From: Martin Kepplinger <martink@posteo.de>
To: Chris Mason <clm@fb.com>
Cc: linux-btrfs@vger.kernel.org, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] btrfs: Don't check for file->private_data on open(). It is set by the core.
Date: Wed, 12 Nov 2014 19:34:50 +0100 [thread overview]
Message-ID: <5463A84A.8010606@posteo.de> (raw)
In-Reply-To: <1415815173.25389.2@mail.thefacebook.com>
Am 2014-11-12 um 18:59 schrieb Chris Mason:
> On Wed, Nov 12, 2014 at 11:38 AM, Martin Kepplinger <martink@posteo.de>
> wrote:
>> The miscdevice core now sets file->private_data to the struct miscdevice
>> so don't fail when this is not NULL.
>>
>> Signed-off-by: Martin Kepplinger <martink@posteo.de>
>> ---
>> This is a question: what does this check provide and does overwriting
>> file->private_data make any difference?
>>
>> Is miscdevice's open() by the user not allowed here, if
>> file->private_data
>> is set?
>>
>> thanks!!
>
> Btrfs uses this in the transaction start ioctl to record the transaction
> handle being started. Ceph is the main user of the ioctl, and we could
> setup a hash table if needed. But which call path in miscdevice is
> doing this?
>
> With your patch in place, btrfs would end up overwriting the miscdevice
> private_data field, which would probably cause problems.
>
> -chris
>
I think i was mistaken, sorry. misc_open() used to set
file->private_data _only_ if you use set .open in struct file_operations.
In current -next this changed and file->private_data is set to struct
miscdevice on a (userspace's) open call (misc_open()) just in any case.
You do set .open so this wouldn't affect you and this patch can be ignored.
martin
next prev parent reply other threads:[~2014-11-12 18:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-12 16:38 [PATCH] btrfs: Don't check for file->private_data on open(). It is set by the core Martin Kepplinger
2014-11-12 17:59 ` Chris Mason
2014-11-12 18:34 ` Martin Kepplinger [this message]
2014-11-13 22:14 ` Al Viro
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