Re: [PATCH rdma-rc v2] RDMA/mlx5: Use xa_lock_irq when access to SRQ table

From: Leon Romanovsky <leon@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Doug Ledford <dledford@redhat.com>,
	Jason Gunthorpe <jgg@mellanox.com>,
	Maor Gottlieb <maorg@mellanox.com>,
	linux-rdma@vger.kernel.org
Subject: Re: [PATCH rdma-rc v2] RDMA/mlx5: Use xa_lock_irq when access to SRQ table
Date: Sun, 12 Jul 2020 20:41:47 +0300	[thread overview]
Message-ID: <20200712174147.GD7287@unreal> (raw)
In-Reply-To: <20200712143306.GT12769@casper.infradead.org>

On Sun, Jul 12, 2020 at 03:33:06PM +0100, Matthew Wilcox wrote:
> On Sun, Jul 12, 2020 at 01:26:41PM +0300, Leon Romanovsky wrote:
> > Fixes: b02a29eb8841 ("mlx5: Convert mlx5_srq_table to XArray")
> > Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
> > Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> > ---
> > v2:
> >  * Dropped wrong hunk
> > v1:
> > https://lore.kernel.org/linux-rdma/20200707131551.1153207-1-leon@kernel.org
> >  * I left Fixes as before to make sure that it is taken properly to stable@.
> >  * xa_lock_irqsave -> xa_lock_irq
>
> But it won't be taken properly to stable.  It's true that that's the
> earliest version that this applies to, but as far as I can tell the
> underlying bug is there a lot earlier.  It doesn't appear to be there
> in e126ba97dba9edeb6fafa3665b5f8497fc9cdf8c as the cq->lock is taken
> irqsafe in mlx5_ib_poll_cq() before calling mlx5_poll_one() which calls
> handle_responder() which calls mlx5_core_get_srq(), but it was there
> before b02a29eb8841.  I think it's up to you to figure out which version
> this bug was introduced in, because stable still cares about trees before
> 5.2 (which is when b02a29eb8841 was introduced).  You'll also have to
> produce a patch for those earlier kernels.

Of course, but first I would like to be sure that Sasha's autosel will
work out-of-box.

Thanks