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get filename->inode mappings in bulk for a live fs?

To: xfs-oss <xfs@xxxxxxxxxxx>
Subject: get filename->inode mappings in bulk for a live fs?
From: Linda Walsh <xfs@xxxxxxxxx>
Date: Thu, 04 Oct 2012 08:30:20 -0700
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I notice that attempts to use utils to get name->inode mappings
(xfs_ncheck) seem to have no option to operate on a mounted filesystem.

Is it practical to xfs_freeze such a file system and then ncheck it? or would
freezing it simply freeze the fact that it is open and provide no benefit?

So how can I get an inode->block mapping on a live fs.

I'm not worried about some smallish number of cases that might be inaccurate.

Out of ~5M files on my most populous volume, having even 1000 files w/wrong
info would be less than .02% -- which would be bad if I wanted an exact backup,
but for purposes a quick-fuzzy look at files that have changed and are finished
being changed (vs. the ones being changed right now),

The man page for xfs_freeze mentions using it to make snapshots -- how long
does such a snapshot usually take?  I.e. how long would a file system be frozen?
Is it something that would take a few ms, few seconds, or multiple minutes?

This may be a weird idea, but I seem to remember when lvm takes a snapshot
it moves the live volume aside and begins to use COW segments to hold changes.

Is it possible to xfs-freeze a COW copy so access to the original FS isn't
suspended thus making the time period of an xfs_freeze/dump_names less
critical?

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