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(+)
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
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 > -- Jan Kara <jack@suse.com> SUSE Labs, CR
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