Request for information on bloated writes using Swift

[Dilip Simha]

Hi,

I have a question regarding speculated preallocation in XFS, w.r.t kernel
version: 3.16.0-46-generic.
I am using Swift version: 1.0 and mkfs.xfs version 3.2.1

When I write a 256KiB file to Swift, I see that the underlying XFS uses 3x
the amount of space/blocks to write that data.
Upon performing detailed experiments, I see that when Swift uses fallocate
(default approach), XFS doesn't reclaim the preallocated blocks that XFS
allocated. Swift fallocate doesn't exceed the body size(256 KiB).

Interestingly, when either allocsize=4k or when swift doesn't use
fallocate, XFS doesn't consume additional space.

Can you please let me know if this is a known bug and if its fixed in the
later versions?

Thanks & Regards,
Dilip
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