Date: Wed, 31 Oct 2018 02:23:29 +0000 From: Rick Macklem <rmacklem@uoguelph.ca> To: Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Filesystems <freebsd-fs@freebsd.org>, Josh Paetzel <josh@tcbug.org>, Andriy Gapon <avg@FreeBSD.org> Subject: Re: How to fill in the fsid for file systems? Message-ID: <YTOPR0101MB11621427AF47133A93311E16DDCD0@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM> In-Reply-To: <20181030012240.GM5335@kib.kiev.ua> References: <YTOPR0101MB11620BAF0E206EE36E927A5ADDF30@YTOPR0101MB1162.CANPRD01.PROD.OUTLOOK.COM>, <20181030012240.GM5335@kib.kiev.ua>
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Konstantin Belousov wrote:
>On Mon, Oct 29, 2018 at 03:56:02PM +0000, Rick Macklem wrote:
>> Hi,
>>
>> I have been working with Josh Paetzel on a patch to add support for
>> the "fsid=3DN" option (like what Linux has) to /etc/exports. (It is used
>> to ensure that the fsid for a file system doesn't change when migrated
>> to a different machine, so that file handles don't change.)
>Why do you consider this an option for exports file and not for nmount(2)
>and fstab ? Do you intend to mangle fsid for mount protocol only ?
Well, Josh Paetzel proposed this. I believe it was because "that's how Linu=
x
does it" (but I can't speak for Josh).
The kernel code currently sets this via an nmount(2) option called "export.=
fsid".
Although Josh's patch has this done in mountd.c, it could simply be used as
a mount option in /etc/fstab or manual mounting. (The code currently proces=
ses
this option in vfs_domount_update(), so it would need to be moved to where
options are processed during mounting, but that wouldn't be hard.)
This would actually avoid patching mountd.c. It would also avoid the fact t=
hat
the "export fsid option" applies to all clients and is not per-host or per-=
net.
(Doing it only for "exports" requires a moderate amount of code change, suc=
h
as a new function to be used instead of vfs_busyfs() to busy the file syste=
m
after looking up the fsid in the export stuff. I haven't coded this, so I'm=
not
sure how much work that would be?)
I actually think making it a generic nmount(2) option and not an export spe=
cific
one sounds like a good idea.
What do others think of making "fsid=3DN" a generic mount option for
overriding the selection of fsid done by the file system?
rick
ps: Although I don't try to be "Linux incompatible", I don't see why we sho=
uld
be compatible when doing it a slightly different way seems more logic=
al.
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