I would like clarification on the how the maximum number of cifs simultaneous requests are enforced, and for which cifs operations they apply to. In part this is to avoid triggering a serious problem in Windows 7 and Windows Vista (when they are run as a server) when exceeding this limit on simultaneous requests.
What I have observed in my testing: - Although Windows 7 and Vista allows more than 10 simultaneous SMB write requests (and Windows 2008 allows more than 50 simultaneous write requests), Windows 7 and Windows Vista appear to have problems when 20 or 30 are in flight at one time. - Windows does not enforce a limit on SMB Negotiate Protocol - Windows seems to ignore checks on maximum simultaneous requests on certain handle based operations (SMB writeX in particular) until after the file is closed (the writes don't get an error, but the next QueryPathInfo after the file is closed gets an error). I need to understand on which requests (besides SMB Negotiate) I should ignore MaxMpxCount. In particular, SMB Echo, seems like an obvious choice to ALWAYS allow to be sent by the client, since SMB Echo is sent to make sure the server is alive (when for example the limit on simultaneous requests has been reached due to slow opens, or writes past end of file) and to prevent timeout. If a client is restricted from sending SMB Echo then there is no reasonably reliable mechanism available to determine whether the server is dead or just hung temporarily processing slow requests. MS-CIFS is not clear on which commands MaxMpxCount is enforced. I would like to ignore MaxMpxCount on (sending one of) SMBEcho (where you could cause data integrity issues if you limited the ability to check server state up/down) and SMBNegotiate (where it is obviously not set yet) and SMBOplockBreak responses (since you can't guarantee the order that these are received/sent from the server relative to other frames which are being processed, and can cause the server session to drop if you don't allow the client to send these) to the server since there is no reasonable mechanism to limit these without risking problems with prematurely taking down a slow session (perhaps opens of offline files for example). It looks like the safest way to handle this is for the client to limit pending requests to the MaxMpxCount, with the exception of the three SMB types listed above. In previous versions of MS-CIFS there were mentions of different processes, and uids on the negotiated tcp session and their relation to the MaxMpxCount - and I would also like to verify whether the limits are considered relative to some combination of the negotiated tcp session and uid and/or pid as earlier discussions implied (or file handle, as our testing hinted at). -- Thanks, Steve _______________________________________________ cifs-protocol mailing list cifs-protocol@cifs.org https://lists.samba.org/mailman/listinfo/cifs-protocol