CVE-2026-46175: f2fs: fix fsck inconsistency caused by FGGC of node block

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix fsck inconsistency caused by FGGC of node block

During FGGC node block migration, fsck may incorrectly treat the migrated node block as fsync-written data.

The reproduction scenario: root@vm:/mnt/f2fs# seq 1 2048 | xargs -n 1 ./testsync // write inline inode and sync root@vm:/mnt/f2fs# rm -f 1 root@vm:/mnt/f2fs# sync root@vm:/mnt/f2fs# f2fsio gcrange // move data block in sync mode and not write CP SPO, "fsck --dry-run" find inode has already checkpointed but still with DENTBITSHIFT set

The root cause is that GC does not clear the dentry mark and fsync mark during node block migration, leading fsck to misinterpret them as user-issued fsync writes.

In BGGC mode, node block migration is handled by f2fssyncnodepages(), which guarantees the dentry and fsync marks are cleared before writing.

This patch move the set/clear of the fsync|dentry marks into writenodefolio to make the logic clearer, and ensures the fsync|dentry mark is cleared in FGGC.