md/raid1: use bio_clone_bioset_partial() in case of write behind

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_bioset_partial() for it.

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

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 7b0f647bcccb..691d6d9bf740 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1345,13 +1345,12 @@ 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;
+                sector_t 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 ?
@@ -1361,8 +1360,13 @@ 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_bioset_partial(bio, GFP_NOIO,
+                                                                mddev->bio_set,
+                                                                offset,
+                                                                max_sectors);
                                 alloc_behind_pages(mbio, r1_bio);
+                        }
 
                         bitmap_startwrite(bitmap, r1_bio->sector,
                                           r1_bio->sectors,
@@ -1370,6 +1374,12 @@ 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;