Log in to the server today, and you will report an error if you open the file through VI:

E297: Write error in swap file
E303: Unable to open swap file for “cron”, recovery impossible

The prompt says that it cannot be written, so check the disk space

df -lh

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              20G   20G   20K 100% /
none                   15G     0   15G   0% /dev/shm

You can see that the root partition is 100% used

After cleaning, it returned to normal