From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: To: 9fans@cse.psu.edu Subject: Re: [9fans] question about union dirs From: "Russ Cox" MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 20 Sep 2002 13:10:00 -0400 Topicbox-Message-UUID: f0dd29f8-eaca-11e9-9e20-41e7f4b1d025 > In the TCP case, suppose this search is the first > operation since the disconnection occurred (no prior > outstanding tcp transmissions). Does the search block > until TCP gives up (13 or so minutes later), or is > the "hungup" condition somehow marked sooner? Yes, it blocks, but TCP should give up after 30 seconds. > Can the user (of say rc) discover this? For example, > suppose I expect to be getting /bin/foo from the > disconnected service. If I quietly get a different > /bin/foo from something further down the union, I might > be baffled. If the user knew what the mount number for that connection was, ls -l would show different numbers. For example: g% ls -l /n/kfs/adm/users --rw-rw-r-- M 25 adm adm 140 Aug 28 08:37 /n/kfs/adm/users g% ls -l /n/emelie/adm/users --rw-rw-r-- M 57 adm adm 10458 Jul 19 11:08 /n/emelie/adm/users g% ls -l /n/kfs/adm/users --rw-rw-r-- M 57 adm adm 10458 Jul 19 11:08 /n/kfs/adm/users g% ls -l /n/kfs/adm|grep users --rw-rw-r-- M 57 adm adm 10458 Jul 19 11:08 /n/kfs/adm/users --rw-rw-r-- M 25 adm adm 140 Aug 28 08:37 /n/kfs/adm/users g% The 'M 25' says that this file is coming from the mount device (it's a 9P service rather than a kernel device) instance number 25. Each mount gets a different instance number. Russ