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SubjectRe: btrfs zero divide
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On Tue, 2013-07-30 at 16:40 -0400, Josef Bacik wrote:
> So stripe_len shouldn't be 0, if it is you have bigger problems :). Is this a
> corrupt fs or something? If there was some sort of corruption that occured then
> I suppose stripe_len could be 0 and we'd need to catch that somewhere higher up
> the stack and error out. Is there a way you could check and see if that's the
> case? Thanks,

Maybe use a temporary check in do_div
Something like this maybe. (uncompiled/untested)
---
include/asm-generic/div64.h | 43 +++++++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/include/asm-generic/div64.h b/include/asm-generic/div64.h
index 8f4e319..cce75fe 100644
--- a/include/asm-generic/div64.h
+++ b/include/asm-generic/div64.h
@@ -19,16 +19,25 @@

#include <linux/types.h>
#include <linux/compiler.h>
+#include <linux/bug.h>
+#include <linux/printk.h>

#if BITS_PER_LONG == 64

-# define do_div(n,base) ({ \
+# define do_div(n, base) \
+({ \
uint32_t __base = (base); \
uint32_t __rem; \
- __rem = ((uint64_t)(n)) % __base; \
- (n) = ((uint64_t)(n)) / __base; \
+ if (__base == 0) { \
+ WARN(1, "Attempted division by 0\n"); \
+ dump_stack(); \
+ __rem = 0; \
+ } else { \
+ __rem = ((uint64_t)(n)) % __base; \
+ (n) = ((uint64_t)(n)) / __base; \
+ } \
__rem; \
- })
+})

#elif BITS_PER_LONG == 32

@@ -37,16 +46,22 @@ extern uint32_t __div64_32(uint64_t *dividend, uint32_t divisor);
/* The unnecessary pointer compare is there
* to check for type safety (n must be 64bit)
*/
-# define do_div(n,base) ({ \
- uint32_t __base = (base); \
- uint32_t __rem; \
- (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
- if (likely(((n) >> 32) == 0)) { \
- __rem = (uint32_t)(n) % __base; \
- (n) = (uint32_t)(n) / __base; \
- } else \
- __rem = __div64_32(&(n), __base); \
- __rem; \
+# define do_div(n, base) \
+({ \
+ uint32_t __base = (base); \
+ uint32_t __rem; \
+ (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
+ if (__base == 0) { \
+ WARN(1, "Attempted division by 0\n"); \
+ dump_stack(); \
+ __rem = 0; \
+ } else if (likely(((n) >> 32) == 0)) { \
+ __rem = (uint32_t)(n) % __base; \
+ (n) = (uint32_t)(n) / __base; \
+ } else { \
+ __rem = __div64_32(&(n), __base); \
+ } \
+ __rem; \
})

#else /* BITS_PER_LONG == ?? */



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