[Bug 10518] rsync hangs (100% cpu)

[samba-bugs at samba.org]

https://bugzilla.samba.org/show_bug.cgi?id=10518

--- Comment #6 from Bram Matthys <syzop at vulnscan.org> 2014-03-28 17:25:22 UTC ---
Thanks for your explanation.

The file in question is an image file (ext4) used by a VM. Since the file is
fresh and not all is in use, it is likely that this file still contains a few
tens of gigabytes of nul bytes, I guess that would explain the unbalanced hash
table.

Your post inspired me to create a workaround.. I'll mount the image file,
create a file in it with random data until the disk is full, then rm the file,
and unmount. Since the (unallocated) space is then no longer all binary zeros I
hope this should temporarily solve the problem. As long as I don't do too many
disk write tests with dd if=/dev/zero ... ;)

I'm a big fan of rsync, use it all the time on numerous servers. I wasn't aware
of this shortcoming until now. In my view rsync is THE tool to use for well..
almost any synchronization.. and it only becomes (or should become) more useful
when the files get bigger.

Any change you can make to eliminate this problem (or make it far less of a
problem) would be appreciated.

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