On Fri, 10 Feb 2012, Sergey Kandaurov wrote:

On 10 February 2012 17:40, Ed Schouten <e...@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
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