Kernel bio layer is sending bio size more than our block device is capable of handling

Kernel bio layer is sending bio size more than our block device is capable of handling

[Umesh Patel]

Hello,

We are registering bio size of our device with linux kernel with below
available kernel API.  blk_queue_max_hw_sectors(dev->osdev.queue,
(dev->aggr_max_size >> KERNEL_SECTOR_SHIFT));.

Max size of bio that our block device can handle is 106496 bytes (104KB) but
linux block device is sending 262144  bytes (256 KB) which is more than we
are registering with kernel.

This issue we are observing in 4.4.0-59-generic kernel version. Until this
we had not seen this issue.
So does anything extra require to tell linux kernel or anything else need to
register ?


Thanks
 



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Re: Kernel bio layer is sending bio size more than our block device is capable of handling

[Christoph Hellwig]

Please post your driver to the linux-block list, and test a recent
kernel.

RE: Kernel bio layer is sending bio size more than our block device is capable of handling

[Umesh Patel]

Hi Christoph Hellwig,

Thanks for reply.
BTW (since I'm new) what is linux-block list ?. Is it subscribe ?.
Can you please let me know which is latest kernel version ?


Thanks,
Umesh

-----Original Message-----
From: Christoph Hellwig [mailto:hch@infradead.org] 
Sent: Thursday, March 2, 2017 9:13 PM
To: Umesh Patel
Cc: linux-kernel@vger.kernel.org
Subject: Re: Kernel bio layer is sending bio size more than our block device is capable of handling

Please post your driver to the linux-block list, and test a recent kernel.

Re: Kernel bio layer is sending bio size more than our block device is capable of handling

[Christoph Hellwig]

Hi Umesh,

it's linux-block@vger.kernel.org, and the place where all block layer
and driver development happens, you can subsribe to it using the
same way you subscribed to linux-kernel, just replacing the list name.

The latest released vesion at this point is Linux 4.10.

RE: Kernel bio layer is sending bio size more than our block device is capable of handling

[Umesh Patel]

Hi Christoph Hellwig,

So 4.4.0-59-generic is not stable one ?. If not then probably it would be problem for us if customer want the same kernel version!.


Thanks,
Umesh



-----Original Message-----
From: Christoph Hellwig [mailto:hch@infradead.org] 
Sent: Thursday, March 2, 2017 9:34 PM
To: Umesh Patel
Cc: Christoph Hellwig; linux-kernel@vger.kernel.org
Subject: Re: Kernel bio layer is sending bio size more than our block device is capable of handling

Hi Umesh,

it's linux-block@vger.kernel.org, and the place where all block layer and driver development happens, you can subsribe to it using the same way you subscribed to linux-kernel, just replacing the list name.

The latest released vesion at this point is Linux 4.10.

Re: Kernel bio layer is sending bio size more than our block device is capable of handling

[Umesh Patel]

>From the kernel source code i came to know below things.

4.1 kernel version onward 
*""nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(map_bh->b_bdev))""*
line has been removed which was considering max_sectors_kb of queue. 

Now new code is something like this* "nr_pages = min(sdio->pages_in_io,
BIO_MAX_PAGES)"*, which is sending 256 bytes of data to our device which we
are not supporting.

Please let me know is there any other place where i can register my
max_sectors_kb to kernel.



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