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[SCSI] libfc, fcoe: fixed locking issues with lport->lp_mutex around lport->link_status

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The fcoe_xmit could call fc_pause in case the pending skb queue len is larger
than FCOE_MAX_QUEUE_DEPTH, the fc_pause was trying to grab lport->lp_muex to
change lport->link_status and that had these issues :-

1. The fcoe_xmit was getting called with bh disabled, thus causing
"BUG: scheduling while atomic" when grabbing lport->lp_muex with bh disabled.

2. fc_linkup and fc_linkdown function calls lport_enter function with
lport->lp_mutex held and these enter function in turn calls fcoe_xmit to send
lport related FC frame, e.g. fc_linkup => fc_lport_enter_flogi to send flogi
req. In this case grabbing the same lport->lp_mutex again in fc_puase from
fcoe_xmit would cause deadlock.

The lport->lp_mutex was used for setting FC_PAUSE in fcoe_xmit path but
FC_PAUSE bit was not used anywhere beside just setting and clear this
bit in lport->link_status, instead used a separate field qfull in fc_lport
to eliminate need for lport->lp_mutex to track pending queue full condition
and in turn avoid above described two locking issues.

Also added check for lp->qfull in fc_fcp_lport_queue_ready to trigger
SCSI_MLQUEUE_HOST_BUSY when lp->qfull is set to prevent more scsi-ml cmds
while lp->qfull is set.

This patch eliminated FC_LINK_UP and FC_PAUSE and instead used dedicated
fields in fc_lport for this, this simplified all related conditional
code.

Also removed fc_pause and fc_unpause functions and instead used newly added
lport->qfull directly in fcoe.

Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Vasu Dev
2009-02-27 10:54:57 -08:00
committed by James Bottomley
parent a7e84f2b83
commit bc0e17f691
5 changed files with 30 additions and 69 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
drivers/scsi/fcoe/libfcoe.c
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@@ -504,7 +504,7 @@ int fcoe_xmit(struct fc_lport *lp, struct fc_frame *fp)
if (rc) {
fcoe_insert_wait_queue(lp, skb);
if (fc->fcoe_pending_queue.qlen > FCOE_MAX_QUEUE_DEPTH)
fc_pause(lp);
lp->qfull = 1;
}
return 0;
@@ -718,7 +718,7 @@ static void fcoe_recv_flogi(struct fcoe_softc *fc, struct fc_frame *fp, u8 *sa)
* fcoe_watchdog - fcoe timer callback
* @vp:
*
* This checks the pending queue length for fcoe and put fcoe to be paused state
* This checks the pending queue length for fcoe and set lport qfull
* if the FCOE_MAX_QUEUE_DEPTH is reached. This is done for all fc_lport on the
* fcoe_hostlist.
*
@@ -728,17 +728,17 @@ void fcoe_watchdog(ulong vp)
{
struct fc_lport *lp;
struct fcoe_softc *fc;
int paused = 0;
int qfilled = 0;
read_lock(&fcoe_hostlist_lock);
list_for_each_entry(fc, &fcoe_hostlist, list) {
lp = fc->lp;
if (lp) {
if (fc->fcoe_pending_queue.qlen > FCOE_MAX_QUEUE_DEPTH)
paused = 1;
qfilled = 1;
if (fcoe_check_wait_queue(lp) < FCOE_MAX_QUEUE_DEPTH) {
if (paused)
fc_unpause(lp);
if (qfilled)
lp->qfull = 0;
}
}
}
@@ -767,8 +767,7 @@ void fcoe_watchdog(ulong vp)
**/
static int fcoe_check_wait_queue(struct fc_lport *lp)
{
int rc, unpause = 0;
int paused = 0;
int rc;
struct sk_buff *skb;
struct fcoe_softc *fc;
@@ -776,10 +775,10 @@ static int fcoe_check_wait_queue(struct fc_lport *lp)
spin_lock_bh(&fc->fcoe_pending_queue.lock);
/*
* is this interface paused?
* if interface pending queue full then set qfull in lport.
*/
if (fc->fcoe_pending_queue.qlen > FCOE_MAX_QUEUE_DEPTH)
paused = 1;
lp->qfull = 1;
if (fc->fcoe_pending_queue.qlen) {
while ((skb = __skb_dequeue(&fc->fcoe_pending_queue)) != NULL) {
spin_unlock_bh(&fc->fcoe_pending_queue.lock);
@@ -791,11 +790,9 @@ static int fcoe_check_wait_queue(struct fc_lport *lp)
spin_lock_bh(&fc->fcoe_pending_queue.lock);
}
if (fc->fcoe_pending_queue.qlen < FCOE_MAX_QUEUE_DEPTH)
unpause = 1;
lp->qfull = 0;
}
spin_unlock_bh(&fc->fcoe_pending_queue.lock);
if ((unpause) && (paused))
fc_unpause(lp);
return fc->fcoe_pending_queue.qlen;
}
@@ -873,7 +870,7 @@ static int fcoe_device_notification(struct notifier_block *notifier,
struct net_device *real_dev = ptr;
struct fcoe_softc *fc;
struct fcoe_dev_stats *stats;
u16 new_status;
u32 new_link_up;
u32 mfs;
int rc = NOTIFY_OK;
@@ -890,17 +887,15 @@ static int fcoe_device_notification(struct notifier_block *notifier,
goto out;
}
new_status = lp->link_status;
new_link_up = lp->link_up;
switch (event) {
case NETDEV_DOWN:
case NETDEV_GOING_DOWN:
new_status &= ~FC_LINK_UP;
new_link_up = 0;
break;
case NETDEV_UP:
case NETDEV_CHANGE:
new_status &= ~FC_LINK_UP;
if (!fcoe_link_ok(lp))
new_status |= FC_LINK_UP;
new_link_up = !fcoe_link_ok(lp);
break;
case NETDEV_CHANGEMTU:
mfs = fc->real_dev->mtu -
@@ -908,17 +903,15 @@ static int fcoe_device_notification(struct notifier_block *notifier,
sizeof(struct fcoe_crc_eof));
if (mfs >= FC_MIN_MAX_FRAME)
fc_set_mfs(lp, mfs);
new_status &= ~FC_LINK_UP;
if (!fcoe_link_ok(lp))
new_status |= FC_LINK_UP;
new_link_up = !fcoe_link_ok(lp);
break;
case NETDEV_REGISTER:
break;
default:
FC_DBG("unknown event %ld call", event);
}
if (lp->link_status != new_status) {
if ((new_status & FC_LINK_UP) == FC_LINK_UP)
if (lp->link_up != new_link_up) {
if (new_link_up)
fc_linkup(lp);
else {
stats = lp->dev_stats[smp_processor_id()];