Patch "block: fix max discard sectors limit" has been added to the 3.9-stable tree

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This is a note to let you know that I've just added the patch titled

    block: fix max discard sectors limit

to the 3.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-fix-max-discard-sectors-limit.patch
and it can be found in the queue-3.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 871dd9286e25330c8a581e5dacfa8b1dfe1dd641 Mon Sep 17 00:00:00 2001
From: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Date: Wed, 24 Apr 2013 08:52:50 -0600
Subject: block: fix max discard sectors limit

From: James Bottomley <JBottomley@xxxxxxxxxxxxx>

commit 871dd9286e25330c8a581e5dacfa8b1dfe1dd641 upstream.

linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
(block: add plug for blkdev_issue_discard )

For example,
1) DISCARD rq-1 with size size 4GB
2) DISCARD rq-2 with size size 1GB

If these 2 discard requests get merged, final request size will be 5GB.

In this case, request's __data_len field may overflow as it can store
max 4GB(unsigned int).

This issue was observed while doing mkfs.f2fs on 5GB SD card:
https://lkml.org/lkml/2013/4/1/292

Info: sector size = 512
Info: total sectors = 11370496 (in 512bytes)
Info: zone aligned segment0 blkaddr: 512
[  257.789764] blk_update_request: bio idx 0 >= vcnt 0

mkfs process gets stuck in D state and I see the following in the dmesg:

[  257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081
[  257.789764]   sector 4194304, nr/cnr 2981888/4294959104
[  257.789764]   bio df3840c0, biotail df3848c0, buffer   (null), len
1526726656
[  257.789764] blk_update_request: bio idx 0 >= vcnt 0
[  257.794921] request botched: dev mmcblk0: type=1, flags=122c8081
[  257.794921]   sector 4194304, nr/cnr 2981888/4294959104
[  257.794921]   bio df3840c0, biotail df3848c0, buffer   (null), len
1526726656

This patch fixes this issue.

Reported-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Signed-off-by: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Tested-by: Max Filippov <jcmvbkbc@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 include/linux/blkdev.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -838,7 +838,7 @@ static inline unsigned int blk_queue_get
 						     unsigned int cmd_flags)
 {
 	if (unlikely(cmd_flags & REQ_DISCARD))
-		return q->limits.max_discard_sectors;
+		return min(q->limits.max_discard_sectors, UINT_MAX >> 9);
 
 	if (unlikely(cmd_flags & REQ_WRITE_SAME))
 		return q->limits.max_write_same_sectors;


Patches currently in stable-queue which might be from JBottomley@xxxxxxxxxxxxx are

queue-3.9/block-fix-max-discard-sectors-limit.patch
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