[3.5.y.z extended stable] Patch "block: properly stack underlying max_segment_size to DM device" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Fri Nov 29 14:02:34 UTC 2013

This is a note to let you know that I have just added a patch titled

    block: properly stack underlying max_segment_size to DM device

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


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

For more information about the 3.5.y.z tree, see



>From 8a71633edf3591e95c8f3ab4c0ec369dedc157c1 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer at redhat.com>
Date: Fri, 18 Oct 2013 09:44:49 -0600
Subject: block: properly stack underlying max_segment_size to DM device

commit d82ae52e68892338068e7559a0c0657193341ce4 upstream.

Without this patch all DM devices will default to BLK_MAX_SEGMENT_SIZE
(65536) even if the underlying device(s) have a larger value -- this is
due to blk_stack_limits() using min_not_zero() when stacking the
max_segment_size limit.


before patch:

after patch:

Reported-by: Lukasz Flis <l.flis at cyfronet.pl>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Jens Axboe <axboe at kernel.dk>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 block/blk-settings.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index d3234fc..191d33e 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -144,6 +144,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
 	lim->max_segments = USHRT_MAX;
 	lim->max_hw_sectors = UINT_MAX;

+	lim->max_segment_size = UINT_MAX;
 	lim->max_sectors = BLK_DEF_MAX_SECTORS;

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