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Commit d12def1b authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
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fuse: limit queued background requests 



Libfuse basically creates a new thread for each new request.  This is fine for
synchronous requests, which are naturally limited.  However background
requests (especially writepage) can cause a thread creation storm.

To avoid this, limit the number of background requests available to userspace.

This is done by introducing another queue for background requests, and a
counter for the number of "active" requests, which are currently available for
userspace.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b57d4264

fs/fuse/dev.c

+67 −46
Original line number Diff line number Diff line
@@ -201,6 +201,55 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) 
	}

}



static unsigned len_args(unsigned numargs, struct fuse_arg *args)

{

	unsigned nbytes = 0;

	unsigned i;



	for (i = 0; i < numargs; i++)

		nbytes += args[i].size;



	return nbytes;

}



static u64 fuse_get_unique(struct fuse_conn *fc)

{

	fc->reqctr++;

	/* zero is special */

	if (fc->reqctr == 0)

		fc->reqctr = 1;



	return fc->reqctr;

}



static void queue_request(struct fuse_conn *fc, struct fuse_req *req)

{

	req->in.h.unique = fuse_get_unique(fc);

	req->in.h.len = sizeof(struct fuse_in_header) +

		len_args(req->in.numargs, (struct fuse_arg *) req->in.args);

	list_add_tail(&req->list, &fc->pending);

	req->state = FUSE_REQ_PENDING;

	if (!req->waiting) {

		req->waiting = 1;

		atomic_inc(&fc->num_waiting);

	}

	wake_up(&fc->waitq);

	kill_fasync(&fc->fasync, SIGIO, POLL_IN);

}



static void flush_bg_queue(struct fuse_conn *fc)

{

	while (fc->active_background < FUSE_MAX_BACKGROUND &&

	       !list_empty(&fc->bg_queue)) {

		struct fuse_req *req;



		req = list_entry(fc->bg_queue.next, struct fuse_req, list);

		list_del(&req->list);

		fc->active_background++;

		queue_request(fc, req);

	}

}



/*

 * This function is called when a request is finished.  Either a reply

 * has arrived or it was aborted (and not yet sent) or some error
@@ -229,6 +278,8 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req) 
			clear_bdi_congested(&fc->bdi, WRITE);

		}

		fc->num_background--;

		fc->active_background--;

		flush_bg_queue(fc);

	}

	spin_unlock(&fc->lock);

	wake_up(&req->waitq);
@@ -320,42 +371,6 @@ static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req) 
	}

}



static unsigned len_args(unsigned numargs, struct fuse_arg *args)

{

	unsigned nbytes = 0;

	unsigned i;



	for (i = 0; i < numargs; i++)

		nbytes += args[i].size;



	return nbytes;

}



static u64 fuse_get_unique(struct fuse_conn *fc)

 {

 	fc->reqctr++;

 	/* zero is special */

 	if (fc->reqctr == 0)

 		fc->reqctr = 1;



	return fc->reqctr;

}



static void queue_request(struct fuse_conn *fc, struct fuse_req *req)

{

	req->in.h.unique = fuse_get_unique(fc);

	req->in.h.len = sizeof(struct fuse_in_header) +

		len_args(req->in.numargs, (struct fuse_arg *) req->in.args);

	list_add_tail(&req->list, &fc->pending);

	req->state = FUSE_REQ_PENDING;

	if (!req->waiting) {

		req->waiting = 1;

		atomic_inc(&fc->num_waiting);

	}

	wake_up(&fc->waitq);

	kill_fasync(&fc->fasync, SIGIO, POLL_IN);

}



void request_send(struct fuse_conn *fc, struct fuse_req *req)

{

	req->isreply = 1;
@@ -375,10 +390,9 @@ void request_send(struct fuse_conn *fc, struct fuse_req *req) 
	spin_unlock(&fc->lock);

}



static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)

static void request_send_nowait_locked(struct fuse_conn *fc,

				       struct fuse_req *req)

{

	spin_lock(&fc->lock);

	if (fc->connected) {

	req->background = 1;

	fc->num_background++;

	if (fc->num_background == FUSE_MAX_BACKGROUND)
@@ -387,8 +401,15 @@ static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req) 
		set_bdi_congested(&fc->bdi, READ);

		set_bdi_congested(&fc->bdi, WRITE);

	}

	list_add_tail(&req->list, &fc->bg_queue);

	flush_bg_queue(fc);

}



		queue_request(fc, req);

static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)

{

	spin_lock(&fc->lock);

	if (fc->connected) {

		request_send_nowait_locked(fc, req);

		spin_unlock(&fc->lock);

	} else {

		req->out.h.error = -ENOTCONN;

fs/fuse/fuse_i.h

+6 −0
Original line number Diff line number Diff line
@@ -296,6 +296,12 @@ struct fuse_conn { 
	/** Number of requests currently in the background */

	unsigned num_background;



	/** Number of background requests currently queued for userspace */

	unsigned active_background;



	/** The list of background requests set aside for later queuing */

	struct list_head bg_queue;



	/** Pending interrupts */

	struct list_head interrupts;

fs/fuse/inode.c

+1 −0
Original line number Diff line number Diff line
@@ -465,6 +465,7 @@ static struct fuse_conn *new_conn(void) 
		INIT_LIST_HEAD(&fc->processing);

		INIT_LIST_HEAD(&fc->io);

		INIT_LIST_HEAD(&fc->interrupts);

		INIT_LIST_HEAD(&fc->bg_queue);

		atomic_set(&fc->num_waiting, 0);

		fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;

		fc->bdi.unplug_io_fn = default_unplug_io_fn;