* [dm-devel] [PATCH v2 0/3] block/dm: fix bio-based DM IO accounting
@ 2022-01-27 22:56 ` Mike Snitzer
0 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: linux-block, dm-devel, hch
Hi Jens,
Just over 3 years ago, with commit a1e1cb72d9649 ("dm: fix redundant
IO accounting for bios that need splitting") I focused too narrowly on
fixing the reported potential for redundant accounting for IO totals.
Which, at least mentally for me, papered over how inaccurate all other
bio-based DM's IO accounting is for bios that get split.
This set fixes things up properly by allowing DM to start IO
accounting _after_ IO is submitted and a split is occurred. The
proper start_time is still established (prior to submission), it is
passed in to a new bio_start_io_acct_time(). This eliminates the need
for any DM hack to rewind block core's excessive accounting in the
face of a split bio recursing back to block core.
All said: If you'd provide your Acked-by(s) I'm happy to send this set
to Linus for v5.17-rc (and shepherd the changes into stable@ kernels).
Or you're welcome to pickup this set to send along (I'd obviously
still do any stable@ backports). NOTE: the 3rd patch references the
linux-dm.git commit id for the 1st patch.. so that'll require tweaking
no matter who sends the changes to Linus.
Please advise, thanks.
Mike
v1 -> v2: made block changes suggested by Christoph
Mike Snitzer (3):
block: add bio_start_io_acct_time() to control start_time
dm: revert partial fix for redundant bio-based IO accounting
dm: properly fix redundant bio-based IO accounting
block/blk-core.c | 25 +++++++++++++++++++------
drivers/md/dm.c | 20 +++-----------------
include/linux/blkdev.h | 1 +
3 files changed, 23 insertions(+), 23 deletions(-)
--
2.15.0
--
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https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply [flat|nested] 11+ messages in thread* [PATCH v2 1/3] block: add bio_start_io_acct_time() to control start_time
2022-01-27 22:56 ` [dm-devel] " Mike Snitzer
@ 2022-01-27 22:56 ` Mike Snitzer
-1 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: hch, dm-devel, linux-block
bio_start_io_acct_time() interface is like bio_start_io_acct() that
allows start_time to be passed in. This gives drivers the ability to
defer starting accounting until after IO is issued (but possibily not
entirely due to bio splitting).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
block/blk-core.c | 25 +++++++++++++++++++------
include/linux/blkdev.h | 1 +
2 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 97f8bc8d3a79..d93e3bb9a769 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1061,20 +1061,32 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end)
}
static unsigned long __part_start_io_acct(struct block_device *part,
- unsigned int sectors, unsigned int op)
+ unsigned int sectors, unsigned int op,
+ unsigned long start_time)
{
const int sgrp = op_stat_group(op);
- unsigned long now = READ_ONCE(jiffies);
part_stat_lock();
- update_io_ticks(part, now, false);
+ update_io_ticks(part, start_time, false);
part_stat_inc(part, ios[sgrp]);
part_stat_add(part, sectors[sgrp], sectors);
part_stat_local_inc(part, in_flight[op_is_write(op)]);
part_stat_unlock();
- return now;
+ return start_time;
+}
+
+/**
+ * bio_start_io_acct_time - start I/O accounting for bio based drivers
+ * @bio: bio to start account for
+ * @start_time: start time that should be passed back to bio_end_io_acct().
