linux-kernel - Re: [PATCH 3.12-rc7] KVM: Fix modprobe failure for kvm_intel/kvm

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Message-ID: <52711121.9030606@linux.vnet.ibm.com>
Date:	Wed, 30 Oct 2013 19:31:05 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	Tim Gardner <tim.gardner@...onical.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Gleb Natapov <gleb@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	KVM list <kvm@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 3.12-rc7] KVM: Fix modprobe failure for kvm_intel/kvm_amd

On 10/30/2013 01:03 AM, Linus Torvalds wrote:
> On Tue, Oct 29, 2013 at 12:27 PM, Raghavendra K T
> <raghavendra.kt@...ux.vnet.ibm.com> wrote:
>>
>> Could one solution be cascading actual error
>> that is lost in fs/debugfs/inode.c:__create_file(), so that we could
>> take correct action in case of failure of debugfs_create_dir()?
>>
>> (ugly side is we increase total number of params for __create_file to
>> 6). or I hope there could be some better solution.
>
> The solution to this would be to simply return an error-pointer. See
> <linux/err.h>. That's what we do for most complex subsystems that
> return a pointer to a struct: rather than returning "NULL" as an
> error, return the actual error number encoded in the pointer itself.

Thank you Linus. Yes, this would have been ideal.

>
> But that would require every user of debugfs_create_dir() to be
> updated to check errors using IS_ERR() instead of checking against
> NULL, and there's quite a few of them.
>
> So I think just making the error be EEXIST is a simpler solution right now.
>

Agree.
I had below patch, and just before sending as formal mail I saw
Paolo's pull request which already took care of it.
---8<---



View attachment "0001-Return-EEXIST-on-debugfs_create_dir-failure-in-kvm.patch" of type "text/x-patch" (1796 bytes)