f2fs: fix to clear dirty inode in f2fs_evict_inode()

As Yanming reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215904

The kernel message is shown below:

kernel BUG at fs/f2fs/inode.c:825!
Call Trace:
 evict+0x282/0x4e0
 __dentry_kill+0x2b2/0x4d0
 shrink_dentry_list+0x17c/0x4f0
 shrink_dcache_parent+0x143/0x1e0
 do_one_tree+0x9/0x30
 shrink_dcache_for_umount+0x51/0x120
 generic_shutdown_super+0x5c/0x3a0
 kill_block_super+0x90/0xd0
 kill_f2fs_super+0x225/0x310
 deactivate_locked_super+0x78/0xc0
 cleanup_mnt+0x2b7/0x480
 task_work_run+0xc8/0x150
 exit_to_user_mode_prepare+0x14a/0x150
 syscall_exit_to_user_mode+0x1d/0x40
 do_syscall_64+0x48/0x90

The root cause is: inode node and dnode node share the same nid,
so during f2fs_evict_inode(), dnode node truncation will invalidate
its NAT entry, so when truncating inode node, it fails due to
invalid NAT entry, result in inode is still marked as dirty, fix
this issue by clearing dirty for inode and setting SBI_NEED_FSCK
flag in filesystem.

output from dump.f2fs:
[print_node_info: 354] Node ID [0xf:15] is inode
i_nid[0]                      		[0x       f : 15]

Cc: stable@vger.kernel.org
Reported-by: Ming Yan <yanming@tju.edu.cn>
Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: chaseyu

fs/f2fs/inode.c

@@ -796,8 +796,22 @@ void f2fs_evict_inode(struct inode *inode)
 		f2fs_lock_op(sbi);
 		err = f2fs_remove_inode_page(inode);
 		f2fs_unlock_op(sbi);
-		if (err == -ENOENT)
+		if (err == -ENOENT) {
 			err = 0;
+
+			/*
+			 * in fuzzed image, another node may has the same
+			 * block address as inode's, if it was truncated
+			 * previously, truncation of inode node will fail.
+			 */
+			if (is_inode_flag_set(inode, FI_DIRTY_INODE)) {
+				f2fs_warn(F2FS_I_SB(inode),
+					"f2fs_evict_inode: inconsistent node id, ino:%lu",
+					inode->i_ino);
+				f2fs_inode_synced(inode);
+				set_sbi_flag(sbi, SBI_NEED_FSCK);
+			}
+		}
 	}
 
 	/* give more chances, if ENOMEM case */