f2fs: handle nat.blkaddr corruption in f2fs_get_node_info()

f2fs: handle nat.blkaddr corruption in f2fs_get_node_info()

F2FS-fs (dm-55): access invalid blkaddr:972878540
Call trace:
 dump_backtrace+0xec/0x128
 show_stack+0x18/0x28
 dump_stack_lvl+0x40/0x88
 dump_stack+0x18/0x24
 __f2fs_is_valid_blkaddr+0x360/0x3b4
 f2fs_is_valid_blkaddr+0x10/0x20
 f2fs_get_node_info+0x21c/0x60c
 __write_node_page+0x15c/0x734
 f2fs_sync_node_pages+0x4f8/0x700
 f2fs_write_checkpoint+0x4a8/0x99c
 __checkpoint_and_complete_reqs+0x7c/0x20c
 issue_checkpoint_thread+0x4c/0xd8
 kthread+0x11c/0x1b0
 ret_from_fork+0x10/0x20

If nat.blkaddr is corrupted, during checkpoint, f2fs_sync_node_pages()
will loop to flush node page w/ corrupted nat.blkaddr.

Although, it tags SBI_NEED_FSCK, checkpoint can not persist it due
to deadloop.

Let's call f2fs_handle_error(, ERROR_INCONSISTENT_NAT) to record such
error into superblock, it expects fsck can detect the error and repair
inconsistent nat.blkaddr after device reboot.

Note that, let's add sanity check in f2fs_get_node_info() to detect
in-memory nat.blkaddr inconsistency, but only if CONFIG_F2FS_CHECK_FS
is enabled.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>