CVE-2026-93798

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

btrfs: fix reloc root cleanup in merge_reloc_roots()

If the root we got has zero root refs in its root item, we are resetting

the root's ->reloc_root without using barriers like we do everywhere else.

Sashiko complained about this while reviewing another patch, and it's

correct (see the Link tag below).

Also, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless

the root points to the reloc root we have.

Fix this by using clear_reloc_root(), which issues the memory barrier

after setting the root's ->reloc_root to NULL and before clearing the bit

BTRFS_ROOT_DEAD_RELOC_TREE from the root.