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mm: debugfs: move rounddown_pow_of_two() out from do_fault path

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do_fault_around() expects fault_around_bytes rounded down to nearest page
order.  Instead of calling rounddown_pow_of_two every time in
fault_around_pages()/fault_around_mask() we could do round down when user
changes fault_around_bytes via debugfs interface.

This also fixes bug when user set fault_around_bytes to 0.  Result of
rounddown_pow_of_two(0) is not defined, therefore fault_around_bytes == 0
doesn't work without this patch.

Let's set fault_around_bytes to PAGE_SIZE if user sets to something less
than PAGE_SIZE

[akpm@linux-foundation.org: tweak code layout]
Fixes: a9b0f861("mm: nominate faultaround area in bytes rather than page order")
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org>	[3.15.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrey Ryabinin 2014-07-30 16:08:35 -07:00 committed by Linus Torvalds
parent 2bcf2e92c3
commit b4903d6e84
1 changed files with 12 additions and 9 deletions
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21
mm/memory.c
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@ -2758,23 +2758,18 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
update_mmu_cache(vma, address, pte);
}
static unsigned long fault_around_bytes = 65536;
static unsigned long fault_around_bytes = rounddown_pow_of_two(65536);
/*
* fault_around_pages() and fault_around_mask() round down fault_around_bytes
* to nearest page order. It's what do_fault_around() expects to see.
*/
static inline unsigned long fault_around_pages(void)
{
return rounddown_pow_of_two(fault_around_bytes) / PAGE_SIZE;
return fault_around_bytes >> PAGE_SHIFT;
}
static inline unsigned long fault_around_mask(void)
{
return ~(rounddown_pow_of_two(fault_around_bytes) - 1) & PAGE_MASK;
return ~(fault_around_bytes - 1) & PAGE_MASK;
}
#ifdef CONFIG_DEBUG_FS
static int fault_around_bytes_get(void *data, u64 *val)
{
@ -2782,11 +2777,19 @@ static int fault_around_bytes_get(void *data, u64 *val)
return 0;
}
/*
* fault_around_pages() and fault_around_mask() expects fault_around_bytes
* rounded down to nearest page order. It's what do_fault_around() expects to
* see.
*/
static int fault_around_bytes_set(void *data, u64 val)
{
if (val / PAGE_SIZE > PTRS_PER_PTE)
return -EINVAL;
fault_around_bytes = val;
if (val > PAGE_SIZE)
fault_around_bytes = rounddown_pow_of_two(val);
else
fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops,