That sounds like a bug in bcache - bcache should be respecting the
queue limits the underlying device exports.

Can you tell me what the various files in /sys/block/<device>/queue/
look like for your device?

On Wed, May 9, 2012 at 8:23 PM, moussa ba <[email protected]> wrote:
> Tried to send this to mailing list but was rejected somehow.
>
> ---------- Forwarded message ----------
> From: moussa ba <[email protected]>
> Date: Wed, May 9, 2012 at 5:17 PM
> Subject: Scatter Gather List in bio exceed driver capabilities
> To: [email protected]
>
>
>
> We are using a micron PCI-E SSD as a caching device.  I am running into
> issues where the driver would fail when we try to register the cache device.
>  The failure is because bcache sends down a bio with 256 entries while the
> device driver can only handle 128 entries.  We could make changes inside our
> driver to chunk the requests (mind you I did not write the driver, but
> driver guys told me so...) and fix it that way.  I am assuming that since
> bcache is creating the bio to get at its metadata, it does not chunk the
> bios to fit the underlying hardware nor does it query it in some way to set
> the bi_vcnt.
>
> Any suggestions on how to properly address this?
>
> Moussa
>
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