On Wed, Oct 25, 2017 at 07:39:48AM +0000, Matthew Wilcox wrote: > Hang on, don't tell me you found this by inspection. Are you not running the > bitmap testcase, enabled by CONFIG_TEST_BITMAP? Either that should be > producing an error, or there's a missing test case, or your inspection is > wrong ...
I did find it by inspection. I was looking for a version of the bitmap_* API that does little-endian style bitmaps on all systems, and the inline bitmap_set() does that in the case where it calls memset, but not in the case where it calls __bitmap_set. I'll fire up a big-endian system tomorrow when I get to work to run the test case. (PPC64 is almost entirely little-endian these days as far as the IBM POWER systems are concerned.) In any case, it's pretty clearly wrong as it is. On a big-endian 64-bit system, bitmap_set(p, 56, 16) should set bytes 0 and 15 to 0xff, and there's no way a single memset can do that. Paul. (and yes, I stuffed up the address for lkml)