Behavior of filesystem when mount option has been specified as error=panic

Question

Background

I have a debian system on which I have something like the following in the fstab file.

/dev/sda1 / ext3 defaults,noatime,errors=panic 0 0

The option I wish to focus on is the errors=panic. According to the man page, it states the following.

Define the behaviour when an error is encountered. (Either ignore errors and just mark the file system erroneous and continue, or remount the file system read‐only, or panic and halt the system.) The default is set in the filesystem superblock, and can be changed using tune2fs(8).

Based on my understanding, an error when mounting would cause a kernel panic, which is fine. What I want to know is what happens when the kernel encounters an error when using the filesystem? Does it cause a kernel panic as specified by the mount option or does it use the option specified in the superblock as shown by tune2fs (or is that option overridden by the mount command) or does it do something else? If it does something else, what does it do and what can I look for for extra reading?

Answer 1

This behaviour can partially be depending on the implementation in the file system. Since in your case you appear to use Ext3, I'm talking about Ext3 here:

Regarding the first question, it will cause a panic whenever an error is encountered. This means if your disk is mounted and running and gets corrupted while already being mounted, once the error is encountered by the file system implementation the kernel will panic.

The value that's specified in the super block is used as default, if you explicitly specify another value in the mount parameter it overrides the value from the super block.

kernel Ext3 documentation