Re: mkfs.f2fs gets stuck with "blk_update_request: bio idx 0 >= vcnt0" on 3.8

[Max Filippov]

Hi,

On Tue, Apr 2, 2013 at 7:41 PM, Max Filippov <jcmvbkbc@xxxxxxxxx> wrote:
> I'm trying to create f2fs filesystem on SD card on pandaboard using
> f2fs-tools v1.0.0.
> It works fine on Linus' v3.6, but fails on both v3.8 and stable v3.8.5:
>
> # mkfs.f2fs /dev/mmcblk0p3
> 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

[...]

>> So, I think that it needs to investigate issue in the direction of
>> BLKDISCARD code on the kernel side. It makes sense to debug
>> f2fs_trim_device() method of mkfs.f2fs utility too. But I can't see
>> anything strange in this function at a glance.
>
> Ok, I'll try to find what has changed in that ioctl handler since 3.6.

the commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9 'block: add plug
for blkdev_issue_discard'
have added merge opportunity for DISCARD requests. When I do
mkfs.f2fs on a 5G partition (0xad8000 sectors) it submits two bios,
one for 0x7fe000 sectors (0xffc00000 bytes) and another for
0x2da000 sectors (0x5b400000 bytes). Prior to that commit these
bios weren't merged into one request. Now the second bio gets
merged with the first, but the request's __data_len field is unsigned int
and it gets wrapped to 0x5b000000 bytes instead of 0x15b000000
in the bio_attempt_back_merge. Later this reduced size is passed to
the blk_update_request causing KERN_ERR and not completed
request. Reverting this commit fixes mkfs.f2fs for me.

-- 
Thanks.
-- Max
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