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fuse: implement exclusive wakeup for blocked_waitq
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>
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parent
0aada88476
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722d2bea8c
1 changed files with 24 additions and 5 deletions
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@ -147,7 +147,7 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
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int intr;
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block_sigs(&oldset);
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intr = wait_event_interruptible(fc->blocked_waitq,
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intr = wait_event_interruptible_exclusive(fc->blocked_waitq,
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!fuse_block_alloc(fc, for_background));
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restore_sigs(&oldset);
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err = -EINTR;
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@ -161,8 +161,11 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
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req = fuse_request_alloc(npages);
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err = -ENOMEM;
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if (!req)
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if (!req) {
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if (for_background)
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wake_up(&fc->blocked_waitq);
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goto out;
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}
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fuse_req_init_context(req);
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req->waiting = 1;
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@ -262,6 +265,17 @@ struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
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void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
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{
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if (atomic_dec_and_test(&req->count)) {
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if (unlikely(req->background)) {
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/*
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* We get here in the unlikely case that a background
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* request was allocated but not sent
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*/
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spin_lock(&fc->lock);
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if (!fc->blocked)
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wake_up(&fc->blocked_waitq);
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spin_unlock(&fc->lock);
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}
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if (req->waiting)
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atomic_dec(&fc->num_waiting);
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@ -359,10 +373,15 @@ __releases(fc->lock)
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list_del(&req->intr_entry);
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req->state = FUSE_REQ_FINISHED;
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if (req->background) {
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if (fc->num_background == fc->max_background) {
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req->background = 0;
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if (fc->num_background == fc->max_background)
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fc->blocked = 0;
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wake_up_all(&fc->blocked_waitq);
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}
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/* Wake up next waiter, if any */
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if (!fc->blocked)
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wake_up(&fc->blocked_waitq);
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if (fc->num_background == fc->congestion_threshold &&
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fc->connected && fc->bdi_initialized) {
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clear_bdi_congested(&fc->bdi, BLK_RW_SYNC);
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