &&
+ atomic_inc_not_zero(&entry->e_refcnt))
goto out;
- }
}
entry = NULL;
out:
@@ -217,7 +240,7 @@
}
EXPORT_SYMBOL(mb_cache_entry_get);
-/* mb_cache_entry_delete - remove a cache entry
+/* mb_cache_entry_delete - try to remove a cache entry
* @cache - cache we work with
* @key - key
* @value - value
@@ -254,6 +277,43 @@
}
EXPORT_SYMBOL(mb_cache_entry_delete);
+/* mb_cache_entry_delete_or_get - remove a cache entry if it has no users
+ * @cache - cache we work with
+ * @key - key
+ * @value - value
+ *
+ * Remove entry from cache @cache with key @key and value @value. The removal
+ * happens only if the entry is unused. The function returns NULL in case the
+ * entry was successfully removed or there's no entry in cache. Otherwise the
+ * function grabs reference of the entry that we failed to delete because it
+ * still has users and return it.
+ */
+struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache,
+ u32 key, u64 value)
+{
+ struct mb_cache_entry *entry;
+
+ entry = mb_cache_entry_get(cache, key, value);
+ if (!entry)
+ return NULL;
+
+ /*
+ * Drop the ref we got from mb_cache_entry_get() and the initial hash
+ * ref if we are the last user
+ */
+ if (atomic_cmpxchg(&entry->e_refcnt, 2, 0) != 2)
+ return entry;
+
+ spin_lock(&cache->c_list_lock);
+ if (!list_empty(&entry->e_list))
+ list_del_init(&entry->e_list);
+ cache->c_entry_count--;
+ spin_unlock(&cache->c_list_lock);
+ __mb_cache_entry_free(cache, entry);
+ return NULL;
+}
+EXPORT_SYMBOL(mb_cache_entry_delete_or_get);
+
/* mb_cache_entry_touch - cache entry got used
* @cache - cache the entry belongs to
* @entry - entry that got used
@@ -263,7 +323,7 @@
void mb_cache_entry_touch(struct mb_cache *cache,
struct mb_cache_entry *entry)
{
- entry->e_referenced = 1;
+ set_bit(MBE_REFERENCED_B, &entry->e_flags);
}
EXPORT_SYMBOL(mb_cache_entry_touch);
@@ -281,34 +341,24 @@
unsigned long nr_to_scan)
{
struct mb_cache_entry *entry;
- struct hlist_bl_head *head;
unsigned long shrunk = 0;
spin_lock(&cache->c_list_lock);
while (nr_to_scan-- && !list_empty(&cache->c_list)) {
entry = list_first_entry(&cache->c_list,
struct mb_cache_entry, e_list);
- if (entry->e_referenced) {
- entry->e_referenced = 0;
+ /* Drop initial hash reference if there is no user */
+ if (test_bit(MBE_REFERENCED_B, &entry->e_flags) ||
+ atomic_cmpxchg(&entry->e_refcnt, 1, 0) != 1) {
+ clear_bit(MBE_REFERENCED_B, &entry->e_flags);
list_move_tail(&entry->e_list, &cache->c_list);
continue;
}
list_del_init(&entry->e_list);
cache->c_entry_count--;
- /*
- * We keep LRU list reference so that entry doesn't go away
- * from under us.
- */
spin_unlock(&cache->c_list_lock);
- head = mb_cache_entry_head(cache, entry->e_key);
- hlist_bl_lock(head);
- if (!hlist_bl_unhashed(&entry->e_hash_list)) {
- hlist_bl_del_init(&entry->e_hash_list);
- atomic_dec(&entry->e_refcnt);
- }
- hlist_bl_unlock(head);
- if (mb_cache_entry_put(cache, entry))
- shrunk++;
+ __mb_cache_entry_free(cache, entry);
+ shrunk++;
cond_resched();
spin_lock(&cache->c_list_lock);
}
@@ -400,11 +450,6 @@
* point.
*/
list_for_each_entry_safe(entry, next, &cache->c_list, e_list) {
- if (!hlist_bl_unhashed(&entry->e_hash_list)) {
- hlist_bl_del_init(&entry->e_hash_list);
- atomic_dec(&entry->e_refcnt);
- } else
- WARN_ON(1);
list_del(&entry->e_list);
WARN_ON(atomic_read(&entry->e_refcnt) != 1);
mb_cache_entry_put(cache, entry);
--
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