fs: assign sb->s_bdi to default_backing_dev_info if the bdi is going away

We don't have proper reference counting for this yet, so we run into
cases where the device is pulled and we OOPS on flushing the fs data.
This happens even though the dirty inodes have already been
migrated to the default_backing_dev_info.

Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Tested-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index c91e139a652e..8fe9d3407921 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -598,7 +598,7 @@ static void bdi_prune_sb(struct backing_dev_info *bdi)
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &super_blocks, s_list) {
                 if (sb->s_bdi == bdi)
-                        sb->s_bdi = NULL;
+                        sb->s_bdi = &default_backing_dev_info;
         }
         spin_unlock(&sb_lock);
 }