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 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. - 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
