Applies some bits.h macros in order to improve readability of
linux/blk_types.h.
Signed-off-by: Leonardo Bras <[email protected]>
---
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)
#define BIO_ISSUE_SIZE_MASK \
- (((1ULL << BIO_ISSUE_SIZE_BITS) - 1) << BIO_ISSUE_SIZE_SHIFT)
-#define BIO_ISSUE_RES_MASK (~((1ULL << BIO_ISSUE_RES_SHIFT) - 1))
+ GENMASK_ULL(BIO_ISSUE_RES_SHIFT - 1, BIO_ISSUE_SIZE_SHIFT)
+#define BIO_ISSUE_RES_MASK GENMASK_ULL(64, BIO_ISSUE_RES_SHIFT)
/* Reserved bit for blk-throtl */
-#define BIO_ISSUE_THROTL_SKIP_LATENCY (1ULL << 63)
+#define BIO_ISSUE_THROTL_SKIP_LATENCY BIT_ULL(63)
struct bio_issue {
u64 value;
@@ -131,7 +132,7 @@ static inline sector_t bio_issue_size(struct bio_issue *issue)
static inline void bio_issue_init(struct bio_issue *issue,
sector_t size)
{
- size &= (1ULL << BIO_ISSUE_SIZE_BITS) - 1;
+ size &= GENMASK_ULL(BIO_ISSUE_SIZE_BITS - 1, 0);
issue->value = ((issue->value & BIO_ISSUE_RES_MASK) |
(ktime_get_ns() & BIO_ISSUE_TIME_MASK) |
((u64)size << BIO_ISSUE_SIZE_SHIFT));
@@ -270,7 +271,7 @@ typedef __u32 __bitwise blk_mq_req_flags_t;
* meaning.
*/
#define REQ_OP_BITS 8
-#define REQ_OP_MASK ((1 << REQ_OP_BITS) - 1)
+#define REQ_OP_MASK GENMASK(REQ_OP_BITS - 1, 0)
#define REQ_FLAG_BITS 24
enum req_opf {
@@ -329,25 +330,25 @@ enum req_flag_bits {
__REQ_NR_BITS, /* stops here */
};
-#define REQ_FAILFAST_DEV (1ULL << __REQ_FAILFAST_DEV)
-#define REQ_FAILFAST_TRANSPORT (1ULL << __REQ_FAILFAST_TRANSPORT)
-#define REQ_FAILFAST_DRIVER (1ULL << __REQ_FAILFAST_DRIVER)
-#define REQ_SYNC (1ULL << __REQ_SYNC)
-#define REQ_META (1ULL << __REQ_META)
-#define REQ_PRIO (1ULL << __REQ_PRIO)
-#define REQ_NOMERGE (1ULL << __REQ_NOMERGE)
-#define REQ_IDLE (1ULL << __REQ_IDLE)
-#define REQ_INTEGRITY (1ULL << __REQ_INTEGRITY)
-#define REQ_FUA (1ULL << __REQ_FUA)
-#define REQ_PREFLUSH (1ULL << __REQ_PREFLUSH)
-#define REQ_RAHEAD (1ULL << __REQ_RAHEAD)
-#define REQ_BACKGROUND (1ULL << __REQ_BACKGROUND)
-#define REQ_NOWAIT (1ULL << __REQ_NOWAIT)
-#define REQ_NOUNMAP (1ULL << __REQ_NOUNMAP)
-#define REQ_HIPRI (1ULL << __REQ_HIPRI)
-
-#define REQ_DRV (1ULL << __REQ_DRV)
-#define REQ_SWAP (1ULL << __REQ_SWAP)
+#define REQ_FAILFAST_DEV BIT_ULL(__REQ_FAILFAST_DEV)
+#define REQ_FAILFAST_TRANSPORT BIT_ULL(__REQ_FAILFAST_TRANSPORT)
+#define REQ_FAILFAST_DRIVER BIT_ULL(__REQ_FAILFAST_DRIVER)
+#define REQ_SYNC BIT_ULL(__REQ_SYNC)
+#define REQ_META BIT_ULL(__REQ_META)
+#define REQ_PRIO BIT_ULL(__REQ_PRIO)
+#define REQ_NOMERGE BIT_ULL(__REQ_NOMERGE)
+#define REQ_IDLE BIT_ULL(__REQ_IDLE)
+#define REQ_INTEGRITY BIT_ULL(__REQ_INTEGRITY)
+#define REQ_FUA BIT_ULL(__REQ_FUA)
+#define REQ_PREFLUSH BIT_ULL(__REQ_PREFLUSH)
+#define REQ_RAHEAD BIT_ULL(__REQ_RAHEAD)
+#define REQ_BACKGROUND BIT_ULL(__REQ_BACKGROUND)
+#define REQ_NOWAIT BIT_ULL(__REQ_NOWAIT)
