From: NeilBrown <neilb@suse.de>
Date: Wed, 23 Jun 2010 01:52:00 +0000 (+1000)
Subject: lafs_space_alloc - avoid underflow of unsigned numbers
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=b1131836a7cf73af33ccacc73b29a2bde11f417c;p=LaFS.git

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 4e2ae3a..ffed5c4 100644
--- 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 */
 		}
 	}