linux-kernel - Re: [PATCH v2 4/4] fat: switch to fsinfo

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Date:	Sat, 14 Apr 2012 14:01:45 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Maling List <linux-kernel@...r.kernel.org>,
	Linux FS Maling List <linux-fsdevel@...r.kernel.org>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>
Subject: Re: [PATCH v2 4/4] fat: switch to fsinfo_inode

On Sat, 2012-04-14 at 19:36 +0900, OGAWA Hirofumi wrote:
> Artem Bityutskiy <dedekind1@...il.com> writes:
> 
> >> Hm, does this guarantee to flush FSINFO at umount?
> >
> > Of course, and I checked it. It is just a dirty inode. If you do not
> > worry that any other inode won't get written-beck, then you should not
> > worry about this one.
> >
> >> FSINFO is last part of data dependency. I.e. inode change can dirty
> >> FSINFO. So, FSINFO has to be flushed after normal inodes.
> >
> > Sorry, I do not see how this can be true. You have a just bunch of dirty
> > inodes, and it does not matter in which order you flush them. See
> > __fat_write_inode() - it does not change the FAT table and does not
> > affect the FSINFO block.
> >
> > Besides, the _current_ code first writes out FSINFO, because VFS calls
> > ->sync_fs() first, then it starts writing back, then VFS calls
> > ->sync_fs() for the second time.

This is actually not exactly correct, but anyway, the first
->sync_fs(sb, 0) may come to FAT FS while it is in the middle of writing
out the inodes.

BTW, fat_clusters_flush() does not wait on the FSINFO block, which I
think is a bug. I mean, it should call 'sync_dirty_buffer()'. I can
submit a separate patch later.

> Common case is delayed allocation though, in the case of FATfs, it would
> be only truncate by last iput().

Sorry, I do not understand what you mean. Do you still want me to take
care of the order or not? If yes, could you please explain why?

-- 
Best Regards,
Artem Bityutskiy

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