/*
 * Quicklist support.
 *
 * Quicklists are light weight lists of pages that have a defined state
 * on alloc and free. Pages must be in the quicklist specific defined state
 * (zero by default) when the page is freed. It seems that the initial idea
 * for such lists first came from Dave Miller and then various other people
 * improved on it.
 *
 * Copyright (C) 2007 SGI,
 * 	Christoph Lameter <cl@linux.com>
 * 		Generalized, added support for multiple lists and
 * 		constructors / destructors.
 */
#include <linux/kernel.h>

#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/quicklist.h>

DEFINE_PER_CPU(struct quicklist [CONFIG_NR_QUICK], quicklist);

#define FRACTION_OF_NODE_MEM	16

static unsigned long max_pages(unsigned long min_pages)
{
	unsigned long node_free_pages, max;
	int node = numa_node_id();
	struct zone *zones = NODE_DATA(node)->node_zones;
	int num_cpus_on_node;

	node_free_pages =
#ifdef CONFIG_ZONE_DMA
		zone_page_state(&zones[ZONE_DMA], NR_FREE_PAGES) +
#endif
#ifdef CONFIG_ZONE_DMA32
		zone_page_state(&zones[ZONE_DMA32], NR_FREE_PAGES) +
#endif
		zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES);

	max = node_free_pages / FRACTION_OF_NODE_MEM;

	num_cpus_on_node = cpumask_weight(cpumask_of_node(node));
	max /= num_cpus_on_node;

	return max(max, min_pages);
}

static long min_pages_to_free(struct quicklist *q,
	unsigned long min_pages, long max_free)
{
	long pages_to_free;

	pages_to_free = q->nr_pages - max_pages(min_pages);

	return min(pages_to_free, max_free);
}

/*
 * Trim down the number of pages in the quicklist
 */
void quicklist_trim(int nr, void (*dtor)(void *),
	unsigned long min_pages, unsigned long max_free)
{
	long pages_to_free;
	struct quicklist *q;

	q = &get_cpu_var(quicklist)[nr];
	if (q->nr_pages > min_pages) {
		pages_to_free = min_pages_to_free(q, min_pages, max_free);

		while (pages_to_free > 0) {
			/*
			 * We pass a gfp_t of 0 to quicklist_alloc here
			 * because we will never call into the page allocator.
			 */
			void *p = quicklist_alloc(nr, 0, NULL);

			if (dtor)
				dtor(p);
			free_page((unsigned long)p);
			pages_to_free--;
		}
	}
	put_cpu_var(quicklist);
}

unsigned long quicklist_total_size(void)
{
	unsigned long count = 0;
	int cpu;
	struct quicklist *ql, *q;

	for_each_online_cpu(cpu) {
		ql = per_cpu(quicklist, cpu);
		for (q = ql; q < ql + CONFIG_NR_QUICK; q++)
			count += q->nr_pages;
	}
	return count;
}

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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=966d2b04e070bc040319aaebfec09e0144dc3341'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools?id=966d2b04e070bc040319aaebfec09e0144dc3341'>tools</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/testing?id=966d2b04e070bc040319aaebfec09e0144dc3341'>testing</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/testing/selftests?id=966d2b04e070bc040319aaebfec09e0144dc3341'>selftests</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/testing/selftests/ptp?id=966d2b04e070bc040319aaebfec09e0144dc3341'>ptp</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/testing/selftests/ptp/.gitignore?id=966d2b04e070bc040319aaebfec09e0144dc3341'>.gitignore</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='966d2b04e070bc040319aaebfec09e0144dc3341'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Douglas Miller &lt;dougmill@linux.vnet.ibm.com&gt;</td><td class='right'>2017-01-28 06:42:20 -0600</td></tr>
<tr><th>committer</th><td>Tejun Heo &lt;tj@kernel.org&gt;</td><td class='right'>2017-01-28 07:49:42 -0500</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/testing/selftests/ptp/.gitignore?id=966d2b04e070bc040319aaebfec09e0144dc3341'>966d2b04e070bc040319aaebfec09e0144dc3341</a> (<a href='/cgit.cgi/linux/net-next.git/patch/tools/testing/selftests/ptp/.gitignore?id=966d2b04e070bc040319aaebfec09e0144dc3341'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=966d2b04e070bc040319aaebfec09e0144dc3341'>4b96156e3d1dd4dfd6039b7c219c9dc4616da52d</a> /<a href='/cgit.cgi/linux/net-next.git/tree/tools/testing/selftests/ptp/.gitignore?id=966d2b04e070bc040319aaebfec09e0144dc3341'>tools/testing/selftests/ptp/.gitignore</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/testing/selftests/ptp/.gitignore?id=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>1b1bc42c1692e9b62756323c675a44cb1a1f9dbd</a> (<a href='/cgit.cgi/linux/net-next.git/diff/tools/testing/selftests/ptp/.gitignore?id=966d2b04e070bc040319aaebfec09e0144dc3341&amp;id2=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>diff</a>)</td></tr></table>
<div class='commit-subject'>percpu-refcount: fix reference leak during percpu-atomic transition</div><div class='commit-msg'>percpu_ref_tryget() and percpu_ref_tryget_live() should return
"true" IFF they acquire a reference. But the return value from
atomic_long_inc_not_zero() is a long and may have high bits set,
e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines
is bool so the reference may actually be acquired but the routines
return "false" which results in a reference leak since the caller
assumes it does not need to do a corresponding percpu_ref_put().

This was seen when performing CPU hotplug during I/O, as hangs in
blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start)
raced with percpu_ref_tryget (blk_mq_timeout_work).
Sample stack trace:

__switch_to+0x2c0/0x450
__schedule+0x2f8/0x970
schedule+0x48/0xc0
blk_mq_freeze_queue_wait+0x94/0x120
blk_mq_queue_reinit_work+0xb8/0x180
blk_mq_queue_reinit_prepare+0x84/0xa0
cpuhp_invoke_callback+0x17c/0x600
cpuhp_up_callbacks+0x58/0x150
_cpu_up+0xf0/0x1c0
do_cpu_up+0x120/0x150
cpu_subsys_online+0x64/0xe0
device_online+0xb4/0x120
online_store+0xb4/0xc0
dev_attr_store+0x68/0xa0
sysfs_kf_write+0x80/0xb0
kernfs_fop_write+0x17c/0x250
__vfs_write+0x6c/0x1e0
vfs_write+0xd0/0x270
SyS_write+0x6c/0x110
system_call+0x38/0xe0

Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS,
and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests.
However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0
and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set.

The fix is to make the tryget routines use an actual boolean internally instead
of the atomic long result truncated to a int.

Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints
Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751
Signed-off-by: Douglas Miller &lt;dougmill@linux.vnet.ibm.com&gt;
Reviewed-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Tejun Heo &lt;tj@kernel.org&gt;
Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints")
Cc: stable@vger.kernel.org # v3.18+
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=966d2b04e070bc040319aaebfec09e0144dc3341'>Diffstat</a> (limited to 'tools/testing/selftests/ptp/.gitignore')</div><table summary='diffstat' class='diffstat'>