lafs_space_alloc - avoid underflow of unsigned numbers

As the numbers in the calc are unsigned, use only additions
to avoid anything going negative.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/segments.c b/segments.c
index 4e2ae3a3c9cb1f069251f60bd3058d2528b82f2c..ffed5c426864aa9ea779ea278ae6aaff3d33f422 100644 (file)
--- a/segments.c
+++ b/segments.c
@@ -615,8 +615,8 @@ int lafs_space_alloc(struct fs *fs, int credits, int why)
                                   * EAGAIN, so never return it
                                   */
                if (fs->rolled) {
-                       if (fs->free_blocks - fs->allocated_blocks
-                           - credits < watermark)
+                       if (fs->free_blocks < fs->allocated_blocks
+                           + credits + watermark)
                                credits = 0; /* Sorry, no room */
                }
        }