svn commit: r231383 - in head: lib/libutil usr.sbin/vipw

[Bruce Evans]

On Fri, 10 Feb 2012, Sergey Kandaurov wrote:

> On 10 February 2012 17:40, Ed Schouten <ed at freebsd.org> wrote:
>> Log:
>>  Detect file modification properly by using tv_nsec.
>>
>>  POSIX 2008 standardizes st_mtim, meaning we can simply use nanosecond
>>  precision to detect file modification.
>
> I am not sure we can use subsecond precision there with currently set
> sysctl vfs.timestamp_precision=0.

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=0.

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