md/raid10: fix "enough" function for detecting if array is failed.
NeilBrown [Thu, 27 Sep 2012 02:35:21 +0000 (12:35 +1000)]
The 'enough' function is written to work with 'near' arrays only
in that is implicitly assumes that the offset from one 'group' of
devices to the next is the same as the number of copies.
In reality it is the number of 'near' copies.

So change it to make this number explicit.

This bug makes it possible to run arrays without enough drives
present, which is dangerous.
It is appropriate for an -stable kernel, but will almost certainly
need to be modified for some of them.

Cc: stable@vger.kernel.org
Reported-by: Jakub Hus├ík <jakub@gooseman.cz>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid10.c

index 1c2eb38..0138a72 100644 (file)
@@ -1512,14 +1512,16 @@ static int _enough(struct r10conf *conf, struct geom *geo, int ignore)
        do {
                int n = conf->copies;
                int cnt = 0;
+               int this = first;
                while (n--) {
-                       if (conf->mirrors[first].rdev &&
-                           first != ignore)
+                       if (conf->mirrors[this].rdev &&
+                           this != ignore)
                                cnt++;
-                       first = (first+1) % geo->raid_disks;
+                       this = (this+1) % geo->raid_disks;
                }
                if (cnt == 0)
                        return 0;
+               first = (first + geo->near_copies) % geo->raid_disks;
        } while (first != 0);
        return 1;
 }