Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 15 Jun 2022 23:07:17 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Dave Chinner <david@fromorbit.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org,
        linux-api@vger.kernel.org, linux-fscrypt@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Keith Busch <kbusch@kernel.org>
Subject: Re: [RFC PATCH v2 1/7] statx: add I/O alignment information
Message-ID: <YqrIlVtI85zF9qyO@infradead.org>
References: <20220518235011.153058-1-ebiggers@kernel.org>
 <20220518235011.153058-2-ebiggers@kernel.org>
 <YobNXbYnhBiqniTH@magnolia>
 <20220520032739.GB1098723@dread.disaster.area>
 <YqgbuDbdH2OLcbC7@sol.localdomain>
 <YqnapOLvHDmX/3py@infradead.org>
 <YqpzqZQgu0Zz+vW1@sol.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YqpzqZQgu0Zz+vW1@sol.localdomain>
Precedence: bulk

On Wed, Jun 15, 2022 at 05:04:57PM -0700, Eric Biggers wrote:
> One more thing.  I'm trying to add support for STATX_DIOALIGN on block devices.
> Unfortunately I don't think it is going to work, at all, since the inode is for
> the device node and not the block device itself.  This is true even after the
> file is opened (I previously thought that at least that case would work).

For an open file the block device inode is pointed to by
file->f_mapping->host.

> Were you expecting that this would work on block devices?  It seems they will
> need a different API -- a new BLK* ioctl, or files in /sys/block/$dev/queue.

blkdev_get_no_open on inode->i_rdev gets you the block device, which
then has bdev->bd_inode point to the underlying block device, although
for a block device those limit probably would be retrieved not from
the inode but the gendisk / request_queue anyway.