Re: [PATCH v1 00/16] NFS/RDMA patches proposed for 4.1

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, May 06, 2015 at 09:09:36AM +0200, Bart Van Assche wrote:
> On 05/05/15 23:06, Christoph Hellwig wrote:
> >The contiguous requirements isn't something we can alway guarantee.
> >While a lot of I/O will have that form the form where there are holes
> >can happen, although it's not common.
> 
> Indeed. That is why there is code in the SRP initiator that uses multiple
> FRWR registrations when a discontiguous SG-list is passed to that driver by
> the SCSI mid-layer. Some time ago I had posted a test program that makes the
> SCSI mid-layer submit a discontiguous I/O request to a SCSI LLD (see also
> https://www.mail-archive.com/linux-rdma@xxxxxxxxxxxxxxx/msg21224.html).

Note that block layer now has the (fairly misnamed) QUEUE_FLAG_SG_GAPS
flag, which ensures drivers don't see S/G lists like this one.  I
haven't ever seen normal TYPE_FS producers submit bios like that, so in
practice the effect is to reject vectored SG_IO uses like your test
program.
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Filesystem Development]     [Linux USB Development]     [Linux Media Development]     [Video for Linux]     [Linux NILFS]     [Linux Audio Users]     [Yosemite Info]     [Linux SCSI]

  Powered by Linux