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Subject[039/129] md/raid1: perform bad-block tests for WriteMostly devices too.
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
Content-Length: 1469
Lines: 46
From: NeilBrown <neilb@suse.de>

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 <mirq-linux@rere.qmqm.pl>
Reported-and-tested-by: Art -kwaak- van Breemen <ard@telegraafnet.nl>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/md/raid1.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -525,8 +525,17 @@ static int read_balance(struct r1conf *c
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

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