Messages in this thread | | | Subject | Re: [PATCH 20/20] iscsi: support for swapping over iSCSI. | From | Peter Zijlstra <> | Date | Thu, 14 Sep 2006 08:17:30 +0200 |
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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 <a.p.zijlstra@chello.nl> > > CC: Mike Christie <michaelc@cs.wisc.edu> > > --- > > 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);
> 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.
I could try again if you prefer that.
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