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From: Alfred Perlstein <bright@mu.org>
Subject: Re: nullfs changes MFC
Date: Sat, 8 Dec 2012 13:12:19 -0800
To: Konstantin Belousov <kostikbel@gmail.com>
Cc: "stable@freebsd.org" <stable@freebsd.org>,
 "fs@freebsd.org" <fs@freebsd.org>
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By combining vop_settext/unset/get into a single call with parameters "op" a=
nd &out (for gettext) you can reduce 3 new vops into a single vop.=20

The same can be done for write count vops.=20


This will allow you to preserve kbi by reducing the vop additions to 2.=20

Sent from my iPhone

On Dec 7, 2012, at 5:01 PM, Konstantin Belousov <kostikbel@gmail.com> wrote:=


> Hi,
> I am going to merge latest batch of the nullfs improvements into
> stable/9. This will bring up significant performance enchancements due
> to use of the shared locks for lookups if the lower layer supports it,
> much better caching on the nullfs layer, and proper handling of the text
> segments on the nullfs. Also, it should improve the error recovery and
> some corner cases with locking.
>=20
> Unfortunately, the merge would break KBI for VFS, since it needs 5 new
> VOP slots, and only three spares are left. We already are very liberal
> with the VFS KBI, so I do not feel that the merge is not acceptable, due
> to the benefits it brings to the nullfs.
>=20
> The merge is available at=20
> http://people.freebsd.org/~kib/misc/nullfs_9.1.patch