Revision 747ffe11b440ef9ea752888806d3aac677ca52a4 authored by Dan Williams on 19 February 2016, 23:21:14 UTC, committed by Dan Williams on 19 February 2016, 23:21:52 UTC
Use the output length specified in the command to size the receive
buffer rather than the arbitrary 4K limit.

This bug was hiding the fact that the ndctl implementation of
ndctl_bus_cmd_new_ars_status() was not specifying an output buffer size.

Cc: <stable@vger.kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
1 parent 6697b2c
Raw File
dynamic_queue_limits.c
/*
 * Dynamic byte queue limits.  See include/linux/dynamic_queue_limits.h
 *
 * Copyright (c) 2011, Tom Herbert <therbert@google.com>
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/dynamic_queue_limits.h>
#include <linux/compiler.h>
#include <linux/export.h>

#define POSDIFF(A, B) ((int)((A) - (B)) > 0 ? (A) - (B) : 0)
#define AFTER_EQ(A, B) ((int)((A) - (B)) >= 0)

/* Records completed count and recalculates the queue limit */
void dql_completed(struct dql *dql, unsigned int count)
{
	unsigned int inprogress, prev_inprogress, limit;
	unsigned int ovlimit, completed, num_queued;
	bool all_prev_completed;

	num_queued = ACCESS_ONCE(dql->num_queued);

	/* Can't complete more than what's in queue */
	BUG_ON(count > num_queued - dql->num_completed);

	completed = dql->num_completed + count;
	limit = dql->limit;
	ovlimit = POSDIFF(num_queued - dql->num_completed, limit);
	inprogress = num_queued - completed;
	prev_inprogress = dql->prev_num_queued - dql->num_completed;
	all_prev_completed = AFTER_EQ(completed, dql->prev_num_queued);

	if ((ovlimit && !inprogress) ||
	    (dql->prev_ovlimit && all_prev_completed)) {
		/*
		 * Queue considered starved if:
		 *   - The queue was over-limit in the last interval,
		 *     and there is no more data in the queue.
		 *  OR
		 *   - The queue was over-limit in the previous interval and
		 *     when enqueuing it was possible that all queued data
		 *     had been consumed.  This covers the case when queue
		 *     may have becomes starved between completion processing
		 *     running and next time enqueue was scheduled.
		 *
		 *     When queue is starved increase the limit by the amount
		 *     of bytes both sent and completed in the last interval,
		 *     plus any previous over-limit.
		 */
		limit += POSDIFF(completed, dql->prev_num_queued) +
		     dql->prev_ovlimit;
		dql->slack_start_time = jiffies;
		dql->lowest_slack = UINT_MAX;
	} else if (inprogress && prev_inprogress && !all_prev_completed) {
		/*
		 * Queue was not starved, check if the limit can be decreased.
		 * A decrease is only considered if the queue has been busy in
		 * the whole interval (the check above).
		 *
		 * If there is slack, the amount of execess data queued above
		 * the the amount needed to prevent starvation, the queue limit
		 * can be decreased.  To avoid hysteresis we consider the
		 * minimum amount of slack found over several iterations of the
		 * completion routine.
		 */
		unsigned int slack, slack_last_objs;

		/*
		 * Slack is the maximum of
		 *   - The queue limit plus previous over-limit minus twice
		 *     the number of objects completed.  Note that two times
		 *     number of completed bytes is a basis for an upper bound
		 *     of the limit.
		 *   - Portion of objects in the last queuing operation that
		 *     was not part of non-zero previous over-limit.  That is
		 *     "round down" by non-overlimit portion of the last
		 *     queueing operation.
		 */
		slack = POSDIFF(limit + dql->prev_ovlimit,
		    2 * (completed - dql->num_completed));
		slack_last_objs = dql->prev_ovlimit ?
		    POSDIFF(dql->prev_last_obj_cnt, dql->prev_ovlimit) : 0;

		slack = max(slack, slack_last_objs);

		if (slack < dql->lowest_slack)
			dql->lowest_slack = slack;

		if (time_after(jiffies,
			       dql->slack_start_time + dql->slack_hold_time)) {
			limit = POSDIFF(limit, dql->lowest_slack);
			dql->slack_start_time = jiffies;
			dql->lowest_slack = UINT_MAX;
		}
	}

	/* Enforce bounds on limit */
	limit = clamp(limit, dql->min_limit, dql->max_limit);

	if (limit != dql->limit) {
		dql->limit = limit;
		ovlimit = 0;
	}

	dql->adj_limit = limit + completed;
	dql->prev_ovlimit = ovlimit;
	dql->prev_last_obj_cnt = dql->last_obj_cnt;
	dql->num_completed = completed;
	dql->prev_num_queued = num_queued;
}
EXPORT_SYMBOL(dql_completed);

void dql_reset(struct dql *dql)
{
	/* Reset all dynamic values */
	dql->limit = 0;
	dql->num_queued = 0;
	dql->num_completed = 0;
	dql->last_obj_cnt = 0;
	dql->prev_num_queued = 0;
	dql->prev_last_obj_cnt = 0;
	dql->prev_ovlimit = 0;
	dql->lowest_slack = UINT_MAX;
	dql->slack_start_time = jiffies;
}
EXPORT_SYMBOL(dql_reset);

int dql_init(struct dql *dql, unsigned hold_time)
{
	dql->max_limit = DQL_MAX_LIMIT;
	dql->min_limit = 0;
	dql->slack_hold_time = hold_time;
	dql_reset(dql);
	return 0;
}
EXPORT_SYMBOL(dql_init);
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