[PATCH 3/4] md/raid1: use bio_clone_slow_mddev_partial in case of write behind

Ming Lei
2017-02-05T06:22:48Z

Write behind need to replace pages in bio's bvecs, and we have
to clone a fresh bio with new bvec table, so use the introduced
bio_clone_slow_mddev_partial() for it.

For other bio_clone_mddev() cases, we will use fast clone since
they don't need to touch bvec table.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
drivers/md/raid1.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 830ff2b20346..e1c5639febdb 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1341,13 +1341,12 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,

first_clone = 1;
for (i = 0; i < disks; i++) {
- struct bio *mbio;
+ struct bio *mbio = NULL;
+ int offset;
if (!r1_bio->bios[i])
continue;

- mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
- bio_trim(mbio, r1_bio->sector - bio->bi_iter.bi_sector,
- max_sectors);
+ offset = r1_bio->sector - bio->bi_iter.bi_sector;

if (first_clone) {
/* do behind I/O ?
@@ -1357,8 +1356,14 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
if (bitmap &&
(atomic_read(&bitmap->behind_writes)
< mddev->bitmap_info.max_write_behind) &&
- !waitqueue_active(&bitmap->behind_wait))
+ !waitqueue_active(&bitmap->behind_wait)) {
+ mbio = bio_clone_slow_mddev_partial(bio,
+ GFP_NOIO,
+ mddev,
+ offset,
+ max_sectors);
alloc_behind_pages(mbio, r1_bio);
+ }

bitmap_startwrite(bitmap, r1_bio->sector,
r1_bio->sectors,
@@ -1366,6 +1371,12 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
&r1_bio->state));
first_clone = 0;
}
+
+ if (!mbio) {
+ mbio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+ bio_trim(mbio, offset, max_sectors);
+ }
+
if (r1_bio->behind_bvecs) {
struct bio_vec *bvec;
int j;
--
2.7.4