I am editing file /proc/self/make-it-fail from root user. This file is having write permission but update not possible, showing "E667: Fsync failed" error.
How did you edit it? I would do:
These 'files' in proc are not like files on disks. The 'file' is pure code, using open and read/write as interfaces to the kernel. As such, editors may make system calls that are not supported on these files. I would limit "editing" to tools such as