+#define REQ_NOUNMAP BIT_ULL(__REQ_NOUNMAP)
+#define REQ_HIPRI BIT_ULL(__REQ_HIPRI)
+
+#define REQ_DRV BIT_ULL(__REQ_DRV)
+#define REQ_SWAP BIT_ULL(__REQ_SWAP)
#define REQ_FAILFAST_MASK \
(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
@@ -415,7 +416,7 @@ static inline int op_stat_group(unsigned int op)
typedef unsigned int blk_qc_t;
#define BLK_QC_T_NONE -1U
#define BLK_QC_T_SHIFT 16
-#define BLK_QC_T_INTERNAL (1U << 31)
+#define BLK_QC_T_INTERNAL BIT(31)
static inline bool blk_qc_t_valid(blk_qc_t cookie)
{
@@ -429,7 +430,7 @@ static inline unsigned int blk_qc_t_to_queue_num(blk_qc_t cookie)
static inline unsigned int blk_qc_t_to_tag(blk_qc_t cookie)
{
- return cookie & ((1u << BLK_QC_T_SHIFT) - 1);
+ return cookie & GENMASK(BLK_QC_T_SHIFT - 1, 0);
}
static inline bool blk_qc_t_is_internal(blk_qc_t cookie)
--
2.20.1
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 <[email protected]>
> ---
> 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
On Fri, 2019-08-02 at 21:18 -0700, Jens Axboe wrote:
> 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.
[]
> 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:
While I'm not at all a proponent of GENMASK/GENMASK_ULL,
and so not a proponent of this patch, latent defects are
possible in both cases.
You'd likely have to look at SOME_SHIFT to see if it's 0
to verify the actual mask is what's really desired.
$ git grep -P '_SHIFT\s+\(?\s*0\s*\)?\b' | wc -l
11907
On 8/4/19 1:17 PM, Joe Perches wrote:
> On Fri, 2019-08-02 at 21:18 -0700, Jens Axboe wrote:
>> 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.
> []
>> 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:
>
> While I'm not at all a proponent of GENMASK/GENMASK_ULL,
> and so not a proponent of this patch, latent defects are
> possible in both cases.
>
> You'd likely have to look at SOME_SHIFT to see if it's 0
> to verify the actual mask is what's really desired.
>
> $ git grep -P '_SHIFT\s+\(?\s*0\s*\)?\b' | wc -l
> 11907
Usually SOME_SHIFT is either a numeric value, and you already know,
or it's part of a series of enums/defines (like in the case that's
being done here) where you already have prior knowledge about the
values. For those cases, GENMASK/GENMASK_ULL adds nothing imho, it
only makes it less readable and more error prone.
--
Jens Axboe
On Fri, 2019-08-02 at 21:18 -0700, Jens Axboe wrote:
> 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 <[email protected]>
> > ---
> > 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.
>
Well, as a newbie, macros like GENMASK(a,b) look way simpler. I to read
than (((1 << a) - 1) << b), or (~((1 << c) - 1)).
I mean, in GENMASK all bits >= a, <=b are set.
But I agree that once you get used to reading masks created with <<, it
doesn't look that harder.
Well, thanks for this feedback.
Regards,
Leonardo Brás