--- IO-AIO/AIO.xs	2012/04/06 11:39:25	1.210
+++ IO-AIO/AIO.xs	2012/04/07 00:50:33	1.211
@@ -166,25 +166,16 @@
   req->result = -1;
 
 #if HAVE_FIEMAP
-  for (;;)
-    {
-      int count = req->int3;
-
-      if (count < 0)
-        {
-          struct fiemap fiemap;
-
-          fiemap.fm_start        = req->offs;
-          fiemap.fm_length       = req->size;
-          fiemap.fm_flags        = req->int2;
-          fiemap.fm_extent_count = 0;
+  int count = req->int3;
 
-          if (ioctl (req->int1, FS_IOC_FIEMAP, &fiemap))
-            return;
-
-          count = fiemap.fm_mapped_extents;
-        }
+  /* heuristic: first try with 64 extents if we don't know how many, */
+  /* as most files have (hopefully) fewer than this many extents */
+  /* in fact, most should have <= 2, so maybe the 72 below is probably overkill */
+  if (count < 0)
+    count = 72; /* for what it's worth, 72 extents fit nicely into 4kb */
 
+  for (;;)
+    {
       struct fiemap *fiemap = malloc (sizeof (*fiemap) + sizeof (struct fiemap_extent) * count);
       errno = ENOMEM;
       if (!fiemap)
@@ -207,6 +198,14 @@
       if (fiemap->fm_extents [fiemap->fm_mapped_extents - 1].fe_flags & FIEMAP_EXTENT_LAST)
         break; /* autosizing successful, we are done */
 
+      fiemap->fm_flags        = req->int2;
+      fiemap->fm_extent_count = 0;
+
+      if (ioctl (req->int1, FS_IOC_FIEMAP, fiemap))
+        return;
+
+      count = fiemap->fm_mapped_extents;
+
       free (fiemap);
     }
 
@@ -547,6 +546,7 @@
           case EIO_CUSTOM:
             if (req->feed == fiemap)
               {
+#if HAVE_FIEMAP
                 if (!req->result)
                   {
                     struct fiemap *fiemap = (struct fiemap *)req->ptr1;
@@ -577,6 +577,7 @@
                         PUSHs (sv_result);
                       }
                   }
+#endif
               }
             else
               PUSHs (sv_result);
@@ -1166,7 +1167,6 @@
 aio_seek (SV *fh, SV *offset, int whence, SV *callback=&PL_sv_undef)
         PPCODE:
 {
-        STRLEN svlen;
         int fd = s_fileno_croak (fh, 0);
         dREQ;
 
@@ -1528,11 +1528,13 @@
         req->int1 = fd;
 
         req->feed = fiemap;
+#if HAVE_FIEMAP
         /* keep our fingers crossed that the next two types are 64 bit */
         req->offs = start;
         req->size = SvOK (length) ? SvVAL64 (length) : ~0ULL;
         req->int2 = flags;
         req->int3 = SvOK (count) ? SvIV (count) : -1;
+#endif
 
 	REQ_SEND;
 }