[PATCH 0/2] iscsi changes for scsi misc

[PATCH 0/2] iscsi changes for scsi misc

[michaelc]

The following 2 patches are for the misc branch in the scsi tree.
They cleanup duplicated code from a previous patch and add
better support for swap over software iscsi by using the
PF_MEMALLOC/__GFP_MEMALLOC flags like what was recently added for
nbd.

[PATCH 1/2] libiscsi: avoid unnecessary multiple NULL assignments

[michaelc]

From: Masatake YAMATO <yamato@redhat.com>

In iscsi_free_task, NULL is assigned to task->sc twice: before and
after kfifo_in invocatoin. Allocating and freeing iscsi_task are guarded
with session->lock, so multiple NULL assignments cause no trouble. But
people reading the source code may be confused.

The second NULL assignment comes from commit:

    3e5c28ad0391389959ccae81c938c7533efb3490

It seems that the line after kfifo_in invocation was introduced
accidentally.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
---
 drivers/scsi/libiscsi.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index d5e5c44..5de9469 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -507,7 +507,6 @@ static void iscsi_free_task(struct iscsi_task *task)
 	kfifo_in(&session->cmdpool.queue, (void*)&task, sizeof(void*));
 
 	if (sc) {
-		task->sc = NULL;
 		/* SCSI eh reuses commands to verify us */
 		sc->SCp.ptr = NULL;
 		/*
-- 
1.7.1

[PATCH 2/2] iscsi_tcp: support PF_MEMALLOC/__GFP_MEMALLOC

[michaelc]

From: Mike Christie <michaelc@cs.wisc.edu>

This patch has software iscsi use PF_MEMALLOC/__GFP_MEMALLOC
to be able to better support swap over iscsi disks similar to
what was added for nbd.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
---
 drivers/scsi/iscsi_tcp.c |   18 +++++++++++++-----
 1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 1b91ca0..9e2588a 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -370,17 +370,24 @@ static inline int iscsi_sw_tcp_xmit_qlen(struct iscsi_conn *conn)
 static int iscsi_sw_tcp_pdu_xmit(struct iscsi_task *task)
 {
 	struct iscsi_conn *conn = task->conn;
-	int rc;
+	unsigned long pflags = current->flags;
+	int rc = 0;
+
+	current->flags |= PF_MEMALLOC;
 
 	while (iscsi_sw_tcp_xmit_qlen(conn)) {
 		rc = iscsi_sw_tcp_xmit(conn);
-		if (rc == 0)
-			return -EAGAIN;
+		if (rc == 0) {
+			rc = -EAGAIN;
+			break;
+		}
 		if (rc < 0)
-			return rc;
+			break;
+		rc = 0;
 	}
 
-	return 0;
+	tsk_restore_flags(current, pflags, PF_MEMALLOC);
+	return rc;
 }
 
 /*
@@ -665,6 +672,7 @@ iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
 	sk->sk_reuse = SK_CAN_REUSE;
 	sk->sk_sndtimeo = 15 * HZ; /* FIXME: make it configurable */
 	sk->sk_allocation = GFP_ATOMIC;
+	sk_set_memalloc(sk);
 
 	iscsi_sw_tcp_conn_set_callbacks(conn);
 	tcp_sw_conn->sendpage = tcp_sw_conn->sock->ops->sendpage;
-- 
1.7.1

Re: [PATCH 1/2] libiscsi: avoid unnecessary multiple NULL assignments

[Mike Christie]

On 04/10/2013 11:24 AM, michaelc@cs.wisc.edu wrote:
> From: Masatake YAMATO <yamato@redhat.com>
> 
> In iscsi_free_task, NULL is assigned to task->sc twice: before and
> after kfifo_in invocatoin. Allocating and freeing iscsi_task are guarded
> with session->lock, so multiple NULL assignments cause no trouble. But
> people reading the source code may be confused.
> 
> The second NULL assignment comes from commit:
> 
>     3e5c28ad0391389959ccae81c938c7533efb3490
> 
> It seems that the line after kfifo_in invocation was introduced
> accidentally.
> 
> Signed-off-by: Masatake YAMATO <yamato@redhat.com>
> Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
> Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>

Sorry about the incorrect signed of chain James. When I sent/made the
patches I added both a reviewed-by and signed-off to this one by accident.

Masatake made the patch. I am just resending to the list.