Re: [PATCH] Allow SysRq emergency sync to thaw frozen filesystems

From: Bodo Eggert
Date: Sat Jan 17 2009 - 09:04:01 EST


Eric Sandeen <sandeen@xxxxxxxxxxx> wrote:
> Valdis.Kletnieks@xxxxxx wrote:
>> On Thu, 15 Jan 2009 21:59:10 CST, Eric Sandeen said:

>>> Oh, actually, I'd think not. If the freeze was done properly by the
>>> filesystem, all data was flushed, the fs was quiesced, and new IO was
>>> blocked. pdflush should never be visiting these...
>>
>> Yes, but a lot of 'if's - and usually you're reaching for sysrq-S precisely
>> *because* you suspect that stuff wasn't happening properly on its own...
>
> Actually, only one if - if the fs implemented freeze properly.
>
> Well, the use case I envision here is something like:
>
> # freeze /my/mount/point/to/fs/to/snapshot
>
> except oops, that wasn't mounted, and you just froze your root fs.

Maybe freeze should protect against that by requiring to specify the exact
mountpount, unless you say freeze --subdir?

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