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Date: Sat, 11 Feb 2012 04:20:22 +1100 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Sergey Kandaurov <pluknet@FreeBSD.org>
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
	src-committers@FreeBSD.org, Ed Schouten <ed@FreeBSD.org>
Subject: Re: svn commit: r231383 - in head: lib/libutil usr.sbin/vipw
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On Fri, 10 Feb 2012, Sergey Kandaurov wrote:

> On 10 February 2012 17:40, Ed Schouten <ed@freebsd.org> wrote:
>> Log:
>> =A0Detect file modification properly by using tv_nsec.
>>
>> =A0POSIX 2008 standardizes st_mtim, meaning we can simply use nanosecond
>> =A0precision to detect file modification.
>
> I am not sure we can use subsecond precision there with currently set
> sysctl vfs.timestamp_precision=3D0.

Also, not all file systems support even seconds precision.  So the
deleted BUGS section applies irrespective of vfs.timestamp_precision,
except it doesn't describe the full extent of the problem.  Sleeping
for just 1 second is not enough if the timestamp precision is large.

The BUGS section also applies respective of vfs.timestamp_precision,
when the user uses the supported setting vfs.timestamp_precision=3D0.

Of course, important databases that need POSIX semantics shouldn't be
put on file systems without POSIX times, but you need a BUGS section
somewhere to tell you not to do that.

Bruce
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