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>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 8387eb1..1d235cc 100644 (file)
--- 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);