From: Christian Brauner <brauner@kernel.org>
Date: Sun, 6 Apr 2025 20:28:52 +0000 (+0200)
Subject: f2fs: fix freezing filesystem during resize
X-Git-Tag: v6.16-rc1~222^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1afe9e7da8c0ab3c17d4a469ed4c0607024cf0d4;p=thirdparty%2Fkernel%2Flinux.git

f2fs: fix freezing filesystem during resize

Using FREEZE_HOLDER_USERSPACE has two consequences:

(1) If userspace freezes the filesystem after mnt_drop_write_file() but
    before freeze_super() was called filesystem resizing will fail
    because the freeze isn't marked as nestable.

(2) If the kernel has successfully frozen the filesystem via
    FREEZE_HOLDER_USERSPACE userspace can simply undo it by using the
    FITHAW ioctl.

Fix both issues by using FREEZE_HOLDER_KERNEL. It will nest with
FREEZE_HOLDER_USERSPACE and cannot be undone by userspace.

And it is the correct thing to do because the kernel temporarily freezes
the filesystem.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 3e8af62c9e15e..dd0ba0532e011 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -2271,12 +2271,12 @@ out_drop_write:
 	if (err)
 		return err;
 
-	err = freeze_super(sbi->sb, FREEZE_HOLDER_USERSPACE, NULL);
+	err = freeze_super(sbi->sb, FREEZE_HOLDER_KERNEL, NULL);
 	if (err)
 		return err;
 
 	if (f2fs_readonly(sbi->sb)) {
-		err = thaw_super(sbi->sb, FREEZE_HOLDER_USERSPACE, NULL);
+		err = thaw_super(sbi->sb, FREEZE_HOLDER_KERNEL, NULL);
 		if (err)
 			return err;
 		return -EROFS;
@@ -2333,6 +2333,6 @@ recover_out:
 out_err:
 	f2fs_up_write(&sbi->cp_global_sem);
 	f2fs_up_write(&sbi->gc_lock);
-	thaw_super(sbi->sb, FREEZE_HOLDER_USERSPACE, NULL);
+	thaw_super(sbi->sb, FREEZE_HOLDER_KERNEL, NULL);
 	return err;
 }