Added exch lock for callers of exch_get()/fc_exch_alloc() to
prevent fc_exch_reset() from freeing exch while these callers
are is still working on just allocated exch.
This change impacted fc_exch_resp() call flow also
since fc_exch_resp() allocats new exchange, this patch
made fc_exch_resp() similar to fc_exch_find()
in terms of exch ref counting by having additional exch
ref to caller of fc_exch_resp() before dropping exch lock
from exchange allocation. This would allow fc_exch_reset()
running in fc_exch_resp() callers without exch being freed
by fc_exch_reset() while caller of fc_exch_resp() are still
working on exch.
This patch also associated exch hold from fc_exch_alloc()
to exch pointer in mp and then called fc_exch_release()
after removing exch pointer in mp to drop this hold
in fc_exch_mgr_delete_ep(). This change eliminated need
for extra exch hold in some error cases such as error
handling case in fc_exch_seq_send() and also removed
exch ref decrement without test in fc_exch_done_locked().
Signed-off-by: Vasu Dev <[EMAIL PROTECTED]>
---
drivers/scsi/libfc/fc_exch.c | 28 +++++++++++++++++++---------
1 files changed, 19 insertions(+), 9 deletions(-)
diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index f307008..3a630c5 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -322,7 +322,6 @@ static int fc_exch_done_locked(struct fc_exch *ep)
ep->state |= FC_EX_DONE;
if (del_timer(&ep->ex_timer))
atomic_dec(&ep->ex_refcnt); /* drop hold for timer */
- atomic_dec(&ep->ex_refcnt); /* drop hold from alloc */
rc = 0;
}
return rc;
@@ -339,6 +338,7 @@ static void fc_exch_mgr_delete_ep(struct fc_exch *ep)
mp->exches[ep->xid - mp->min_xid] = NULL;
list_del(&ep->ex_list);
spin_unlock_bh(&mp->em_lock);
+ fc_exch_release(ep); /* drop hold for exch in mp */
}
/*
@@ -553,6 +553,7 @@ struct fc_exch *fc_exch_alloc(struct fc_exch_mgr *mp, u16
xid)
fc_seq_alloc(ep, ep->seq_id++);
mp->total_exches++;
spin_unlock_bh(&mp->em_lock);
+ fc_exch_hold(ep); /* hold for exch in mp */
/*
* update exchange
@@ -567,7 +568,12 @@ struct fc_exch *fc_exch_alloc(struct fc_exch_mgr *mp, u16
xid)
spin_lock_init(&ep->ex_lock);
setup_timer(&ep->ex_timer, fc_exch_timeout, (unsigned long)ep);
- fc_exch_hold(ep); /* hold for caller */
+ /*
+ * Hold exch lock for caller to prevent
+ * fc_exch_reset() from releasing exch
+ * while caller is still working on exch.
+ */
+ spin_lock_bh(&ep->ex_lock);
out:
return ep;
}
@@ -652,6 +658,8 @@ static struct fc_exch *fc_exch_resp(struct fc_exch_mgr *mp,
struct fc_frame *fp)
WARN_ON(rxid != FC_XID_UNKNOWN);
fh->fh_rx_id = htons(ep->rxid);
}
+ fc_exch_hold(ep); /* hold for caller */
+ spin_unlock_bh(&ep->ex_lock); /* lock from exch_get */
}
return ep;
}
@@ -665,7 +673,7 @@ static enum fc_pf_rjt_reason
fc_seq_lookup_recip(struct fc_exch_mgr *mp, struct fc_frame *fp)
{
struct fc_frame_header *fh = fc_frame_header_get(fp);
- struct fc_exch *ep = NULL, *new_ep = NULL;
+ struct fc_exch *ep = NULL;
struct fc_seq *sp = NULL;
enum fc_pf_rjt_reason reject = FC_RJT_NONE;
u32 f_ctl;
@@ -715,7 +723,7 @@ fc_seq_lookup_recip(struct fc_exch_mgr *mp, struct fc_frame
*fp)
reject = FC_RJT_RX_ID;
goto rel;
}
- new_ep = ep = fc_exch_resp(mp, fp);
+ ep = fc_exch_resp(mp, fp);
if (!ep) {
reject = FC_RJT_EXCH_EST; /* XXX */
goto out;
@@ -758,9 +766,8 @@ fc_seq_lookup_recip(struct fc_exch_mgr *mp, struct fc_frame
*fp)
out:
return reject;
rel:
- fc_exch_release(ep);
- if (new_ep)
- fc_exch_release(new_ep);
+ fc_exch_done(&ep->seq);
+ fc_exch_release(ep); /* hold from fc_exch_find/fc_exch_resp */
return reject;
}
@@ -1850,6 +1857,7 @@ struct fc_seq *fc_exch_seq_send(struct fc_lport *lp,
struct fc_seq *sp = NULL;
struct fc_frame_header *fh;
u16 fill;
+ int rc = 1;
ep = lp->tt.exch_get(lp, fp);
if (!ep) {
@@ -1895,7 +1903,6 @@ struct fc_seq *fc_exch_seq_send(struct fc_lport *lp,
if (unlikely(lp->tt.frame_send(lp, fp)))
goto err;
- spin_lock_bh(&ep->ex_lock);
if (timer_msec)
fc_exch_timer_set_locked(ep, timer_msec);
sp->f_ctl = f_ctl; /* save for possible abort */
@@ -1907,7 +1914,10 @@ struct fc_seq *fc_exch_seq_send(struct fc_lport *lp,
spin_unlock_bh(&ep->ex_lock);
return sp;
err:
- fc_exch_done(sp);
+ rc = fc_exch_done_locked(ep);
+ spin_unlock_bh(&ep->ex_lock);
+ if (!rc)
+ fc_exch_mgr_delete_ep(ep);
return NULL;
}
EXPORT_SYMBOL(fc_exch_seq_send);
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