On Wed, Dec 04 2019 at 12:06P -0500,
Nikos Tsironis <ntsironis@xxxxxxxxxxx> wrote:
> Since we flush the data device as part of a metadata commit, it's
> redundant to then submit any deferred REQ_PREFLUSH bios.
>
> Add a check in process_deferred_bios() for deferred REQ_PREFLUSH bios
> and complete them immediately.
>
> Signed-off-by: Nikos Tsironis <ntsironis@xxxxxxxxxxx>
> ---
> drivers/md/dm-thin.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> index e0be545080d0..40d8a255dbc3 100644
> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
> @@ -2383,8 +2383,18 @@ static void process_deferred_bios(struct pool *pool)
> while ((bio = bio_list_pop(&bio_completions)))
> bio_endio(bio);
>
> - while ((bio = bio_list_pop(&bios)))
> - generic_make_request(bio);
> + while ((bio = bio_list_pop(&bios))) {
> + if (bio->bi_opf & REQ_PREFLUSH) {
> + /*
> + * We just flushed the data device as part of the
> + * metadata commit, so there is no reason to send
> + * another flush.
> + */
> + bio_endio(bio);
> + } else {
> + generic_make_request(bio);
> + }
> + }
> }
>
> static void do_worker(struct work_struct *ws)
> --
> 2.11.0
>
Don't we need to check if the the bio is an empty flush? I have this incremental:
---
drivers/md/dm-thin.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 40d8a255dbc3..9c9a323c0c30 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -2384,16 +2384,15 @@ static void process_deferred_bios(struct pool *pool)
bio_endio(bio);
while ((bio = bio_list_pop(&bios))) {
- if (bio->bi_opf & REQ_PREFLUSH) {
- /*
- * We just flushed the data device as part of the
- * metadata commit, so there is no reason to send
- * another flush.
- */
+ /*
+ * The data device was flushed as part of metadata commit,
+ * so complete additional deferred empty REQ_PREFLUSH bios
+ * immediately.
+ */
+ if ((bio->bi_opf & REQ_PREFLUSH) && !bio_has_data(bio))
bio_endio(bio);
- } else {
+ else
generic_make_request(bio);
- }
}
}
--
2.15.0
--
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