On Fri, 5 Aug 2016 23:48:21 +0800 zijun_hu <zijun...@zoho.com> wrote:
> From: zijun_hu <zijun...@htc.com>
> Date: Fri, 5 Aug 2016 22:10:07 +0800
> Subject: [PATCH 1/1] mm/vmalloc: fix align value calculation error
>
> it causes double align requirement for __get_vm_area_node() if parameter
> size is power of 2 and VM_IOREMAP is set in parameter flags
>
> get_order_long() is implemented and used instead of fls_long() for
> fixing the bug
Makes sense. I think.
> --- a/include/linux/bitops.h
> +++ b/include/linux/bitops.h
> @@ -192,6 +192,23 @@ static inline unsigned fls_long(unsigned long l)
> }
>
> /**
> + * get_order_long - get order after rounding @l up to power of 2
> + * @l: parameter
> + *
> + * it is same as get_count_order() but long type parameter
> + * or 0 is returned if @l == 0UL
> + */
> +static inline int get_order_long(unsigned long l)
> +{
> + if (l == 0UL)
> + return 0;
> + else if (l & (l - 1UL))
> + return fls_long(l);
> + else
> + return fls_long(l) - 1;
> +}
> +
> +/**
> * __ffs64 - find first set bit in a 64 bit word
> * @word: The 64 bit word
> *
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 91f44e7..7d717f3 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1360,7 +1360,7 @@ static struct vm_struct *__get_vm_area_node(unsigned
> long size,
>
> BUG_ON(in_interrupt());
> if (flags & VM_IOREMAP)
> - align = 1ul << clamp_t(int, fls_long(size),
> + align = 1ul << clamp_t(int, get_order_long(size),
> PAGE_SHIFT, IOREMAP_MAX_ORDER);
>
> size = PAGE_ALIGN(size);
It would be better to call this get_count_order_long(), I think? To
match get_count_order()?
get_count_order() is a weird name and perhaps both of these should be
renamed to things which actually make sense. That's a separate issue.
--- a/include/linux/bitops.h~mm-vmalloc-fix-align-value-calculation-error-fix
+++ a/include/linux/bitops.h
@@ -75,6 +75,23 @@ static inline int get_count_order(unsign
return order;
}
+/**
+ * get_count_order_long - get order after rounding @l up to power of 2
+ * @l: parameter
+ *
+ * The same as get_count_order() but accepts a long type parameter
+ * or 0 is returned if @l == 0UL
+ */
+static inline int get_count_order_long(unsigned long l)
+{
+ if (l == 0UL)
+ return 0;
+ else if (l & (l - 1UL))
+ return fls_long(l);
+ else
+ return fls_long(l) - 1;
+}
+
static __always_inline unsigned long hweight_long(unsigned long w)
{
return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
@@ -192,23 +209,6 @@ static inline unsigned fls_long(unsigned
}
/**
- * get_order_long - get order after rounding @l up to power of 2
- * @l: parameter
- *
- * it is same as get_count_order() but long type parameter
- * or 0 is returned if @l == 0UL
- */
-static inline int get_order_long(unsigned long l)
-{
- if (l == 0UL)
- return 0;
- else if (l & (l - 1UL))
- return fls_long(l);
- else
- return fls_long(l) - 1;
-}
-
-/**
* __ffs64 - find first set bit in a 64 bit word
* @word: The 64 bit word
*
--- a/mm/vmalloc.c~mm-vmalloc-fix-align-value-calculation-error-fix
+++ a/mm/vmalloc.c
@@ -1360,7 +1360,7 @@ static struct vm_struct *__get_vm_area_n
BUG_ON(in_interrupt());
if (flags & VM_IOREMAP)
- align = 1ul << clamp_t(int, get_order_long(size),
+ align = 1ul << clamp_t(int, get_count_order_long(size),
PAGE_SHIFT, IOREMAP_MAX_ORDER);
size = PAGE_ALIGN(size);
_
