Ulrich Windl wrote: > (Trimmed the list of reply-to:) > On 5 Mar 2009 at 11:42, Mike Christie wrote: > > [...] >> The second issue is that we normally do zero copy for writes. I do not >> think it is FS bug or net bug or a bug in the iscsi layer. Maybe more of >> a bug in what the user expects (who reads the man page for write() to >> check if the data is committed to disk when write() returns). We >> discussed this a couple times. For open-iscsi we tried to close the gap, >> by not doing zero copy writes when data digests are used. And a long >> long time ago this was discussed for linux-iscsi, and I think that is >> one of the reasons we added DID_IMM_RETRY to the scsi layer (we can then >> avoid the 5 retry limit in this case and retry until it is resolved). > > Hi Mike, > > I have no idea about the buffer handling in networking, etc, but as far as I > understand, you are telling the iSCSI/networking code to transmit some data > blocks > in menory via networking without making a copy of the data blocks. Now I > wonder if > there are some flags to tell the kernel not to update that data blocks, > because a > transfer is "in progress" (when actually the transfer is just queued for > progress). In buffer_head.h there are some flags, but I don't know what they > exactly mean. The other solution that comes to my mind would be a type of > call- > back when a buffer was changed after being queued for transport; the call > back > would then have to re-calculate the data disgest. > > Am I completely wrong here, or is it more or less the problem we are talking > about?
I think we are talking about the same problem. I am not sure about some of the details in what you propose. Probably, the iscsi list is not the appropriate forum since we do not have a deep expertise in the vm or networking code. But I think if you ask on the other lists, they might tell you to just write your app so you do a sync after the write. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to email@example.com To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/open-iscsi -~----------~----~----~----~------~----~------~--~---