[PATCH 4.9 02/62] dm snapshot: introduce account_start_copy() and account_end_copy()

Greg Kroah-Hartman
2019-11-04T21:50:04Z

From: Mikulas Patocka <mpatocka@redhat.com>

[ Upstream commit a2f83e8b0c82c9500421a26c49eb198b25fcdea3 ]

This simple refactoring moves code for modifying the semaphore cow_count
into separate functions to prepare for changes that will extend these
methods to provide for a more sophisticated mechanism for COW
throttling.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/dm-snap.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index e5b0e13f5c92d..ef51ab8a5dcb2 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1399,6 +1399,16 @@ static void snapshot_dtr(struct dm_target *ti)
kfree(s);
}

+static void account_start_copy(struct dm_snapshot *s)
+{
+ down(&s->cow_count);
+}
+
+static void account_end_copy(struct dm_snapshot *s)
+{
+ up(&s->cow_count);
+}
+
/*
* Flush a list of buffers.
*/
@@ -1581,7 +1591,7 @@ static void copy_callback(int read_err, unsigned long write_err, void *context)
}
list_add(&pe->out_of_order_entry, lh);
}
- up(&s->cow_count);
+ account_end_copy(s);
}

/*
@@ -1605,7 +1615,7 @@ static void start_copy(struct dm_snap_pending_exception *pe)
dest.count = src.count;

/* Hand over to kcopyd */
- down(&s->cow_count);
+ account_start_copy(s);
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, copy_callback, pe);
}

@@ -1625,7 +1635,7 @@ static void start_full_bio(struct dm_snap_pending_exception *pe,
pe->full_bio = bio;
pe->full_bio_end_io = bio->bi_end_io;

- down(&s->cow_count);
+ account_start_copy(s);
callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
copy_callback, pe);

--
2.20.1