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From: Stephen Rust <srust@blockbridge.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Rob Townley <rob.townley@gmail.com>,
	Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-scsi@vger.kernel.org, martin.petersen@oracle.com,
	target-devel@vger.kernel.org, Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>, Sagi Grimberg <sagi@grimberg.me>,
	Max Gurtovoy <maxg@mellanox.com>
Subject: Re: Data corruption in kernel 5.1+ with iSER attached ramdisk
Date: Wed, 4 Dec 2019 21:28:43 -0500
Message-ID: <CAAFE1bcwcdVuzAG5+x1UNcTaa22bf0tOaT=QOWrTup98sFXxuQ@mail.gmail.com> (raw)
In-Reply-To: <20191204230225.GA26189@ming.t460p>

Hi Ming,

Thanks for all your help and insight. I really appreciate it.

> > Presumably non-brd devices, ie: real scsi devices work for these test
> > cases because they accept un-aligned buffers?
>
> Right, not every driver supports such un-aligned buffer.

Can you please clarify: does the block layer require that it is called
with 512-byte aligned buffers? If that is the case, would it make
sense for the block interface (bio_add_page() or other) to reject
buffers that are not aligned?

It seems that passing these buffers on to underlying drivers that
don't support un-aligned buffers can result in silent data corruption.
Perhaps it would be better to fail the I/O up front. This would also
help future proof the block interface when changes/new target drivers
are added.

I'm also curious how these same unaligned buffers from iSER made it to
brd and were written successfully in the pre "multi-page bvec" world.
(Just trying to understand, if you have any thoughts, as this same
test case worked fine in 4.14+ until 5.1)

> I am not familiar with RDMA, but from the trace we have done so far,
> it is highly related with iser driver.

Do you think it is fair to say that the iSER/block integration is
causing corruption by using un-aligned buffers?

Thanks,
Steve

  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAAFE1bd9wuuobpe4VK7Ty175j7mWT+kRmHCNhVD+6R8MWEAqmw@mail.gmail.com>
2019-11-28  1:57 ` Ming Lei
     [not found]   ` <CA+VdTb_-CGaPjKUQteKVFSGqDz-5o-tuRRkJYqt8B9iOQypiwQ@mail.gmail.com>
2019-11-28  2:58     ` Ming Lei
     [not found]       ` <CAAFE1bfsXsKGyw7SU_z4NanT+wmtuJT=XejBYbHHMCDQwm73sw@mail.gmail.com>
2019-11-28  4:25         ` Stephen Rust
2019-11-28  5:51           ` Rob Townley
2019-11-28  9:12         ` Ming Lei
2019-12-02 18:42           ` Stephen Rust
2019-12-03  0:58             ` Ming Lei
2019-12-03  3:04               ` Stephen Rust
2019-12-03  3:14                 ` Ming Lei
2019-12-03  3:26                   ` Stephen Rust
2019-12-03  3:50                     ` Stephen Rust
2019-12-03 12:45                       ` Ming Lei
2019-12-03 19:56                         ` Stephen Rust
2019-12-04  1:05                           ` Ming Lei
2019-12-04 17:23                             ` Stephen Rust
2019-12-04 23:02                               ` Ming Lei
2019-12-05  0:16                                 ` Bart Van Assche
2019-12-05 14:44                                   ` Stephen Rust
2019-12-05  2:28                                 ` Stephen Rust [this message]
2019-12-05  3:05                                   ` Ming Lei
2019-12-05  9:17                                 ` Sagi Grimberg
2019-12-05 14:36                                   ` Stephen Rust
2019-12-04  2:39                           ` Ming Lei
2019-12-03  4:15                     ` Ming Lei

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