diff options
| author | Christian Brauner <brauner@kernel.org> | 2025-04-02 16:07:34 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-05-09 12:41:23 +0200 |
| commit | ef2ed04eba999b13096ace4fafc2e7ed04176950 (patch) | |
| tree | b5a76542ad235152d8f2a55f2932aceff7c4436b | |
| parent | eacfbf74196f91e4c26d9f8c78e1576c1225cd8c (diff) | |
kernfs: add warning about implementing freeze/thaw
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.
Link: https://lore.kernel.org/r/20250402-work-freeze-v2-4-6719a97b52ac@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/kernfs/mount.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c index 5124e196c2bf..46d773411ba8 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, |