linux-ext4 - Re: [Drbd-dev] [PATCH 28/42] drbd: switch to proc_create

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Date:   Fri, 18 May 2018 14:55:54 +0200
From:   Lars Ellenberg <lars.ellenberg@...bit.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-rtc@...r.kernel.org, Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-ide@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        jfs-discussion@...ts.sourceforge.net,
        linux-afs@...ts.infradead.org, linux-acpi@...r.kernel.org,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        Jiri Slaby <jslaby@...e.com>, linux-ext4@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        megaraidlinux.pdl@...adcom.com, drbd-dev@...ts.linbit.com
Subject: Re: [Drbd-dev] [PATCH 28/42] drbd: switch to proc_create_single

On Wed, May 16, 2018 at 11:43:32AM +0200, Christoph Hellwig wrote:
> And stop messing with try_module_get on THIS_MODULE, which doesn't make
> any sense here.

The idea was to increase module count on /proc/drbd access.

If someone holds /proc/drbd open, previously rmmod would
"succeed" in starting the unload, but then block on remove_proc_entry,
leading to a situation where the lsmod does not show drbd anymore,
but /proc/drbd being still there (but no longer accessible).

I'd rather have rmmod fail up front in this case.
And try_module_get() seemed most appropriate.

    Lars