On Mon, 2005-04-18 at 12:22 +0100, Christoph Hellwig wrote:
> > Mingming Cao <[email protected]> said:
> > The ext2 handle discard preallocation differently at that time, it discard the
> > preallocation at each iput(), not in input_final(), so we think it's
> > unnecessary to thrash it so frequently, and the right thing to do, as we did
> > for ext3 reservation, discard preallocation on last iput(). So we moved the
> > ext2_discard_preallocation from ext2_put_inode(0 to ext2_clear_inode.
> >
> > Since ext2 preallocation is doing pre-allocation on disk, so it is possible
> > that at the unmount time, someone is still hold the reference of the inode, so
> > the preallocation for a file is not discard yet, so we still mark those blocks
> > allocated on disk, while they are not actually in the inode's block map, so
> > fsck will catch/fix that error later.
> >
> > This is not a issue for ext3, as ext3 reservation(pre-allocation) is done in
> > memory.
>
> Shouldn't we have a pass to discard on unmount instead? ->put_inode is
> a really bad interface and all usages including this one are racy (not that
> it matters too much here, but I'd like to get rid of it eventually).
> As a band-aid to avoid the corruption it's certainly okay (and needed), but
> we should try to fix this for real. Mingming, do you want to look into it
> or should I put it on my TODO list?
>
>
Hi Christoph,
I dislike the fact that ext2 discard preallocation on every iput rather
than the last iput. Yes, I think doing a check of the preallocated
blocks at umount time is doable. Please go for it. Thanks for asking.
Mingming
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