f2fs: fix a race condition between f2fs_write_end_io and f2fs_del_fsync_node_entry

Under some condition, the __write_node_page will submit a page which is not
f2fs_in_warm_node_list and will not call f2fs_add_fsync_node_entry.
f2fs_gc continue to run to invoke f2fs_iget -> do_read_inode to read the same node page
and set code node, which make f2fs_in_warm_node_list become true,
that will cause f2fs_bug_on in f2fs_del_fsync_node_entry when f2fs_write_end_io called.

- f2fs_write_end_io
					- f2fs_iget
					 - do_read_inode
					  - set_cold_node
					  recover cold node flag
 - f2fs_in_warm_node_list
  - is_cold_node
  if node is cold, assume we have added
  node to fsync_node_list during writepages()
 - f2fs_del_fsync_node_entry
  - f2fs_bug_on() due to node page
  is not in fsync_node_list

[   34.966133] Call trace:
[   34.969902]  f2fs_del_fsync_node_entry+0x100/0x108
[   34.976071]  f2fs_write_end_io+0x1e0/0x288
[   34.981539]  bio_endio+0x248/0x270
[   34.986289]  blk_update_request+0x2b0/0x4d8
[   34.991841]  scsi_end_request+0x40/0x440
[   34.997126]  scsi_io_completion+0xa4/0x748
[   35.002593]  scsi_finish_command+0xdc/0x110
[   35.008143]  scsi_softirq_done+0x118/0x150
[   35.013610]  blk_done_softirq+0x8c/0xe8
[   35.018811]  __do_softirq+0x2e8/0x578
[   35.023828]  irq_exit+0xfc/0x120
[   35.028398]  handle_IPI+0x1d8/0x330
[   35.033233]  gic_handle_irq+0x110/0x1d4
[   35.038433]  el1_irq+0xb4/0x130
[   35.042917]  kmem_cache_alloc+0x3f0/0x418
[   35.048288]  radix_tree_node_alloc+0x50/0xf8
[   35.053933]  __radix_tree_create+0xf8/0x188
[   35.059484]  __radix_tree_insert+0x3c/0x128
[   35.065035]  add_gc_inode+0x90/0x118
[   35.069967]  f2fs_gc+0x1b80/0x2d70
[   35.074718]  f2fs_disable_checkpoint+0x94/0x1d0
[   35.080621]  f2fs_fill_super+0x10c4/0x1b88
[   35.086088]  mount_bdev+0x194/0x1e0
[   35.090923]  f2fs_mount+0x40/0x50
[   35.095589]  mount_fs+0xb4/0x190
[   35.100159]  vfs_kern_mount+0x80/0x1d8
[   35.105260]  do_mount+0x478/0xf18
[   35.109926]  ksys_mount+0x90/0xd0
[   35.114592]  __arm64_sys_mount+0x24/0x38

Signed-off-by: Wuyun Zhao <zhaowuyun@wingtech.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>