On Thu, 2006-09-14 at 14:22 -0500, Mike Christie wrote: > Peter Zijlstra wrote: > > On Wed, 2006-09-13 at 15:50 -0500, Mike Christie wrote: > >> Peter Zijlstra wrote: > >>> Implement sht->swapdev() for iSCSI. This method takes care of reserving > >>> the extra memory needed and marking all relevant sockets with SOCK_VMIO. > >>> > >>> When used for swapping, TCP socket creation is done under GFP_MEMALLOC and > >>> the TCP connect is done with SOCK_VMIO to ensure their success. Also the > >>> netlink userspace interface is marked SOCK_VMIO, this will ensure that > >>> even > >>> under pressure we can still communicate with the daemon (which runs as > >>> mlockall() and needs no additional memory to operate). > >>> > >>> Netlink requests are handled under the new PF_MEM_NOWAIT when a swapper is > >>> present. This ensures that the netlink socket will not block. User-space > >>> will > >>> need to retry failed requests. > >>> > >>> The TCP receive path is handled under PF_MEMALLOC for SOCK_VMIO sockets. > >>> This makes sure we do not block the critical socket, and that we do not > >>> fail to process incomming data. > >>> > >>> Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]> > >>> CC: Mike Christie <[EMAIL PROTECTED]> > >>> --- > >>> drivers/scsi/iscsi_tcp.c | 103 > >>> +++++++++++++++++++++++++++++++----- > >>> drivers/scsi/scsi_transport_iscsi.c | 23 +++++++- > >>> include/scsi/libiscsi.h | 1 > >>> include/scsi/scsi_transport_iscsi.h | 2 > >>> 4 files changed, 113 insertions(+), 16 deletions(-) > >>> > >>> Index: linux-2.6/drivers/scsi/iscsi_tcp.c > >>> =================================================================== > >>> --- linux-2.6.orig/drivers/scsi/iscsi_tcp.c > >>> +++ linux-2.6/drivers/scsi/iscsi_tcp.c > >>> @@ -42,6 +42,7 @@ > >>> #include <scsi/scsi_host.h> > >>> #include <scsi/scsi.h> > >>> #include <scsi/scsi_transport_iscsi.h> > >>> +#include <scsi/scsi_device.h> > >>> > >>> #include "iscsi_tcp.h" > >>> > >>> @@ -845,9 +846,13 @@ iscsi_tcp_data_recv(read_descriptor_t *r > >>> int rc; > >>> struct iscsi_conn *conn = rd_desc->arg.data; > >>> struct iscsi_tcp_conn *tcp_conn = conn->dd_data; > >>> - int processed; > >>> + int processed = 0; > >>> char pad[ISCSI_PAD_LEN]; > >>> struct scatterlist sg; > >>> + unsigned long pflags = current->flags; > >>> + > >>> + if (sk_has_vmio(tcp_conn->sock->sk)) > >>> + current->flags |= PF_MEMALLOC; > >>> > >> Is this too late or not needed or what is it for? This function gets run > >> from the network layer's softirq and at this point we have a skbuff with > >> data that we want to process. The iscsi layer also does not allocate > >> memory for read or write IO in this path. > > > > I thought I found allocations in that path, lemme search... > > found this: > > > > iscsi_tcp_data_recv() > > iscsi_data_rescv() > > iscsi_complete_pdu() > > __iscsi_complete_pdu() > > iscsi_recv_pdu() > > alloc_skb( GFP_ATOMIC); > > > > You are right that is for the netlink interface. Could we move the > PF_MEMALLOC setting and clearing to iscsi_recv_pdu and and add it to > iscsi_conn_error in scsi_transport_iscsi.c so that iscsi_iser and > qla4xxx will have it set when they need it. I will send a patch for this > along with a way to have the netlink sock vmio set for all iscsi drivers > that need it.
I already have such a patch, look at: http://programming.kicks-ass.net/kernel-patches/vm_deadlock/current/iscsi_vmio.patch but what conditional do you want to use for PF_MEMALLOC, an unconditional setting will be highly unpopular. Hmm, perhaps you could key it of sk_has_vmio(nls)... > >> I think we would want to set this flag at a lower level. Something > >> closer to where the skbuf is allocated? > > > > Is that the skbuff you were talking about? If so, I'd need to carve a > > path to pass the swapper information. I had that in a previous patch, > > but that was large and ugly. I had to go carrying gfp_t flags all > > through that call chain. > > > > In my original post I was just concerned about the sk_buff that gets > passed to the iscsi layer in iscsi_tcp_data_recv. I was wondering if the > chunk of code in the network layer or network driver that allocated that > skbuff needed to set PF_MEMALLOC. (yeah I got that) No, that got allocated because its a receive skb and !sk_vmio_socks(), and got passed up because sk_has_vmio(iscsi_tcp_conn->sock->sk). - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
