1 files changed, 63 insertions, 54 deletions

diff --git a/libhurd-mm/madvise.c b/libhurd-mm/madvise.c
index d3985c2..b9494cd 100644
--- a/libhurd-mm/madvise.c
+++ b/libhurd-mm/madvise.c
@@ -31,6 +31,8 @@
 int
 madvise (void *addr, size_t length, int advice)
 {
+  debug (5, "(%p, %x, %d)", addr, length, advice);
+
   if (((uintptr_t) addr & (PAGESIZE - 1)) != 0)
     {
       debug (0, "Address %x not multiple of pagesize.", addr);
@@ -68,65 +70,72 @@ madvise (void *addr, size_t length, int advice)
 
   struct region region = { (uintptr_t) addr, length };
 
+  debug (5, "Region: %x-%x",
+	 region.start, region.start + region.length - 1);
+
   maps_lock_lock ();
 
-  /* Find any pager that overlaps within the designated region.  */
-  struct map *map = map_find (region);
-  if (! map)
-    /* There are none.  We're done.  */
+  /* Find the first map that overlaps with the designated region.  */
+  struct map *map;
+  while (region.length > 0
+	 && (map = hurd_btree_map_find_first (&maps, &region)))
     {
-      maps_lock_unlock ();
-      return 0;
+      uintptr_t map_start = map->region.start;
+      uintptr_t map_end = map_start + map->region.length - 1;
+
+      debug (5, "(%x-%x): considering %x-%x",
+	     start, end, map_start, map_end);
+
+      /*
+	map_start/map->offset                map_end
+	/   \                           /  \
+	v     v                         v    v
+	+------------------------------------+
+	|                                    | <- pager
+	+------------------------------------+
+
+	^     ^     ^                        ^     ^     ^
+	\    |    /                          \    |   /
+	start                                 end
+
+      */
+      uintptr_t s = map->offset;
+      uintptr_t l = map->region.length;
+      if (start > map_start)
+	{
+	  s += start - map_start;
+	  l -= start - map_start;
+	}
+      if (end < map_end)
+	l -= map_end - end;
+
+      /* Advance region to just after MAP.  */
+      if (map_end >= region.start + region.length)
+	region.length = 0;
+      else
+	{
+	  region.length -= map_end - region.start + 1;
+	  region.start += map_end - region.start + 1;
+	}
+
+      struct pager *pager = map->pager;
+      if (pager->advise)
+	{
+	  maps_lock_unlock ();
+	  pager->advise (map->pager, s, l, advice);
+
+	  /* If REGION.LENGTH is zero, don't bother to retake the
+	     lock: we are done.  */
+	  if (region.length > 0)
+	    maps_lock_lock ();
+	  else
+	    return 0;
+	}
+
+      debug (5, "Region: %x-%x",
+	     region.start, region.start + region.length - 1);
     }
 
-  /* There may be pagers that come lexically before as well as after
-     PAGER.  We start with PAGER and scan forward and then do the same
-     but scan backwards.  */
-  struct map *prev = hurd_btree_map_prev (map);
-
-  int dir;
-  for (dir = 0; dir < 2; dir ++, map = prev)
-    for (;
-	 map;
-	 map = (dir == 0 ? hurd_btree_map_next (map)
-		: hurd_btree_map_prev (map)))
-      {
-	uintptr_t map_start = map->region.start;
-	uintptr_t map_end = map_start + map->region.length - 1;
-
-	debug (5, "(%x-%x): considering %x-%x",
-	       start, end, map_start, map_end);
-
-	if (map_start > end || map_end < start)
-	  break;
-
-	/*
-	    map_start/map->offset                map_end
-                   /   \                           /  \
-                  v     v                         v    v
-	          +------------------------------------+
-	          |                                    | <- pager
-	          +------------------------------------+
-
-            ^     ^     ^                        ^     ^     ^
-	     \    |    /                          \    |   /
-                start                                 end
-
-	 */
-	uintptr_t s = map->offset;
-	uintptr_t l = map->region.length;
-	if (start > map_start)
-	  {
-	    s += start - map_start;
-	    l -= start - map_start;
-	  }
-	if (end < map_end)
-	  l -= map_end - end;
-
-	if (map->pager->advise)
-	  map->pager->advise (map->pager, s, l, advice);
-      }
-
   maps_lock_unlock ();
 
   return 0;