Use spin_lock_bh on recinf->lock to fix softirq deadlock

timer_callback() runs in softirq context and acquires recinf->lock,
but the process-context callers (scoutfs_recov_prepare, _begin,
_finish, _is_pending, _next_pending, _shutdown) were taking the
same lock with plain spin_lock(), leaving softirqs enabled. Found
by Lockdep:

```
	================================
	WARNING: inconsistent lock state
	5.14.0-427.35.1.el9_4.x86_64+debug #1 Tainted: G           OE     -------  ---
	--------------------------------
	inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
	swapper/2/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
	ffff88813cdd9c20 (&recinf->lock){+.?.}-{2:2}, at: timer_callback+0x26/0x380 [scoutfs]
	{SOFTIRQ-ON-W} state was registered at:
	  __lock_acquire+0x7d0/0x1900
	  lock_acquire+0x1da/0x640
	  _raw_spin_lock+0x34/0x80
	  scoutfs_recov_finish+0x80/0x830 [scoutfs]
	  server_greeting+0x244/0xe60 [scoutfs]
	  scoutfs_net_proc_worker+0x28a/0xce0 [scoutfs]
	  recv_one_message+0x7e3/0xd10 [scoutfs]
	  scoutfs_net_recv_worker+0x441/0xe00 [scoutfs]
	  process_one_work+0x8e5/0x1530
	  worker_thread+0x598/0xf70
	  kthread+0x2a4/0x350
	  ret_from_fork+0x29/0x50
	irq event stamp: 549813370
	hardirqs last  enabled at (549813370): [<ffffffffabe25cb4>] _raw_spin_unlock_irq+0x24/0x50
	hardirqs last disabled at (549813369): [<ffffffffabe2594e>] _raw_spin_lock_irq+0x5e/0x90
	softirqs last  enabled at (549813356): [<ffffffffabe28c91>] __do_softirq+0x621/0x9c2
	softirqs last disabled at (549813363): [<ffffffffa9a44665>] __irq_exit_rcu+0x185/0x230

	other info that might help us debug this:
	 Possible unsafe locking scenario:
	       CPU0
	       ----
	  lock(&recinf->lock);
	  <Interrupt>
	    lock(&recinf->lock);

	 *** DEADLOCK ***
```

Convert the six process-context sites to spin_lock_bh()/spin_unlock_bh().

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/recov.c

@@ -103,7 +103,7 @@ int scoutfs_recov_prepare(struct super_block *sb, u64 rid, int which)
 	if (!alloc)
 		return -ENOMEM;
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 
 	pend = lookup_pending(recinf, rid, SCOUTFS_RECOV_ALL);
 	if (pend) {
@@ -116,7 +116,7 @@ int scoutfs_recov_prepare(struct super_block *sb, u64 rid, int which)
 		list_sort(NULL, &recinf->pending, cmp_pending_rid);
 	}
 
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	kfree(alloc);
 	return 0;
@@ -153,7 +153,7 @@ int scoutfs_recov_begin(struct super_block *sb, void (*timeout_fn)(struct super_
 	DECLARE_RECOV_INFO(sb, recinf);
 	int ret;
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 
 	recinf->timeout_fn = timeout_fn;
 	recinf->timer.expires = jiffies + msecs_to_jiffies(timeout_ms);
@@ -161,7 +161,7 @@ int scoutfs_recov_begin(struct super_block *sb, void (*timeout_fn)(struct super_
 
 	ret = recov_finished(recinf);
 
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	if (ret > 0)
 		del_timer_sync(&recinf->timer);
@@ -183,7 +183,7 @@ int scoutfs_recov_finish(struct super_block *sb, u64 rid, int which)
 	struct recov_pending *pend;
 	int ret = 0;
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 
 	pend = lookup_pending(recinf, rid, which);
 	if (pend) {
@@ -196,7 +196,7 @@ int scoutfs_recov_finish(struct super_block *sb, u64 rid, int which)
 		}
 	}
 
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	if (ret > 0)
 		del_timer_sync(&recinf->timer);
@@ -215,9 +215,9 @@ bool scoutfs_recov_is_pending(struct super_block *sb, u64 rid, int which)
 	DECLARE_RECOV_INFO(sb, recinf);
 	bool is_pending;
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 	is_pending = lookup_pending(recinf, rid, which) != NULL;
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	return is_pending;
 }
@@ -236,10 +236,10 @@ u64 scoutfs_recov_next_pending(struct super_block *sb, u64 rid, int which)
 	DECLARE_RECOV_INFO(sb, recinf);
 	struct recov_pending *pend;
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 	pend = next_pending(recinf, rid, which);
 	rid = pend ? pend->rid : 0;
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	return rid;
 }
@@ -257,10 +257,10 @@ void scoutfs_recov_shutdown(struct super_block *sb)
 
 	del_timer_sync(&recinf->timer);
 
-	spin_lock(&recinf->lock);
+	spin_lock_bh(&recinf->lock);
 	list_splice_init(&recinf->pending, &list);
 	recinf->timeout_fn = NULL;
-	spin_unlock(&recinf->lock);
+	spin_unlock_bh(&recinf->lock);
 
 	list_for_each_entry_safe(pend, tmp, &list, head) {
 		list_del(&pend->head);