Since dm-crypt queues writes (and sometimes reads) to a different kernel
thread (workqueue), the bios will dispatch from tasks with different
io_context->ioprio settings than the submitting task, thus giving
incorrect ioprio hints to the io scheduler.
By assigning the ioprio to the bio before queuing to a workqueue, the
original submitting task's io_context->ioprio setting can be retained
through the life of the bio. We only set the bio's ioprio in dm-crypt
if not already set (by somewhere else, higher in the stack).
Signed-off-by: Eric Wheeler <dm-de...@linux.ewheeler.net>
Cc: Mikulas Patocka <mpato...@redhat.com>
Cc: Alasdair Kergon <a...@redhat.com>
Cc: Mike Snitzer <snit...@redhat.com>
Cc: Shaohua Li <s...@kernel.org>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: sta...@vger.kernel.org
---
block/bio.c | 1 +
drivers/md/dm-crypt.c | 11 +++++++++--
include/linux/bio.h | 23 +++++++++++++++++++++++
3 files changed, 33 insertions(+), 2 deletions(-)
diff --git a/block/bio.c b/block/bio.c
index db85c57..1a529ff 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -584,6 +584,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src)
bio->bi_iter = bio_src->bi_iter;
bio->bi_io_vec = bio_src->bi_io_vec;
+ bio_set_prio(bio, bio_prio(bio_src));
bio_clone_blkcg_association(bio, bio_src);
}
EXPORT_SYMBOL(__bio_clone_fast);
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 9b99ee9..ea7e102 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1133,6 +1133,7 @@ static void clone_init(struct dm_crypt_io *io, struct bio
*clone)
clone->bi_private = io;
clone->bi_end_io = crypt_endio;
clone->bi_bdev = cc->dev->bdev;
+ bio_set_prio(clone, bio_prio(io->base_bio));
bio_set_op_attrs(clone, bio_op(io->base_bio), bio_flags(io->base_bio));
}
@@ -2070,10 +2071,16 @@ static int crypt_map(struct dm_target *ti, struct bio
*bio)
io->ctx.req = (struct skcipher_request *)(io + 1);
if (bio_data_dir(io->base_bio) == READ) {
- if (kcryptd_io_read(io, GFP_NOWAIT))
+ if (kcryptd_io_read(io, GFP_NOWAIT)) {
+ if (!ioprio_valid(bio_prio(io->base_bio)))
+ bio_set_task_prio(io->base_bio, current);
kcryptd_queue_read(io);
- } else
+ }
+ } else {
+ if (!ioprio_valid(bio_prio(io->base_bio)))
+ bio_set_task_prio(io->base_bio, current);
kcryptd_queue_crypt(io);
+ }
return DM_MAPIO_SUBMITTED;
}
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 97cb48f..0b4f8bb 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -62,6 +62,29 @@
#define bio_sectors(bio) ((bio)->bi_iter.bi_size >> 9)
#define bio_end_sector(bio) ((bio)->bi_iter.bi_sector + bio_sectors((bio)))
+/* Set the bio's ioprio to that of the task's io_context->ioprio, if any.
+ * Always returns io_context->ioprio (or 0 if none); bio can be NULL.
+ */
+static inline unsigned short bio_set_task_prio(
+ struct bio *bio, struct task_struct *task)
+{
+ struct io_context *ioc;
+ unsigned short ioprio = 0;
+
+ ioc = get_task_io_context(current, GFP_NOIO, NUMA_NO_NODE);
+ if (ioc) {
+ if (ioprio_valid(ioc->ioprio)) {
+ ioprio = ioc->ioprio;
+ put_io_context(ioc);
+ }
+
+ if (bio != NULL && ioprio_valid(ioprio))
+ bio_set_prio(bio, ioc->ioprio);
+ }
+
+ return ioprio;
+}
+
/*
* Check whether this bio carries any data or not. A NULL bio is allowed.
*/
--
1.8.3.1
--
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