On Sep 6, 2007, at 2:09 PM, Phil Carns wrote:
Hi Phil,
The trove layer caches the position -> name mapping for positions
it returns back to the client on a readdir. The problem is
probably related to caching those entries, where the readdir for
the rm is iterating over the directory, and so inserting position
-> name entries into the cache, and then ls is coming along and
replacing those entries with its own, where the position is the
same but the name is further down in the directory (because rm
has removed some of them). That's just a guess though. You
could see if disabling that position cache helps fix the problem,
disabling it will cause the berkeley db iterate to walk through
all the entries up to the position though, so its going to be
much slower. The position cache is in dbpf-keyval-pcache.c.
Probably the right long term solution is to return the name as
the position, instead of an int.
I just replicated this using just 1000 files (each about 200 bytes)
in a single directory, again with one client doing an rm -rf and
another client doing an ls in the same directory.
Unfortunately, it doesn't look like disabling the pcache made any
difference. I first tried disabling it by adding a "return 0" at
the top of the PINT_dbpf_keyval_pcache_insert() function. I also
tried modifying the dbpf_keyval_iterate_skip_to_position() function
to not call PINT_dbpf_keyval_pcache_lookup().
Is there anything else I could do to make sure the pcache isn't
being used, or does this indicate that the problem is elsewhere?
Yeah, must be somewhere else. Sorry for the red herring. Hmm. Is
the file that's not getting deleted regular? i.e. Every file with
positions in multiples of 32 or something. If we had support for *
in pvfs2-rm you could verify that its not the kernel module -- the
position stuffing with iget4/5 in there has always seemed a bit
crufty. Otherwise, I would add gossip messages to the iterate code
to see what positions were being given and returned.
-sam
-Phil
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