Re: [PATCH 2/2] fs: print a message when freezing/unfreezing filesystems

Theodore Ts'o
2014-05-15T12:47:36Z

On Thu, May 15, 2014 at 12:01:57PM +0200, Jan Kara wrote:
> I was tracking down a couple of times what the hell is freezing the
> filesystem (and not unfreezing it) and I agree with Mateusz it would be
> nice if we could tell after the fact who froze the fs. Maybe we could store
> that information in superblock and dump it during emergency thaw?

Saving it in the superblock would require changing a bunch of file
systems. What if we store this information in memory, and print it
out under certain conditions (i.e., after a soft lockup detection, or
upon request of some magic sysrq request)?

Or we could create a tunable threshold and print a message after a
file system has been frozen more than a particular specified duration,
with that duration set conservatively to something like 60 or 120
seconds by default.

- Ted