On 2012/09/14 09:57, Dave Chinner wrote:
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....
As I commented to Eric, In virtualization environments it comes in
handy sometimes. For example, in an emergency case where a guest
agent dies leaving one or more filesystems frozen emergency thaw
is useful.
Hopefully my fix is correct and we can keep this feature.
Thanks,
Fernando
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
