3.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: NeilBrown commit 307729c8bc5b5a41361af8af95906eee7552acb1 upstream. We normally try to avoid reading from write-mostly devices, but when we do we really have to check for bad blocks and be sure not to try reading them. With the current code, best_good_sectors might not get set and that causes zero-length read requests to be send down which is very confusing. This bug was introduced in commit d2eb35acfdccbe2 and so the patch is suitable for 3.1.x and 3.2.x Reported-and-tested-by: Michał Mirosław Reported-and-tested-by: Art -kwaak- van Breemen Signed-off-by: NeilBrown Signed-off-by: Greg Kroah-Hartman --- drivers/md/raid1.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -508,8 +508,17 @@ static int read_balance(conf_t *conf, r1 if (test_bit(WriteMostly, &rdev->flags)) { /* Don't balance among write-mostly, just * use the first as a last resort */ - if (best_disk < 0) + if (best_disk < 0) { + if (is_badblock(rdev, this_sector, sectors, + &first_bad, &bad_sectors)) { + if (first_bad < this_sector) + /* Cannot use this */ + continue; + best_good_sectors = first_bad - this_sector; + } else + best_good_sectors = sectors; best_disk = disk; + } continue; } /* This is a reasonable device to use. It might