On 06/16/2017 09:59 AM, Jens Axboe wrote:
> On 06/16/2017 09:52 AM, Christoph Hellwig wrote:
>> On Fri, Jun 16, 2017 at 08:35:07AM -0600, Jens Axboe wrote:
>>>> Agreed. In fact I'd go a little further: we should have a
>>>>
>>>> u16 hints;
>>>>
>>>> that goes all the way down from fcntl to the driver, right now
>>>> we'll allocate the first 3 bits for the write lifetime hints (2.5,
>>>> so we have one value spare, as they don't need to flags but can be
>>>> enum values), leaving more space for other kinds of hints.
>>>
>>> Did you see v5? It adds enum write_hint and passes it all the way down,
>>> until we transform them into rq/bio flags.
>>
>> Yes. But with all the way down I mean all the way down to the driver :)
>
> Only missing part is the request flags. And why make that any different
> than the flags we already have now? It'd be trivial to pack the value
> into the request flags as well, but I'm struggling to see the point of
> that, honestly.
>
> Please expand on why you think changing the request flags to also
> carry that value would be useful, as opposed to just mapping it when
> we setup the request. If you have a valid concern I don't mind making
> the change, but I just don't see one right now.
So that would look like the below change on top of the current v5. I
skipped the callers, since those are all easy
s/bio_op_write_hint/write_hint_to_opf changes.
diff --git a/block/bio.c b/block/bio.c
index 758d83d91bb0..888e7801c638 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -2082,22 +2082,6 @@ void bio_clone_blkcg_association(struct bio *dst, struct bio *src)
#endif /* CONFIG_BLK_CGROUP */
-static const unsigned int rwf_write_to_opf_flag[] = {
- 0, REQ_WRITE_SHORT, REQ_WRITE_MEDIUM, REQ_WRITE_LONG, REQ_WRITE_EXTREME
-};
-
-/*
- * Convert WRITE_LIFE_* hints into req/bio flags
- */
-unsigned int bio_op_write_hint(enum write_hint hint)
-{
- if (WARN_ON_ONCE(hint >= ARRAY_SIZE(rwf_write_to_opf_flag)))
- return 0;
-
- return rwf_write_to_opf_flag[hint];
-}
-EXPORT_SYMBOL_GPL(bio_op_write_hint);
-
static void __init biovec_init_slabs(void)
{
int i;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index e9360dc5ea07..d1b04b0e99cf 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -443,7 +443,6 @@ extern struct bio *bio_copy_kern(struct request_queue *, void *, unsigned int,
gfp_t, int);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(struct bio *bio);
-extern unsigned int bio_op_write_hint(enum write_hint hint);
void generic_start_io_acct(int rw, unsigned long sectors,
struct hd_struct *part);
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 23646eb433e7..f4d348cd3a6b 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -7,6 +7,7 @@
#include <linux/types.h>
#include <linux/bvec.h>
+#include <linux/fs.h>
struct bio_set;
struct bio;
@@ -201,10 +202,9 @@ enum req_flag_bits {
__REQ_PREFLUSH, /* request for cache flush */
__REQ_RAHEAD, /* read ahead, can fail anytime */
__REQ_BACKGROUND, /* background IO */
- __REQ_WRITE_SHORT, /* short life time write */
- __REQ_WRITE_MEDIUM, /* medium life time write */
- __REQ_WRITE_LONG, /* long life time write */
- __REQ_WRITE_EXTREME, /* extremely long life time write */
+ __REQ_WRITE_HINT_SHIFT, /* 3 bits for life time hint */
+ __REQ_WRITE_HINT_PAD1,
+ __REQ_WRITE_HINT_PAD2,
/* command specific flags for REQ_OP_WRITE_ZEROES: */
__REQ_NOUNMAP, /* do not free blocks when zeroing */
@@ -225,13 +225,12 @@ enum req_flag_bits {
#define REQ_PREFLUSH (1ULL << __REQ_PREFLUSH)
#define REQ_RAHEAD (1ULL << __REQ_RAHEAD)
#define REQ_BACKGROUND (1ULL << __REQ_BACKGROUND)
-#define REQ_WRITE_SHORT (1ULL << __REQ_WRITE_SHORT)
-#define REQ_WRITE_MEDIUM (1ULL << __REQ_WRITE_MEDIUM)
-#define REQ_WRITE_LONG (1ULL << __REQ_WRITE_LONG)
-#define REQ_WRITE_EXTREME (1ULL << __REQ_WRITE_EXTREME)
+#define REQ_WRITE_SHORT (WRITE_HINT_SHORT << __REQ_WRITE_HINT_SHIFT)
+#define REQ_WRITE_MEDIUM (WRITE_HINT_MEDIUM << __REQ_WRITE_HINT_SHIFT)
+#define REQ_WRITE_LONG (WRITE_HINT_LONG << __REQ_WRITE_HINT_SHIFT)
+#define REQ_WRITE_EXTREME (WRITE_HINT_EXTREME << __REQ_WRITE_HINT_SHIFT)
-#define REQ_WRITE_LIFE_MASK (REQ_WRITE_SHORT | REQ_WRITE_MEDIUM | \
- REQ_WRITE_LONG | REQ_WRITE_EXTREME)
+#define REQ_WRITE_LIFE_MASK (0x7 << __REQ_WRITE_HINT_SHIFT)
#define REQ_NOUNMAP (1ULL << __REQ_NOUNMAP)
@@ -328,4 +327,9 @@ static inline bool op_write_hint_valid(unsigned int opf)
return (opf & REQ_WRITE_LIFE_MASK) != 0;
}
+static inline unsigned int write_hint_to_opf(enum write_hint hint)
+{
+ return hint << __REQ_WRITE_HINT_SHIFT;
+}
+
#endif /* __LINUX_BLK_TYPES_H */
--
Jens Axboe
