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.