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fuse: Optimize request_end() by not taking fiq->waitq.lock

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We take global fiq->waitq.lock every time, when we are in this function,
but interrupted requests are just small subset of all requests. This patch
optimizes request_end() and makes it to take the lock when it's really
needed.

queue_interrupt() needs small change for that. After req is linked to
interrupt list, we do smp_mb() and check for FR_FINISHED again. In case of
FR_FINISHED bit has appeared, we remove req and leave the function:

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Kirill Tkhai 2018-11-08 12:05:25 +03:00 committed by Miklos Szeredi
parent 8da6e91832
commit 217316a601
1 changed files with 20 additions and 8 deletions
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28
fs/fuse/dev.c
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@ -431,10 +431,16 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
if (test_and_set_bit(FR_FINISHED, &req->flags))
goto put_request;
spin_lock(&fiq->waitq.lock);
list_del_init(&req->intr_entry);
spin_unlock(&fiq->waitq.lock);
/*
* test_and_set_bit() implies smp_mb() between bit
* changing and below intr_entry check. Pairs with
* smp_mb() from queue_interrupt().
*/
if (!list_empty(&req->intr_entry)) {
spin_lock(&fiq->waitq.lock);
list_del_init(&req->intr_entry);
spin_unlock(&fiq->waitq.lock);
}
WARN_ON(test_bit(FR_PENDING, &req->flags));
WARN_ON(test_bit(FR_SENT, &req->flags));
if (test_bit(FR_BACKGROUND, &req->flags)) {
@ -473,12 +479,18 @@ put_request:
static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
{
spin_lock(&fiq->waitq.lock);
if (test_bit(FR_FINISHED, &req->flags)) {
spin_unlock(&fiq->waitq.lock);
return;
}
if (list_empty(&req->intr_entry)) {
list_add_tail(&req->intr_entry, &fiq->interrupts);
/*
* Pairs with smp_mb() implied by test_and_set_bit()
* from request_end().
*/
smp_mb();
if (test_bit(FR_FINISHED, &req->flags)) {
list_del_init(&req->intr_entry);
spin_unlock(&fiq->waitq.lock);
return;
}
wake_up_locked(&fiq->waitq);
kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
}