On Mon, 14 Jun 2004 [EMAIL PROTECTED] wrote: > On Fri, 21 May 2004, Jim Carter wrote:
> > > For a a cache hit we can: > > > > > > 1. Check if the map entry has exceeded a given time to live, say > > > the map expire time. > > > 2. If not continue as normal otherwise lookup the individual map > > > entry and compare it to the cached entry. > > > 3. If they are identical continue as normal otherwise it's a hint > > > the map has changed so re-read it. > > > > Suggestion: set a flag saying "we know that this map is out of date", but > > only re-read the whole thing when userspace expects to see up-to-date ghost > > mounts. Understood, that to read any one row from a file map you have to > > read the whole thing; the suggestion makes a difference only for NIS and > > LDAP -- where it makes a big difference. > What were you thinking of as defining "out of date" Jim? Item 3 -- we did the NIS lookup on this one entry because the TTL had expired, and NIS gave a different answer than the cache, so every cached entry from that map is probably wrong. But there's no need to read the whole map; just clear the cached entries that came from it (except the one just read, known to be up to date). In subsequent discussion we may or may not have agreed that the only time you need to read the whole map is when the caller does readdir, as results from "ls /net" or "ls /net/hostname". In that case you can't trust the cache, because entries might have been added to the map and you'd never know. Someone pointed out that readdir may have to be used on an ordinary file lookup if you have to dig through the directory to find the file. I'm assuming that a successful cache lookup bypasses this readdir. James F. Carter Voice 310 825 2897 FAX 310 206 6673 UCLA-Mathnet; 6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA 90095-1555 Email: [EMAIL PROTECTED] http://www.math.ucla.edu/~jimc (q.v. for PGP key) _______________________________________________ autofs mailing list [EMAIL PROTECTED] http://linux.kernel.org/mailman/listinfo/autofs