+ */
+void bio_start_io_acct_time(struct bio *bio, unsigned long start_time)
+{
+ __part_start_io_acct(bio->bi_bdev, bio_sectors(bio),
+ bio_op(bio), start_time);
}
+EXPORT_SYMBOL_GPL(bio_start_io_acct_time);
/**
* bio_start_io_acct - start I/O accounting for bio based drivers
@@ -1084,14 +1096,15 @@ static unsigned long __part_start_io_acct(struct block_device *part,
*/
unsigned long bio_start_io_acct(struct bio *bio)
{
- return __part_start_io_acct(bio->bi_bdev, bio_sectors(bio), bio_op(bio));
+ return __part_start_io_acct(bio->bi_bdev, bio_sectors(bio),
+ bio_op(bio), jiffies);
}
EXPORT_SYMBOL_GPL(bio_start_io_acct);
unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
unsigned int op)
{
- return __part_start_io_acct(disk->part0, sectors, op);
+ return __part_start_io_acct(disk->part0, sectors, op, jiffies);
}
EXPORT_SYMBOL(disk_start_io_acct);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9c95df26fc26..f35aea98bc35 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1258,6 +1258,7 @@ unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
void disk_end_io_acct(struct gendisk *disk, unsigned int op,
unsigned long start_time);
+void bio_start_io_acct_time(struct bio *bio, unsigned long start_time);
unsigned long bio_start_io_acct(struct bio *bio);
void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
struct block_device *orig_bdev);
--
2.15.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* [dm-devel] [PATCH v2 1/3] block: add bio_start_io_acct_time() to control start_time
@ 2022-01-27 22:56 ` Mike Snitzer
0 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: linux-block, dm-devel, hch
bio_start_io_acct_time() interface is like bio_start_io_acct() that
allows start_time to be passed in. This gives drivers the ability to
defer starting accounting until after IO is issued (but possibily not
entirely due to bio splitting).
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
block/blk-core.c | 25 +++++++++++++++++++------
include/linux/blkdev.h | 1 +
2 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 97f8bc8d3a79..d93e3bb9a769 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1061,20 +1061,32 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end)
}
static unsigned long __part_start_io_acct(struct block_device *part,
- unsigned int sectors, unsigned int op)
+ unsigned int sectors, unsigned int op,
+ unsigned long start_time)
{
const int sgrp = op_stat_group(op);
- unsigned long now = READ_ONCE(jiffies);
part_stat_lock();
- update_io_ticks(part, now, false);
+ update_io_ticks(part, start_time, false);
part_stat_inc(part, ios[sgrp]);
part_stat_add(part, sectors[sgrp], sectors);
part_stat_local_inc(part, in_flight[op_is_write(op)]);
part_stat_unlock();
- return now;
+ return start_time;
+}
+
+/**
+ * bio_start_io_acct_time - start I/O accounting for bio based drivers
+ * @bio: bio to start account for
+ * @start_time: start time that should be passed back to bio_end_io_acct().
+ */
+void bio_start_io_acct_time(struct bio *bio, unsigned long start_time)
+{
+ __part_start_io_acct(bio->bi_bdev, bio_sectors(bio),
+ bio_op(bio), start_time);
}
+EXPORT_SYMBOL_GPL(bio_start_io_acct_time);
/**
* bio_start_io_acct - start I/O accounting for bio based drivers
@@ -1084,14 +1096,15 @@ static unsigned long __part_start_io_acct(struct block_device *part,
*/
unsigned long bio_start_io_acct(struct bio *bio)
{
- return __part_start_io_acct(bio->bi_bdev, bio_sectors(bio), bio_op(bio));
+ return __part_start_io_acct(bio->bi_bdev, bio_sectors(bio),
+ bio_op(bio), jiffies);
}
EXPORT_SYMBOL_GPL(bio_start_io_acct);
unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
unsigned int op)
{
- return __part_start_io_acct(disk->part0, sectors, op);
+ return __part_start_io_acct(disk->part0, sectors, op, jiffies);
}
EXPORT_SYMBOL(disk_start_io_acct);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9c95df26fc26..f35aea98bc35 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1258,6 +1258,7 @@ unsigned long disk_start_io_acct(struct gendisk *disk, unsigned int sectors,
void disk_end_io_acct(struct gendisk *disk, unsigned int op,
unsigned long start_time);
+void bio_start_io_acct_time(struct bio *bio, unsigned long start_time);
unsigned long bio_start_io_acct(struct bio *bio);
void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
struct block_device *orig_bdev);
--
2.15.0
--
dm-devel mailing list
dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v2 2/3] dm: revert partial fix for redundant bio-based IO accounting
2022-01-27 22:56 ` [dm-devel] " Mike Snitzer
@ 2022-01-27 22:56 ` Mike Snitzer
-1 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: hch, dm-devel, linux-block
Reverts a1e1cb72d9649 ("dm: fix redundant IO accounting for bios that
need splitting") because it was too narrow in scope (only addressed
redundant 'sectors[]' accounting and not ios, nsecs[], etc).
