On Wed 02-04-25 16:07:34, Christian Brauner wrote:
> Sysfs is built on top of kernfs and sysfs provides the power management
> infrastructure to support suspend/hibernate by writing to various files
> in /sys/power/. As filesystems may be automatically frozen during
> suspend/hibernate implementing freeze/thaw support for kernfs
> generically will cause deadlocks as the suspending/hibernation
> initiating task will hold a VFS lock that it will then wait upon to be
> released. If freeze/thaw for kernfs is needed talk to the VFS.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Yeah, good idea. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/kernfs/mount.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
> index 1358c21837f1..d2073bb2b633 100644
> --- a/fs/kernfs/mount.c
> +++ b/fs/kernfs/mount.c
> @@ -62,6 +62,21 @@ const struct super_operations kernfs_sops = {
>
> .show_options = kernfs_sop_show_options,
> .show_path = kernfs_sop_show_path,
> +
> + /*
> + * sysfs is built on top of kernfs and sysfs provides the power
> + * management infrastructure to support suspend/hibernate by
> + * writing to various files in /sys/power/. As filesystems may
> + * be automatically frozen during suspend/hibernate implementing
> + * freeze/thaw support for kernfs generically will cause
> + * deadlocks as the suspending/hibernation initiating task will
> + * hold a VFS lock that it will then wait upon to be released.
> + * If freeze/thaw for kernfs is needed talk to the VFS.
> + */
> + .freeze_fs = NULL,
> + .unfreeze_fs = NULL,
> + .freeze_super = NULL,
> + .thaw_super = NULL,
> };
>
> static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
>
> --
> 2.47.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
