fix partmap_load(size=0), because mmap fails on that since Linux 2.6.12

diff --git a/ucw/partmap.c b/ucw/partmap.c
index 93a7e1ba02689b5c3bd4a0f0c5e6c43b81b45db1..a823d3d157fa29d1355db9c68ad5bd040b83f5c6 100644 (file)
--- a/ucw/partmap.c
+++ b/ucw/partmap.c
@@ -2,7 +2,7 @@
  *     UCW Library -- Mapping of File Parts
  *
  *     (c) 2003--2006 Martin Mares <mj@ucw.cz>
- *     (c) 2003--2005 Robert Spalek <robert@ucw.cz>
+ *     (c) 2003--2009 Robert Spalek <robert@ucw.cz>
  *
  *     This software may be freely distributed and used according to the terms
  *     of the GNU Lesser General Public License.
@@ -69,13 +69,18 @@ partmap_load(struct partmap *p, ucw_off_t start, uns size)
   ucw_off_t end = start + size;
   ucw_off_t win_start = start/CPU_PAGE_SIZE * CPU_PAGE_SIZE;
   size_t win_len = PARTMAP_WINDOW;
-  if (win_len > p->file_size - win_start)
+  if (win_len > (size_t) (p->file_size - win_start))
     win_len = ALIGN_TO(p->file_size - win_start, CPU_PAGE_SIZE);
   if ((ucw_off_t) (win_start+win_len) < end)
     die("partmap_map: Window is too small for mapping %d bytes", size);
-  p->start_map = ucw_mmap(NULL, win_len, p->writeable ? (PROT_READ | PROT_WRITE) : PROT_READ, MAP_SHARED, p->fd, win_start);
-  if (p->start_map == MAP_FAILED)
-    die("mmap failed at position %lld: %m", (long long)win_start);
+  if (win_len)
+    {
+      p->start_map = ucw_mmap(NULL, win_len, p->writeable ? (PROT_READ | PROT_WRITE) : PROT_READ, MAP_SHARED, p->fd, win_start);
+      if (p->start_map == MAP_FAILED)
+       die("mmap failed at position %lld: %m", (long long)win_start);
+    }
+  else
+    p->start_map = NULL;
   p->start_off = win_start;
   p->end_off = win_start+win_len;
   madvise(p->start_map, win_len, MADV_SEQUENTIAL);