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-rw-r--r--support/support_descriptor_supports_holes.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/support/support_descriptor_supports_holes.c b/support/support_descriptor_supports_holes.c
index fc2aa76f10..d3d5d3a938 100644
--- a/support/support_descriptor_supports_holes.c
+++ b/support/support_descriptor_supports_holes.c
@@ -34,8 +34,10 @@ support_descriptor_supports_holes (int fd)
       write_offset = 16 * 1024 * 1024,
 
       /* Our write may add this number of additional blocks (see
-         block_limit below).  */
-      block_headroom = 8,
+         block_limit below): writing at offset 16M can require two data block
+         indirections, each of which can be as large as 8KB on ext2, thus 32
+         512B sectors.  */
+      block_headroom = 32,
     };
 
   struct stat64 st;