f2fs: fix bio memleak when committing super block

[ Upstream commit 554d9b72 ]

When committing new super block, bio is allocated but not freed, and
kmemleak complains:

  unreferenced object 0xffff88801d185600 (size 192):
    comm "kworker/3:2", pid 128, jiffies 4298624992
    hex dump (first 32 bytes):
      00 00 00 00 00 00 00 00 80 67 c3 00 81 88 ff ff  .........g......
      01 08 06 00 00 00 00 00 00 00 00 00 01 00 00 00  ................
    backtrace (crc 650ecdb1):
      kmem_cache_alloc_noprof+0x3a9/0x460
      mempool_alloc_noprof+0x12f/0x310
      bio_alloc_bioset+0x1e2/0x7e0
      __f2fs_commit_super+0xe0/0x370
      f2fs_commit_super+0x4ed/0x8c0
      f2fs_record_error_work+0xc7/0x190
      process_one_work+0x7db/0x1970
      worker_thread+0x518/0xea0
      kthread+0x359/0x690
      ret_from_fork+0x34/0x70
      ret_from_fork_asm+0x1a/0x30

The issue can be reproduced by:

  mount /dev/vda /mnt
  i=0
  while :; do
      echo '[h]abc' > /sys/fs/f2fs/vda/extension_list
      echo '[h]!abc' > /sys/fs/f2fs/vda/extension_list
      echo scan > /sys/kernel/debug/kmemleak
      dmesg | grep "new suspected memory leaks"
      [ $? -eq 0 ] && break
      i=$((i + 1))
      echo "$i"
  done
  umount /mnt

Fixes: 5bcde455 ("f2fs: get rid of buffer_head use")
Signed-off-by: Sheng Yong <shengyong1@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>