Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem checker)

[Eric Sandeen <sandeen@redhat.com>]

Theodore Tso wrote:
> On Sat, Apr 19, 2008 at 01:44:51PM +0400, Alexey Zaytsev wrote:
>> If it is a block containing a metadata object fsck has already read,
>> than we already know what kind of object it is (there must be a way
>> to quickly find all cached objects derived from a given block), and
>> can update the cached version. And if fsck has not yet read the
>> block, it can just be ignored, no matter what kind of data it
>> contains. If it contains metadata and fsck is intrested in it, it
>> will read it sooner or later anyway. If it contains file data, why
>> should fsck even care?

It seems to me that what the proposed project really does, in essence,
is a read-only check of a filesystem snapshot.  It's just that the
snapshot is proposed to be constructed in a complex and non-generic (and
maybe impossible) way.

If you really just want to verify a snapshot of the fs at a point in
time, surely there are simpler ways.  If the device is on lvm, there's
already a script floating around to do it in automated fasion.  (I'd
pondered the idea of introducing META_WRITE (to go with META_READ) and
maybe lvm could do a "metadata-only" snapshot to be lighter weight?)

-Eric