From: Mike Snitzer Fix a regression in the calculation of the stripe_width in the dm stripe target which led to incorrect processing of device limits. The stripe_width is the stripe device length divided by the number of stripes. The group of commits in the range f14fa69 ("dm stripe: fix size test") to eb850de ("dm stripe: support for non power of 2 chunksize") interfered with each other (a merging error) and led to the stripe_width being set incorrectly to the stripe device length divided by chunk_size * stripe_count. For example, a stripe device's table with: 0 33553920 striped 3 512 ... should result in a stripe_width of 11184640 (33553920 / 3), but due to the bug it was getting set to 21845 (33553920 / (512 * 3)). The impact of this bug is that device topologies that previously worked fine with the stripe target are no longer considered valid. In particular, there is a higher risk of seeing this issue if one of the stripe devices has a 4K logical block size. Resulting in an error message like this: "device-mapper: table: 253:4: len=21845 not aligned to h/w logical block size 4096 of dm-1" The fix is to swap the order of the divisions and to use a temporary variable for the second one, so that width retains the intended value. Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org # 3.6+ Signed-off-by: Alasdair G Kergon --- drivers/md/dm-stripe.c | 7 ++++--- drivers/md/dm-stripe.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) Index: linux/drivers/md/dm-stripe.c =================================================================== --- linux.orig/drivers/md/dm-stripe.c +++ linux/drivers/md/dm-stripe.c @@ -94,7 +94,7 @@ static int get_stripe(struct dm_target * static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct stripe_c *sc; - sector_t width; + sector_t width, tmp_len; uint32_t stripes; uint32_t chunk_size; int r; @@ -116,15 +116,16 @@ static int stripe_ctr(struct dm_target * } width = ti->len; - if (sector_div(width, chunk_size)) { + if (sector_div(width, stripes)) { ti->error = "Target length not divisible by " - "chunk size"; + "number of stripes"; return -EINVAL; } - if (sector_div(width, stripes)) { + tmp_len = width; + if (sector_div(tmp_len, chunk_size)) { ti->error = "Target length not divisible by " - "number of stripes"; + "chunk size"; return -EINVAL; }