Re: [PATCH] let fat handle MS_SYNCHRONOUS flag

[OGAWA Hirofumi]

Matt Mackall <mpm@xxxxxxxxxxx> writes:

> On Wed, Nov 24, 2004 at 05:24:36AM +0900, OGAWA Hirofumi wrote:
>> Colin Leroy <colin@xxxxxxxxxx> writes:
>> 
>> > It adds MS_SYNCHRONOUS support to FAT filesystem, so that less
>> > filesystem breakage happen when disconnecting an USB key, for 
>> > example. I'd like to have comments about it, because as it 
>> > seems to work fine here, I'm not used to fs drivers and could
>> > have made mistakes.
>> 
>> What cases should these patches guarantee that users can unplug the
>> USB key?  And can we guarantee the same cases by improving autofs or
>> the similar stuff?
>
> Well there can be no guarantees - there will always be a race between
> flush and hot unplug. If we're careful with write ordering, we can
> perhaps arrange to avoid the worst sorts of corruption, provided the
> device does the right thing when it's in the middle of an IO.
>
> But generally I think this is a good idea as it shrinks the window.

Things which I want to say here - do we really need the bogus
sync-mode?

Current fatfs is not keeping the consistency of data on the disk at
all.  So, after all, the data on a disk is corrupting until all
syscalls finish, right?

If so, isn't this too slow? I doubt this is good solution for this
problem (USB key unplugging)...

Well, it seems good as start of sync-mode though.
-- 
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
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