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm.c | 15 ---------------
1 file changed, 15 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c0ae8087c602..9849114b3c08 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1442,9 +1442,6 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
ci->sector = bio->bi_iter.bi_sector;
}
-#define __dm_part_stat_sub(part, field, subnd) \
- (part_stat_get(part, field) -= (subnd))
-
/*
* Entry point to split a bio into clones and submit them to the targets.
*/
@@ -1480,18 +1477,6 @@ static void __split_and_process_bio(struct mapped_device *md,
GFP_NOIO, &md->queue->bio_split);
ci.io->orig_bio = b;
- /*
- * Adjust IO stats for each split, otherwise upon queue
- * reentry there will be redundant IO accounting.
- * NOTE: this is a stop-gap fix, a proper fix involves
- * significant refactoring of DM core's bio splitting
- * (by eliminating DM's splitting and just using bio_split)
- */
- part_stat_lock();
- __dm_part_stat_sub(dm_disk(md)->part0,
- sectors[op_stat_group(bio_op(bio))], ci.sector_count);
- part_stat_unlock();
-
bio_chain(b, bio);
trace_block_split(b, bio->bi_iter.bi_sector);
submit_bio_noacct(bio);
--
2.15.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* [dm-devel] [PATCH v2 2/3] dm: revert partial fix for redundant bio-based IO accounting
@ 2022-01-27 22:56 ` Mike Snitzer
0 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: linux-block, dm-devel, hch
Reverts a1e1cb72d9649 ("dm: fix redundant IO accounting for bios that
need splitting") because it was too narrow in scope (only addressed
redundant 'sectors[]' accounting and not ios, nsecs[], etc).
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm.c | 15 ---------------
1 file changed, 15 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c0ae8087c602..9849114b3c08 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1442,9 +1442,6 @@ static void init_clone_info(struct clone_info *ci, struct mapped_device *md,
ci->sector = bio->bi_iter.bi_sector;
}
-#define __dm_part_stat_sub(part, field, subnd) \
- (part_stat_get(part, field) -= (subnd))
-
/*
* Entry point to split a bio into clones and submit them to the targets.
*/
@@ -1480,18 +1477,6 @@ static void __split_and_process_bio(struct mapped_device *md,
GFP_NOIO, &md->queue->bio_split);
ci.io->orig_bio = b;
- /*
- * Adjust IO stats for each split, otherwise upon queue
- * reentry there will be redundant IO accounting.
- * NOTE: this is a stop-gap fix, a proper fix involves
- * significant refactoring of DM core's bio splitting
- * (by eliminating DM's splitting and just using bio_split)
- */
- part_stat_lock();
- __dm_part_stat_sub(dm_disk(md)->part0,
- sectors[op_stat_group(bio_op(bio))], ci.sector_count);
- part_stat_unlock();
-
bio_chain(b, bio);
trace_block_split(b, bio->bi_iter.bi_sector);
submit_bio_noacct(bio);
--
2.15.0
--
dm-devel mailing list
dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v2 3/3] dm: properly fix redundant bio-based IO accounting
2022-01-27 22:56 ` [dm-devel] " Mike Snitzer
@ 2022-01-27 22:56 ` Mike Snitzer
-1 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: hch, dm-devel, linux-block
Record the start_time for a bio but defer the starting block core's IO
accounting until after IO is submitted using bio_start_io_acct_time().
This approach avoids the need to mess around with any of the
individual IO stats in response to a bio_split() that follows bio
submission.
Reported-by: Bud Brown <bubrown@redhat.com>
Cc: stable@vger.kernel.org
Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9849114b3c08..144436301a57 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -489,7 +489,7 @@ static void start_io_acct(struct dm_io *io)
struct mapped_device *md = io->md;
struct bio *bio = io->orig_bio;
- io->start_time = bio_start_io_acct(bio);
+ __bio_start_io_acct(bio, io->start_time);
if (unlikely(dm_stats_used(&md->stats)))
dm_stats_account_io(&md->stats, bio_data_dir(bio),
bio->bi_iter.bi_sector, bio_sectors(bio),
@@ -535,7 +535,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io->md = md;
spin_lock_init(&io->endio_lock);
- start_io_acct(io);
+ io->start_time = READ_ONCE(jiffies);
return io;
}
@@ -1482,6 +1482,7 @@ static void __split_and_process_bio(struct mapped_device *md,
submit_bio_noacct(bio);
}
}
+ start_io_acct(ci.io);
/* drop the extra reference count */
dm_io_dec_pending(ci.io, errno_to_blk_status(error));
--
2.15.0
^ permalink raw reply related [flat|nested] 11+ messages in thread* [dm-devel] [PATCH v2 3/3] dm: properly fix redundant bio-based IO accounting
@ 2022-01-27 22:56 ` Mike Snitzer
0 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-27 22:56 UTC (permalink / raw)
To: axboe; +Cc: linux-block, dm-devel, hch
Record the start_time for a bio but defer the starting block core's IO
accounting until after IO is submitted using bio_start_io_acct_time().
