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fuse: implement exclusive wakeup for blocked_waitq

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The patch solves thundering herd problem. So far as previous patches ensured
that only allocations for background may block, it's safe to wake up one
waiter. Whoever it is, it will wake up another one in request_end() afterwards.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Maxim Patlasov 2013-03-21 18:02:36 +04:00 committed by Miklos Szeredi
parent 0aada88476
commit 722d2bea8c
1 changed files with 24 additions and 5 deletions
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29
fs/fuse/dev.c
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@ -147,7 +147,7 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
int intr;
block_sigs(&oldset);
intr = wait_event_interruptible(fc->blocked_waitq,
intr = wait_event_interruptible_exclusive(fc->blocked_waitq,
!fuse_block_alloc(fc, for_background));
restore_sigs(&oldset);
err = -EINTR;
@ -161,8 +161,11 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
req = fuse_request_alloc(npages);
err = -ENOMEM;
if (!req)
if (!req) {
if (for_background)
wake_up(&fc->blocked_waitq);
goto out;
}
fuse_req_init_context(req);
req->waiting = 1;
@ -262,6 +265,17 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
{
if (atomic_dec_and_test(&req->count)) {
if (unlikely(req->background)) {
/*
* We get here in the unlikely case that a background
* request was allocated but not sent
*/
spin_lock(&fc->lock);
if (!fc->blocked)
wake_up(&fc->blocked_waitq);
spin_unlock(&fc->lock);
}
if (req->waiting)
atomic_dec(&fc->num_waiting);
@ -359,10 +373,15 @@ __releases(fc->lock)
list_del(&req->intr_entry);
req->state = FUSE_REQ_FINISHED;
if (req->background) {
if (fc->num_background == fc->max_background) {
req->background = 0;
if (fc->num_background == fc->max_background)
fc->blocked = 0;
wake_up_all(&fc->blocked_waitq);
}
/* Wake up next waiter, if any */
if (!fc->blocked)
wake_up(&fc->blocked_waitq);
if (fc->num_background == fc->congestion_threshold &&
fc->connected && fc->bdi_initialized) {
clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);