Re: [PATCH] devtmpfs: don't use vfs_getattr_nosec to query i_mode

[Heiko Carstens <hca@linux.ibm.com>]

On Wed, Apr 23, 2025 at 06:59:41AM +0200, Christoph Hellwig wrote:
> The recent move of the bdev_statx call to the low-level vfs_getattr_nosec
> helper caused it being used by devtmpfs, which leads to deadlocks in
> md teardown due to the block device lookup and put interfering with the
> unusual lifetime rules in md.
> 
> But as handle_remove only works on inodes created and owned by devtmpfs
> itself there is no need to use vfs_getattr_nosec vs simply reading the
> mode from the inode directly.  Switch to that to avoid the bdev lookup
> or any other unintentional side effect.
> 
> Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> Reported-by: Xiao Ni <xni@redhat.com>
> Fixes: 777d0961ff95 ("fs: move the bdex_statx call to vfs_getattr_nosec")
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
> Tested-by: Xiao Ni <xni@redhat.com>
> ---
>  drivers/base/devtmpfs.c | 20 ++++++++------------
>  1 file changed, 8 insertions(+), 12 deletions(-)

Tested-by: Heiko Carstens <hca@linux.ibm.com>