RFC: deprecate allocation roundup size

[Björn JACKE]

Hi,

I was debugging a problem with strict allocate = yes and our current default of
"allocation roundup size", which is 1MB. While I understand that a large
allocation roundup size was supposed to the a performance tuning for old SMB1
clients, this has the side effect that with "strict allocate = yes" this makes
even small files take at least 1MB on the disk, because smbd allocates that
ammount of disk space which is given back by smb_roundup. This is an issue for
some setups, because the extra ammount of needed disk space can be huge
actually.

To work around the issue, I tested to remove the smb_roundup in places wherere
disk space allocation is being done so that the allocation roundup size value
is only used to announce this 1MB "block size" to the clients. I'm not sure if
there can be other negative side effect thought if we announce that large block
size but behave with the actual space allocation with out normal small block
size.

As this performance trick is not needed for modern SMB clients any more, it
might also be be better idea to just reset the value of "allocation roundup
size" to 4k again, deprecate the option and remove it with one of the next
releases completely to behave more windows standard conforming and to just cut
off this source of irritation.

Björn
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