On Sat, Nov 27, 2010 at 7:01 AM, Jeff Layton <jlayton@xxxxxxxxxxxxxxx> wrote: > This patchset is intended to fix the unreliable behavior in CIFS in the > face of a server that's taking a long time to process requests. > > In general, the current code sets a timeout for all requests that are > sent on the wire. If the server doesn't respond to the request within > that timeout, the client performs a reconnect and retries the request. > > This is dangerous and wasteful behavior for the client. Much of the > state of a CIFS mount is bound to the socket connection. Break the > socket connection and state is lost. > > I believe this the root cause of some data corruption issues that have > been reported to me. We had a partner report that when they copied a > large file to a CIFS server and then compare the result to the original, > there is sometimes a mismatch. The problem is highly correlated to > messages in the ring buffer that indicate that the client reconnected > the socket during the test run. > > Another problem that I can reliably reproduce -- I have win2k8 > installed as a VM guest. When I run connectathon tests to that server, > it frequently fails on the test that writes 4GB past the EOF. The > storage on this server is slow, and it can take longer than 180s for > it to zero-fill the output file. > > The intent of this patchset is to fundamentally change when the client > decides to reconnect the socket. Instead of the old behavior, this > patchset makes the client wait indefinitely for a response. Rather than > waiting in TASK_UNINTERRUPTIBLE sleep however, the client waits in > TASK_KILLABLE sleep so that fatal signals will end the sleep and > return -ERESTARTSYS to the caller. > > In order to determine whether the server is completely dead or just > taking a long time to process requests, this patchset has the client > do an asynchronous SMB echo request every 60s when the client hasn't > gotten a reponse. If the server doesn't respond after 5 mins, the > client will attempt to reconnect the socket. > > With this patchset, I can reliably run the connectathon tests against > my slow server. Preliminary results using the proprietary test that > was seeing data corruption have also been promising. > > I'd like to see this set considered for inclusion into 2.6.38. > > Comments and suggestions welcome. > > Jeff Layton (14): > cifs: move mid result processing into common function > cifs: wait indefinitely for responses > cifs: don't reconnect server when we don't get a response > cifs: clean up handle_mid_response > cifs: allow for different handling of received response > cifs: don't fail writepages on -EAGAIN errors > cifs: handle cancelled requests better > cifs: make wait_for_free_request take a TCP_Server_Info pointer > cifs: add cifs_call_async > cifs: add ability to send an echo request > cifs: set up recurring workqueue job to do SMB echo requests > cifs: reconnect unresponsive servers > cifs: make hard mounts the default > cifs: remove code for setting timeouts on requests > > fs/cifs/cifs_debug.c | 8 +- > fs/cifs/cifsglob.h | 19 ++-- > fs/cifs/cifspdu.h | 15 +++ > fs/cifs/cifsproto.h | 7 + > fs/cifs/cifssmb.c | 55 ++++++++- > fs/cifs/connect.c | 128 +++++++++++++++---- > fs/cifs/file.c | 48 ++------ > fs/cifs/sess.c | 2 +- > fs/cifs/transport.c | 344 ++++++++++++++++++++++---------------------------- > 9 files changed, 355 insertions(+), 271 deletions(-) > > -- > 1.7.3.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-cifs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > I am not sure if smb echo is a good indicator. What if server is so overloaded that smb echo may not get a response within its timeout period? Does not mean server is dead, it is just working its way up to respond to all the requests and if given enough time, will eventually respond, without any need to reconnect that connection (because smb echo was not echo'ed back in time). -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
