Don't use jiffies as a glorified bool because jiffies can/will
rollover to 0.
Also use xchg(), instead of spin_lock_irq{save,restore} and
smp_load_acquire/smp_store_release, to avoid performance impact of
disabling and enabling interrupts.
Suggested-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-core.h | 2 +-
drivers/md/dm.c | 34 ++++++++++++----------------------
2 files changed, 13 insertions(+), 23 deletions(-)
diff --git a/drivers/md/dm-core.h b/drivers/md/dm-core.h
index 3ecd6f294f53..d3c116866fd7 100644
--- a/drivers/md/dm-core.h
+++ b/drivers/md/dm-core.h
@@ -230,7 +230,7 @@ struct dm_io {
atomic_t io_count;
struct bio *orig_bio;
unsigned long start_time;
- unsigned long io_acct_time;
+ int was_accounted;
spinlock_t lock;
struct dm_stats_aux stats_aux;
/* last member of dm_target_io is 'struct bio' */
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ad512f40716e..329f0be64523 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -487,17 +487,6 @@ EXPORT_SYMBOL_GPL(dm_start_time_ns_from_clone);
static void __start_io_acct(struct dm_io *io, struct bio *bio)
{
- unsigned long flags;
-
- /* Ensure IO accounting is only ever started once */
- spin_lock_irqsave(&io->lock, flags);
- if (smp_load_acquire(&io->io_acct_time)) {
- spin_unlock_irqrestore(&io->lock, flags);
- return;
- }
- smp_store_release(&io->io_acct_time, jiffies);
- spin_unlock_irqrestore(&io->lock, flags);
-
bio_start_io_acct_time(bio, io->start_time);
if (unlikely(dm_stats_used(&io->md->stats)))
dm_stats_account_io(&io->md->stats, bio_data_dir(bio),
@@ -507,8 +496,8 @@ static void __start_io_acct(struct dm_io *io, struct bio *bio)
static void start_io_acct(struct dm_io *io, struct bio *bio)
{
- /* Only start_io_acct() once for this IO */
- if (smp_load_acquire(&io->io_acct_time))
+ /* Ensure IO accounting is only ever started once */
+ if (xchg(&io->was_accounted, 1) == 1)
return;
__start_io_acct(io, bio);
@@ -518,8 +507,8 @@ static void clone_and_start_io_acct(struct dm_io *io, struct bio *bio)
{
struct bio io_acct_clone;
- /* Only clone_and_start_io_acct() once for this IO */
- if (smp_load_acquire(&io->io_acct_time))
+ /* Ensure IO accounting is only ever started once */
+ if (xchg(&io->was_accounted, 1) == 1)
return;
bio_init_clone(io->orig_bio->bi_bdev,
@@ -530,9 +519,6 @@ static void clone_and_start_io_acct(struct dm_io *io, struct bio *bio)
static void end_io_acct(struct mapped_device *md, struct bio *bio,
unsigned long start_time, struct dm_stats_aux *stats_aux)
{
- if (!start_time)
- return;
-
bio_end_io_acct(bio, start_time);
if (unlikely(dm_stats_used(&md->stats)))
@@ -562,7 +548,7 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
spin_lock_init(&io->lock);
io->start_time = jiffies;
- io->io_acct_time = 0;
+ io->was_accounted = 0;
return io;
}
@@ -819,6 +805,7 @@ void dm_io_dec_pending(struct dm_io *io, blk_status_t error)
blk_status_t io_error;
struct bio *bio;
struct mapped_device *md = io->md;
+ bool was_accounted = false;
unsigned long start_time = 0;
struct dm_stats_aux stats_aux;
@@ -852,11 +839,14 @@ void dm_io_dec_pending(struct dm_io *io, blk_status_t error)
}
io_error = io->status;
- if (io->io_acct_time)
+ if (io->was_accounted) {
+ was_accounted = true;
start_time = io->start_time;
- stats_aux = io->stats_aux;
+ stats_aux = io->stats_aux;
+ }
free_io(io);
- end_io_acct(md, bio, start_time, &stats_aux);
+ if (was_accounted)
+ end_io_acct(md, bio, start_time, &stats_aux);
/* nudge anyone waiting on suspend queue */
if (unlikely(wq_has_sleeper(&md->wait)))
--
2.15.0
--
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