From mboxrd@z Thu Jan  1 00:00:00 1970
From: keith.busch@intel.com (Keith Busch)
Date: Thu, 21 Aug 2014 13:07:06 -0600 (MDT)
Subject: [PATCH] NVMe: Fix partition detection issue(Hot Remove followed
 by Hot Add)
In-Reply-To: <060001cfb175$a1c44c00$e54ce400$@samsung.com>
References: <060001cfb175$a1c44c00$e54ce400$@samsung.com>
Message-ID: <alpine.LRH.2.03.1408211209220.4696@AMR>

On Wed, 6 Aug 2014, Indraneel Mukherjee wrote:
> This patch addresses the same issue that has been discussed at
> http://lists.infradead.org/pipermail/linux-nvme/2014-August/001093.html
> recently
> and provides the best of both worlds (both static & dynamic minor allocation
> schemes similar to SCSI driver(sd)).
>
> - Partially reverts the dynamic minor allocation scheme (but retains the
> GENHD_FL_EXT_DEVT flag to allow allocating very large of minors dynamically)
>
>  introduced in commit 469071a37afc8a627b6b2ddf29db0a097d864845 and
> re-introduces static minor allocation.
> - Aligns Hot-Plug behaviour to SCSI.
> - Uses one common ida allocation routine for allocating namespace & dev
> instances.
> - Introduces a new module parameter nvme_minors to manage the static minor
> allocations(default is 64).
>
> Signed-off-by: Indraneel M <indraneel.m at samsung.com>


Your patch has formatting issues (bad email client?) so it doesn't apply
without some fixing.

I do think we need to something like this though; the block_device that
should go with the new disk is already opened against the removed disk
and so the new one isn't usable.


> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index 28aec2d..6d01164 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -65,6 +65,10 @@ MODULE_PARM_DESC(retry_time, "time in seconds to retry
> failed I/O");
> static int nvme_major;
> module_param(nvme_major, int, 0);
>
> +static int nvme_minors = 64;
> +module_param(nvme_minors, int, 0644);
> +MODULE_PARM_DESC(nvme_minors, "Minors numbers to allocate per Namespace");

You definitely don't want to make this parameter writeable; changing it
after the minors were setup will cause breakage. I think the permissions
should be set to 0, but if you really want to be able to read it, 0444
is okay.

You also need to make sure the nvme_minors parameter is not 0 otherwise
you'll hit a divide-by-zero error.