#ifndef _PGTABLE_NOPMD_H
#define _PGTABLE_NOPMD_H

#ifndef __ASSEMBLY__

#include <asm-generic/pgtable-nopud.h>

struct mm_struct;

#define __PAGETABLE_PMD_FOLDED

/*
 * Having the pmd type consist of a pud gets the size right, and allows
 * us to conceptually access the pud entry that this pmd is folded into
 * without casting.
 */
typedef struct { pud_t pud; } pmd_t;

#define PMD_SHIFT	PUD_SHIFT
#define PTRS_PER_PMD	1
#define PMD_SIZE  	(1UL << PMD_SHIFT)
#define PMD_MASK  	(~(PMD_SIZE-1))

/*
 * The "pud_xxx()" functions here are trivial for a folded two-level
 * setup: the pmd is never bad, and a pmd always exists (as it's folded
 * into the pud entry)
 */
static inline int pud_none(pud_t pud)		{ return 0; }
static inline int pud_bad(pud_t pud)		{ return 0; }
static inline int pud_present(pud_t pud)	{ return 1; }
static inline void pud_clear(pud_t *pud)	{ }
#define pmd_ERROR(pmd)				(pud_ERROR((pmd).pud))

#define pud_populate(mm, pmd, pte)		do { } while (0)

/*
 * (pmds are folded into puds so this doesn't get actually called,
 * but the define is needed for a generic inline function.)
 */
#define set_pud(pudptr, pudval)			set_pmd((pmd_t *)(pudptr), (pmd_t) { pudval })

static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address)
{
	return (pmd_t *)pud;
}

#define pmd_val(x)				(pud_val((x).pud))
#define __pmd(x)				((pmd_t) { __pud(x) } )

#define pud_page(pud)				(pmd_page((pmd_t){ pud }))
#define pud_page_vaddr(pud)			(pmd_page_vaddr((pmd_t){ pud }))

/*
 * allocating and freeing a pmd is trivial: the 1-entry pmd is
 * inside the pud, so has no extra memory associated with it.
 */
#define pmd_alloc_one(mm, address)		NULL
static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
{
}
#define __pmd_free_tlb(tlb, x, a)		do { } while (0)

#undef  pmd_addr_end
#define pmd_addr_end(addr, end)			(end)

#endif /* __ASSEMBLY__ */

#endif /* _PGTABLE_NOPMD_H */
ysfs.h?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>tree</a><a class='active' href='/cgit.cgi/linux/net-next.git/commit/net/batman-adv/sysfs.h?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>commit</a><a href='/cgit.cgi/linux/net-next.git/diff/net/batman-adv/sysfs.h?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>diff</a></td><td class='form'><form class='right' method='get' action='/cgit.cgi/linux/net-next.git/log/net/batman-adv/sysfs.h'>
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>net</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/batman-adv?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>batman-adv</a>/<a href='/cgit.cgi/linux/net-next.git/commit/net/batman-adv/sysfs.h?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>sysfs.h</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='h' value='nds-private-remove'/><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/net/batman-adv/sysfs.h?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>966d2b04e070bc040319aaebfec09e0144dc3341</a> (<a href='/cgit.cgi/linux/net-next.git/patch/net/batman-adv/sysfs.h?id=966d2b04e070bc040319aaebfec09e0144dc3341'>patch</a>)</td></tr>
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<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/?h=nds-private-remove&amp;id=966d2b04e070bc040319aaebfec09e0144dc3341'>Diffstat</a> (limited to 'net/batman-adv/sysfs.h')</div><table summary='diffstat' class='diffstat'>