Date: Sun, 10 Oct 2021 05:48:58 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: Alan Somers <asomers@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: RFC: Use of VOP_ALLOCATE() by NFSV4.2 nfsd Message-ID: <YQXPR0101MB09682A058479CF95ED4FE76FDDB49@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM> In-Reply-To: <CAOtMX2hyoyLam%2BOY7_hziiX7%2BEP8h2Ca4qiTpkj8suKZnkv68g@mail.gmail.com> References: <YQXPR0101MB0968322C2DEBFAA672FFBC8EDDB49@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM> <CAOtMX2hyoyLam%2BOY7_hziiX7%2BEP8h2Ca4qiTpkj8suKZnkv68g@mail.gmail.com>
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________________________________________ From: Alan Somers <asomers@freebsd.org> Sent: Saturday, October 9, 2021 11:52 PM To: Rick Macklem Cc: FreeBSD Current Subject: Re: RFC: Use of VOP_ALLOCATE() by NFSV4.2 nfsd CAUTION: This email originated from outside of the University of Guelph. Do= not click links or open attachments unless you recognize the sender and kn= ow the content is safe. If in doubt, forward suspicious emails to IThelp@uo= guelph.ca On Sat, Oct 9, 2021 at 7:13 PM Rick Macklem <rmacklem@uoguelph.ca> wrote: > > Hi, > > I ran into an issue this week during the nfsv4@ietf.org's testing event. > UFS - supports VOP_ALLOCATE() by using vop_stdallocate(). > ZFS - just return EINVAL for VOP_ALLOCATE(). > > An NFSv4.2 server can either support Allocate or not, but it has to be > for all exported file systems. That seems like a protocol bug to me. Could this be fixed in a future NFS revision? > > This leads me to a couple of questions: > - Is there a good reason for not using vop_stdallocate() for ZFS? Yes. posix_fallocate is supposed to guarantee that subsequent writes to the file will not fail with ENOSPC. But ZFS, being a copy-on-write file system, cannot possibly guarantee that. See SVN r325320. > - Should I try and support both file system types via vop_stdallocate() > or not support Allocate at all? Since you can't possibly support it for ZFS (not to mention other file systems like fusefs) you'll have to not support it at all. > > Btw, as a bit of an aside, "cc" uses posix_fallocate() and in weird ways, > such as offset=3D0, len=3D1. Why, I have no idea? > > Thanks in advance for any comments, rick >
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