Re: [RFC 0/9 v3] fsfreeze: miscellaneous fixes and cleanups

[Dave Chinner <david@fromorbit.com>]

On Thu, Sep 13, 2012 at 07:57:42PM +0900, Fernando Luis Vázquez Cao wrote:
> This patch set is to address long standing issues in the filesytem freeze code
> and to fill some functionality gaps in the API. Some minor code rearrangements
> are included too.
> 
> The following patches are included:
> 
> ---
> [1/9] vfs: add __iterate_supers() helper
> [2/9] fsfreeze: add unlocked version of thaw_super
> 
> Preparatory patches to fix s_umount lockup of emergency thaw code.
> 
> [3/9] fsfreeze: Prevent emergency thaw from looping infinitely
> 
> Fix thaw_bdev so that it propagates the error code properly to the caller.
> This bug caused emergency thaw to loop infinitely. This is a forward port of
> a previous patch by Dave Chinner.
> 
> [4/9] fsfreeze: emergency thaw will deadlock on s_umount
> 
> Avoid emergency thaw deadlock on s_umount by using unlocked version of
> thaw_super() and __iterate_supers()i (introduced in patches 2 and 1
> respectively).

Given the problems with emergency thaw, this interface has never
really worked. In the absence of any obvious need for the
functionality (i.e. nobody has reported that it is broken since it
was introduced), why don't we simply remove it?

IIRC, the emergency thaw code was only added to alleviate
fear-mongering about systems getting stuck with unfreezable ext4
filesystems (after the "freeze w/ timeout" extensions were knocked
back), and time has indicated those fears were unfounded.

So, rather than trying to fix the emergency thaw mess, I say we
nuke it from orbit....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com
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