On 8/1/19 6:00 PM, Leonardo Bras wrote: > Applies some bits.h macros in order to improve readability of > linux/blk_types.h. > > Signed-off-by: Leonardo Bras <leona...@linux.ibm.com> > --- > include/linux/blk_types.h | 55 ++++++++++++++++++++------------------- > 1 file changed, 28 insertions(+), 27 deletions(-) > > diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h > index 95202f80676c..31c8c6d274f6 100644 > --- a/include/linux/blk_types.h > +++ b/include/linux/blk_types.h > @@ -9,6 +9,7 @@ > #include <linux/types.h> > #include <linux/bvec.h> > #include <linux/ktime.h> > +#include <linux/bits.h> > > struct bio_set; > struct bio; > @@ -101,13 +102,13 @@ static inline bool blk_path_error(blk_status_t error) > #define BIO_ISSUE_SIZE_BITS 12 > #define BIO_ISSUE_RES_SHIFT (64 - BIO_ISSUE_RES_BITS) > #define BIO_ISSUE_SIZE_SHIFT (BIO_ISSUE_RES_SHIFT - BIO_ISSUE_SIZE_BITS) > -#define BIO_ISSUE_TIME_MASK ((1ULL << BIO_ISSUE_SIZE_SHIFT) - 1) > +#define BIO_ISSUE_TIME_MASK GENMASK_ULL(BIO_ISSUE_SIZE_SHIFT - 1, 0)
Not sure why we even have these helpers, I'd argue that patches like this HURT readability, not improve it. When I see ((1ULL << SOME_SHIFT) - 1) I know precisely what that does, whereas I have to think about the other one, maybe even look it up to be sure. For instance, without looking now, I have no idea what the second argument is. Looking at the git log, I see numerous instances of: "xxx: Fix misuses of GENMASK macro Arguments are supposed to be ordered high then low." Hence it seems GENMASK_ULL is easy to misuse or get wrong, the very opposite of what you'd want in a helper. How is it helping readability if the helper is easy to misuse? Ditto with (1ULL << SOME_SHIFT) vs BIT_ULL. But at least that one doesn't have a mysterious 2nd argument. Hence I'm not inclined to apply this patch. -- Jens Axboe