This approach avoids the need to mess around with any of the
individual IO stats in response to a bio_split() that follows bio
submission.
Reported-by: Bud Brown <bubrown@redhat.com>
Cc: stable@vger.kernel.org
Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9849114b3c08..144436301a57 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -489,7 +489,7 @@ static void start_io_acct(struct dm_io *io)
struct mapped_device *md = io->md;
struct bio *bio = io->orig_bio;
- io->start_time = bio_start_io_acct(bio);
+ __bio_start_io_acct(bio, io->start_time);
if (unlikely(dm_stats_used(&md->stats)))
dm_stats_account_io(&md->stats, bio_data_dir(bio),
bio->bi_iter.bi_sector, bio_sectors(bio),
@@ -535,7 +535,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
io->md = md;
spin_lock_init(&io->endio_lock);
- start_io_acct(io);
+ io->start_time = READ_ONCE(jiffies);
return io;
}
@@ -1482,6 +1482,7 @@ static void __split_and_process_bio(struct mapped_device *md,
submit_bio_noacct(bio);
}
}
+ start_io_acct(ci.io);
/* drop the extra reference count */
dm_io_dec_pending(ci.io, errno_to_blk_status(error));
--
2.15.0
--
dm-devel mailing list
dm-devel@redhat.com
https://listman.redhat.com/mailman/listinfo/dm-devel
^ permalink raw reply related [flat|nested] 11+ messages in thread* Re: [PATCH v2 3/3] dm: properly fix redundant bio-based IO accounting
2022-01-27 22:56 ` [dm-devel] " Mike Snitzer
(?)
@ 2022-01-28 3:48 ` kernel test robot
-1 siblings, 0 replies; 11+ messages in thread
From: kernel test robot @ 2022-01-28 3:48 UTC (permalink / raw)
To: kbuild-all
[-- Attachment #1: Type: text/plain, Size: 2635 bytes --]
Hi Mike,
I love your patch! Yet something to improve:
[auto build test ERROR on axboe-block/for-next]
[also build test ERROR on device-mapper-dm/for-next hch-configfs/for-next v5.17-rc1 next-20220127]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Mike-Snitzer/block-dm-fix-bio-based-DM-IO-accounting/20220128-065741
base: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
config: alpha-allmodconfig (https://download.01.org/0day-ci/archive/20220128/202201281121.YMTa5Abg-lkp(a)intel.com/config)
compiler: alpha-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/8bce71c28a009209a279db6200c981596b769dd1
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Mike-Snitzer/block-dm-fix-bio-based-DM-IO-accounting/20220128-065741
git checkout 8bce71c28a009209a279db6200c981596b769dd1
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=alpha SHELL=/bin/bash drivers/
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
drivers/md/dm.c: In function 'start_io_acct':
>> drivers/md/dm.c:492:9: error: implicit declaration of function '__bio_start_io_acct'; did you mean 'bio_start_io_acct'? [-Werror=implicit-function-declaration]
492 | __bio_start_io_acct(bio, io->start_time);
| ^~~~~~~~~~~~~~~~~~~
| bio_start_io_acct
cc1: some warnings being treated as errors
vim +492 drivers/md/dm.c
486
487 static void start_io_acct(struct dm_io *io)
488 {
489 struct mapped_device *md = io->md;
490 struct bio *bio = io->orig_bio;
491
> 492 __bio_start_io_acct(bio, io->start_time);
493 if (unlikely(dm_stats_used(&md->stats)))
494 dm_stats_account_io(&md->stats, bio_data_dir(bio),
495 bio->bi_iter.bi_sector, bio_sectors(bio),
496 false, 0, &io->stats_aux);
497 }
498
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH v2 3/3] dm: properly fix redundant bio-based IO accounting
2022-01-27 22:56 ` [dm-devel] " Mike Snitzer
@ 2022-01-28 4:08 ` Mike Snitzer
-1 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-28 4:08 UTC (permalink / raw)
To: axboe; +Cc: hch, dm-devel, linux-block
On Thu, Jan 27 2022 at 5:56P -0500,
Mike Snitzer <snitzer@redhat.com> wrote:
> Record the start_time for a bio but defer the starting block core's IO
> accounting until after IO is submitted using bio_start_io_acct_time().
