block/blk-core.c | 4 ++-- block/blk-mq.c | 5 ++--- block/blk.h | 22 ++++++++++++++++++++++ 3 files changed, 26 insertions(+), 5 deletions(-)
From: Tang Yizhou <yizhou.tang@shopee.com>
Now when I/O is submitted to a partition, the per-CPU in_flight[]
counter is incremented only on the partition's block_device, not on the
underlying whole disk. This leads to a problem which can be shown by a
fio test:
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
mydev 252:1 0 20G 0 disk
└─mydev1 259:0 0 10G 0 part
iostat -xp 1
Device r/s rkB/s ... aqu-sz %util
mydev 128153.00 512612.00 ... 13.22 72.20
mydev1 128154.00 512616.00 ... 13.22 100.00
%util is different between mydev and mydev1, which is unexpected.
This is the cumulative effect of a series of patches. The root cause is
commit e016b78201a2 ("block: return just one value from part_in_flight"),
which deleted the branch in part_in_flight() that aggregated the whole-disk
in_flight count on top of the partition's. Then the second commit is
commit 10ec5e86f9b8 ("block: merge part_{inc,dev}_in_flight into their
only callers"), which folded the whole-disk in_flight accounting into
generic_start_io_acct() and generic_end_io_acct(). Those two helpers
were then removed by commit e722fff238bb ("block: remove
generic_{start,end}_io_acct"), and from that point on the whole disk's
in_flight is no longer accounted at all.
In update_io_ticks(), if calling bdev_count_inflight() finds that the
inflight value of the whole device is 0, the accumulation of io_ticks will
be skipped, causing the reported util% value to be underestimated.
Fix it by restoring the whole-disk in_flight accounting.
Fixes: e016b78201a2 ("block: return just one value from part_in_flight")
v2: Update commit message.
v3: Take Christoph's advice and factor the common code into two helpers.
Suggested-by: Leon Hwang <leon.huangfu@shopee.com>
Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
---
block/blk-core.c | 4 ++--
block/blk-mq.c | 5 ++---
block/blk.h | 22 ++++++++++++++++++++++
3 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 17450058ea6d..81b322b8a385 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1042,7 +1042,7 @@ unsigned long bdev_start_io_acct(struct block_device *bdev, enum req_op op,
{
part_stat_lock();
update_io_ticks(bdev, start_time, false);
- part_stat_local_inc(bdev, in_flight[op_is_write(op)]);
+ bdev_inc_in_flight(bdev, op);
part_stat_unlock();
return start_time;
@@ -1073,7 +1073,7 @@ void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
part_stat_inc(bdev, ios[sgrp]);
part_stat_add(bdev, sectors[sgrp], sectors);
part_stat_add(bdev, nsecs[sgrp], jiffies_to_nsecs(duration));
- part_stat_local_dec(bdev, in_flight[op_is_write(op)]);
+ bdev_inc_in_flight(bdev, op);
part_stat_unlock();
}
EXPORT_SYMBOL(bdev_end_io_acct);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index d0c37daf568f..6bdfe642bd93 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1082,8 +1082,7 @@ static inline void blk_account_io_done(struct request *req, u64 now)
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);
- part_stat_local_dec(req->part,
- in_flight[op_is_write(req_op(req))]);
+ bdev_dec_in_flight(req->part, req_op(req));
part_stat_unlock();
}
}
@@ -1143,7 +1142,7 @@ static inline void blk_account_io_start(struct request *req)
part_stat_lock();
update_io_ticks(req->part, jiffies, false);
- part_stat_local_inc(req->part, in_flight[op_is_write(req_op(req))]);
+ bdev_inc_in_flight(req->part, req_op(req));
part_stat_unlock();
}
diff --git a/block/blk.h b/block/blk.h
index b998a7761faf..05099aab6863 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -4,6 +4,7 @@
#include <linux/bio-integrity.h>
#include <linux/blk-crypto.h>
+#include <linux/part_stat.h>
#include <linux/lockdep.h>
#include <linux/memblock.h> /* for max_pfn/max_low_pfn */
#include <linux/sched/sysctl.h>
@@ -11,6 +12,7 @@
#include <xen/xen.h>
#include "blk-crypto-internal.h"
+
struct elv_change_ctx;
/*
@@ -485,6 +487,26 @@ static inline void req_set_nomerge(struct request_queue *q, struct request *req)
q->last_merge = NULL;
}
+static inline void bdev_inc_in_flight(struct block_device *bdev,
+ enum req_op op)
+{
+ bool rw = op_is_write(op);
+
+ part_stat_local_inc(bdev, in_flight[rw]);
+ if (bdev_is_partition(bdev))
+ part_stat_local_inc(bdev_whole(bdev), in_flight[rw]);
+}
+
+static inline void bdev_dec_in_flight(struct block_device *bdev,
+ enum req_op op)
+{
+ bool rw = op_is_write(op);
+
+ part_stat_local_dec(bdev, in_flight[rw]);
+ if (bdev_is_partition(bdev))
+ part_stat_local_dec(bdev_whole(bdev), in_flight[rw]);
+}
+
/*
* Internal io_context interface
*/
--
2.43.0
On 5/22/26 7:14 AM, Tang Yizhou wrote:
> Fixes: e016b78201a2 ("block: return just one value from part_in_flight")
>
> v2: Update commit message.
> v3: Take Christoph's advice and factor the common code into two helpers.
>
> Suggested-by: Leon Hwang <leon.huangfu@shopee.com>
> Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
> ---
Changelog goes _below_ this line, we don't want it in the git commit
message. And Fixes goes with the other tags.
--
Jens Axboe
On 2026/5/22 21:14, Tang Yizhou wrote:
> From: Tang Yizhou <yizhou.tang@shopee.com>
>
[...]
> diff --git a/block/blk.h b/block/blk.h
> index b998a7761faf..05099aab6863 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -4,6 +4,7 @@
>
> #include <linux/bio-integrity.h>
> #include <linux/blk-crypto.h>
> +#include <linux/part_stat.h>
> #include <linux/lockdep.h>
> #include <linux/memblock.h> /* for max_pfn/max_low_pfn */
> #include <linux/sched/sysctl.h>
> @@ -11,6 +12,7 @@
> #include <xen/xen.h>
> #include "blk-crypto-internal.h"
>
> +
NIT: I think this new line is added unintentionally. Should be dropped.
Thanks,
Leon
> struct elv_change_ctx;
>
> /*
> @@ -485,6 +487,26 @@ static inline void req_set_nomerge(struct request_queue *q, struct request *req)
> q->last_merge = NULL;
> }
>
> +static inline void bdev_inc_in_flight(struct block_device *bdev,
> + enum req_op op)
> +{
> + bool rw = op_is_write(op);
> +
> + part_stat_local_inc(bdev, in_flight[rw]);
> + if (bdev_is_partition(bdev))
> + part_stat_local_inc(bdev_whole(bdev), in_flight[rw]);
> +}
> +
> +static inline void bdev_dec_in_flight(struct block_device *bdev,
> + enum req_op op)
> +{
> + bool rw = op_is_write(op);
> +
> + part_stat_local_dec(bdev, in_flight[rw]);
> + if (bdev_is_partition(bdev))
> + part_stat_local_dec(bdev_whole(bdev), in_flight[rw]);
> +}
> +
> /*
> * Internal io_context interface
> */
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