locks: give the blocked_hash its own spinlock
There's no reason we have to protect the blocked_hash and file_lock_list
with the same spinlock. With the tests I have, breaking it in two gives
a barely measurable performance benefit, but it seems reasonable to make
this locking as granular as possible.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/locks.c b/fs/locks.c
index 6242e0b..04e2c1f 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -159,10 +159,11 @@
* by the file_lock_lock.
*/
static HLIST_HEAD(file_lock_list);
+static DEFINE_SPINLOCK(file_lock_lock);
/*
* The blocked_hash is used to find POSIX lock loops for deadlock detection.
- * It is protected by file_lock_lock.
+ * It is protected by blocked_lock_lock.
*
* We hash locks by lockowner in order to optimize searching for the lock a
* particular lockowner is waiting on.
@@ -175,8 +176,8 @@
static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
/*
- * This lock protects the blocked_hash and the file_lock_list. Generally, if
- * you're accessing one of those lists, you want to be holding this lock.
+ * This lock protects the blocked_hash. Generally, if you're accessing it, you
+ * want to be holding this lock.
*
* In addition, it also protects the fl->fl_block list, and the fl->fl_next
* pointer for file_lock structures that are acting as lock requests (in
@@ -191,7 +192,7 @@
* both the i_lock and the blocked_lock_lock (acquired in that order). Deleting
* an entry from the list however only requires the file_lock_lock.
*/
-static DEFINE_SPINLOCK(file_lock_lock);
+static DEFINE_SPINLOCK(blocked_lock_lock);
static struct kmem_cache *filelock_cache __read_mostly;
@@ -544,7 +545,7 @@
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
*
- * Must be called with file_lock_lock held.
+ * Must be called with blocked_lock_lock held.
*/
static void __locks_delete_block(struct file_lock *waiter)
{
@@ -555,9 +556,9 @@
static void locks_delete_block(struct file_lock *waiter)
{
- spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
__locks_delete_block(waiter);
- spin_unlock(&file_lock_lock);
+ spin_unlock(&blocked_lock_lock);
}
/* Insert waiter into blocker's block list.
@@ -565,9 +566,9 @@
* the order they blocked. The documentation doesn't require this but
* it seems like the reasonable thing to do.
*
- * Must be called with both the i_lock and file_lock_lock held. The fl_block
+ * Must be called with both the i_lock and blocked_lock_lock held. The fl_block
* list itself is protected by the file_lock_list, but by ensuring that the
- * i_lock is also held on insertions we can avoid taking the file_lock_lock
+ * i_lock is also held on insertions we can avoid taking the blocked_lock_lock
* in some cases when we see that the fl_block list is empty.
*/
static void __locks_insert_block(struct file_lock *blocker,
@@ -584,9 +585,9 @@
static void locks_insert_block(struct file_lock *blocker,
struct file_lock *waiter)
{
- spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
__locks_insert_block(blocker, waiter);
- spin_unlock(&file_lock_lock);
+ spin_unlock(&blocked_lock_lock);
}
/*
@@ -601,12 +602,12 @@
* blocked requests are only added to the list under the i_lock, and
* the i_lock is always held here. Note that removal from the fl_block
* list does not require the i_lock, so we must recheck list_empty()
- * after acquiring the file_lock_lock.
+ * after acquiring the blocked_lock_lock.
*/
if (list_empty(&blocker->fl_block))
return;
- spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
while (!list_empty(&blocker->fl_block)) {
struct file_lock *waiter;
@@ -618,7 +619,7 @@
else
wake_up(&waiter->fl_wait);
}
- spin_unlock(&file_lock_lock);
+ spin_unlock(&blocked_lock_lock);
}
/* Insert file lock fl into an inode's lock list at the position indicated
@@ -772,7 +773,7 @@
return NULL;
}
-/* Must be called with the file_lock_lock held! */
+/* Must be called with the blocked_lock_lock held! */
static int posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
@@ -920,12 +921,12 @@
* locks list must be done while holding the same lock!
*/
error = -EDEADLK;
- spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
if (likely(!posix_locks_deadlock(request, fl))) {
error = FILE_LOCK_DEFERRED;
__locks_insert_block(fl, request);
}
- spin_unlock(&file_lock_lock);
+ spin_unlock(&blocked_lock_lock);
goto out;
}
}
@@ -2212,12 +2213,12 @@
{
int status = 0;
- spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
if (waiter->fl_next)
__locks_delete_block(waiter);
else
status = -ENOENT;
- spin_unlock(&file_lock_lock);
+ spin_unlock(&blocked_lock_lock);
return status;
}
EXPORT_SYMBOL(posix_unblock_lock);
@@ -2332,6 +2333,7 @@
loff_t *p = f->private;
spin_lock(&file_lock_lock);
+ spin_lock(&blocked_lock_lock);
*p = (*pos + 1);
return seq_hlist_start(&file_lock_list, *pos);
}
@@ -2345,6 +2347,7 @@
static void locks_stop(struct seq_file *f, void *v)
{
+ spin_unlock(&blocked_lock_lock);
spin_unlock(&file_lock_lock);
}