What is Emergency Thaw on mtdblock5?

For Developers
1

[ 484.056000] Emergency Thaw on mtdblock5
[ 484.064000] Emergency Thaw on mtdblock5
[ 484.072000] Emergency Thaw on mtdblock5
[ 484.080000] Emergency Thaw on mtdblock5
Emergency Thaw on mtdblock5
[ 484.096000] Emergency Thaw on mtdblock5
[ 484.104000] Emergency Thaw on mtdblock5
[ 484.112000] Emergency Thaw on mtdblock5
[ 484.120000] Emergency Thaw on mtdblock5
[ 484.128000] Emergency Thaw on mtdblock5
[ 484.136000] Emergency Thaw on mtdblock5
[ 484.144000] Emergency Thaw on mtdblock5
[ 484.148000] Emergency Thaw on mtdblock5
[ 484.156000] Emergency Thaw on mtdblock5

2

which device? which file system on that mtd5 ?

That is some kind of major file system error noticed by the Linux kernel. File system superblock corrupted, or so.

I do not remember ever seeing that or hearing about that in OpenWrt context. And google finds pretty much nothing:
https://www.google.com/search?q=openwrt+"Emergency+Thaw"

Linux context:
https://www.google.com/search?q=linux+"Emergency+Thaw"

Ps. based on Linux search results, it can be triggered by "SysRq+J", what ever that means in practice. (Alt + SysRq/Printscreen + J key combination?)
https://en.wikipedia.org/wiki/Magic_SysRq_key