>
> This approach avoids the need to mess around with any of the
> individual IO stats in response to a bio_split() that follows bio
> submission.
>
> Reported-by: Bud Brown <bubrown@redhat.com>
> Cc: stable@vger.kernel.org
> Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> ---
> drivers/md/dm.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 9849114b3c08..144436301a57 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -489,7 +489,7 @@ static void start_io_acct(struct dm_io *io)
> struct mapped_device *md = io->md;
> struct bio *bio = io->orig_bio;
>
> - io->start_time = bio_start_io_acct(bio);
> + __bio_start_io_acct(bio, io->start_time);
> if (unlikely(dm_stats_used(&md->stats)))
> dm_stats_account_io(&md->stats, bio_data_dir(bio),
> bio->bi_iter.bi_sector, bio_sectors(bio),
This should be calling bio_start_io_acct_time().
I updated the header but somehow dropped the code change before
sending.
Mike
> @@ -535,7 +535,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
> io->md = md;
> spin_lock_init(&io->endio_lock);
>
> - start_io_acct(io);
> + io->start_time = READ_ONCE(jiffies);
>
> return io;
> }
> @@ -1482,6 +1482,7 @@ static void __split_and_process_bio(struct mapped_device *md,
> submit_bio_noacct(bio);
> }
> }
> + start_io_acct(ci.io);
>
> /* drop the extra reference count */
> dm_io_dec_pending(ci.io, errno_to_blk_status(error));
> --
> 2.15.0
>
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [dm-devel] [PATCH v2 3/3] dm: properly fix redundant bio-based IO accounting
@ 2022-01-28 4:08 ` Mike Snitzer
0 siblings, 0 replies; 11+ messages in thread
From: Mike Snitzer @ 2022-01-28 4:08 UTC (permalink / raw)
To: axboe; +Cc: linux-block, dm-devel, hch
On Thu, Jan 27 2022 at 5:56P -0500,
Mike Snitzer <snitzer@redhat.com> wrote:
> Record the start_time for a bio but defer the starting block core's IO
> accounting until after IO is submitted using bio_start_io_acct_time().
>
> This approach avoids the need to mess around with any of the
> individual IO stats in response to a bio_split() that follows bio
> submission.
>
> Reported-by: Bud Brown <bubrown@redhat.com>
> Cc: stable@vger.kernel.org
> Depends-on: f9893e1da2e3 ("block: add bio_start_io_acct_time() to control start_time")
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> ---
> drivers/md/dm.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 9849114b3c08..144436301a57 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -489,7 +489,7 @@ static void start_io_acct(struct dm_io *io)
> struct mapped_device *md = io->md;
> struct bio *bio = io->orig_bio;
>
> - io->start_time = bio_start_io_acct(bio);
> + __bio_start_io_acct(bio, io->start_time);
> if (unlikely(dm_stats_used(&md->stats)))
> dm_stats_account_io(&md->stats, bio_data_dir(bio),
> bio->bi_iter.bi_sector, bio_sectors(bio),
This should be calling bio_start_io_acct_time().
I updated the header but somehow dropped the code change before
sending.
Mike
> @@ -535,7 +535,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
> io->md = md;
> spin_lock_init(&io->endio_lock);
>
> - start_io_acct(io);
> + io->start_time = READ_ONCE(jiffies);
>
> return io;
> }
> @@ -1482,6 +1482,7 @@ static void __split_and_process_bio(struct mapped_device *md,
> submit_bio_noacct(bio);
> }
> }
> + start_io_acct(ci.io);
>
> /* drop the extra reference count */
> dm_io_dec_pending(ci.io, errno_to_blk_status(error));
> --
> 2.15.0
>
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^ permalink raw reply [flat|nested] 11+ messages in thread