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



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