[PATCH V2 05/13] block: only account passthrough IO from userspace
Christoph Hellwig
hch at lst.de
Mon Jan 24 23:19:06 PST 2022
On Tue, Jan 25, 2022 at 07:16:34AM +0100, Christoph Hellwig wrote:
> So why not key off accouning off "rq->bio && rq->bio->bi_bdev"
> and remove the need for the flag and the second half of the assignment
> above? That is much less error probe and removes code size.
Something like this, lightly tested:
---
>From 5499d013341b492899d1fecde7680ff8ebd232e9 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch at lst.de>
Date: Tue, 25 Jan 2022 07:29:06 +0100
Subject: block: remove the part field from struct request
All file system I/O and most userspace passthrough bios have bi_bdev set.
Switch I/O accounting to directly use the bio and stop copying it into a
separate struct request field.
This changes behavior in that e.g. /dev/sgX requests are not accounted
to the gendisk for the SCSI disk any more, which is the correct thing to
do as they never went through that gendisk, and fixes a potential race
when the disk driver is unbound while /dev/sgX I/O is in progress.
Signed-off-by: Christoph Hellwig <hch at lst.de>
---
block/blk-merge.c | 12 ++++++------
block/blk-mq.c | 32 +++++++++++++-------------------
block/blk.h | 6 +++---
include/linux/blk-mq.h | 1 -
4 files changed, 22 insertions(+), 29 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 4de34a332c9fd..43e46ea2f0152 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -739,11 +739,11 @@ void blk_rq_set_mixed_merge(struct request *rq)
static void blk_account_io_merge_request(struct request *req)
{
- if (blk_do_io_stat(req)) {
- part_stat_lock();
- part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
- part_stat_unlock();
- }
+ if (!blk_do_io_stat(req))
+ return;
+ part_stat_lock();
+ part_stat_inc(req->bio->bi_bdev, merges[op_stat_group(req_op(req))]);
+ part_stat_unlock();
}
static enum elv_merge blk_try_req_merge(struct request *req,
@@ -947,7 +947,7 @@ static void blk_account_io_merge_bio(struct request *req)
return;
part_stat_lock();
- part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
+ part_stat_inc(req->bio->bi_bdev, merges[op_stat_group(req_op(req))]);
part_stat_unlock();
}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f3bf3358a3bb2..01b3862347965 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -132,10 +132,12 @@ static bool blk_mq_check_inflight(struct request *rq, void *priv,
{
struct mq_inflight *mi = priv;
- if ((!mi->part->bd_partno || rq->part == mi->part) &&
- blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
- mi->inflight[rq_data_dir(rq)]++;
+ if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
+ return true;
+ if (mi->part->bd_partno && rq->bio && rq->bio->bi_bdev != mi->part)
+ return true;
+ mi->inflight[rq_data_dir(rq)]++;
return true;
}
@@ -331,7 +333,6 @@ void blk_rq_init(struct request_queue *q, struct request *rq)
rq->tag = BLK_MQ_NO_TAG;
rq->internal_tag = BLK_MQ_NO_TAG;
rq->start_time_ns = ktime_get_ns();
- rq->part = NULL;
blk_crypto_rq_set_defaults(rq);
}
EXPORT_SYMBOL(blk_rq_init);
@@ -368,7 +369,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
rq->start_time_ns = ktime_get_ns();
else
rq->start_time_ns = 0;
- rq->part = NULL;
#ifdef CONFIG_BLK_RQ_ALLOC_TIME
rq->alloc_time_ns = alloc_time_ns;
#endif
@@ -687,11 +687,11 @@ static void req_bio_endio(struct request *rq, struct bio *bio,
static void blk_account_io_completion(struct request *req, unsigned int bytes)
{
- if (req->part && blk_do_io_stat(req)) {
+ if (blk_do_io_stat(req)) {
const int sgrp = op_stat_group(req_op(req));
part_stat_lock();
- part_stat_add(req->part, sectors[sgrp], bytes >> 9);
+ part_stat_add(req->bio->bi_bdev, sectors[sgrp], bytes >> 9);
part_stat_unlock();
}
}
@@ -859,11 +859,12 @@ EXPORT_SYMBOL_GPL(blk_update_request);
static void __blk_account_io_done(struct request *req, u64 now)
{
const int sgrp = op_stat_group(req_op(req));
+ struct block_device *bdev = req->bio->bi_bdev;
part_stat_lock();
- update_io_ticks(req->part, jiffies, true);
- part_stat_inc(req->part, ios[sgrp]);
- part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
+ update_io_ticks(bdev, jiffies, true);
+ part_stat_inc(bdev, ios[sgrp]);
+ part_stat_add(bdev, nsecs[sgrp], now - req->start_time_ns);
part_stat_unlock();
}
@@ -874,21 +875,14 @@ static inline void blk_account_io_done(struct request *req, u64 now)
* normal IO on queueing nor completion. Accounting the
* containing request is enough.
*/
- if (blk_do_io_stat(req) && req->part &&
- !(req->rq_flags & RQF_FLUSH_SEQ))
+ if (blk_do_io_stat(req) && !(req->rq_flags & RQF_FLUSH_SEQ))
__blk_account_io_done(req, now);
}
static void __blk_account_io_start(struct request *rq)
{
- /* passthrough requests can hold bios that do not have ->bi_bdev set */
- if (rq->bio && rq->bio->bi_bdev)
- rq->part = rq->bio->bi_bdev;
- else if (rq->q->disk)
- rq->part = rq->q->disk->part0;
-
part_stat_lock();
- update_io_ticks(rq->part, jiffies, false);
+ update_io_ticks(rq->bio->bi_bdev, jiffies, false);
part_stat_unlock();
}
diff --git a/block/blk.h b/block/blk.h
index 8bd43b3ad33d5..a7a5a5435e09d 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -320,12 +320,12 @@ int blk_dev_init(void);
/*
* Contribute to IO statistics IFF:
*
- * a) it's attached to a gendisk, and
- * b) the queue had IO stats enabled when this request was started
+ * a) the queue had IO stats enabled when this request was started, and
+ * b) it has an assigned block_device
*/
static inline bool blk_do_io_stat(struct request *rq)
{
- return (rq->rq_flags & RQF_IO_STAT) && rq->q->disk;
+ return (rq->rq_flags & RQF_IO_STAT) && rq->bio && rq->bio->bi_bdev;
}
void update_io_ticks(struct block_device *part, unsigned long now, bool end);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index d319ffa59354a..81769c01e6e4b 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -99,7 +99,6 @@ struct request {
struct request *rq_next;
};
- struct block_device *part;
#ifdef CONFIG_BLK_RQ_ALLOC_TIME
/* Time that the first bio started allocating this request. */
u64 alloc_time_ns;
--
2.30.2
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