md: raid5: avoid sector values going negative when testing reshape pr…

…ogress. As sector_t in unsigned, we cannot afford to let 'safepos' etc go negative. So replace a -= b; by a -= min(b,a); Signed-off-by: NeilBrown <[email protected]>
berg · May 26, 2009 · 848b318 · 848b318
1 parent b6a9ce6
commit 848b318
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
@@ -3811,13 +3811,13 @@ static sector_t reshape_request(mddev_t *mddev, sector_t sector_nr, int *skipped
 	safepos = conf->reshape_safe;
 	sector_div(safepos, data_disks);
 	if (mddev->delta_disks < 0) {
-		writepos -= reshape_sectors;
+		writepos -= min(reshape_sectors, writepos);
 		readpos += reshape_sectors;
 		safepos += reshape_sectors;
 	} else {
 		writepos += reshape_sectors;
-		readpos -= reshape_sectors;
-		safepos -= reshape_sectors;
+		readpos -= min(reshape_sectors, readpos);
+		safepos -= min(reshape_sectors, safepos);
 	}
 
 	/* 'writepos' is the most advanced device address we might write.