Re: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH]device arguments from lookup)

[Linus Torvalds]

On Tue, 22 May 2001, Andreas Dilger wrote:
> 
> Actually, the LVM snapshot interface has (optional) hooks into the filesystem
> to ensure that it is consistent at the time the snapshot is created.

Note that this is still fundamentally a broken interface: the filesystem
may not _have_ a block device underneath it, yet you might very well like
to do defragmentation and backup none-the-less.

Also, lvm snapshots are fundamentally limited to read-only data, which
means that the LVM interfaces cannot be used for defragmentation and lazy
fsck etc anyway. You _have_ to do those at a filesystem level.

disk snapshots are useful, but they are not the answer.

                Linus

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