locks: avoid taking global lock if possible when waking up blocked waiters
Since we always hold the i_lock when inserting a new waiter onto the fl_block list, we can avoid taking the global lock at all if we find that it's empty when we go to wake up blocked waiters. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Родитель
1c8c601a8c
Коммит
4e8c765d38
15
fs/locks.c
15
fs/locks.c
|
@ -548,7 +548,10 @@ static void locks_delete_block(struct file_lock *waiter)
|
|||
* the order they blocked. The documentation doesn't require this but
|
||||
* it seems like the reasonable thing to do.
|
||||
*
|
||||
* Must be called with file_lock_lock held!
|
||||
* Must be called with both the i_lock and file_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
|
||||
* in some cases when we see that the fl_block list is empty.
|
||||
*/
|
||||
static void __locks_insert_block(struct file_lock *blocker,
|
||||
struct file_lock *waiter)
|
||||
|
@ -576,6 +579,16 @@ static void locks_insert_block(struct file_lock *blocker,
|
|||
*/
|
||||
static void locks_wake_up_blocks(struct file_lock *blocker)
|
||||
{
|
||||
/*
|
||||
* Avoid taking global lock if list is empty. This is safe since new
|
||||
* 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.
|
||||
*/
|
||||
if (list_empty(&blocker->fl_block))
|
||||
return;
|
||||
|
||||
spin_lock(&file_lock_lock);
|
||||
while (!list_empty(&blocker->fl_block)) {
|
||||
struct file_lock *waiter;
|
||||
|
|
Загрузка…
Ссылка в новой задаче