| Message ID | 20250402-work-freeze-v2-4-6719a97b52ac@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | power: wire-up filesystem freeze/thaw with suspend/resume | expand |
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@kernel.org> Yeah, good idea. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> 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 >
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,
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@kernel.org> --- fs/kernfs/mount.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)