Patchwork [3.8.y.z,extended,stable] Patch "dm stripe: fix regression in stripe_width calculation" has been added to staging queue

login
register
mail settings
Submitter Kamal Mostafa
Date May 22, 2013, 9:55 p.m.
Message ID <1369259727-25260-1-git-send-email-kamal@canonical.com>
Download mbox | patch
Permalink /patch/245741/
State New
Headers show

Comments

Kamal Mostafa - May 22, 2013, 9:55 p.m.
This is a note to let you know that I have just added a patch titled

    dm stripe: fix regression in stripe_width calculation

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

From d94d4790e795508f58d7d701f25566b2fe66aa42 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Fri, 10 May 2013 14:37:14 +0100
Subject: dm stripe: fix regression in stripe_width calculation

commit d793e684277124d55c5d2444007e224635821346 upstream.

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 <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/md/dm-stripe.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--
1.8.1.2

Patch

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index aaecefa..852eab4 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -94,7 +94,7 @@  static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
 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 *ti, unsigned int argc, char **argv)
 	}

 	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;
 	}