From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: References: Date: Mon, 7 Mar 2011 19:17:22 -0600 Message-ID: From: Eric Van Hensbergen To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [9fans] Listing a directory Topicbox-Message-UUID: b8996f78-ead6-11e9-9d60-3106f5b1d025 On Mon, Mar 7, 2011 at 7:09 PM, Venkatesh Srinivas wrote: > > In 9P, if I wish to list a directory, I need to TWalk to the directory, > TOpen the directory fid from the walk, and then TRead till I have all of the > contents of the directory. > If the directory's contents do not fit in a single read, I imagine I need to > loop around TOpen / Tread / .... / Tread / TOpen, till I get the whole > contents and see the same QIDs in each open, to get a coherent listing. (is > this accurate?) > Offsets track where you are in the metadata, servers have multiple approaches to dealing with this, usually there is some form of cookie in the fid which tracks the last offset red and maybe a cache of where it was in the directory listing. I think the QID matching and coalescing is more of a union bind mechanism and happens if I am not mistaken by a higher level entity (like ls) > Unfortunately, a TOpened FID to a directory cannot be used for walking it > (why?); so the only use of a TOpened fid to a directory is to list it or to > get a QID. Would it be reasonable for a TOpened fid to a directory to create > a copy of the directory listing at the time of the RPC? That may be a potential back-end implementation on the server, I believe it to be the only way to avoid the sort of race conditions you might expect otherwise. But I haven't implemented the server side of that code, only the client which is tricky, but easier -- so I'm sure someone else may have a better opinion. -eric