Re: [RFC] ext3 freeze feature

Takashi Sato
2008-01-28T13:08:52Z

Hi,

Thank you for your comments.

> That's inherently unsafe - you can have multiple unfreezes
> running in parallel which seriously screws with the bdev semaphore
> count that is used to lock the device due to doing multiple up()s
> for every down.
>
> Your timeout thingy guarantee that at some point you will get
> multiple up()s occuring due to the timer firing racing with
> a thaw ioctl.
>
> If this interface is to be more widely exported, then it needs
> a complete revamp of the bdev is locked while it is frozen so
> that there is no chance of a double up() ever occuring on the
> bd_mount_sem due to racing thaws.....

My patch has the race condition as you said.
I will fix it.

Cheers, Takashi