Re: [PATCH 4/6] block: clear BIO_PERCPU_CACHE flag if polling isn't supported

[Jens Axboe <axboe@kernel.dk>]

On 8/12/21 11:31 AM, Keith Busch wrote:
> On Thu, Aug 12, 2021 at 09:41:47AM -0600, Jens Axboe wrote:
>> -	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
>> +	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) {
>> +		/* can't support alloc cache if we turn off polling */
>> +		bio_clear_flag(bio, BIO_PERCPU_CACHE);
>>  		bio->bi_opf &= ~REQ_HIPRI;
>> +	}
> 
> It looks like you should also clear BIO_PERCPU_CACHE if this bio gets
> split in blk_bio_segment_split().

Indeed. Wonder if we should make that a small helper, as any clear of
REQ_HIPRI should clear BIO_PERCPU_CACHE as well.


diff --git a/block/blk-core.c b/block/blk-core.c
index 7e852242f4cc..d2722ecd4d9b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -821,11 +821,8 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio)
 		}
 	}
 
-	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) {
-		/* can't support alloc cache if we turn off polling */
-		bio_clear_flag(bio, BIO_PERCPU_CACHE);
-		bio->bi_opf &= ~REQ_HIPRI;
-	}
+	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
+		bio_clear_hipri(bio);
 
 	switch (bio_op(bio)) {
 	case REQ_OP_DISCARD:
diff --git a/block/blk-merge.c b/block/blk-merge.c
index f8707ff7e2fc..985ca1116c32 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -285,7 +285,7 @@ static struct bio *blk_bio_segment_split(struct request_queue *q,
 	 * iopoll in direct IO routine. Given performance gain of iopoll for
 	 * big IO can be trival, disable iopoll when split needed.
 	 */
-	bio->bi_opf &= ~REQ_HIPRI;
+	bio_clear_hipri(bio);
 
 	return bio_split(bio, sectors, GFP_NOIO, bs);
 }
diff --git a/block/blk.h b/block/blk.h
index db6f82bbb683..7dba254b45f2 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -367,4 +367,11 @@ extern struct device_attribute dev_attr_events;
 extern struct device_attribute dev_attr_events_async;
 extern struct device_attribute dev_attr_events_poll_msecs;
 
+static inline void bio_clear_hipri(struct bio *bio)
+{
+	/* can't support alloc cache if we turn off polling */
+	bio_clear_flag(bio, BIO_PERCPU_CACHE);
+	bio->bi_opf &= ~REQ_HIPRI;
+}
+
 #endif /* BLK_INTERNAL_H */

-- 
Jens Axboe