mirrors/linux
2
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2026-07-22 03:27:30 -04:00
Code Issues Packages Projects Releases Wiki Activity

block: propagate in_flight to whole disk on partition I/O

Browse Source 
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 e016b78201 ("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 10ec5e86f9 ("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 e722fff238 ("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: e016b78201 ("block: return just one value from part_in_flight")
Suggested-by: Leon Hwang <leon.huangfu@shopee.com>
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260526021555.359500-1-yizhou.tang@shopee.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tang Yizhou
2026-05-26 10:15:55 +08:00
committed by Jens Axboe
parent 0fd835f5e9
commit 5bdb8ec58b
4 changed files with 26 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
block/blk-core.c
View File

@@ -1038,7 +1038,7 @@ 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;
@@ -1069,7 +1069,7 @@ 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_dec_in_flight(bdev, op);
part_stat_unlock();
}
EXPORT_SYMBOL(bdev_end_io_acct);

3
block/blk-merge.c
View File

@@ -721,8 +721,7 @@ static void blk_account_io_merge_request(struct request *req)
if (req->rq_flags & RQF_IO_STAT) {
part_stat_lock();
part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
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();
}
}

5
block/blk-mq.c
View File

@@ -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();
}
}
@@ -1113,7 +1112,7 @@ 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();
}

21
block/blk.h
View File

@@ -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>
@@ -487,6 +488,26 @@ 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
*/