From: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
Subject: mm: debugfs: move rounddown_pow_of_two() out from do_fault path
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@xxxxxxxxxxxxxxxxxxxx: tweak code layout]
Fixes: a9b0f861("mm: nominate faultaround area in bytes rather than page order")
Signed-off-by: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.15.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff -puN mm/memory.c~mm-debugfs-move-rounddown_pow_of_two-out-from-do_fault-path mm/memory.c
--- a/mm/memory.c~mm-debugfs-move-rounddown_pow_of_two-out-from-do_fault-path
+++ a/mm/memory.c
@@ -2758,23 +2758,18 @@ void do_set_pte(struct vm_area_struct *v
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 *
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,
_
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html