Re: [PATCH 2/2] fat: mark fs as dirty on mount and clean on umount

[Oleksij Rempel]

Am 03.01.2013 00:44, schrieb Andrew Morton:
> On Fri, 28 Dec 2012 02:20:20 +0900
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> wrote:
>
> > There is no documented methods to mark FAT as dirty. Unofficially MS
> > started to use reserved Byte in boot sector for this purpose,
> > at least since Win 2000. With Win 7 user is warned if fs is dirty
> > and asked to clean it.
> > Different versions of Win, handle it in different ways,
> > but always have same meaning:
> > - Win 2000 and XP, set it on write operations and
> >    remove it after operation was finnished
> > - Win 7, set dirty flag on first write and remove it on umount.
> >
> > We will do it as fallow:
> > - set dirty flag on mount. If fs was initially dirty, warn user,
> >    remember it and do not do any changes to boot sector.
> > - clean it on umount. If fs was initially dirty, leave it dirty.
> > - do not do any thing if fs mounted read-only.
> > - TODO: leave fs dirty if we found some error after mount.
>
> The changelog doesn't describe why we're making this change.  Nor does
> it describe the user-visible effects of this change.
>
> AFAICT the effect is to issue a warning at mount-time to tell the
> user that the fs wasn't cleanly unmounted and that the user should fsck
> the volume, correct?
>
> If so, why is this considered a desirable feature?  (I can guess, but
> would prefer to hear it spelled out by the experts, please).

FAT is old and still intensively used file system with high number of 
data lost. This patch set is a try to reduce this numbers.
To make this work complete, we need some changes in user space too. But 
even stand alone, this patchset can warn M$ Windows 7 about probably 
damaged FS. In this case Win 7 will inform user and give option to start 
checkdisk.
--
Regards,
Oleksij
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