linux-kernel - Re: [RFC PATCH 4/4] vfs: add filesystem freeze/thaw callbacks for power management

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Message-ID: <a7e6dee45ac11519c33a297797990fce6bb32bff.camel@HansenPartnership.com>
Date: Fri, 28 Mar 2025 10:36:00 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Jan Kara <jack@...e.cz>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
 mcgrof@...nel.org, hch@...radead.org, david@...morbit.com,
 rafael@...nel.org,  djwong@...nel.org, pavel@...nel.org,
 peterz@...radead.org, mingo@...hat.com,  will@...nel.org,
 boqun.feng@...il.com
Subject: Re: [RFC PATCH 4/4] vfs: add filesystem freeze/thaw callbacks for
 power management

On Fri, 2025-03-28 at 10:21 -0400, James Bottomley wrote:
> [...]
> That's right.  I'm happy to post my patch below, but it depends on Al
> accepting the simple_next_child() proposal, so it doesn't apply to
> any
> tree.

And here's the patch I forgot to attach.

Regards,

James

---

diff --git a/fs/efivarfs/internal.h b/fs/efivarfs/internal.h
index ac6a1dd0a6a5..f913b6824289 100644
--- a/fs/efivarfs/internal.h
+++ b/fs/efivarfs/internal.h
@@ -17,7 +17,6 @@ struct efivarfs_fs_info {
 	struct efivarfs_mount_opts mount_opts;
 	struct super_block *sb;
 	struct notifier_block nb;
-	struct notifier_block pm_nb;
 };
 
 struct efi_variable {
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 7d47f8d7ad1d..3398ec5c60b3 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -119,12 +119,15 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 
 	return 0;
 }
+
+static int efivarfs_thaw(struct super_block *sb, enum freeze_holder who);
 static const struct super_operations efivarfs_ops = {
 	.statfs = efivarfs_statfs,
 	.drop_inode = generic_delete_inode,
 	.alloc_inode = efivarfs_alloc_inode,
 	.free_inode = efivarfs_free_inode,
 	.show_options = efivarfs_show_options,
+	.thaw_super = efivarfs_thaw,
 };
 
 /*
@@ -367,8 +370,6 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (err)
 		return err;
 
-	register_pm_notifier(&sfi->pm_nb);
-
 	return efivar_init(efivarfs_callback, sb, true);
 }
 
@@ -432,24 +433,17 @@ static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
 	return err;
 }
 
-static int efivarfs_pm_notify(struct notifier_block *nb, unsigned long action,
-			      void *ptr)
+static int efivarfs_thaw(struct super_block *sb, enum freeze_holder who)
 {
-	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info,
-						    pm_nb);
 	static bool rescan_done = true;
-	struct dentry *parent = sfi->sb->s_root;
+	struct dentry *parent = sb->s_root;
 	struct dentry *child = NULL;
 
-	if (action == PM_HIBERNATION_PREPARE) {
-		rescan_done = false;
-		return NOTIFY_OK;
-	} else if (action != PM_POST_HIBERNATION) {
-		return NOTIFY_DONE;
-	}
+	if ((who & FREEZE_FOR_HIBERNATE) == 0)
+		return 0;
 
 	if (rescan_done)
-		return NOTIFY_DONE;
+		return 0;
 
 	pr_info("efivarfs: resyncing variable state\n");
 
@@ -488,9 +482,9 @@ static int efivarfs_pm_notify(struct notifier_block *nb, unsigned long action,
 	 * then loop over variables, creating them if there's no matching
 	 * dentry
 	 */
-	efivar_init(efivarfs_check_missing, sfi->sb, false);
+	efivar_init(efivarfs_check_missing, sb, false);
 
-	return NOTIFY_OK;
+	return 0;
 }
 
 static int efivarfs_init_fs_context(struct fs_context *fc)
@@ -510,9 +504,6 @@ static int efivarfs_init_fs_context(struct fs_context *fc)
 	fc->s_fs_info = sfi;
 	fc->ops = &efivarfs_context_ops;
 
-	sfi->pm_nb.notifier_call = efivarfs_pm_notify;
-	sfi->pm_nb.priority = 0;
-
 	return 0;
 }
 
@@ -521,7 +512,6 @@ static void efivarfs_kill_sb(struct super_block *sb)
 	struct efivarfs_fs_info *sfi = sb->s_fs_info;
 
 	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
-	unregister_pm_notifier(&sfi->pm_nb);
 	kill_litter_super(sb);
 
 	kfree(sfi);