Re: [PATCH] block: fix max discard sectors limit

[James Bottomley <jbottomley@parallels.com>]

On Wed, 2013-04-24 at 22:55 +0900, Namjae Jeon wrote:
> From: James Bottomley <JBottomley@Parallels.com>
> 
> 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@gmail.com>
> Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
> Signed-off-by: James Bottomley <JBottomley@Parallels.com>
> Tested-by: Max Filippov <jcmvbkbc@gmail.com>
> Cc: <stable@vger.kernel.org>

The two signoffs need to be reversed (they follow the chain of
transmission from the author into the kernel), but other than that, this
looks great.  I assume Jens can just hand edit this one issue.

Thanks,

James