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Commit 2b30a533 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Miklos Szeredi
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fuse: add locking to max_background and congestion_threshold changes 



Functions sequences like request_end()->flush_bg_queue() require that
max_background and congestion_threshold are constant during their
execution. Otherwise, checks like

	if (fc->num_background == fc->max_background)

made in different time may behave not like expected.

Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 2a23f2b8

fs/fuse/control.c

+24 −6
Original line number Diff line number Diff line
@@ -125,7 +125,12 @@ static ssize_t fuse_conn_max_background_write(struct file *file, 
	if (ret > 0) {

		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);

		if (fc) {

			spin_lock(&fc->lock);

			fc->max_background = val;

			fc->blocked = fc->num_background >= fc->max_background;

			if (!fc->blocked)

				wake_up(&fc->blocked_waitq);

			spin_unlock(&fc->lock);

			fuse_conn_put(fc);

		}

	}
@@ -155,18 +160,31 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file, 
						    size_t count, loff_t *ppos)

{

	unsigned uninitialized_var(val);

	struct fuse_conn *fc;

	ssize_t ret;



	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,

				    max_user_congthresh);

	if (ret > 0) {

		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);

		if (fc) {

	if (ret <= 0)

		goto out;

	fc = fuse_ctl_file_conn_get(file);

	if (!fc)

		goto out;



	spin_lock(&fc->lock);

	fc->congestion_threshold = val;

			fuse_conn_put(fc);

	if (fc->sb) {

		if (fc->num_background < fc->congestion_threshold) {

			clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);

			clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);

		} else {

			set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);

			set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);

		}

	}



	spin_unlock(&fc->lock);

	fuse_conn_put(fc);

out:

	return ret;

}