[PATCH] x86/mm/cpa: Add missing comment in populate_pdg()

[Andy Lutomirski <luto@kernel.org>]

In commit 21cbc2822aa1 ("x86/mm/cpa: Unbreak populate_pgd(): stop
trying to deallocate failed PUDs"), I intended to add this comment,
but I failed at using git.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/mm/pageattr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 2bc6ea153f76..47870a534877 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1091,6 +1091,11 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 
 	ret = populate_pud(cpa, addr, pgd_entry, pgprot);
 	if (ret < 0) {
+		/*
+		 * Leave the PUD page in place in case some other CPU or thread
+		 * already found it, but remove any useless entries we just
+		 * added to it.
+		 */
 		unmap_pud_range(pgd_entry, addr,
 				addr + (cpa->numpages << PAGE_SHIFT));
 		return ret;
-- 
2.7.4