Remove the P_BUFEXHAUST flag from the syncer process (leaving

it only on the buf_daemon process). The problem is that when the
syncer process starts running the worklist, it wants to delete
lots of files. It does this by VFS_VGET'ing the vnodes, clearing
the blocks in them and bdwrite'ing the buffer. It can process close
to a thousand files per second which generates a large number of
dirty buffers. So, giving it special priviledge at the buffer trough
leads to trouble as the buf_daemon does occationally need a free
buffer to proceed and if the syncer has used every last one up,
we are toast.

sys/kern/vfs_export.c

@@ -981,8 +981,6 @@ sched_sync(void)
 	EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, p,
 	    SHUTDOWN_PRI_LAST);   
 
-	p->p_flag |= P_BUFEXHAUST;
-
 	for (;;) {
 		kproc_suspend_loop(p);
 

sys/kern/vfs_subr.c

@@ -981,8 +981,6 @@ sched_sync(void)
 	EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, p,
 	    SHUTDOWN_PRI_LAST);   
 
-	p->p_flag |= P_BUFEXHAUST;
-
 	for (;;) {
 		kproc_suspend_loop(p);