On Tue, Oct 30, 2012 at 5:47 AM, ching [off-list ref] wrote:

Hi all,

I try to defrag my btrfs root partition (run by root privilege)

find / -type f -o -type d -print0 | xargs --null --no-run-if-empty btrfs filesystem defragment -t $((32*1024*1024))


1. This kind of error messages is prompted:

    failed to open /bin/bash
    open:: Text file busy
    total 1 failures
    failed to open /lib64/ld-2.15.so
    open:: Text file busy
    total 1 failures
    failed to open /sbin/agetty
    open:: Text file busy
    failed to open /sbin/btrfs
    open:: Text file busy
    failed to open /sbin/dhclient
    open:: Text file busy
    failed to open /sbin/init
    open:: Text file busy
    failed to open /sbin/udevd

    It seems that locked files cannot be defragged, is it expected behaviour?

I can't reproduce that behaviour here, although maybe you're running
an older kernel with some bug that's since been fixed?

2. Btrfs Wiki mentions that defrag directory will defrag metadata, is symlink/hardlink considered as metadata?

    P.S. inline data is already disabled by "max_inline=0"

Well, that's a silly thing to do, causing every small file to take up
a separate 4kb block rather than its size * 2, and requiring extra
seeks to read/write them (i.e., if you have a million 10 byte files,
they'll now take up 4GB instead of 20MB).

3. Is any possible to online defrag a btrfs partition without hindered by mount point/polyinstantied directories?

If you're asking if you can defrag an unmounted btrfs, not at this
time.  It's possible in principle, nobody has cared enough to
implement it yet.