md/raid1: fix writebehind bio clone

After bio is submitted, we should not clone it as its bi_iter might be
invalid by driver. This is the case of behind_master_bio. In certain
situration, we could dispatch behind_master_bio immediately for the
first disk and then clone it for other disks.

https://bugzilla.kernel.org/show_bug.cgi?id=196383

Reported-and-tested-by: Markus <m4rkusxxl@web.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Fix: 841c1316c7da(md: raid1: improve write behind)
Cc: stable@vger.kernel.org (4.12+)
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 13 insertions, 21 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 8387eb1540cd..1d235cc8b402 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -484,10 +484,6 @@ static void raid1_end_write_request(struct bio *bio)
         }
 
         if (behind) {
-                /* we release behind master bio when all write are done */
-                if (r1_bio->behind_master_bio == bio)
-                        to_put = NULL;
-
                 if (test_bit(WriteMostly, &rdev->flags))
                         atomic_dec(&r1_bio->behind_remaining);
 
@@ -1080,7 +1076,7 @@ static void unfreeze_array(struct r1conf *conf)
         wake_up(&conf->wait_barrier);
 }
 
-static struct bio *alloc_behind_master_bio(struct r1bio *r1_bio,
+static void alloc_behind_master_bio(struct r1bio *r1_bio,
                                            struct bio *bio)
 {
         int size = bio->bi_iter.bi_size;
@@ -1090,11 +1086,13 @@ static struct bio *alloc_behind_master_bio(struct r1bio *r1_bio,
 
         behind_bio = bio_alloc_mddev(GFP_NOIO, vcnt, r1_bio->mddev);
         if (!behind_bio)
-                goto fail;
+                return;
 
         /* discard op, we don't support writezero/writesame yet */
-        if (!bio_has_data(bio))
+        if (!bio_has_data(bio)) {
+                behind_bio->bi_iter.bi_size = size;
                 goto skip_copy;
+        }
 
         while (i < vcnt && size) {
                 struct page *page;
@@ -1115,14 +1113,13 @@ skip_copy:
         r1_bio->behind_master_bio = behind_bio;;
         set_bit(R1BIO_BehindIO, &r1_bio->state);
 
-        return behind_bio;
+        return;
 
 free_pages:
         pr_debug("%dB behind alloc failed, doing sync I/O\n",
                  bio->bi_iter.bi_size);
         bio_free_pages(behind_bio);
-fail:
-        return behind_bio;
+        bio_put(behind_bio);
 }
 
 struct raid1_plug_cb {
@@ -1475,7 +1472,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
                             (atomic_read(&bitmap->behind_writes)
                              < mddev->bitmap_info.max_write_behind) &&
                             !waitqueue_active(&bitmap->behind_wait)) {
-                                mbio = alloc_behind_master_bio(r1_bio, bio);
+                                alloc_behind_master_bio(r1_bio, bio);
                         }
 
                         bitmap_startwrite(bitmap, r1_bio->sector,
@@ -1485,14 +1482,11 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
                         first_clone = 0;
                 }
 
-                if (!mbio) {
-                        if (r1_bio->behind_master_bio)
-                                mbio = bio_clone_fast(r1_bio->behind_master_bio,
-                                                      GFP_NOIO,
-                                                      mddev->bio_set);
-                        else
-                                mbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
-                }
+                if (r1_bio->behind_master_bio)
+                        mbio = bio_clone_fast(r1_bio->behind_master_bio,
+                                              GFP_NOIO, mddev->bio_set);
+                else
+                        mbio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
 
                 if (r1_bio->behind_master_bio) {
                         if (test_bit(WriteMostly, &conf->mirrors[i].rdev->flags))
@@ -2346,8 +2340,6 @@ static int narrow_write_error(struct r1bio *r1_bio, int i)
                         wbio = bio_clone_fast(r1_bio->behind_master_bio,
                                               GFP_NOIO,
                                               mddev->bio_set);
-                        /* We really need a _all clone */
-                        wbio->bi_iter = (struct bvec_iter){ 0 };
                 } else {
                         wbio = bio_clone_fast(r1_bio->master_bio, GFP_NOIO,
                                               mddev->bio_set);