When a process attempts to read from an empty file originating from
psshfs mount, it waits indefinitely. Until the hanged process is
interrupted, the mounted filesystem appears to work as expected,
except for the directory containing the empty file. Processes trying
to list that directory also hang, and cause misbehaviour of the
containing directory. It is possible to create a chain of hanged
processes trying to read directories up to the mount point. At the
same time, psshfs generates some network traffic (around 5KB/s, in
my case). Interrupting the first hanged process causes emission of
an error message by all other hanged processes, and psshfs ceases
to generate network traffic. Subsequent trials to list any affected
directory or if one of the affected directories is the mount point
to unmount the filesystem, fail with the same error.
POSIX allows for the atime (or technically, any of the times) to be
updated as a side effect of searching a directory (allows, not requires).
The NetBSD UDF implementation apparently works that way, treating a
directory search as a read of the directory, and hence updating the
access time. Compensate for that in the test (rather than just
expecting failure) by verifying that the atime after the directory
search is within a small margin of the atime before the search
(currently, "small" is 1 second). We could fetch the time before
the mkdir and both stat() calls, do all of that, fetch the time after,
subtract, and require the after stat() atime to be bounded by the atime
set by the original mkdir and returned in the first stat() and that time
+ the difference in elapsed time - that would be more accurate, but is
a lot more work for little real benefit.
Should anyone be interested in doing that extra work, remember to use
monotonic time (clock_gettime(CLOCK_MOMNOTONIC, ...)) not the time of day
clock for measuring the elapsed time.
Along with this, remove the "if (udf) failure expected" and the
if (udf && we haven't failed yet) fail("random failure failed to happen")
stuff... (the "random" would have been that sometimes the mkdir and
two lookups (stat() calls) would all occur within the same clock tick,
meaning that the atimes would all be the same. Other times the clock
would tick somewhere between the mkdir() and the 2nd stat().)
